Chennai River Basin Micro Level Report - Rainwater … · Web viewProblems should be described using systems terminologies: entities, attributes, levels, and interrelations. The nature

INTRODUCTIONThe Centre for Science and Environment, New Delhi, envisages a detailed Scientific

Study to assess the Surface Water and Groundwater Resources and the utilisation of Ground

and Surface Water Resources in the Chennai Basin since the total available potential, goes

beyond the Static Reserve, due to the indiscriminate growth of population, industries and

agricultural development, causes depletion of groundwater levels and seawater incursion.

Meanwhile due to the discharge of the industrial and municipal sewerages into most of the

surface water bodies and into groundwater aquifer system either directly or indirectly, in most

of the places, both the surface water and groundwater get polluted and contaminated to a

maximum extent. Now it is necessitated to assess the quantum of such impact and its

appropriate remedial measures to find a lasting solution.

This present study entrusted by The Centre for Science and Environment, New Delhi,

aims at to assess the total Surface Water and Groundwater potential to meet the water

requirement of the people of the stakeholders of Chennai Basin Area and Chennai

Metropolitan Area and its suburb, especially to find a solution within a permissible financial

constraint. This type of study aims to substitute and to reduce the impact on natural resources

within the study areas, to preserve the groundwater and surface water reserve for sustainable

development.

Through intervention of innovative technologies, the limit can be enhanced and reset

at a higher level of scientific ways and means, discharges within the limit of collection with

suitable population growth, with a new set of gradual increase in collection of sewage from

point source which should again bring the mutual balance as stated above. Till date many

studies were carry out in these areas by estimating both the surface water and groundwater

potential either by Adhoc norms or by collection of hydrological and hydrogeological data

collection and rapid assessment. Almost all these studies estimated the total available water

potential, its usage and its balance but as on date the condition of both the surface water and

groundwater reserve is very much limited due to various changes in the hydrological and

hydrogeological changes. Till date all effective steps taken for solving the water crisis was

overcome and were futile by inorderly growth of population, housing, industries and

agriculturists, that was indiscriminate, unpredicted, uncontrolled and irrational, taking place

both in urban and in rural areas. But within a given set of technology, the present status of

surface water and groundwater can be make use off by doing better water management,

conservation and by recycling of waste water generated and wasted.

Chennai River Basin

Water pollution can be diluted, minimize the aerial extent and its intensity with space,

depth and time, at a finite / definite limit. The developmental activities are compatible with

its special, physical & ecological characteristics. A Eco friendly approach for sustainable

development, there is a greater need to involve the private sector for the distribution and

supply for utlisation of such treated effluent for better use so as to maximize the returns for

the expenditure involved in such projects, which will also meet the daily recurring

expenditure involved for the maintenance of the project and also to improve the socio

economic status of the peoples in those areas fully. Briefly, when we analyze problems and

their causes we must use a systems framework. Problems should be described using systems

terminologies: entities, attributes, levels, and interrelations. The nature of interrelations

between various attributes belonging to different entities must also be studied in the context

of the three basic aspects - direct vs. inverse, linear vs. non-linear and immediate vs.

delayed effects.

While doing so it will be possible to develop a visual perspective of the problem

being analyzed and avoid delayed effects. The systems approach involves the use of specific

tools, which enable the development of a visual description of a problem. Once a visual

description of a problem is available then it is possible to model the system's behavior using

other tools such as cross-impact analysis, and system dynamics. Through the application of

these tools we can understand better and can hope to gain greater control over the

development and environment, which should go hand in hand to create a database.

If such systems are developed for one river basin, this may be adopted and

implemented in other metropolitan areas of other river basins where huge quantity of treated

sewages are utilised for non-commercial purposes or thrown as a waste, which causes the

contamination of groundwater reserve and can be used for many number of productivity

purposes. A pilot project can be designed, implemented, executed and commissioned for

Chennai city as a forerunner in India by Tamilnadu Government. The concept behind in

suggesting this sample study is to develop such technology to other major cities in Tamilnadu

itself as a whole for, proper utilization. The Center for Science and Environment, New Delhi,

has requested us to study and prepare a Micro-level Status Report of Chennai River Basin

with a Special Emphasis on Chennai City and its Environs including Chennai

Metropolitan Area. The study now taken covers the assessment of surface water and

groundwater potential, present condition of groundwater levels and quality, future demand

and stages of development.

K.R.Sivaraman & Dr. S. Thillaigovindarajan Page 2 5/7/2023

Chennai River Basin

2. OBJECTIVES OF THE STUDY:The objectives of this study addressing the above issues needs elaborate data base on

the past 10 to 30 years data on groundwater and surface water resources, present

Groundwater and Water Supply Status and the future demand of water resources for various

disciplines of Chennai Metropolitan Limit and its Environs covering whole Greater Chennai

Metropolitan Area on the following aspects: -

i. Assess the Surface water and Groundwater Potential, utilisation, extraction and

balance available to meet the future demand.

ii. Analysis of the Surface Water & Groundwater quality of the whole Chennai River

Basins over long period of 10 years.

iii. Land value, land use and the economic benefits / losses attained over a long run

by the landholders.

iv. Socio and Economic analysis to increase the status of the people settled in the

entire river basin covering the Greater Chennai Metropolitan Limit and its

environs covering parts of Thiruvallore, Kanjeepuram and Vellore Districts,

especially to find out a lasting solution within a permissible financial constraint.

v. To assess the level of groundwater pollution by the discharge of effluent in the

Cooum and Adyar Rivers and Buckingham Canal.

vi. To assess the groundwater quality, utilisation of such treated effluent for

appropriate usage; create awareness among the people, the ways and means to

solve these issues forever.

The detailed work plan also includes: -i. Collection of hydrological, hydrogeological and hydrometeriological data both

secondary and at primary level to create a comprehensive database for Greater

Chennai Metropolitan Area on Hydrology and Hydrogeology.

ii. Preparation of Thematic Maps of Chennai & its environs, such as Geology,

Geomorphology, Landuse, Soil using conventional data and satellite / aerial data and

geophysical data.

iii. Generation of map showing recharge and catchment areas of Greater Chennai.

iv. Data processing and location sketches, hydrogeological cross-sections, wherever

possible groundwater conditions, groundwater quality and groundwater recharge.

Integration of the above data and preparation of action plan, documentation and

analysis.


Chennai River Basin

3. CHENNAI RIVER BASIN.The most fundamental concept of the Micro-level Status Report of Chennai River

Basin mainly to evaluate the optional utilisation of surface and ground water resources.

3.1 GeneralThe Chennai Basin is situated between latitudes 12°40'N and 13°40'N and longitudes

79°10'E and 80°25'E at the north east corner of Tamilnadu. Andhra Pradesh lies on it north;

Palar River basin lies on west and south and the Bay of Bengal on the east were the main

boundaries of this basin. The total area of the basin is 7282 km². Out of that 5542 km² lies in

Tamilnadu and the rest is in Andhra Pradesh. Araniyar (covers 763 km²), Kosathalayar

(covers 3.240 km²), Cooum (682 km²) and Adayar (857 km²) are the four rivers of this basin

group. This basin group covers partly or fully 26 blocks of Tiruthani, Thiruvallore, Saidapet,

Tambaram, Ponneri, Sriperumbudur, Arakonam, and Walajapet taluks of Thiruvallore,

Kanjeepuram, Chennai and Vellore districts. The major part of the basin area comes under

Thiruvallore and Chennai districts (fully covered) and only a few area covers Vellore and

Kanjeepuram districts. Of the four rivers, the Adayar River carries the floodwater and

drainage of Chennai city and its environs. It does not have any direct irrigation and carries

only the flood discharge during the northeast monsoon period for few days. The Cooum

River serves as drainage and sewerage carrier within the Chennai city limit.

The Administrative boundary of the Chennai Basin is enclosed vide Plate: I.

Chennai River basin, models of inter department basin transfer of surface water from

western Nagari Hills and originate from Andhra Pradesh hilly area and also forms part one of

the seventeen important river basins of Tamilnadu. This has got a very good network

distribution for irrigation, contributes a very high agricultural production of the state

exchequer. It attributes greater importance in the existence, climate, physiography,

unpredictable rainfall, distinct hydrogeology and water quality problems due to pollution on

various grounds and also due to coastal environment. To evaluate the water resources of the

basin various monitoring network data observed were employed.

3.2 Physiography.Physiographically the basin can be divided into three units viz. they are Western

mountainous terrain with valley complex; Central elevated terrain and Eastern coastal plain.

Physiography deals with the actual existing in-situ conditions of the land, depending upon the

structures, formational changes and available natural agencies such as Hydrogiene and

Epigiene agents.


Chennai River Basin

The Physiography of an area can be classified as hills, plateau, plains, deltaic plain

and coast. Physiographically the Chennai River Basin is an interdependent river basin of

Araniar, Kosathalayar, Cooum and Adyar all rivers mostly flow from west to east with a man

made artificial Buckingham canal runs from north to south. The river Araniar and

Kosathalayar originate from Andhra Pradesh whereas the Cooum and Adyar originate from

surplus courses of Cooum tank in Thiruvallore Taluk and Chembarambakkam Tank in

Sriperumbudur Taluk. All these four rivers stretching from west to east and confluence with

Bay of Bengal in the East.

The length of the river is 200 km.; width varies from 180 to 120 km. The Maximum

elevation 1219 m above m.s.l. and minimum elevation is 5 to 15 m above mean sea level. The

main tributaries are Nagari River, Araniar, Korathalayar, Cooum, Adyar and Buckingham

canal. There are four major reservoirs situated in this basin. They are Poondi (Sathyamoorthy

Sagar), Red Hills, Sholavaram and Chembarambakkam.

The total command area in Chennai Basin: is 1,31,665 hectares. There are 1,304

tanks by which 85,208 ha are irrigated. The storage capacity of the tanks is 410 mcm and the

total capacity of the basin is 1069 mcm. The main study area of Greater Chennai, is more or

less lays on the East Coast, hence the plain to gentle and the Coastal Physiography only

occurs. The trend of coast is more or less uniform throughout the length of the study area.

However broken natures in the trendline forms small parts and fishing point's etc.

Normally the coast spreads 750 m to 1000 m towards west from the tidal points with

coverage of sands and sandy clay materials. In coastal area of the study, more or less plain

topography is seen. Physiographically this basin is covered by parts of 12 Taluks & 26

Blocks falls in four districts of Tamilnadu State alone, mostly occupies the northern

boundaries of Tamilnadu State. This is entry point to Tamilnadu from other states.

Small beach ridges and sand hillocks are occurring in and around the coastal belt near

Pulicat Lake to Adayar creek and extend upto Injambakkam. Mostly backwater zones are

seen in Pulicat and at Adayar Estuary in this basin area. Sea erosion prone, broken coasts are

observed in Thiruvottiuyur to Ennore area. In Inland, topography, Insel bergs, (at

Manjankaranai near Periyapalayam) smaller hillocks and elevated social forests were present.

The maximum and minimum elevations of the study area are between 2 to 15 m in the coastal

plain, 10 to 25 m in the central region and more in the hills and reserve forests, which covers

a small area mostly on the northwest and west. The nominal topography is generally slopping

towards the East and Southeast. The general trend of dipping ranges from West to East. The

Hydraulic gradient and the flow lines of ground and surface water are towards east, the sea.


Chennai River Basin

They’re some small hills and hillocks lie just near Pallavaram, Thiruneermalai and

Tambaram, leaving the major hills and hill ranges lies on the northwestern and western part

of the study area. Most of the hill catchments lie on the Andhrapradesh region.

The study area comprises of the major rivers like Araniyar and Korathalayar in the

north and the Adyar and Cooum in the south. Apart from these rivers, there is a manmade

canal, the Buckingham Canal runs north to south along the eastern narrow coastal strip,

which actually starts from Visakhapattnam (Andhrapradesh State) in the north and ends near

Marakkanam at Kaluveli tank in Tamilnadu State. Some years back, it was used for

navigation and transportation, which has to be rejuvenated and revived. This canal will be

very well useful and beneficial for tourism, resorts and for transportation. There is a large

catchment area commanded by the rivers Araniar and Korathalayar, leaving the rest of the

rivers such as Adyar and Cooum are having a very small catchment.

There is more number of systems and non-system rainfed tanks lies in the study area.

These water bodies were very specifically useful in meeting the drinking water needs of the

Chennai Metropolitan Area and rarely for irrigation and for industrial uses of many number

of industries located around Chennai city and its urban agglomerate. All the drainages of the

study area flow from west to east and confluence into Bay of Bengal. The specific drainage

pattern in Araniar and Kosathalayar are interdependent. Leaving this some quantum of

surface water too transferred from Palar River for irrigation purposes.

Road Network (Plate No: II), Elevation (Plate No: III), the Physiographic Map showing

the Drainages and Water bodies (Plate No: IV) and Slope (Plat No: V) are enclosed.

3.3. Climate & Rainfall For any water resources evaluation, planning, development and management studies,

knowledge of the rainfall over the basin area as well as other hydrometeriological features is

a pre-requisite. The basic factors, which influence agriculture, are climatological features

such as rainfall, temperature, humidity, wind, sunshine and evaporation. Rainfall is the major

input for the water resources in a basin and is a vital component to be studied in detail.

Another important Hydrometeriological parameter is evaporation.

As Tamilnadu falls in the tropical zone, (arid, semi-arid climatic regions) evaporation

plays a major role in agriculture and the same has to be studied in detail. The study now

made on the hydrometeriological characteristics of the Chennai Basin (Araniar, Kosathalayar,

Cooum and Adayar) includes analysis of rainfall, temperature, humidity, wind speed and

sunshine.


Chennai River Basin

A study of the rainfall pattern, its distribution in time and space and its variability and

probability of occurrence is highly useful for water resources evaluation and planning. A

detailed study has been made on the hydrometeriological parameters for Chennai Basin and

the results of the analysis of the data collected are tabulated and analysed below.

Rain Gauge Stations

The Araniar and Kosathalayar River Basin – Chennai Basin has an aerial extent of

7282 km². Out of that 5542 km² lies in Tamilnadu and the rest in Andhra Pradesh. There are

46 non-recording rain gauge stations installed in this basin. Out of this, 24 stations having

long-term records spatially distributed are considered for this study. In addition to that there

are also 15 self-recording Auto Graphic Rain Gauge Stations located in this basin.

Araniar & Kosathalayar River Basin has a monsoonal climate as it lies within the

tropical monsoon zone. Based on the hydrometeriological feature of the basin, year is divided

into 2 periods Monsoon period spanning from June to December and Non-monsoon period

spanning from January to May. The monsoon period is further sub-divided into 1) South

West monsoon period spanning from June to September (4 months) and 2) Northeast

monsoon period spanning from October to December (3 months). Similarly, the non-

monsoon period is further sub-divided into (1) Winter period spanning January and February

(2 months) and (2) Summer period spanning from March to May (3 months). As the monsoon

period brings heavy rainfall it improves the recharging of ground water and storage of surface

water. Hence, the monsoon period is hydrologically significant for water resources analysis,

but whereas the Non-monsoon, it is insignificant.

Chennai Basin

The Annual rainfall for the 31 rainfall stations, for all the years and the average

annual rainfall have been arrived and tabulated. The Probable Mean aerial rainfall analysis

for 50%, 75% dependable rainfall in each of the sub basin and the basin group based on the

rainfall data from 1971 to 2001 (for latest 30 years were taken into account) as a whole are

below and the average for South West and North East and annual Rainfall for all the 31

rainfall stations have been analysed and tabulated.

The rainfall pattern of this basin along with Theisen Polygon was drawn based on 31

Rainfall Stations data were enclosed Vide Plate No: VI.

The annual normal rainfalls of the 31 Rain Fall Stations located within the Chennai

Basin collected were furnished season wise below.


Chennai River Basin

Table NO: 1 Details of Rainfall Stations falls in the Chennai basin.


Chennai River Basin

Table No: 2 - The following are the Districts that are covered by the river basin.

S.No. District District Area in Sq.

Km.

District Area falling in the basin in Sq.

Km.

Percentage of Area in the Basin

Percentage of District Area

with reference to Basin Area.

1 Chennai 174 174 100 3.12 Thiruvallore and

Kanjeepuram * 7857 4275 54.4 77.13 Vellore 6077 1093 17.98 19.8

Total 14,108 5,542 100(Note: * Combined Thiruvallore and Kanjeepuram of Old Chengalpet District)

Table No: 3 - The long term (1920 – 2000) average annual rainfall in hilly, plain and coastal regions are as follows.S. No. Region Location Average Annual Rainfall in mm

1 Hilly Region

SholingarTiruthaniPallipet

9521047895

2 Plain Region

ThiruvalloreSholavaramMinnalPoondiArakonam

1088128995912921070

3 Coastal Region

TambaramMeenambakkamSaidapetNungambakkamChepauk.

14241324128612151112

Table No: 4 -The following are the long-term average monsoon and annual values (1920 to 2000) of rainfall and rainy days in the basin group.

Southwest Northeast Winter1 Rainfall in mm 422 596 1131

2 Percentage of component of normal rainfall

37.3 % 52.9 % 100 %

3

i.

Average rainy days (based on 10 years record from

1991 – 2000) at Nungambakkam

49 35 93

ii. Tambaram 29 27 64iii. Tiruthani 29 22 58

Refer Map showing the Isohyets and Theissen Polygon of Annual Rainfall and Rainfall – Histogram & Water Level - Hydrograph Relationship of this Chennai Basin.


Chennai River Basin

Table No: 5 - Details of the area of the each sub Basin

S.No. Name of the Sub Basin Area of the Sub Basin in Sq. Km.1 Araniar 7632 Kosathalayar 3,2403 Cooum 6824 Adayar 857

Total 5,542Table No: 6 – Rainfall Dependability of the Sub Basin of Chennai Basin

S.No Name of the Sub Basin Rainfall Dependability – Unit in mm50 % 75 %

SwM NeM Annual SwM NeM Annual1 Araniyar 423 838 1474 347 615 10992 Kosathalayar 393 579 1072 305 427 8183 Cooum 445 765 1245 376 505 10304 Adyar 524 788 1385 361 717 1211

Chennai Basin Group Weighted 424 670 1197 328 507 943

The climatological features of this basin group have been studied from the data available at Tiruthani weather station, maintained by State Groundwater Department of PWD. Table No: 7 - The following weather stations are also located in this basin.

S.No. Name of the Weather station

Maintained By

Name of the Sub Basin

Remarks

123

NungambakkamMeenambakkam

Poondi

IMDIMD

IHH Poondi

CooumAdayar

Kosathalayar

Pan evaporation and sunshine hoursnot recorded by IMD

Table No: 8 - The salient climatologically Parameters are shown below.

S. No CLIMATICAL PARAMETER SW NE WINTER SUMMER

1

Monthly mean Temperature max. /min. in. o Celsius a) Hilly area b) Plain area

15.35/14.331.5/29/9

12.5/14.028.5/25.65

13.3/12.527/25.55

16.55/14.632/29.2

2

Average temperature in o Celsius a) Hilly area b) Plain area

14.6730.59

13.1726.98

12.926.3

15.6230.68

3

Average relative humidity in % a) Hilly area b) Plain area

84.053.13

84.069.17

66.2562.25

67.8354.67

4

Average wind velocity in kmph. a) Hilly area b) Plain area

14.158.1

11.635.67

12.66.95

12.575.73

5 Average sunshine hours/day 6.43 6.32 9.05 8.966 Average pan evaporation in

mm/month232.42 mm/months

(Average of Tiruthani Watershed Data)


Chennai River Basin

Temperature

The meteorological features of the basin have been studied from the data collected

from three weather stations. The average Mean, Minimum and Maximum Temperature for

the above rainfall stations, season wise i.e. South West, North East, Winter, Summer and

annual have been computed and tabulated. The lowest average minimum temperature

occurred in hills of Tiruthani among the all stations. The highest average maximum

temperature occurred in Chennai station in all seasons and all stations. The lowest minimum

average temperature occurred in winter season among the all seasons in all stations. The

highest minimum average temperature occurred in summer season. The highest average

maximum temperature occurred in Chennai station. The lowest average maximum

temperature occurred in hills of Tiruthani area. The highest average maximum temperature

occurred in summer season. The average mean maximum and minimum temperature

occurred in summer and winter seasons respectively in all the stations.

EvapotranspirationThe monthly Average ETO in mm for the selected rainfall stations season wise i.e.

SW, NE, Winter, Summer and annual have been computed. The highest ETO has found to

take place during the all seasons in Tiruthani. Similarly the lowest ETO has found to take

place during all the seasons in both Nungambakkam and Meenambakkam. In summer season

ETO is higher when compared to all seasons, in all the stations. Long-term average annual

rainfall over the basin is 982 mm. Here weighted rainfall of the each sub-basin was used to

present the rainfall conditions for a given sub-basin. For each sub-basin monthly distribution

with dependability of 25%, 50%, 75% and 90% were computed. The total rainfall was taken,

as effective rainfall because of the predominant irrigation method is basin irrigation.

SunshineThe average sunshine hours/day for the various rainfall stations Season–wise i.e. SW,

NE, winter, summer and annual have been computed and tabulated. In SW and NE the

average sunshine hours lies in between 5.5 to 7 hours/day in all stations. In summer season

the average sunshine lies in between 8.5 to 9.1 hours/day. The highest sunshine hours/day has

occurred in winter at Chennai station among all other stations. The lowest sunshine hours/day

has occurred in NE monsoon among all the stations and all seasons.

Reference crop Evapotranspiration (ETO)

The climatic stations representing the basin boundaries are Tiruthani, Nungambakkam

and Meenambakkam. Tiruthani was selected as representative of upper Chennai Basin and

Chennai Nungambakkam and Meenambakkam as representative of lower reaches. The

compiled monthly average ETO values are given in Table. No: 9.


Chennai River Basin

Table No: 9 – The ETO Data of Nungambakkam, Meenambakkam and Tiruthani1. Climatic Station Name: Chennai Nungambakkam Evapotranspiration (ETO) data

Month Jan. Feb. Mar Apr May Jun Jul Aug Sep Oct Nov Dec Annual

ETO-Reference Crop Evapotranspiration (mm)

131 138 191 179 187 174 174 165 161 134 104 110 1847

2. Climatic Station Name: Chennai – Meenambakkam Evapotranspiration Data.



138 149 200 187 193 178 180 179 168 138 114 119 1943

3. Climatic Station Name: Tiruthani Evapotranspiration Data



165 179 224 212 227 206 185 198 186 158 135 142 2217

Rainfall Theisen Polygon map with Isohyets showing the contours of the Chennai Basin

prepared and appended vide Plate No: VI. The data of rainfalls collected for various

stations both within and outside collected were tabulated and appended for reference.

Data of stations falls outside basin area were too accounts for generating maps.

Potential Evaporation

The monthly average Pan Evaporation in mm for the three weather stations, season

wise i.e. SW, NE, Winter, Summer and annual are computed and tabulated. Lowest amount

of monthly average evaporation occurred in the Tiruthani among all other stations in all

seasons. The highest amount of monthly average evaporation occurred in the Chennai

Meenambakkam in all the seasons due to highest wind velocity. In the SW and summer

seasons the monthly average evaporation is almost equal in all stations except in Tiruthani,


Chennai River Basin

recorded a slightly higher in the summer. In the NE monsoon monthly average evaporation is

less than the winter due to low sunshine hours and comparatively less wind velocity.

Relative Humidity

The monthly average percentage of relative humidity is given in the Table No: 8. The

average Relative Humidity in the six weather stations, season-wise i.e. Southwest, North

East, winter, summer and annual has been computed and tabulated in Tables. In Tiruthani

and Chennai (both Nungambakkam and Meenambakkam) stations, the average relative

humidity is almost equal in all the seasons in which Tiruthani station has recorded

comparatively lesser relative humidity. Comparatively relative humidity in Nungambakkam

and Meenambakkam recorded the highest during SW and NE seasons among all seasons.

Wind SpeedThe Average wind velocity in KMPH for the three weather stations season-wise i.e.

Southwest, Northeast, winter, summer and annual have been analysed. The maximum wind

velocity i.e. 10.84 kmph occurred in Chennai Nungambakkam station during SW monsoon.

The lowest wind velocity occurred in Tiruthani station during summer. In Chennai

Meenambakkam station the highest wind velocity occurred during the NE monsoon among

all stations. In Tiruthani station wind velocity is less and the next higher wind velocity

occurred in Nungambakkam station.

3.4 Soil Classifications.Hydrologic part is much controlled by different types of soils. Soils are classified by

taking their color, texture, fertilities and chemical combinations includes salts, minerals and

the solution effect over them. As far as the agricultural and groundwater point of view, the

soil types of the study area are described based on the thematic maps collected.

Entisols:

These are alluvial soils comprising sand and sandy materials occurring on the beaches

and at the confluence of rivers and by the side of the rivers & channels. Because of their

permeability, these soils while being good storehouses of groundwater are not fit for

cultivation. These are found along coastal belt in small strips, eastern part of Ponneri Taluk,

south of Pulicat Lake to Ennore Creek, south of Cooum confluence to Adyar Estuary and

Thiruvanmiyur - Covelong stretch, throughout the length of beach of the Eastern Coast.

Inceptisols:

This major soil group consists of the red sandy to brownish clayey soil fragments

derived from parent rock and is spread all along the westward side of the East Coast Road.

The Inceptisols are suitable for agricultural hold moderate groundwater reserves. Systematic


Chennai River Basin

water bearing rocks are bordering this type and percolate more water into these soil

formations for effective agriculture. The agricultural pattern in this type of soils is intensive.

Vertisols:

The Vertisols are clayey in nature with high specific water retention capacity but poor

in supporting agriculture. These are found as groundmass in extreme northern portion around

Gummidipoondi, Ponneri, Minjur, Madhavaram, and Manali and in the western portion of the

East Coast Road around Thiruporur. Hydrogeologically Vertisols is grouped under Aquitard.

The age of these formations of soils is of Tertiary. The capacity of water bearing and yielding

character of this type is null and void. The Valudhavoor patches of clay and the Manali,

Mathur clayey soils are the significant members of this type of soil. Vertisols are exclusively

used for dwelling and other industrial locals only. The rate of infiltration varies from 1 to 3

cm / hr for fine red sandy clay, clayey sand, sandy clay, sand fine to medium, sand medium to

coarse and very coarse and gravel and for weathered rock, fractured and jointed rock it varies

from 0.2 to 0.5 cm / hr. which normally occur in the study area

Table No: 10 - INFILTRATION RATE (IN CM / HR) IN THE STUDY AREA.

S.No. TEXTUREINFILTRATION RATE IN

CM / HR.1 Coarse sand (River sandy) 2.0 to 252 Fine Sandy (River Sandy) 1.3 to 2.03 Fine sandy Loam (Red Sandy) / Sandstone M – C 1.0 to 1.2 4 Silty Loam 0.8 to 1.05 Clay Loam 0.6 to 0.86 Clay 0.5 to 0.67 Coarse Sandy (Red Sandy) Gravely 2.5 to 3.08 Kankar / Gondwana Siltstone / Weathered Rock 0.5 to 0.69 Fractured & Jointed Rock 0.2 to 0.5

Table No: 11 - The SPECIFIC YIELD of the different formation of the top river alluvial sand, red sandy, laterite, Tertiary sand and clays, Gondwana siltstone and Crystalline formations are furnished in the following Table.

SPECIFIC YIELD OF THE DIFFERENT FORMATION.

S.No. TEXTUREPERCENTAGE OF SPECIFIC YIELD

1 Clay 01 – 102 Red Sandy 10 – 303 Red Gravely Sandy 15 – 304 Sand And Gravel (Red) 15 – 255 Thick Plastic Clay 05 – 10


Chennai River Basin

6 Kankar / Gondwana formation / Weathered Rock 02 – 057 Fractured & Jointed Rock 01 – 05

Alfisols:

This is a special type of soil, which has a peculiar color shade differing from one area

to other. These red sandy and red loamy soils, deep to very deep, coarse loamy to fine loamy

are found along the seashore. Due to indiscriminate drawal of groundwater seawater

incursion occurred. Due to this the soil has been affected in about 10,000 ha in

Gummidipoondi and Ponneri Taluks. Alfisols, though not fit for intensive cultivation, can

support moderate cultivation, particularly the raising of dry crops. The groundwater reserve

potential of these soils is moderate.

The different soil patterns encountered were shown in a map vide Plate No: VII.

3.5. Geology

Table No: 12 - The geological formation encountered in the Chennai River Basin is furnished below along with their groundwater conditions.

S.No Group System LithologyAquifer

Characteristics

1. Quaternary Recent –Sub-recent

Soils, coastal /river Alluvium (sand & silt), Black Clay

Moderate to good porous aquifer system

2. TertiaryCuddalore S.St (Eocene to Pliocene)

Sandstone & and shale Moderately porous Aquifer.

3. MesozoicUpper Gondwana (Sriperumbudur Beds)

Sandstone and siltstone; Grey shale; Black shale.

Less Porous aquifer.

4. Azoic ArchaeanCharnockites, Granites, Gneisses. Fractured Aquifer.

Chennai is built on marine, estuarine and fluvial alluvium over-lying Precambrian

gneisses and Chamockites. The hard rocks include granite, gneissic complex, schist’s and

chamockites associated with basic and ultra-basic intrusive. The chamockites form the major

rock types and constitute the residual hills around Pallavaram, Tambaram and Vandalur. Beds

of upper Gondwanas are found in and around Anna Nagar Mogapair, Valasarawakkam,

Mambalam, and upto Sriperumbudur. They comprise conglomerates, shale, and sandstone,

and are covered by a thick cover of laterite. Tertiary sandstone is seen in small patches in the


Chennai River Basin

area around Perambur, and around northwest of Chennai city and upto Satyavedu, and is

capped by lateritic soil. (Vide the Geology map of Chennai Basin map Plate No: VIII).

The distribution of the various alluvial units has not been mapped in detail, but fluvial

alluvium undoubtedly crops out along the shallow valleys of the Araniyar, Kosathayar,

Cooum and Adyar, two other disused rivers flowing through the city. The thickness of the

alluvial sediments is poorly defined, but consists of inter-layered clays, silts, sand and gravel

and pebble beds. Some lagoonal sediment may also be found. Aeolian dune and beach sands

occur along a narrow coastal strip. Wells exist in the landward edge of the beach sand and the

white quartz sand below the dunes is a significant water supply source in the southern part of

the city. The marine types occupy the coast region, extending from Ennore in the North to

Mahabalipuram in the South. The fluvial type alluvium is also noticed within the Araniar and

Kosathalayar basins (A.K. Basins). The Kosathalayar river alluvium consists of reddish

loamy sands intermixed with clay. The deposits of Araniar comprise mostly pure sands.

According to the study made by Somasundaram et al (1993), the near- surface

samples of the Cooum alluvium have permeability in the range of 0.002 to 0.25 m / d with a

porosity of 30-40 per cent. In spite of its low permeability, the Cooum alluvium supplies

water through dug-wells and hand- pumped tube wells. Well-water levels are typically found

to be within 7 m of the ground surface level. The aquifers of this region are recharged by

precipitation, irrigation return, flow from riverbeds and surface water bodies. The shallow

alluvial aquifer is unconfined in the western recharge zone, changing to unconfined and semi-

confined formations in the eastern abstraction zone, with limited ground water yield. The

ground water potential penetrating the rock for depths greater than 500 m, as in developed

countries such as the United Kingdom, is yet to be explored. Borewells drilled to depths

ranging from 10 to 455m below the ground-level show the presence of 56m of alluvium and

tertiary deposits, and 397m of Gondwana sediments. (Vide based on borewell data observed).

CGWB has drilled a borewell at Oragadam to a depth upto 288 m bgl. There were no

potential aquifer zones from ground level to 174 m bgl. Granular zones of very thin strips

were encountered between 175 m to 280 m bgl at random in very few depths. The yield was

very low around 60 lpm only. The alluvium includes sand and clay, of which the former

constitutes the aquifers. These deposits generally occur at depths in other places ranging

between 9-15m and 20- 47m. The hydro-geological framework of the Madras urban district

is, by and large, controlled by the quantum and distribution of rainfall, geological-setting and

facilities of movement of groundwater through interconnected primary and secondary pore


Chennai River Basin

spaces of the geological formation controlling the aquifers, through which an assessment of

the Water Resource Potential of Chennai Basin was attempted.

3.6 Geomorphology (External Landforms) The geomorphologic character of any area, that is the external landforms, gives a

reliable picture of the underground strata and its physio-chemical condition. The different

formations and the layer confirms and cogent to its geomorphology. The geomorphology of

the area is one of the special types, which covers both hard rock and coastal sedimentary

components. The eastern part adjoining to beach and shores covers coastal geomorphic units.

The inland topographical units are being described as the piedmont geomorphology.

Beaches: The beaches are landforms covered by sand and sandy materials having high

porosity and unconsolidated loose formation with voids and spaces. These features are ideal

for groundwater storage. Beaches are found in east of Minjur & Injambakkam to Nilangarai.

Beach Ridges: Beach Ridges are elevated sandy tops adjoining the beaches and are good

horizons for groundwater presence. However due to variation gradient these forms are having

perched vadoze water table conditions. It comprises of sand, sub parallel ridges of sand, shell

or pebbles varying in amplitude from a few inches to several feet normally parallel to the

coastline. The occurrence of beach ridges is low in the coastal belt being mostly confined to

pockets around Eliot Beach, Injambakkam and Muttukkadu etc. In the beach ridges, the

thickness of sand ranges from 4 m to 7 m, with the water level coming up as high as 0 - 2 m

in the monsoon season. In pre monsoon season, the groundwater level varies from 2-6 m.

Beach terraces: The step like projection bordering the sandy terrain and the shoreline are

called as beach terraces. These terraces are undulated and according to the forces of the tide

and their deposition. These terraces were having a very low ground water gradient that too

towards the sea as they are slopping towards them.

Buried Pediments: These are surfaces with thin soil cover bordering streams or rivers.

Watercourses and water channels are found in the buried pediments adjoining Araniar,

Kosathalayar, Cooum and Adyar Confluences and certain interior parts adjoining these rivers.

Wash Plains: A smooth surface evidenced the erosion called wash plains. These wash plains

are the inland topography where the terrain sediment such as laterite, limestone and other

calcareous sedimentary have been leached and washed away by sedimentation. According to

groundwater point of view they are serving poorer ground water storage. The surface of

these formations are showing a honeycomb structures and the water level are medium to high

from the top surface. These were located around north of Kosathayar riverbed adjoining


Chennai River Basin

Manjankaranai and around. Certain spots were too located as isolated patches in between

Araniar and Kosathalayar River.

Salt Pans: Salt Pans are fairly common on the shoreline near Mouthambedu, Ennore and

Muttukkadu. Salt Pan activity makes use of both seawater brought through channels and

brackish groundwater pumped out from the ground.

Swamps: Swamps are intruding waterways discharging water from the sea to the low-lying

land. The accumulation of such water in a naturally occurring canal like depressions is called

a swale. They are near Pulicat Lake are good examples of swales. The swamps and swales,

though an incapable of supporting agriculture, are ideal for developing fisheries and

aquaculture. They also provide a congenial environment for mangroves and dense vegetation.

Swale: The swales are the lengthy prolonged canal like projection extruded from the sea and

covers a specified area in land existing in a low cut surface. This form also gives rise the salty

water.

Deltaic Plains: These are wide landforms occurring along river combs and hydrological

structures passing from the origin of the rivers to the mouth of the sea. These plains covered

by sediments deposited by the rivers have high water holding capacities. The sediments,

which are deposited by these rivers and other agencies by transportation on the banks and

spreads, have a voluminous thick with unconsolidated layers of interspecies nature. These are

highly heterogeneous and having high water holding capacities. Deltaic plains occur from

Panjetty to Minjur and Ponneri.

Deep Pediment: In piedmont zones, and piedmont morphology deep (or) buried pediments

are the significant forms for tapping groundwater. The thickness of sediments are more and

well stratified, the intertrapped water are sometimes serves as a storage as they have well

sorted and gapped with different size wise sedimentary particles. These were widely spread.

Pediment and Shallow Pediment: These are thin soil cover observed on the inland terrain

having less thick and poorly sorted materials and weathered to fresh basement beneath the top

soils. The water bearing capacity of these formations are generally poor. Unless otherwise

met with a contact zone over other porous formations.

Buried Course & Channels: If a waterway due to sedimentation and earth movement

activities changes its passage, the newly formed depositional character along those old way of

water courses are called as the buried course or channel. The thickness of sediments on this

form is heavy which gives raise high potentials of groundwater. Sometimes these forms will

serves as reservoirs by following under ground routing to the present flowing river and other

systems of river sand tanks and these are the major and main water holding forms.


Chennai River Basin

Tertiary Uplands: Tertiary uplands are located on the southern sides of the Kosathalayar

River around Kumanur, Manjankaranai, Erumaivathipalayam and Sholavaram.

Flood Plains: Flood plains consisting of sand clay are found along the boundaries of Araniar

and Kosathalayar rivers. The thickness of the alluvial sand varies from 1 to 7 m and the flood

plain itself is found spread over width varying from 0.25 to 5.0 km from the riverbanks,

Piedmont: Constitutes boulders, cobbles, pebbles, grovels, sand, silt and clay of varying

lithology. Formed by coalescence of several alluvial fans by streams covering large area at

the foothills, with gentle slopes, in humid to sub humid in regions (upper humid to sub humid

regions). Upper and lower units are marked by variation in slopes and thickness of sediments.

It is good to moderate groundwater prospective zones.

Inter Fluveo: The inter Fluveo is a land form in between the buried channel and down

stream of lake and are very few only in the study area. They are near southwest of Pulicat

Lake. Copious supply of groundwater is available and the water level will be at the top ever.

The various geomorphologic features are shown in the drawing vide Plat No: X.

3.7 Landuse PatternPrimarily, the major land use in the coastal belt is agriculture. Based on the system of

cultivation and cropping practices, the land could be divided into three groups namely ayacut,

non-ayacut and elevated top lands. The ayacut area derives its water supply from rivers,

tanks, canals, open dug wells and borewells. The alluvial tracts along Araniar, Kosathalayar,

Adayar and Cooum rivers support intensive ayacut cultivation. The non-ayacut areas lying

mostly on the western fringes of the 15-km belt depend on rainfall and groundwater for

supporting agriculture.

The classifications of the land of this basin are grouped and are as follows. The

intensively irrigated area occupies 20% and the sparsely irrigated area occupies only 25%.

The land covered under water bodies is 25%, wasteland 25% and the rest 5% is of forest

cover. Non-ayacut cultivation practices are found in tank bed area. The area under non-ayacut

accounts for more than half of the cultivated area in the 15-km wide coastal belt. In this basin

where Chennai Metropolitan City occupies most of the areas, the pressure for land is mainly

from all sectors like housing, industries and only very few occupies for irrigation, which

slowly vanishes once for all within peripherals of the city limit.

Table no: 13 - The details of agriculturists (farmers) based on the land holdings in the four sub basins of Chennai Basin are grouped as follows - Size of Land Holdings.

S.No. Category Size of Holdings Numbers Percentage to Total1 Marginal Below 1.00 ha 2,89,869 81.80 %2 Small 1.00 – 2.00 ha 36,833 10.40 %


Chennai River Basin

3 Medium 2.00 – 5.00 ha 21,956 6.20 %4 Big Above 5.00 ha 5.664 1.60 %5 Total 3,54,322 100.00 %

Table No: 14 - The land use pattern of the Chennai Basin (5,54,200 ha.) as per nine-fold classification adopted by the Government of India is furnished below:

S.No. Land use Classification of Geographical Area.

5,54,200 Ha. 100%

1 Forests 28,264 ha 5.10%2 Barren and uncultivable wastes 17,734 ha 3.2%3 Land put to non agricultural uses 1,45,755 ha 26.3 %4 Cultivable waste 12,192 ha 2.2 %5 Permanent pastures and grazing land 12,192 ha 2.2 %6 Current fallows 74,817 ha 13.5 %7 Other fallows 52,649 ha 9.50 %8 Land under Miscellaneous crops & groves 15,518 ha 2.80 %9 Net area sown 1,95,078 ha 35.20 %

Area sown more than once 58,302 ha 10.50 %Gross area sown 2,53,380 ha 45.70 %Cropping intensity 129.9 %

Ayacut Area:

The net Ayacut Area of this basin is around 1,17,787 hectares, consisting of 11,579 ha

of direct ayacut and 1,06,208 ha of indirect ayacut fewer than 1,519 tanks. The storage

capacity of major reservoirs is 320 MCM. The total gross storage capacity of this basin is 939

MCM as on date. Irrigation through wells and tanks are most predominant in this basin. Well

irrigation occupies about 46.5 % and tank irrigation occupies around 42.2 % and the rest are

rainfed. In the irrigated area, in the River and in the Coastal alluvial region has much number

of tubewells and open wells. This may look surprising in the light of the high groundwater

tables in this area, sometime back and now since twenty years due to unpredictable rainfall

and also due to continuous failure of monsoon since three years. This is also due to

indiscriminate sinking of tubewells and wells groundwater levels has gone down below mean

sea level on the 15 km coastal belt and in area around west it has gone down below 12 to 24

m bgl. The groundwater quality also becoming saline in the coastal agglomeration due to

seawater incursion. In certain areas wells are very few and the reason for the absence of wells

seems to be lie in the land being unfit for agricultural operations. Wells located in the coastal

settlements around Ennore, Thiruvottiyur, Triplicane Mylapore, Adyar, Beasant Nagar,

Thiruvanmiyur, and Injambakkam, serve mostly domestic consumption. Agriculture is

practiced in only inland tracts. In the sedimentary tracts of the ayacut area located around the

river basins, irrigation helps in raising two wet crops and one dry crop in a year.

In the rest of the ayacut, generally only one wet and one dry crop are raised. Though

there are some irrigation wells located in the peripherals of Chennai City, they were used to


Chennai River Basin

meet the drinking water demand of the Chennai City people through tankers. The rest of the

land was uncultivated since many years and are converted into building layouts.

Non-Ayacut:

In the non ayacut area which is several times more than the ayacut, the depth of the

wells ranges from 7 m to 18 m and tubewells ranging from 18 m to 100 m below ground

level. In 50% of the nonayacut area one wet and one dry crop are raised in a year. The rest of

the areas support one or two dry crops depending upon the availability upon the availability

of groundwater. The net area sown are 1,95,076 hectares and the area sown more than once

are 58,302 hectares only. The total gross area sown are 2,53,380 hectares which occupies

45.70 % of the total area of the basin. Apart from it there are some cultivable waste land

around 12,192 hectares are available.

For the implementation of latest scientific irrigation practices like drip irrigation

sprinkler irrigation, enforcement of better water conservation and management techniques, it

is very difficult to enforce the farmers to do so. It is because lack of adequate educational

knowledge, fear over changing from traditional methods to the improved one, lack of result

oriented experimental farm practices among the Agricultural Experts and field officers,

controlling of very fast movement and attacking of pests and insets, financial aspects, per

capita availability of lands, low agricultural return, losses and havoc due to unprecedented

drought and flood.

Forests & Other lands

There are forests land of 28,264 ha occupies 5.1% of the total basin area, located

within the basin. Mostly of social forest and few reserve forests.

There are no mangroves located within the basin area. The patches of shrubs and

thorny bushes, categorized as reserve forests, are found beyond 15 km of the coastline, except

few casuarinas and coconut plantations are raised near settlements. Leaving the total Ayacut,

Non-ayacut and dry cultivation lands, there are some barren and uncultivable wasteland of

around 17,734 ha occupies 3.2 % of area of this basin. Permanent pastures and grazing land

which occupies 12,192 ha – 2.2 %; Cultivable Waste occupies 12,192 ha – 2.2 %; Current

fallow lands occupies 74,817 ha – 13.50 %; other fallow lands occupies 52,649 ha – 9.5 %;

and finally land put into non agricultural purposes including domestic buildings, industries

and other commercial sectors occupies 1,45,755 ha – 26.3 ha.

Even though these cultivable lands were hold by more than 3.55 lakh farmers, out of which

80 % of the landholders has less than 1.00 ha, it is fortunate that this basin has got more than

45 to 50 % of the area under intensively and partially cultivable, even though most of the


Chennai River Basin

areas were occupied by major cities and towns and industries. Landuse map prepared

required thorough field check up for accuracy. Vide Landuse Map appended Plate No: IX.

3.8 HydrogeologyThe occurrence, movement and availability of groundwater of an area depends upon

the geological structures, geomorphic setup etc. The top river alluvium of the main two river

basins of Araniar and Kosathalayar plays an important role followed by Tertiary sandstone,

these two were the major aquifer zones of the interdependent Araniar and Kosathayar basin.

These aquifer zones comprises of thick top river alluvial sand with clay loams between 60’ to

70’ below ground level followed by thick sands, clays and friable medium to coarse grained

Tertiary sandstone encountered between 70’ to 172’ / m 185’ below ground level followed

by thick Gondwana siltstone / claystone / yellowish or black clay or grit as a contact zone. In

certain areas around Kannigaipair, Tamaraipakkam and Poondi, these aquifer zones are

extending beyond 145’ to 200’ bgl.

The recharge and storage of water underneath the surface are due to the rainfall and

the prevailing Hydrogeological conditions due the existence of the Araniar and Kosathalayar

basin. Mainly these aquifer zones were concentrated and flanked by two rivers of Araniar

and Kosathalayar, an interdependent basin having three different aquifer. These three aquifer

were once acts phereotic / leaky, non-leaky and semi confined of three-tier aquifer system.

The thickness of these three aquifer zones varies from ground level to 60’ / 80’ (Top Aquifer

- Minjur Aquifer), 60’ to 140’ / 170’ (Middle level Aquifer - Panjetty Aquifer) and 120’ to

180’ / 200’ (Bottom Aquifer – Tamaraipakkam / Kannigaipair / Poondi). But since the water

level has gone down below 70’ to 90’ it is now becoming leaky and unconfined single aquifer

system as a whole. The top Minjur aquifer is dry almost having no base flow and the

remaining zones are partly productive. Due to continuous extraction of groundwater by

indiscriminate sinking of wells and borewells seawater incursion occur upto 13 km from the

seacoast. These shallow aquifer zones were encountered between 40’ to 70’ in the north,

northeastern, eastern and southeastern region especially near the riverbed and its

environment, were almost dry or poorly saturated specifically for drinking water purposes.

The alluvium, parting more recharge of groundwater than that of the Tertiary

Sandstone or rock environs. The recharge and storage of water underneath the surface are

due to the rainfall and the hydrogeological conditions. The general hydrogeological

conditions and final output has been arrived at by taking water level, rainfall, seasonal

fluctuations in wells, rise in water levels, drawdown and recuperation in hydro-structures.


Chennai River Basin

From the hydrogeological point of view, it constitutes a very good to good groundwater

bearing zones.

Its deposits consists of top reddish / reddish brown sandy soil, / sandy clay, gravelly

soil, boulder bed of unconformity formation, kankar, highly weathered, weathered, fractured,

jointed and highly sheared zones, whose thickness varies from 40' to 400’ (12m to 120 m)

below ground level. There are many number of borewells (96 borewells by UNDP and 28

borewells by Groundwater Cell Division, PWD) drilled during UNDP Groundwater

Investigation Project from 1966 to 1969 for investigation purposes. On completion of the

project work, most of the high yielding borewells were kept as production wells numbering

around 70 to 80, to meet the drinking water needs of the Chennai City. Some of the borewells

were drilled specifically for drinking water purposes only. The Groundwater Potential was

estimated as 7.5 mgd from Minjur Well Fields, 9.0 mgd from Panjetty well Fields and 13.3

mgd from Tamaraipakkam well Fields, a total of 29.8 mgd. However the UNDP has

recommended extracting only 27.5 mgd from these three aquifer zones.

Slowly in course of time by continuous extraction of groundwater by installing 35

horsepower pumps, the yields from these borewells are reduced and some of the borewells

were abandoned. In lieu of it certain additional borewells were drilled and was maintained by

Groundwater wing of Public Works Department. During July 1978 the Madras Metropolitan

Water Supply and Sewerage Board was formed and the well field wells were taken over by

them. As on date around 68 drinking water borewells are maintained by Metro water Agency

and extract around 20 to 22 mgd, apart from many number of irrigations wells and tubewells,

borewells intended for aquaculture and other industrial purposes. In addition to the borewells

drilled for various purposes, monitoring borewells were too drilled and were maintained by

PWD, CMWSSB and CGWB.

The depth of these borewells varies from 100 to 350’ below ground level and the

yield varies from 100 to 2,000 litres per minute. Totally 96 borewells were drilled by UNDP,

28 by Groundwater Cell Division, PWD Chennai, 305 by TWAD Board, 76 by CMWSSB

484 by Groundwater division, Chennai, 11 by ETO, CGWB, BTAO and other agencies.

Roughly various Government and Quasi Government Organisations drilled altogether 1,100

borewells for various purposes from 1966 to till date apart from the many number by private

agencies. Presently, the number of tubewells drilled by all agencies and for all purposes may

workout around 7,330 to 8,500 based on ‘A – Registers’ maintained by Revenue department,

since some of the shallow borewells were abandoned or said to be dry or not functioning due

to inadequate water. Other than these tubewells there are many number of shallow and


Chennai River Basin

medium tube wells spread over south of Kosathalayar River, adjoining Cooum and Adyar,

where a thin river alluvium followed by Tertiary and or Gondwana Sandstone encountered.

Though these aquifers were not so much productive as compared to the alluvial

terrain of Araniar and Kosathalayar, hereto certain quantity of groundwater were pumped by

many number of wells and borewells spread over. Mostly these bore wells were shallow

ranging between 100’ to 150’ below ground level. Presently, the yield of these borewells

varies from 40 to 400 litres per minute. This is not the case as in the case of wells and

borewells located within the Chennai Metropolitan City irrespective Geological conditions.

Even though it constitutes thousands and thousands of wells and borewells housed atleast one

each for every individual house, the yield is very much limited due to adequate recharge

factor. There are more than 3.2 lakhs numbers of wells and borewells located within the

Chennai Metropolitan areas to meet the domestic requirement of water. The correct well

census assessment was now under progress by the State Groundwater Wing of the Public

Works Department.

As on date around 1.5 lakhs wells and borewells were said to be dry or defunct out of

the 3.2 lakhs number of wells and borewells. Most of the city areas were either occupied by

constructed buildings or by road or by concrete paved areas. Hence there is no enough space

to allow the rainwater percolate into the ground. Only the baseflow water through other

means was being extracted till now and it also gradually gets reduced. Now the entire

dynamic groundwater reserve were fully evacuated and as on date wells and borewells yield,

were being tapped from the static reserve.

This is the reason that, even though normal monsoonal rains occurs, there is no

sufficient raise in groundwater levels noticed. As such mining of groundwater takes place

within the Chennai Metropolitan City, since six to seven years. Except in one or two areas, in

rest of the areas, groundwater levels never retain the original position. Infact every year there

is a decline in water level at the rate of 0.6 to 2.5 m per annum, resulted for lowering of water

levels beyond 6 to 12 m below ground level even during monsoonal season. Similarly in

Gondwana region, it is still worst, like even during monsoonal season the recuperation took

more than 24 to 48 hours duration.

Refer the water level contour map generated through the observations made during

From January 1998 to September 2004 shows the declining of groundwater levels gradually.

As we comes to hard rock terrain, which occupies the rest of the areas, the highly fractured

and jointed formations with good amount of groundwater flow encountered were very few

only. In general these shallow and deep borewells were yielding between 20 to 200 litres per


Chennai River Basin

minute upto 1990 and due to indiscriminate sinking of deep borewells at very closer intervals,

this discharge was very well reduced to 10 to 100 liters per minute.

Based on the detailed Hydrogeological mapping and on the borewells drilled by

various agencies, it is ascertained that there is no good potential aquifer zone beyond 300’

below ground level. The winter water level varies from ground level to 10’ to 20’ in the

borewells located in the sedimentary terrain and from ground level to 15’ below ground level

in the borewells located in the hard crystalline terrain. The recuperation time varies from 4 to

8 hours for normal years. It is slightly vary during below normal rainfall years and drought

years. The summer water level varies from 20’ to 40’ bgl and the recuperation time varies

from 12 to 24 hours in sedimentary terrain. Sometimes it goes beyond 36 to 48 hours during

below normal rainfall years and during drought years. In some of the borewells the water

level goes below 45’ to 80’ bgl due to continuous extraction of groundwater. Normally

groundwater extraction is done mainly for domestic purposes within the Chennai city and its

suburban except the wells in the Araniar and Kosathalayar basin, where it is intended for

irrigation purposes.

In very few number of borewells inventoried, bedrock has not been met with and

those borewells can be deepening further to increase the groundwater withdrawal. The

aquifer zones are mainly top sandy, kankar, highly weathered, weathered, fractured and

jointed granetic gneiss / Charnockites with quartzite and feldspar intrusions. Groundwater

recharge in this area is mainly due to direct infiltration of rainfall; return flow from the

nearby-irrigated field, especially located on the western, northwestern side, northern and

eastern side between the two rivers. Also some seepage from the rivers, canals, and water

bodies were too helps to increase the groundwater recharge. The elevated areas such as

northwestern, western and southwestern part of the area around, the surface runoff are more

during rainy season, which naturally drains into the investigated area both in surface and as

well as in sub surface. Certain areas covered by outcrops and surface exposures, scope of

groundwater development is very freak in those areas. In general each borewell located

around the peripherals of the investigated area, can irrigate 2 to 3 acres of wet crop during

monsoon and one dry crop during non-monsoon season.

In ayacut areas, either one or two wet crop such as paddy or one wet crop of banana /

sugarcane whose time requires for harvesting a minimum of 11 to 12 months, and or one wet

crop with one dry crop and or two dry crops are being irrigated. In some of the selected

pockets one borewell can irrigate about 3 to 4 acres of wet crop even during non-monsoon

also season. In these areas, lift irrigations are prominent rather than surface water irrigation.


Chennai River Basin

The seepages from the rivers and canals workouts to 1.2mm / day and from tanks workout to

2.2 mm / day. It also depends upon the number of day’s water available or flow on it.

The seepages from the irrigated paddy field, banana or sugarcane and dry crops are in

the order of 16", 31”, and 9” to 12” per crop respectively. Losses due to evaporation and sub

surface base flow are roughly about 10% of the total annual recharge. Since most of the area

fall between these two rivers, which was under intensively irrigated land of wet crops of

ayacut, seepages from water bodies, canal, streams and river are substantially increases the

groundwater levels, apart from the groundwater recharge through return flow from these

fields. Whereas in the non-ayacut elevated terrain certain dry crops were irrigated using lift

irrigation, there the seepages from water bodies, canal, streams and river especially during

non-monsoon is meager except the return flow from the applied water, which is very less.

These data were derived from GWREC Norms published during 2003. The average number

of rainy days in a year is only 56 to 64 days, out of which more than 40% of the rainy days,

rainfall occurs between 5 to 10 mm, it has no significant effect regarding the recharge of

groundwater through rainfall precipitation, during non-monsoonal seasons.

Even though the Groundwater Legislation was introduced in 305 villages covering the

whole Chennai Metropolitan area there was no strict enforcement of it till date. The detailed

study made by the UNDP Groundwater Investigation Project during 1967 – 69 emphases

much care should be given in extracting groundwater from these three distinct aquifer zones.

Even though recommendations were done to extract 27.5 mgd of groundwater from these

three aquifers, it should not be done continuously. The groundwater available in this aquifer

should be controlled and can be extracted for emergency purposes only. However, till now,

the groundwater available in these aquifer zones were evacuated fully by all sectors. Hence

while extracting groundwater from these multiple layer aquifer systems much care should be

given. However the abstract of the characteristics of the three-aquifer zones assessed by

UNDP Technical Consultants from June 1967 – Nov 1971 were furnished below.

Minjur Well Field: Minjur well field has an alluvial deposit of ground level to 170’ bgl and

17 borewells were drilled by UNDP apart from the 10 borewells drilled by PWD and public

and industrial sector. Based upon the pumping test conducted the Transmissivity values are

ranges between 1,58,000 to 3,00,00 gpd / ft and the Permeability values ranges between

2,000 to 5,000 gpd / sq.ft. The storage coefficient of S = 2.1 x 10¯4 by UNDP. The net

overall groundwater potential assessed for the Minjur Well Field was around 7.5 mgd. During

that time 10 borewells drilled was pump tested and the discharge was around 500 gpm and

these borewells were tested continuously for three full days. Within a day each borewells has


Chennai River Basin

a discharge of 0.72 mgd and the whole recommended groundwater recharge of 7.5 mgd was

discharged by these 10 borewells.

Moreover there are many number of private borewells used by agriculture and

industrial sector and if all these borewells were pumped out at a time, the net recommended

groundwater recharge will be evacuated fully and overdraft will take place. During those days

all entrepreneurs were over extracted the Minjur Aquifer at the rate of 3 to 4 mgd, causes for

Seawater Intrusion {(3 x 8,000) / (2 x 365) = 35 years} within 30 to 35 years fully at the rate

of 400’ per annum, which happened before 2000 itself.

Recommendations are done for the barest minimum extraction only for irrigation

purposes in the Minjur Aquifer since most of the water used for irrigation will return back to

the aquifer system itself. The alluvial aquifer in the Minjur well field is of a channel-type and

has a moderate geometric characteristic; it is replenished mainly by precipitation. The aquifer

is semi-confined but, due to the numerous wells with gravel packed in the annular space

throughout the entire drilled depth, is connected with the top zone under water-table

condition and both form one hydraulic unit with coinciding responses to any draft imposed.

The aquifer in the east is in hydraulic contact with the fresh water-saline water

interface located 2.5 miles away from the most easterly Minjur production tube-wells. From

the Minjur aquifer, 3.0 Mgd can be extracted continuously with little effect on the interface.

Extraction greater than 3.0 Mgd would induce the interface to move landward, but it would

contaminate production wells only after several years, depending on their total discharge and

present distance from the interface. The original calculated rate of the fresh water - saline

water interface landward movement was 400 feet per year. However, actual observations

indicate the rate to be only l60’ per year, but the geometric characteristics of the interface

appeared to be complicated and require further investigation.

The location and spacing of the production wells in relation to the aquifer's hydraulic

characteristics is of utmost importance, particularly within such an aquifer as the Minjur. The

production potential of the tube wells already constructed is too concentrated and greater than

the long-term exploitable resources of the aquifer. Some of the existing wells should be

withdrawn from production and a few kept as standby or used for observation of groundwater

level. There is room for an additional 2 wells east and west of well 21 (near Palikkulam,

aquifer II), for 2 wells between Palikkulam and wells 20 and 21 at Ponneri in aquifer III and

for one well northeast of well 20. This would require the extension of a water main in that

direction but it would also permit a more even distribution of the pumping load on the Minjur

area and farther west, thus increasing the safety margin against saline water encroachment.


Chennai River Basin

The extraction from the Minjur well field for normal recharge was tentatively recommended

at the rate of 7.5 Mgd.

However, after the emergency extraction for Madras City during 1969, the recovery

of the aquifer in Minjur area was low and 15 feet was left unreplenished. If the aquifer fails to

recuperate this deficiency during the succeeding seasons it is possible that even the current

extraction rate of 6.5 Mgd may have to be cut down in the course of years or the distribution

of the production wells may have to be changed or wells supplying for paddy irrigation in

areas of concentrated extraction will have to be retired. This would extend the effective life

of the aquifer, but ultimately the Minjur well field was depleted. The effect of extraction on

water table and on pumping for paddy irrigation, the relationship between precipitation,

aquifer recharge and extraction from tube-wells and for paddy irrigation should be evaluated

in good detail and on a monthly basis.

The Lithological Cross Section drawn for the borewells drilled in the Minjur

Aquifer were drawn and shown in the Plate No: 15.

Panjetty – Duranallur Well Field:

The second well-field has been developed along the National Highway 5 between

Panjetty and Duranallur and along the road connecting Panjetty with Ponneri, Of the 22 wells

constructed in that area, 12 wells are equipped with turbine pumps. The distance between the

central part of this field and the Minjur field is about six miles. About seven miles farther

southwest from Panjetty, a third field with 11 wells has partly been established in the

Tamaraipakkam area. Later this field was extended farther southwest and another l8 wells,

fully equipped, were added to provide emergency groundwater supply to Madras City.

Duranallur – Panjetty well field has alluvial deposits of ground level to 250’ bgl and 22

borewells were drilled by UNDP apart from the 8 borewells drilled by PWD and public and

industrial sector. Based upon the pumping test conducted the Transmissivity values are


3,000 to 5,500 gpd / sq.ft.

The storage coefficient of S = 3.0 x 10¯4 was accepted by UNDP. The net overall

groundwater potential assessed for the Minjur Well Field was around 9.0 mgd. During that

time 12 borewells drilled by UNDP was pump tested using turbine pumps and the discharge

was around 500 to 600 gpm and these borewells were tested continuously for three full days.

Within one day each borewells has discharge 0.72 to 0.864 mgd and the overall groundwater

extraction by these 12 borewells was around 9.0 to 10.37 mgd. Moreover there are many

number of UNDP borewells and private borewells used by agriculture and industrial sector


Chennai River Basin

and if all these borewells were pumped out at a time, the net recommended groundwater

recharge will be evacuated fully and overdraft will take place.

During 1968 itself all entrepreneurs over extracted the Duranallur – Panjetty Aquifer

at the rate of 2 to 3 mgd and if the conditions sustains the groundwater levels will gets

depleted and the average discharge rate from each borewells will be get reduced. It is

recommended to reduce the discharge in the Panjetty Aquifer also to the barest minimum.

Drilling of additional borewells for extraction of groundwater continuously especially

abetting to the Minjur Aquifer for more than 6 to 8 hours has to be curtailed.

The above well fields indicate that the well field along the NH 5 has been located over

the area where the alluvial aquifer divides into four channels. The hydraulic principle of cone

of depression development and its propagation, as discussed in respect to Minjur well field,

applies with the same force to these two well fields. The three well-fields are located on the

same comparatively narrow aquifer and a simultaneous exploitation of them is bound to

induce within a short time leads to rapid decline of groundwater-level.

The recommended rate of exploitation from the Panjetty-Duranallur for the normal

aquifer's replenishment was about 9.0 Mgd. The distribution of wells within this area of about

25 sq. miles from the point of view of aquifer's hydraulics and geometric characteristics is

better than in the Minjur area. The overall average area per well is about 1.1 sq.miles. The

spacing between the wells is from 0.5 to 1.0 mile. At Minjur 27 tube-wells (excluding the 5

most westerly wells) are, in an irregular pattern, concentrated within about 15 sq.miles, which

gives an average of 0.5 sq. mile per well.

The distance between the central parts of these two fields is 6 miles. The calculated

cone of depression in the Minjur area at the end of 5 years of continuous pumping at 7.2 Mgd

indicated a possible induced decline of groundwater level in the central part of the Panjetty-

Duranallur area, to about 50 feet below the ground surface or about 15 feet below the lowest

water-table level recorded in 1966.

The Hydrogeological condition in both fields is about the same. Assuming that the

extraction of 9.0 Mgd from the Panjetty-Duranallur area after 5 years pumping will have a

similar hydraulic effect as the production from Minjur, the resultant mutual interference

caused by simultaneous extraction from these fields would amount to from 75 to 100 % of

additional lowering of the aquifers' piestic head in both fields. Moreover, such concentrated

exploitation of a common semi-confined aquifer (channel-type) is bound to lower the water-

table of the whole area which in a few years might interfere with the centrifugal pumps of


Chennai River Basin

farmers so much that irrigation of paddy fields, at least in some areas, would have to be

abandoned.

One year after completion of this assessment (1968) an emergency groundwater

supply was provided to Madras City to relieve a shortage of water caused by drought. This

provided an excellent practical test on the aquifer's overall hydraulic performance,

particularly since deficient rains had left the aquifer not fully replenished. Providing of the

emergency supply lasted from May to October 1969 and involved the following extractions:

15.5 Mgd from the Tamaraipakkam- Kilanur extended field and 7.7 Mgd from the Panjetty-

Duranallur field plus 5.5 Mgd from the Minjur field for the industrial use, a total of 24.5

Mgd, as against the maximum of 27.5 Mgd recommended in the project technical report.

As the result of this short-term but considerable extraction the groundwater level in

the Panjetty-Duranallur field declined to between 8 and 10 feet below M.S.L, and in the

Minjur field to a depth between 15 and 19 feet below M.S.L. During the subsequent normal

monsoon rains the groundwater-level over the Minjur field recovered to between 2 and 9 feet

below M.S.L. and over the eastern part of the Panjetty-Duranallur field to about M.S.L.

The low recovery of 10 feet only and the 15 feet left unrecovered in the Minjur field

is rather disturbing as it indicates that the alluvial aquifer is in general sensitive to a

concentrated extraction and that its rate of replenishment is not as fast as originally

anticipated. Also it shows that the aquifer does not have enough water in storage to meet

effectively the requirements during an extended year of drought and the well field is already

over drafted, at least locally. After the emergency, the extraction from the Panjetty-

Duranallur field was continued at the rate of 1.5 Mgd, ultimately to be increased to 7.7 Mgd.

The rate of extraction from the Minjur field was gradually increased and beginning

with 1971 the rate was held at 6.5 Mgd. Later during 1980 and further onwards, since the

seawater intrusion occurs up to Minjur, extraction of groundwater from Minjur Aquifer was

curtailed by Metro water. However there was no control in extraction of groundwater by the

private irrigation well owners. Since then both the water and the water quality gets

deteriorated.

Tamaraipakkam Well Field:

The main granular zone in Tamaraipakkam area follows the Kosathalayar River and is

about 1.5 miles wide. The aquifer is mainly confined. Observation on water level in tube-

wells indicated that this aquifer had an average 4.6 feet surplus head over the water level in

shallow dug wells. Pumping tests indicated Transmissivity between T = 3,00,000 and

4,00,000 gpd/ft and storage coefficient S = 5.0 x 1¯4. The hydraulic gradient in August 1968


Chennai River Basin

was 4.0 feet per mile. On the basis of the above information the natural flow of the aquifer

was computed as follows: 3,50,000 x 1.5 x 4 = 2.0 Mgd.

The extraction that could be sustained by the 4.6 feet surplus head was computed

using Theis well function and calculating distance-draw down relationship for a single well

pumping steady at a rate of 500 gpm for 270 days per year (January-September). On this

basis a cumulative draw down resulting from the mutual interference of a number of

equidistant wells constructed in a linear pattern and each pumping at the same rate was

calculated. The linear pattern was chosen because of the rather narrow width of the aquifer.

Also no allowance was made for the numerous boundary conditions or for leakage from the

intercalated semi-permeable beds, which, in any case, would be difficult to evaluate. For

five tube-wells constructed 5,000 feet apart along the central line of the aquifer and each

pumping at a steady rate of Q = 500 gpm (a total of 2.1 Mgd) the cumulative draw down

resulting from the mutual interference at the end of 270 days would be as follows: in the

vicinity of the central well 5.6-6.0 feet; in the vicinity of each well at the end of the line about

5.9 feet; along the line perpendicular to the wells alignment and passing through the central

well and 5,000 feet away from the latter on either side the drawdown caused by the 5 wells

would be about 5.1 feet.

The average of the four calculated cumulative effects is 4.8 feet. It follows that the

extraction of 4.1 Mgd (2.0 + 2.1) would bring, by the end of the dry season, the 4.6 feet

surplus head of the bottom aquifer just flush or slightly below the water level in shallow wells

and, therefore, it should not interfere with the daily supply for irrigation. Since the

drawdown is directly proportional to the rate of extraction (Q) the addition of another 4.2

Mgd draft would depress the bottom aquifer head for 10 feet more. Taking into account that

the heads of the top and bottom aquifers both decline during the dry season at about the same

rate and that the lowest water level during the year 1967 was at 22 feet depth the increased

draft to 8.5 Mgd (4.1 + 4.2) would depress the head of the bottom aquifer to 52 feet below the

ground level by the end of the dry season.

The pumping levels would probably be kept at 42-45 feet depth, i.e., always a few

feet above the tube wells screens. The imposed draft would represent about 24 per cent of the

daily extraction for irrigation and is bound to have some effect on it. This effect, however,

will depend on how fully the aquifers were recharged during the preceding wet season but it

is probable that centrifugal pumps in some of the irrigation wells tapping both aquifers, and

where the two aquifers are hydraulically connected, will have to be set. However, it is quite

feasible that by extending the Tamaraipakkam area for 5 miles in southwesterly direction


Chennai River Basin

towards Kilanur and Poondi reservoir a further supplementary extraction of about 4.0 to 5.0

Mgd could be secured.

Thus, by reducing the output from Tamaraipakkam to, 7.0 Mgd in order to reduce the

possible interference with centrifugal pumps and, instead, including the potential from the

area in the direction of Kilanur, a cumulative supply of 11.0 to 12.0 Mgd could be pumped

into the nearby concrete-lined Sholavaram canal. Assuming that each tube-well would be

pumping at a rate of 500 gpm, the above supply would require 24 to 28 tube-wells. Thus, if 8

out of the 11 existing P.W.D, tube-wells were put to production, another 16-20 tube-wells

would have to be constructed. The Hydrogeological conditions in Tamaraipakkam appeared

to be highly irregular and similar conditions could be expected to occur in the area toward

Kilanur as well.

The individual and multiple pumping tests indicated considerable long-distance

mutual interference, therefore the additional tube-wells would need to be carefully selected.

The more evenly the load of draft is distributed over the Tamaraipakkam-Kilanur aquifer and

the more attention is given to the Hydrogeological conditions the better will be the results

achieved and most likely, with the least mutual Interference and minimum effect on the local

withdrawal for paddy irrigation. The Lithological Cross Section drawn for the borewells

drilled in the Tamaraipakkam Aquifer are shown in the Plate No: 15.

In general the quality of water in Tamaraipakkam is good and the in creased draft

during years with normal recharge should, not lower its quality. The reason for increased

salinity in certain areas seems to be inadequate flushing due to the higher content of clayey

deposits with low Transmissivity. All such areas in the field are characterized by lack of

shallow or deeper wells and consequently are sparsely cultivated.

In general, the Tamaraipakkam area there are two water-bearing zones, namely, (a) an

upper zone extending 30 or 35 feet below the surface and only partially confined condition,

(as on date totally dry) and (b) a lower zone ranging in thickness from 30 to 70 feet occurring

between 75 and 190 feet below the surface, now yielding moderately. The lower zone is

mainly confined and is the best water-bearing granular deposit in the Tamaraipakkam area

once, now yielding moderately.

The three-dimensional extent (shape) of both granular zones is highly irregular and

subject to thinning and interfingering with clayey deposits. The central part of the bottom

main granular zone follows the alignment of the southern bank of the Kosathalayar River and

is about 1.5 miles wide. The confined condition of both granular zones is, to some extent

offset by about 240 shallow wells deepened by boreholes 6 inches in diameter to the top of


Chennai River Basin

the lower aquifer and fitted with centrifugal pumps. Apart from this, both granular zones in

places merge and surface at ground level.

This condition especially occurs in the area immediately west of the Tamaraipakkam

Anicut. The alluvial deposits were laid down directly on the Tertiary and Gondwana

formations, which are predominantly clayey and have lower Transmissivity. Pump testing in

tube wells constructed by the Public Works Department indicated considerable mutual

interference and occurrence of numerous hydraulic boundaries. Tamaraipakkam well field

has alluvial deposits of ground level to 220 to 290’ bgl and totally 29 borewells (11 +18)

were drilled by UNDP apart from the 10 borewells drilled by PWD and public and industrial

sector. Based upon the pumping test conducted by UNDP the Transmissivity values are


3,000 to 5,500 gpd / sq.ft. The storage coefficient of S = 5.1 x 10¯4 was accepted by UNDP.

The Transmissive characteristics of the bottom main aquifer are within the range of

3,00,000 and 4,00,000 gpd/ft, South of Tamaraipakkam Anicut and the Transmissivity ranges

from T = 150,000 gpd/ft to 18,000 gpd/ft while in the other region. The present extraction of

groundwater for irrigation of paddy amounts to about 35.0 Mgd extracted in a day from 15

borewells at the rate 0.350 to 6.05 mgd per borewells during 1969. The cumulative area under

irrigation amounts to 7,600 acres. Rainfall (average 40 inches per year) is the main source of

recharge. This is augmented, to a certain degree by the infiltration from the Poondi reservoir

estimated to be in the order of about 1,600 (?) M.c.ft. for the average annual replenishment.

On the basis of Hydrogeological condition, it was estimated that during the years of normal

rainfall and recharge an additional draft of 7.0 Mgd could be extracted from Tamaraipakkam

with little or no interference with the water supply for irrigation of paddy. An increased

supply of 11 to 12 Mgd is feasible by constructing additional tube-wells along the

southwestern line towards Kilanur village and collecting all output into the nearby concrete-

lined canal. If the City of Madras required an emergency supply, it is recommended that a

supplement up to 12.0 Mgd be taken from Tamaraipakkam-Kilanur area provided that: (a)

Firm attention be given to Hydrogeological conditions when sitting and constructing new

tube-wells; (b) a careful watch be kept on groundwater-level and the eventual effect on

shallow wells supplying irrigation water for paddy; (c) a special observation be continued on

all boreholes and selected wells with the oncoming rains to evaluate the hydraulics of

recharge.

The recommendations of the Phase I UNDP investigation suggested that: The Minjur

Well Field with a permanent extraction of 3.3 mgd and in the Panjetty – Duranallur Well


Chennai River Basin

Field with a daily extraction of 7.7 mgd, the depletion of groundwater levels is safe to a

certain extent.

However the recovery for this much extraction during non-monsoon summer season

is rather disturbing as such the hydraulic condition is bound to enhance the intrusion of

seawater intrusion. In the Tamaraipakkam Well Field the aquifer under imposed extraction of

groundwater of 13.3 mgd, even though it has been recommended to pump such quantity, it is

very much safe to extract for a continuous extraction of not more than 8.0 mgd only.

Also it is ascertained that the assessed and the recommended yield from all these three

well fields may be slightly more but under any circumstances it is certainly not under

estimated. During 1969 drought groundwater was extracted from the three well fields to

meet the Chennai City Water Supply Requirement and the pumped groundwater from the

borewells was transported through pipelines. The impact of groundwater extraction was

studied during Phase II.

The follow-up work during June 1969 to November 1971 - Phase II confirmed the

conclusions reached during Phase I, namely, that the available water resources in Area I as a

whole are fully utilized and that long-term overdraft is a distinct probability although the rate

of that overdraft is less than originally interpreted.

Study of water-level fluctuations in the three well fields confirmed the possibility of

further limited extraction as assessed during the Phase I investigation. From March 1966 to

March 1969 the United Nations carried out a survey of groundwater potential in the city of

Madras and its environs. The objective was to determine the technical and economic potential

for groundwater development with special emphasis on a supplementary supply for the city

of Madras. The conclusions drawn were:

i) All available water resources are from a practical viewpoint, fully utilized in

Madras City and environs.

ii) There is not sufficient additional groundwater to meet the increasing demands of

the city of Madras in this area.

iii) Within the immediate area of the city there is no suitable source of groundwater.

iv) In the Minjur, Duranallur - Panjetty and Tamaraipakkam areas, northwest of the

city, it should be possible to extract about 125 thousand cubic meters (Tm³) (27.5

mgd.) from the Quaternary alluvium during years of normal rainfall, but the

possibility of long-term overdraft should be further assessed.


Chennai River Basin

v) An interface between fresh water and seawater was detected in the groundwater

body at a distance of 3.2 km (2 miles) inland and the theoretical rate of

encroachment was calculated as 120 m (400 ft) per year.

During Phase II the works involves comprises of collection and re-appraisal of

rainfall, quantity of groundwater extraction, observations of groundwater level fluctuation

both in the water table aquifer and deep confined or semi-confined aquifers, study of

geochemical quality and a few geophysical traverses to check for changes in sea-water

intrusion. Monthly water level observations were recorded in 374 wells and in 15 Automatic

Water Level Recorders. With the information collected through various reports, analysis was

done to illustrate the behaviour of the aquifers.

Change in groundwater storage: During the Groundwater Investigation in Tamil Nadu -

Phase I the observation of groundwater-levels in the alluvial aquifer, stretching north and

northwest of Madras, showed a downward trend in aquifer's storage indicating an overdraft.

But as 1966 was a year of above-normal rainfall, 1967 was of nearly normal rainfall, and

1968 was a year of drought, it was concluded that although there was qualitative evidence of

long-term overdraft, the quantitative data could only substantiate a short-term overdraft. It

was further concluded that long-range observations were mandatory in order to establish

whether there was a definite long-term overdraft in the alluvial aquifer. The observation on

groundwater levels behaviour in this aquifer was followed-up throughout Phase II.

The composite hydrograph showing the cumulative change in groundwater storage for

this aquifer from January 1966 through March 1969 has updated through September 1971.

This graph of cumulative change in storage shows that in spite of the normal rainfall in 1969

and the above-normal rainfall in 1970, the storage in the aquifer was replenished in both these

years to about the same level, although considerably lower than the level of storage recorded

in January 1966. The average rate of storage decline in the abnormal period of 1966-1968 has

been, during the two succeeding rainy seasons, substantially reduced. However, for the 5-

year period (1966-1970) the rate of depletion has been 30 mm (1.2 inches) of water per year,

i.e., about 30.0 cm (one foot) per year in terms of groundwater-level decline.

The cumulative storage in 1971 shows downward trend until about mid- September,

which leaves approximately 3 months time for the aquifer to get replenished from the

northeast monsoon as against 5½ months in 1970 and 3½ months in 1969. Similar protracted

decremental trend was shown, in 1971, by the water levels recorded in boreholes at Kattur

(1141) and Duranallur (1123). The aquifer was subjected to heavy extraction @ 110 Tm³ per

day (24 Mgd) during the emergency supply to the city of Madras from May to October 1969.


Chennai River Basin

During the succeeding monsoon the piestic head in the most easterly part of the aquifer,

(Minjur) facing the fresh/sea water interface, recovered to about 2 meters below MSL and

more or less to M.S.L. in its central part at Panjetty about 10 kilometers farther west.

The present extraction amounts to about 36 Tm³ per day (8.0 Mgd) and of this, 7 Tm³

per day (1.5 Mgd) is pumped from the central part of the aquifer and 29 Tm³ per day (6.5

Mgd) from its eastern part. The above observations point to the possible further extension of

the downward trend in aquifer's storage and to the hazardous imbalance that is taking place in

this aquifer between extraction, replenishment and potential salt-water intrusion. If quality of

water in the eastern part of the aquifer shows signs of deterioration, the most easterly

production wells should be retired and the extraction moved to stand-by wells farther west.

However, it should be clearly recognized that, in spite of the more immediate danger from

salt-water intrusion from the east, although proper well distribution in the Panjetty/Duranallur

area, and others more centrally located should permit additional extraction for the next 20

years, if the now recognized probability of long-term overdraft is further confirmed,

ultimately the entire aquifer system would be depleted.

The weighted rainfall for 15 stations was plotted and the increase in groundwater

storage was compared with the amount of the monsoon rains. Table No: 15 - The relationship of Change in Groundwater Levels with

Rainfall.

Year

Rainfall

Period in cm & Inches

Long-term average in

cm & inches

Deviations from long-term average

in cm & inches

Increase in groundwater

storage in cm & inches

1966 Aug – Nov 111.00 (43.74)

68.90 (27.14)

+ 42.20 (excess) (+16.60)

35.15(13.84)

1967 Jul – Dec 88.80(34.95)

79.20(31.18)

+ 9.57 (normal)(+ 3.77)

19.42(7.64)

1968 Sep – Dec 46.80(18.41)

64.9025.58)

-- 18.10 (drought)(--7.17)

6.73(2.66)

1969 Sep – Dec 81.50(30.21)

64.90(25.58)

+11.76 (normal)(+ 4.63)

33.00(12.98)

1970 Jul – Dec 108.00(42.44)

79.20(31.18)

+ 28.60 (excess)(+ 11.26)

23.60(9.28)


Chennai River Basin

The tabulated values indicate that when the rainfall was considerably more than the

long-term average, the increase in groundwater storage was also more. For example, in 1966

for 111.0 cm of rainfall (excess of + 42.2 cm over average) the increase in groundwater

storage was 35.15 cm whereas in 1970 for 108.0 cm rainfall (excess of + 28.6 cm over

average) the increase in groundwater storage was only 23.6 cm.

The observation during 1969 and 1970 indicated an increase in storage for 184

million cubic meters (Mm³), (6425 million cu ft) and 24.8 Mm³ (865 million cu ft),

respectively. Another observation made on the well fields was that the heavy extraction

during the period May-October of 1969 from the deeper semi-confined aquifer did not affect

appreciably the water-table aquifer, the rise or fall of which is entirely dependent on the

rainfall. The anticipated surplus-rainfall years might therefore restore the water table aquifer

to its 1967 or 1966 level irrespective of the extraction from the deeper confined aquifers.

While the condition of alluvial aquifer recharge has improved during the follow-up

time, further study over a period of another five years provide a firmer answer to the problem

of long-term groundwater deficit. The study results are as follows:

Minjur – Panjetty – Tamaraipakkam Well fields:

Minjur Well Fields:

The storage capacity of the aquifer was estimated at about 36.7 Mm³/ km² (335

million cu ft/sq mile) of aquifer surface. It was also concluded that a few feet could depress

the groundwater level more and a certain proportion of the storage could be used for

augmenting the water supply to Madras City. The droughts towards the end of Phase I term

(mid-1969) provided good opportunity to put this possibility into practice. About 22-

production tube wells in Minjur, 14 between Duranallur and Panjetty and 23 in the

Tamaraipakkam area were put into operation. The fluctuations of water levels in these areas

both in shallow dug wells and deep tube wells were recorded and with corresponding rainfall

and extraction were analysed.

Panjetty-Duranallur well field:

The Panjetty-Duranallur well field is about 20.7 km (13 miles) from the sea. The

emergency extraction was maintained during May through October 1969 and after an

interval, pumping was resumed at steadily increasing rate from December 1970 on. During

the drought period of 1969 a total 1417 million gallons was pumped out giving an average of

31 Tm³ per day (7 Mgd.) as against the 41 Tm³ per day (9 Mgd.) recommended in the United

Nations technical report. The hydrographs shows that the groundwater level declined rapidly

during heavy pumping, it was subsequently maintained at more or less a constant but lower


Chennai River Basin

level. The water table level in 54 shallow well appeared to be unaffected by the pumping and

even showed recovery to the 1966 level as the result of recharge from rainfall. As the

emergency extraction from the lower semi-confined aquifer did not appreciably affect the

water-table aquifer, the extraction of 41 Tm³ per day (9 Mgd.) as recommended in the United

Nations report during the years with normal recharge appeared to be feasible.

Tamaraipakkam Well Fields:

In the Tamaraipakkam well field located 38 km from the coast, emergency pumping

was maintained during May through October 1969. A total of 10.6 Mm³ (2338 million

gallons) of water was extracted giving an average of 49 Tm³ per day (10.8 mgd.) as against

the 50 Tm³ per day (11 mgd.) recommended. The hydrograph of the wells shows that upon

termination of pumping the piezometric head was fully restored, and even during pumping

the rainfall recharged the aquifer appreciably. While 74 shallow dug well did not seem to be

influenced by the pumping, 104 shallow well appeared to be affected.

The effect of pumping on 104 shallow well is not fully clear and it will be kept under

observation whenever pumping is resumed. From the observation it was concluded that

during the years with normal recharge, the extraction of 50 Tm³ (11 mgd.) as recommended

in the project report was feasible.

Seawater / Freshwater Intrusion:

The Minjur well field is the nearest to the sea and plans for extraction must take into

account possible salt-water intrusion from the east. A draft of 34.0 Tm³ per day (7.5 Mgd.)

was the maximum recommended from this well field, which feeds a number of industries in

the area. The extraction from the mid-1967 to date shows that the pumping rate was steadily

increasing from the beginning of 1969 and has subsequently been kept at a fairly constant

level of 195 million gallons per month or 29.5 Tm³ per day (6.5 Mgd.).

The hydrographs of shallow wells show that while the fluctuations of the piezometric

head in the deeper aquifer was independent of the fluctuation of the water table, the

piezometric head itself was falling as the result of continuous extraction. While shallow well

has recovered completely, tube well showed considerable lowering of the head. This leads to

the conclusion that even extraction of the rate of 29.5 Tm³ per day (6.5 Mgd.) while so far not

affecting the shallow aquifer may have to be reduced over the course of time. The behaviour

of the piestic heads in the Minjur well field should be kept under close observation. East of

the Minjur well field fresh water in the aquifer is in contact with seawater. The interface

between fresh and seawater was originally traced geophysically by the resistivity method and

a line of piezometers was established to detect movement of the interface.


Chennai River Basin

During Phase I it was estimated that the seawater encroached inland about 3 km and

was found at 60 m (200 feet) depth in piezometers 1160 and 1138A. The theoretical rate of

encroachment was calculated to be 120 m (400 feet) per year. The piezometers were kept

under constant observation and another resistivity profile was taken in May 1970 and

compared with the profile taken in Feb-Mar 1968.

Constant separation profiles were run at electrode spacing of 10, 25 and 50 meters

and, in some cases, 75 meters. The location of the interface was taken at the point west of

which all the resistivity graphs showed a pronounced tendency to rise above 5 ohmmeter

values indicating a fresher-water condition. The results revealed that while the interface was

located 1.3 km from the piezometers 1060 in 1968, the sane was located 1.4 km from

piezometers 1060 in 1970 thereby showing a westerly shift of 100 meters (328 feet) in a 2-

year time. The resistivity was increasing with depth, which indicated the presence of less

saline water in the lower layers than in the upper layers.

This requires further clarification. The salinity of water at different depths in the different

piezometers was tested and plotted against time (from 1968 to 1971). Three zones were

considered: 18 m (60 feet), 36.5 m (120 feet) and 55 m (180 feet) depths. The conductivity at

55 m (180 feet) depth varies from 55,000 micromhos/cm in the easternmost piezometers

(1160 and 1138-A) to 15,000 micromhos/cm in the westernmost piezometers (1141). Salinity

in piezometers 1160 and 1138-A was more concentrated than the seawater. Water from the

36.5 m (120 feet) zone had low salinity, (even up to the easternmost borehole, 1160A) except

in piezometers 1140-B where the salinity was high, in the order of 20,000 micromhos/cm.

Water in the 18 m (60 feet) zone has low salinity. These observations indicated that the

salinity has not increased with time. The highly concentrated salinity, more than sea water

and occurrence of water with high salinity at shallow depths in small patches cannot be fully

explained as yet but it may be due to the connate water of the marine sediments.

(Refer cross section Plat No: 15 drawn with seawater / freshwater movement)

To conclude, the geometric characteristics of the interface appeared to be more

complicated than originally accepted and it remains to be established whether the movement

of the interface, in fact, takes place at the location of the piezometers. Towards this objective

it was planned to construct more piezometers both on the eastern and western sides of the

Buckingham Canal in a line with the existing piezometers and to continue the observations

both at depth and for change in salinity. Since Nov 1971 the Directorate of Groundwater and

later the State Ground & Surface Water Resources Data Centre attached to PWD took up this


Chennai River Basin

work and as on date seawater intruded towards inland near Minjur, 13 km from east to west

from the seacoast.

Enormous study on various patterns including Isotope Trace Element studies was

conducted elaborately. Moreover there are many number of private borewells used by

agriculture and industrial sector and if all these borewells were pumped out at a time, the net

recommended groundwater recharge will be evacuated fully and overdraft will take place.

The groundwater levels was stood between 6.0 to 7.5 m bgl and if over extraction take

place within another 30 years the groundwater levels may go down below 12 to 18 m bgl.

The rate of discharge will also considerably less in course of time. They have recommended

to drill only very few additional borewells by adopting spacing norms. The recommendations

suggest that the groundwater recharge available as on the date of investigation were of

decades old and if extracted over than the net annual recharge, the dynamic groundwater

reserve will be evacuated fully within a short while and leads to mining of groundwater

reserve / static groundwater reserve.

This was happening in all these five well fields as on date. That is the reason that the

groundwater levels were depleted considerably below the pumping level of monoblock

centrifugal pump level, which was at the time of investigation. In addition to that the net safe

yield available from each borewells and also available for extraction were reduced totally.

Today, most of the borewells were said to be dry and are said to be defunct. Today around 74

borewells were maintained by CMWSSB, Chennai. In total 96 borewells were drilled by

UNDP and 28 borewells by PWD Groundwater Cell Division for investigation purposes and

around 28 borewells were not constructed due to devoid of granular zones. Apart from the

borewells drilled by UNDP and PWD Groundwater Cell Division, the Exploratory Tube

wells Organization, Government of India Unit (ETO) and BTAO – A British Organization

was also drilled by some borewells for investigation purposes, in these three well fields They

are only very few. If we go back to the yield of wells and borewells located in these three

aquifer zones, the Transmissivity and Permeability values were 10 to 100 times of to day’s

ranges. In continuation of the UNDP Investigation project detailed study, the Groundwater

Wing of the Public Works Department were drilled deep and shallow borewells in the entire

Chennai Basin for investigation purposes from 1970 to till date in more than 464 locations

and conducted a elaborate study. The details of 165 borewells drilled for which complete

details available were compiled and documented and enclosed. During earlier days at the time

of drilling, the extracted groundwater was on the higher side and nowadays these were

considerably reduced from these borewells and to date most of the borewells were defunct.


Chennai River Basin

Very few borewells drilled in the three well fields were functioning to meet the city

drinking water requirement, maintained by CMWSSB. Similarly the Tamilnadu Water

Supply Drainage Board, the Chennai Metropolitan Water Supply and Drainage Board, the

Central Groundwater Board were too drilled many number of borewells for drinking and

investigation purposes.

(Vide Plat Nos: 15 A to F, Hydrogeological Cross Sections Drawn for the borewells data.

Outlining the strategy to table the water problem, under the third Chennai Basin

Project, the consultancy study made by M/S. Scott Wilson Limited has reassess the

Groundwater Potential and introducing transferable water rights in Araniar – Kosathalayar

Basin, which is now in progress. This study was conducted during 2002. The water level

contour drawn for Pre & Post monsoon season of 1998 to 2004 clearly shows the depletion of

water levels below 22 m bgl. This study indicates the possibility of extraction of additional

groundwater in the Araniar – Kosathalayar Basin apart from the present extraction being

done by all borewells located in the well fields. Based on these findings adequate

infrastructure facilities were done to extract additional quantity of groundwater by

CMWSSB.

However in this circumstances, irrespective many number of investigations and

studies by various national and international organisations, the extraction from these three

well fields was considerably reduced to one third of what the village farmers or even the

Metro Water Officials extracted during 1990 to 2000 (based upon the borewell data collected

during April – September 2004 furnished as statement) periods from their respective tube

wells in the three major well fields. The field survey shows that the present yield from these

five well fields were drastically reduced and only one third of the total quantity previously

extracted some 20 years back was now extracted as on date. This is also due to the utilisation

of extracted water being used for irrigation purposes, otherwise there won’t be any return

flow which will deplete the groundwater levels still below the present pumping level.

The fluctuations in water level and quality with respect the annual rainfall since

January 1998 to December 2003 were analysed and also insitu data were also observed. It is

significantly noticed within a small pockets there is vast changes in groundwater levels and

groundwater quality due to variations in the hydraulic continuity of different heads with

respect to the place. Previously it was homogeneous and now it is highly heterogeneous.

Keeping this pros and cons in mind the mining of groundwater from these three well

fields should be dispensed with immediately. Based on the present groundwater condition of

the Chennai Basin Aquifer System, it is wise enough to stop drilling of additional borewells,


Chennai River Basin

even though many number of detailed investigations suggested drilling additional borewells

to meet the immediate demand. These studies were confined to the three well fields only and

not covered the whole river basin. Based on the present macro level insitu survey covering

the entire Chennai Basin, it is a well known accepted fact that as on date, the net groundwater

potential of the Araniar – Kosathalayar Basin was considered to be drastically get reduced

and goes beyond the dynamic level and was not recovered since four to five years.

The Hydrogeology map of the Chennai Basin showing the geological setup, water

level contour and groundwater quality in the form of Total Dissolved Solids (there is no spot

having > 500 ppm within the Chennai city limit) was prepared and appended for reference.

Other than the wells located in the Araniar – Kosathalayar basin, there are many numbers of

wells and borewells located all around the study area. The water level and water quality

observations done by various agencies since 1971 to till date were obtained and are analysed.

Insitu water level and water quality observations (TDS only) were made during April to

September 2004 in most of the areas, where irrigation wells and borewells were concentrated.

Water levels were depleted drastically in the wells and borewells located in the Well Fields

areas. Mostly the open wells were dry and groundwater is extracted only from dug cum

borewells and borewells.

The depth of the borewells varies from 80’ to 220’ bgl. The winter water level ranges

from 20’ to 40’ bgl and the recuperation time varies from 6 to 12 hours. The yield varies from

100 liters to 250 liters per minute. Groundwater levels during summer vary from 30’ to 80’

bgl and the recuperation time varies from 12 to 24 hours. The safe yield from these borewells

varies from 100 to 200 liters per minute and mostly these wells are extracting groundwater

less than 4 to 6 hours duration in a day. The quality of the groundwater was sometime back

less than 500 ppm, whereas now it is ranges from 500 to 1100 ppm. The irrigation potential

of these borewells were reduced from two wet crops per annum with one dry crop during

1970 to 1990 and each borewells can irrigate 3 to 5 acres. As on date most of the borewells

water is available only during monsoon season capable of irrigating one wet crop Very

rarely water is available for second dry crop. The acreage per well are also reduced to 2 to 3

acre per well. Around 30 to 35 % of the total wells and borewells are dry or not yielding.

Most of these areas were converted into housing plot or into orchards or sold for industrial

purposes. Some portion of the wet ands was left as fallow land. Apart from these present

statuses, for livelihood, farmers are practicing for keeping livestock, dairy, poultry and other

activities. The intensive irrigation practices are slowly reduced. Most of the farmers with

their existing borewells extract the water from their borewells and sold to water tankers to get


Chennai River Basin

higher market rate instead of practicing irrigation and get financial losses. In the cities, towns

and village settlement wells and borewells drilled were used to meet the domestic

requirement. Wells and borewells were thickly populated in city and urban settlements and

since three consecutive years, these wells / borewells were also dry or not yielding sufficient

quantity of groundwater, even to meet their domestic need. Vide water level and quality

contour drawn from 1998 to 2003 both for pre and post monsoon season Plat Nos. 12 & 13.

3.9. Watershed Management Resource management on watershed basis is given a renewed thrust Conservation of

water assumes significance in view of the growing population and simultaneous increase in

water needs of the people. Spasmodic rainfall adds a challenge to the efforts of proper

utilization of the resource. Vagaries of nature may apparently seem to cloud the results of

artificial recharge structures. A bad rainfall year for example after adopting conservation

practices in an area effectively nullifies shortage in storage of reservoirs.

Analysis of long term water level fluctuations combined with rainfall data, crop

yields, and etc on the same timescale will give meaningful and statistically significant results.

The diversification in the cropping pattern as well as introduction of high yielding varieties of

crops has greatly helped to attain self-sufficiency in food. Application of fertilizers and

pesticides in the field becoming a common practice of farmers indirectly polluting the

groundwater gradually. Technical and scientific findings of water management must reach

the farmers for adoption.

Further saline water having an EC value more than 5,000 micro siemens/cm can be

used for raising crops by drip irrigation, provided the SAR value is not exceeding 5 to 7.

(Higher SAR ratio water will reduce the yield per acre). The fertilizers are mixed and used

with the saline water. In these techniques waste and fallow land can be developed and

converted into orchards and garden lands.

This method was very well operated in this basin in the eastern coastal plain. To

conserve soil moisture, asphalt spraying and adding press mate / coir mulching techniques are

being done on the ground surface to avoid evaporation losses. Though our economy may not

permit such costly irrigation practices, it is quite possible and within our reach to adopt water

management methods to conserve waters. Thus the management of surface water and

groundwater sources in an integrated manner is possible and equitable distribution can be

assured.


Chennai River Basin

Apart from the main task of monitoring of Surface water and Groundwater network

activities, site-specific studies are also being undertaken which will help in proper planning

of the groundwater resource. This is also a useful evaluation of the watershed activity and a

proper socio economic evaluation can be attempted. Participatory Watershed Management is

the best method to maximize the irrigation potential available to irrigate maximum area for

long-term strategy. One of the best techniques is Conjunctive use of surface water and

groundwater resources.

3.10 Surface Water Resources There are four rivers flows in this basin. They are Araniyar, Kosathalayar, Cooum and

Adyar with 8 gauging stations. They are A.N. Kupam Anicut, Lakshmipuram anicut,

Kesavaram Anicut, Poondi Reservoir, Tamaraipakkam Anicut, Valliyur Anicut, Korattur

Anicut and Chembarambakkam Surplus Weir. There are four major reservoirs with their

capacities after being raised recently were Poondi – 97.88 MCM (Sathyamoorthy Sagar), Red

Hills – 93.46 MCM, Sholavaram – 25.30 MCM and Chembarambakkam – 103.23 MCM. The

Chembarambakkam reservoir alone has an extent of ayacut of 5,452 ha for irrigation. The

Poondi, Red Hills and Sholavaram Reservoirs were earmarked as drinking water sources for

Chennai City Drinking water need. The direct ayacut in this basin is 11,579 ha.

There are about 1,304 tanks by which 85,208 ha are being irrigated. In addition to that

215 tanks were irrigating an extent of 21,000 ha get water diversion from Palar River Basin

to Kosathalayar Sub Basin through Poiney Anicut and Palar anicut. Hence the total ayacut of

this basin works out 1,17,787 ha consisting of 11,579 ha of direct ayacut and 1,06,208 ha of

indirect ayacut fewer than 1,519 tanks.

The storage capacity of the existing major reservoirs is 320 MCM Irrigation through

wells and tanks are most predominant in this basin with 46.5 % and 42.2 % of the gross

irrigated area respectively. Assuming two filling, the approximate storage capacity of 1,519

tanks for a duty of 85.80 ha / MCM workout to 619 MCM. Hence the total storage capacity

of the basin as created now as on date is 939 MCM.

The Southwest monsoon, Northeast monsoon and annual yield have been assessed

using runoff co-efficient method that is around 0.15 has been adopted. The total surface water

potential for 75 % probability has been assessed for Chennai Basin is Southwest – 248 MCM

and Northeast – 422 MCM and the total Annual Surface Water Potential works out 784

MCM.


Chennai River Basin

Irrigation area supplemented by Poiney Anicut and Palar anicut under 215 tanks is

21,000 ha. Adopting a duty of 85.80 ha / MCM, the annual storage received is 21,000/85.80

= 244.76 MCM. Adopting two fillings for the tanks, the capacity of these 215 tanks

workouts to 122 MCM. It is assumed that one filling is received from the catchments area of

tanks due to rainfall in the catchment and another filling is supplemented by the diversion of

Palar water through Poiney and Palar Anicuts. Hence the total annual surface water potential

of this basin are 906 MCM inclusive of 122 MCM of diverted water from Palar Basin. There

are no discharge measuring sites in the supply and feeder channels.

No S.W Flume or Parshall flume exists in the channels below the irrigation sluice/

outlet. The discharge is calculated from the area of vent opening and the available driving

head.. S.W. Flumes should be constructed in channels below sluice carrying more than 30

liters per second (one cusec). Field channels with capacity of 30 liters per second or less

should have parshall flumes or V. Notches to monitor the flow.

The Irrigation Water requirement has been worked out also for the four climatic

stations of 90%, 75%, 50% and 25% dependability for present and future conditions. The

water requirement works out especially for agriculture, has been assessed based on the

anticipated implementation of better Watershed Management and Conservation Techniques,

as suggested above. More over when compared to the demand of the previous years, most of

the surface water used for irrigation was diverted to domestic drinking water need and also

due to the implementation of changing of cropping pattern by many of the landholders, the

irrigation water requirement has been reduced considerably.

Also side by side most of the irrigated land were recently be converted into major

industries and industrial complexes, domestic – housing development (both by Government

Housing Units and by Private entrepreneurs) and Recreational – Amusement parks, the net

water requirement were assessed according to the prevailing and future expansion

anticipated, since this basin got a peculiar setup, viz comprising of Major cities and towns.

Total water requirement of this basin by various sectors Viz. domestic, agriculture,

livestock, industries, tourism, power and etc has been assessed for the years 2000, 2005, 2020

and 2040 and are furnished below. Table No: 16 - The total water requirements for various sectors (in MCM).

S.No. Sector 2000 2005 2020 2040

1 Domestic 235 260 350 4252 Agriculture 2900 2600 2400 2200


Chennai River Basin

3 Livestock 40 40 40 40

4All type of Industries inclusive of Small, Medium and Large Scale Industries

125 160 260 400

5Tourism, Recreation, Amusement parks and other Environment Aspects

30 30 30 30

6 Power 22 25 28 31

7 Total 3352 3115 3108 3126

3.11 Groundwater ResourcesThe basin area is underlined by formations of Archaean to recent age. Crystalline

rocks of Archaean age comprising granetic gneiss, Charnockite and associated basic and ultra

basic Igneous and Metamorphic rocks cover 40% of the area in the western and southern part.

The remaining 60% of the area, which occur in the northern, eastern and southeastern coastal

plain, consists of sedimentary formations of Gondwana, Tertiary, Quaternary and Alluvial

deposits. They contain shale, clay, sandy clay, gravels, pebbles and fine to coarse sand.

Ground water occurs under confined, semi confined, unconfined and leaky conditions.

In the Quaternary formation of Chennai Basin viz. Cooum, Kosathalayar and

Araniyar alluvium are the important aquifer bearing formations. The yield varies from 160

lpm to 2500 lpm till 1980 and later on it gradually reduced. Now the present yield from these

quaternary alluvial aquifer zones varies from 160 lpm to 400 lpm only. As on date high

yielding tubewells are very few only, not even 10% of the total number of borewells

available. The Araniar and Kosathalayar alluvium is found to contain highly promising

aquifers in three well fields namely Minjur, Panjetty, and Tamarapakkam areas. During the

UNDP Project (1982-85) the two new well fields were identified in Poondi and Kannigaipair

areas and in the flood plains of Kosathalayar River.

The overall Groundwater Recharge and Safe Yield of these five well Fields was

estimated as 27.0 mgd. The Chennai Basin group consists of Araniyar, Kosathalayar, Cooum

and Adayar sub basins. The depth to ground water level in the different sub basins are in the

range of 8 to 29 m. Over the years (since 1972) progressive lowering in the ground water

level is observed in the lower reaches of the entire four-sub basin. The State Groundwater

Department (162 wells and 70 DWLR’s) and Chennai Metropolitan water Supply and

Drainage Board are monitoring the ground water level fluctuations of this basin group.


Chennai River Basin

Monthly water level data were observed in the control wells and periodical water

levels were recorded in the DWLR installed borewells. These water level data is available for

these wells since 1972 to till date. Vide the water level statement No: XIV appended.

Data observed from January 1998 to December 2003 is appended and contours were

drawn along with the insitu data collected showing the present trend of the water levels.

Water level fluctuation is also observed by the other organizations viz., Tamilnadu Water

Supply and Drainage Board (TWAD Board) in 57 wells (bi-annually), Chennai Metropolitan

Water Supply and Sewerage Board (CMWSSB) in 76 wells (monthly) and Central Ground

Water Board (CGWB) five times a year in 58 wells.

Insitu spot water levels were observed during this reporting period and contours were

drawn for the month of April - September 2004 covering the Chennai Basin is enclosed. The

gradient of the water level for Araniyar, Kosathalayar, Cooum and Adayar sub-basins are in

the order of 1:250 & 1:800 in upper and lower reaches respectively. The assessment of

groundwater recharge was estimated by deploying the Groundwater Resources Estimation

Committee Norms 1997 and the assessment were done based on the prevailing hydrological,

hydrogeological well census data using cropping pattern. It was initially estimated for

revenue division – block wise regarding groundwater recharge, discharge and balance of

Groundwater potential, as on January 2003 as per the norms of the Ground Water Estimation

Committee. The assessment was reworked to get the sub basin wise ground water potential.

The utilisable ground water recharge, draft and balance potential of Chennai basin was

estimated as 1119.39, 768.86 and 350.53 MCM respectively. This was estimated based on the

well census data provided in the census report of 2001. Presently the State Groundwater

Wing of the Public Works Department is updating the well censuses. Previously most of the

domestic wells and borewells, which occupy most of the wells located within the basin, were

not included in the well census. Hence the assessment of groundwater extraction has to be

reassessed. This has to be reassessed based on the present well census taken by State

Groundwater Department, as it seems to be on higher side.

Block wise groundwater potential is attached Vide statement No: VI enclosed. Table No: 17 - Sub Basin wise details are furnished below for reference.

S.No. Name of theSub Basin

Utilisable Groundwater Recharge in

MCM

Net Groundwater

Draft in MCM

Balance Groundwater Potential in

MCM

Percentage of development

1 Araniyar 140.49 69.10 71.39 49.18


Chennai River Basin

2 Kosathalayar 549.99 448.66 101.33 81.573 Cooum 206.70 148.28 58.42 71.344 Adayar 222.21 102.82 119.39 46.27

Total 1119.39 768.86 350.53 68.69

The annual Groundwater Potential of the Chennai Basin, as per the Groundwater

Estimation Committee Norms works out 1,119.39 MCM. The water drawn from Palar

River through infiltration wells annually to meet the drinking water requirement of

Pallavaram, Alandur, Tambaram, Pammal and Vandalur were account for 0.83 MCM.

Hence the total annual groundwater Potential workout 1,120.22 MCM annually.

During UNDP Phase I period 96 borewells were drilled for investigation purposes in

the three Well Field of Araniar and Kosathalayar Basin. Side-by-side the Groundwater Cell

Division of Public works Department were too drilled 28 investigation borewells in the same

well field area. Besides for investigation purposes the ETO (the present CGWB) and the

BTAO were too drilled some borewells during the same period. Out of these borewells most

of the borewells after completion of investigation, the UNDP and the PWD Officials were

pulled out the pipes. During July 1978 the Chennai Metro Water has taken over these

borewells for the city water supply scheme. Vide borewell data enclosed.

Subsequently certain borewells were drilled and some of the old borewells were

abandoned and were said to be defunct. Presently the Chennai Metro Water left now only 74

borewells as production wells, covering the five well fields. The extracted groundwater were

transported through pipelines to Chennai City to meet the drinking water demand and were

useful especially during drought periods of 1969, 1987, 1994 and since then to date.

In the Chennai Basin, there are around 36,706 energized wells (in some of the wells,

borewells were drilled and the pumps were lowered at the bottom since water levels were

gone down as on date), 6,572 diesel engine wells, 18,696 bullock bailing wells (only very

few, not even 10% were functioning rest were totally dry or abandoned based on field

reconnaissance survey made during Apr.–Sep. 2004), 1,466 shallow tube wells, 3,023

medium tube wells and 539 deep tube wells are located (based on Census 2001).

Among these tubewells, field observations were made in 325 tubewells and open

wells between April to September 2004, documentation of all available data covering the

entire basin and the details are appended. Vide Statement I, II, III and IV. These wells were

used for irrigation, domestic (some of the borewells were used by the Chennai Metropolitan

Authorities concerned to meet the present drinking water crisis, so to say a war for drinking

water) and industrial purposes. The total numbers of wells furnished were based on 2001 well


Chennai River Basin

census furnished in the Statistical Department. Wells and borewells located within the

Chennai Metropolitan Area used by individual dwelling and commercial sectors used for

their domestic and industrial purposes respectively were not included, since well censes are

not available regarding this in any of the agencies. Anyhow the number of these domestic

wells and borewells exceeds 3.2 as on date and out of which more than 1.0 lakhs were either

dry or defunct. Now the State Groundwater Wing of the Public Works Department have

geared up and initiated their departmental officials to prepare a well census regarding wells

and borewells located in each and every dwellings and industries not only located within the

Chennai Metropolitan Limit, but also throughout the state.

The groundwater level contour map generated by water level observation made

during April -September 2004 covering the Chennai Metropolitan area is enclosed for

reference. The assessment made as per the Groundwater Resources Estimation Committee

Norms 1997, assessed for the year as on January 2003 has to be refined based on the present

well census now collected as on date. Since the present Hydrogeological conditions is not

conducive to improve the groundwater recharge even during heavy monsoon season. Normal

method of applying for the assessment of Groundwater Potential, the criteria deployed cannot

be used for the Greater Chennai Metropolitan Area. Groundwater Resources of Chennai

Basin is of great importance for the survival of the people of Chennai city and also for the

population of whole Chennai Metropolitan Limit, since the groundwater source are the only

source especially during failure of monsoon periods. During drought years the Chennai

Metropolitan Water Supply System is exploiting the groundwater resources to the maximum

extent possible only to cater the need of the people in city limit by acquiring the rights of

pumping of these high yield borewells specifically for the drinking water purposes.

Hence in the upper part of the basin, the exploitation of groundwater for irrigation

purposes is in vogue since many number years. In the lower part of the basin exploitation has

progressively increased since 1960 for augmenting the drinking water supply and industrial

requirement of Chennai Metropolitan area. Due to over exploitation of groundwater in the

eastern coastal alluvial plain, in most of the areas seawater incursion took place even to a

wide range of 13 km in the northern part of the basin area around Minjur and Mouthambedu.

This gradually get reduced as we go down towards south in the areas around Ennore,

Thiruvottiuyur, Triplicane, Mylapore, Adyar, Beasant Nagar, Thiruvanmiyur, Injambakkam

and still south to 4 km from the sea coast. In these zones the groundwater not only become

saline due to seawater incursion but also contaminated mostly due to discharge of sewerage

into the tail end of these rivers especially in the Cooum and Adyar. In these zones these rivers


Chennai River Basin

were intended only to carry mostly the city sewerage and only during heavy unprecedented

cyclonic storm (which does not happen since three years) these two rivers carries flood

waters. The groundwater level as on date varies from 4.5 m to 22.0 m below ground level.

The present drinking water condition both in quantity and quality wise it is becoming very

worst and worst and as on date it is very difficult and unfit for purification for immediate use.

The ranges of Total Dissolved Solids during the years from 1960 to 1980 - it was

potable between 750 to 1000; between 1980 to 2000 - it was marginal and permissible

between 1000 to 3000 and now it is polluted and contaminated more than 40 to 50 % between

1, 000 to 4000, leaving few exceptions.

Contour maps were drawn showing the groundwater quality observed from the

Observation wells and based on the table survey conducted during April to September 2004.

These contours were drawn for periods continuously from January 1998 to September 2004.

Vide Groundwater quality contour drawn from 1998 to 2004 & the data tabulated.

Considering these aspects, the assessment of groundwater potential now calculated

has to be reassessed since the present assessment includes the saline quality of groundwater

in the coastal zones and contaminated and polluted water by artificial means in most of the

places. Mostly the groundwater has high chlorides, nitrates, iron and sulphates contents. As

on date, even for that contaminated groundwater, most of the peoples in Chennai City were

toilering in need irrespective of its quality. Recently due to the implementation of the

Rainwater Harvesting Techniques, which was done by force by the Government of

Tamilnadu, a slightest improvement was noticed both in groundwater recharge and quality.

However because of the unprecedented severe drought the conditions was becoming

still worst. Every year the Chennai Metropolitan Water Supply and Sewage Board has

acquired and brought under their control some of the high yielding irrigation tubewells

located in the five major well fields (Minjur, Panjetty, Tamaraipakkam, Kannigaipair and

Poondi well fields) located in the Araniar and Kosathalayar Basin to meet the drinking water

demand of Chennai city people, apart from transporting groundwater through tankers from

southern river basins.

This year apart from the 74 tubewells drilled and maintained by the CMWSSB

specifically for the drinking water purposes in the five well fields located in the Araniar –

Kosathalayar River Basin, around 208 irrigation tube wells owned by private agriculturists

were to acquired. Leaving these 208 irrigation borewells acquired by Chennai Metro Water,

equal number private borewells owners were too pump out their borewells water to private

water tankers instead of using it for irrigation purposes, since it is highly profitable and more


Chennai River Basin

safe without taking risk. This pumped groundwater were the main source for hoteliers, flat

owners, industrialists, and some individuals. The net overall groundwater transported through

water tankers from these well fields (well located in Chennai basin and as well as from

southern side of Chennai city, wells located upto Thindivanam) workout 120 MLD (Vide

CMWSSB Web Site dated 4th September 2004).

Due to continuous drawal of groundwater from these identified tubewells, not only

the groundwater levels has gone down and some of the tubewells, why not most of the tube

wells were totally dry and the existing owners / farmers were unable utilise their tubewells

for irrigating dry crops during subsequent years. It will become a never-ending crisis.

There was a water problem arising during 1969 to 1972, (solved temporarily by

drilling tubewells in the three well fields by the erstwhile Groundwater Wing of the Public

Works Department) become severe during latter years and now it is becoming a crisis. Since

then the Chennai City and its environments were mainly depend upon groundwater from

these well fields. In order to meet the growing demand for water, an agreement has been

entered between the Govt. of Tamil Nadu and Andhra Pradesh on 18.04.1983. As per the

agreement, Andhra Pradesh has to deliver at the border of Tamil Nadu (at a constant rate of

1000 cusec.) 8 tmc of water during July to October and 4 tmc of water during January to

April of every year. Now the Government was initiated in bringing water through TG Project.

The New Veeranam scheme to Chennai was commenced on 24th November 2002 and

the works was completed and trial run was run on 15th April 2004 including laying of

pipelines to 228 km length along the highway. Since the rainfall around the catchments areas

of Veeranam and in Cauvery Basin is not full scale, sufficient water is not available in

Veeranam Lake to transport through the new pipelines. In the meantime, now as on date

through this Veeranam Pipelines, around 80 MLD (vide Dinamalar Daily dated 13th

September 2004) of Groundwater was being pumped out from the 45 deep bore wells drilled

along the highway between Vadakuthu – Panruti, within a distance of 25 km length and

pumped to the City Distribution System through newly constructed Water Distribution

Station at Porur. Due to the recent rains, the Veeranam Lake overflows and surface water

from Veeranam Lake was pumped through the New Veeranam Pipelines as programmed. The

quantum of water now pumped out is around 180 MLD.

Water Potential Of Chennai BasinThe total Water Potential of the Chennai Basin was as follows: -

Surface water potential : 784 MCM


Chennai River Basin

Diversion from Palar Basin through Palar & Poiney Anicuts : 122 MCM

The supply of water to Chennai City by the Inter Basin Transfer(Expected from the year 2001 onwards and obtained a portion of it)

Diversion expected from Krishna River : 340 MCM

Diversion expected from Veeranam Tank : 65 MCM

Total Surface Potential Expected : 1311 MCM

Groundwater Potential of the Chennai Basin based on GWREC : 1119.39 MCM

Groundwater drawn from Palar through Infiltration Wells : 0000.83 MCM

Total Groundwater Potentials available as on 1st January 2003 : 1120.22 MCMT

Total Water Potential as on 1st January 2003 Settlement : 2431.22 MCM

The water potential assessed and furnished above were hold good subject to the

following conditions only: -

The net surface water potential of 784 MCM was assessed on subjected to 75 %

rainfall dependability. Diversion of water from Palar and Poiney Anicut from Palar Basin of

122 MCM can be taken into account only during normal rainfall or above rainfall years only,

during drought or below normal rainfall years it was considerably reduced and sometimes nil.

Diversion of water from Krishna River of 340 MCM by Andrapradesh Government, this so

far we are able to realize only 30 % that is also not fully received till date.

Diversion of Veeranam Lake water through the new scheme of 0.065 MCM, though

the implementations of the schemes were completed. The groundwater Resources available

based on GWERC 1997 assessment of 1119 MCM.

This quantity includes all quality of groundwater, subject to normal rainfall and all

prevailing conditions holed good. Finally the subsoil water through infiltration galleries

constructed in Palar River bed of 0.83 MCM, this normally reduced to the barest minimum

due to higher pumping in the upstream side and failure of rainfall. There is always more

uncertainty under prevailing hydrological and Hydrogeological conditions than over

scientific assessment. The Total Water Potential assessed as on 1st January 2003 of 2431.22

MCM is only in paper and the real available resources is a big question. That is why we are

all facing the water crisis. Hence water budgeting has to be done very carefully and safely, by

considering the estimated net water potential really available.

Out of the 26 blocks covered in this Chennai Basin the Groundwater Potential

Available for further development were categorized by GWREC Norms 1997 assessed as on

January 2003 (vide Statement VI) and also the abstract is furnished below:

Chennai City Agglomeration. (Over extracted)


Chennai River Basin

Thiruvallore Out of 14 blocks falls in this basin, 6 blocks over exploited, 2

Blocks critical, 5 blocks semi critical and 1 block safe.

Kanjeepuram Out of 7 blocks falls in this basin, 5 blocks semi critical and 2

Blocks safe.

Vellore Out of 5 blocks falls in this basin, 1 block over exploited, 1

blocks

critical and 3 blocks semi critical.

Out of the 26 blocks (either partly or fully) covered in this Chennai Basin, the stages of

groundwater development groundwater as on January 2003 were, 7 blocks over exploited, 3

blocks critical, 13 blocks semi critical and 3 blocks were safe. It is seen that as on date there

is very minimum quantity of groundwater available for further development.

3.12 Method of Irrigation & AgricultureAgriculture occupies 50 % of the main industry in this Chennai Basin - Araniar and

Kosathalayar, represents as the important sources, but the direct surface water irrigation

occupies less cropping area when compared to the lift irrigation practices. The irrigation

practices developed in this basin occupies more than 45 % of the total area, which also acts as

very good recharge for groundwater, through return flow, seepages and etc. Intensive

agriculture practices are followed in the banks of these rivers and spouse. Cultivation's are

also being done using surface water resources through many number of tanks and

groundwater resources.

Agricultural activities are commonly observed during monsoon season. In non-

monsoon season, dry crops are being raised using groundwater. In the Chennai Basin, there

are around 36,706 energized wells, 6,572 diesel engine wells, 18,696 bullock bailing wells

(as on date only very few were functioning rest were totally dry or abandoned, not even 10%

based on field reconnaissance survey made during April – September 2004), 1,466 shallow

tube wells, 3,023 medium tube wells and 539 deep tube wells are located. Based upon the

hydrogeological field investigation made during April – September 2004, we have observed

data in 325 borewells located spread over the entire Chennai Basin and ascertained that the

present yield is reduced to one tenth of the yield during 1980 to 1990.

The Chembarambakkam reservoir alone has an extent of ayacut of 5,452 ha for

irrigation. The Poondi, Red Hills and Sholavaram Reservoirs were earmarked as drinking

water sources for Chennai City Drinking water need. The direct ayacut in this basin is 11,579

ha. There are about 1,304 tanks by which 85,208 ha are being irrigated. In addition to that


Chennai River Basin

215 tanks were irrigating an extent of 21,000 ha get water diversion from Palar River Basin

to Kosathalayar Sub Basin through Poiney Anicut and Palar anicut.

Hence the total ayacut of this basin works out 1,17,787 ha consisting of 11,579 ha of

direct ayacut and 1,06,208 ha of indirect ayacut fewer than 1,519 tanks. The storage capacity

of the existing major reservoirs is 320 MCM Irrigation through wells and tanks are most

predominant in this basin with 46.5 % and 42.2 % of the gross irrigated area respectively.

Assuming two filling, the approximate storage capacity of 1,519 tanks for a duty of 85.80 ha /

MCM workout to 619 MCM.

Hence the total storage capacity of the basin as created now as on date and the total

annual surface water potential is 939 MCM, inclusive of diverted water of 122 mcm from

Palar basin through Palar anicut and Poiney anicut is 122 mcm.

Agriculture

The recent sandy soils (Entisols), which are immature soils, are most predominant in

this basin group. The soils are generally poor in soil nutrients with medium to high

permeability and low water holding capacity. The soils do not pose many problems for

cropping. However due to indiscriminate drawal and use of ground water along the seacoast,

seawater intrusion has started resulting in the occurrence of problem soils.

Close monitoring of such salt affected areas is needed to raise suitable crops. As this

basin area is mostly urban in nature, most of the agricultural lands are being converted into

housing sites, which result in loss of cultivable lands, leading to lesser agricultural food

production.

In G.O.Ms.No.605 Agriculture (AP.1) Department dated 11.11.91, the Government

have given clear guidelines for regulating the issue of concurrence by the Joint Directors of

Agriculture for conversion of wet lands for non-agricultural purposes like house sites,

establishment of factories etc. Strict enforcement of these existing laws for conversion of

existing agricultural lands into non-agricultural purposes should be made and authorities in

charge of approving such layouts may be asked to take all precautionary steps to save

valuable agricultural lands.

The total area of forests located in the basin group is 29,855 ha, which forms 5.1% of

the total area. As the forest area percentage is far below the national norms of 33%, action

may be taken to cover more areas falling under wasteland for afforestation purposes. Leaving

the total Ayacut, Non-ayacut and dry cultivation lands, there are some barren and

uncultivable waste land of around 17,734 ha which occupies 3.2 % of the total area of this

basin.


Chennai River Basin

Permanent pastures and grazing land which occupies around 12,192 ha – 2.2 %;

Cultivable Waste occupies about 12,192 ha – 2.2 %; Current fallow lands occupies 74,817 ha

– 13.50 %; other fallow lands occupies about 52,649 ha – 9.5 %; and finally land put into non

agricultural purposes including domestic buildings, industries and other commercial sectors

occupies around 1,45,755 ha – 26.3 ha.

3.13 Cropping Pattern The cropping pattern and crop calendar of the predominant varieties adopted in the Chennai

Basin group area are as follows. Table No: 17 - The cropping patterns Season wise.

1st Crop 2nd Crop 3rd Crop

IRRIGATED CROPPING PATTERN.

1 Paddy (Samba)(September – January)

Paddy (Navarai)(January – March)


Paddy (Sornavari)April – July)

3 Paddy (Sornavari)(April – July)

Paddy (Samba)(August – December)

Groundnut / PulsesGingelly / Millets(January – April)


Chillies / Vegetables(February – August)


Sugarcane (Planted)(January – November)

Sugarcane (Rattoon)(December – November)

RAINFED (UNIRRIGATED) CROPPING PATTERN.


Chennai River Basin

1 Ground nut(July - October)

Millets / Pulses (October – January)

SEMI – DRY

1 Paddy (September – January)

Rice Fallow, Pulses(January – February

Table No: 18 - The varieties of crops raised in this basin.

Crop Season Varieties

I. IRRIGATED CROPS

1 Paddy Samba, Navarai, Sornavari

Improved White Ponni, CO43, CR1009, IR20, ADT36, ADT37, ADT39, CO64, IR50, TKM9, ADT36, ADT 37.

2 Ragi January – April CO7, INDAF53 Cholam January – April CO264 Groundnut January – April TMV7, TMV2, VR125 Chillies February – August K1, K26 Gingelly January – April TMV57 Pulses

Black gram, Green gram

January – FebruaryKM1, KM2, T9, CO4, K851, KM1, KM2

8 Sugarcane January – November COC651, COC 771

II. RAINFED CROPS

1 Paddy (Samba) Semi Dry

September – January IR20, ADT 39

2 Groundnut July – October TMV7, JL243 Pulses

Black gramGreen gram

July – October TMV1, T9, KM1K851, CO4

4 Cholam October – January CO265 Ragi October – January CO12, CO7, INDAF 5


Chennai River Basin

Total Area Sown Rainfed Agriculture Irrigated Agriculture

Units in Ha Units in Ha

Net Area Sown 1,56,484 38,594

Gross area Sown 1,90,110 63,270

Cropping Intensity 121.49 5 163.94 5

Table No: 19 - The areas of the crops in the basin.

S.No. Crop Season Area Ha.Percentage of Gross Area Irrigated

1 PaddySamba (Aug. Sep. Dec. & Jan.)Navarai (Jan. to Mar.)Sornavari (Apr. to Jul.)

79,39029,20523,070

60.30 %22.20 %17.50 %

Sub Total 1,31,665 100 %2 Groundnut (Dec. to April) 37,622 19.80 %3 Sugarcane (Jan. to Nov.) 8,546 4.50 %4 Cholam5 Cumbu (March to June) 5,395 2.80 %6 Ragi7 Vegetables (February to July) 3,545 1.90 %8 Pulses (Black

Gram & Green Gram)

(February to April) 1,279 0.70 %

9 Gingelly (January to May) 1,039 0.50 %10 Chillies (February to July) 1,019 0.50 %

Total 1,90,110 100 %In this basin, the major crop is paddy as it occupies 69.30 % of the gross cropped area.

Oil seed crop like groundnut and gingelly, millets like cholam, cumbu and ragi, pulses like

black and green gram and sugarcane occupy the remaining area. In this basin 3,66,858 tones

of paddy, 51,098 tones of oil seeds, 8,206 tones of millets, 541 tones of pulses and 7,77,849

tones of sugarcane are produced on an average per annum.

3.14 Surface Water and Groundwater Quality Surface Water Quality – Water Pollution

The B.O.D. content, heavy metals content and the Coliforms content in the fluids

collected from the Cooum, Adayar, and Buckingham Canal are much in excess of permissible

limits for domestic use. The surface water quality is generally good in other parts of the basin


Chennai River Basin

except Chennai city. Pollution of surface water in Chennai city is very high due to addition of

industrial and municipal wastes. The colour of water in the major surface streams and rivers

viz., Adayar, Cooum and Buckingham canal and Otteri Nallah is black and a sore to the eye.

The turbidity is also high with a bad colour. The water is also very unhygienic. These

watercourses also are a breeding place for mosquitoes and at a few places also add to

groundwater pollution. Because of the pollution and insufficient maintenance the navigation

and inland transport has been discontinued in Buckingham canal. These watercourses need

much improvement. The water quality characteristics for the surface streams viz., Adayar,

Cooum, Buckingham Canal, and Otteri Nallah are not potable and unsuitable for any

purposes, certified by Tamilnadu Pollution Control Board.

The Irrigation Wing of the Public Works Department, Government of Tamilnadu with

the foreign assistance try improve the water ways of Cooum, Adayar, Otteri Nallah,

Mambalam Canal and Buckingham Canal in a time bound programme. Government under

the control of the Irrigation Wing of the Public works Department do desilting works and

rejunuvated the Adyar River Course and the work is almost under completion stage. It is the

duty of the Chennai City people to maintain the condition of the River Adyar after

rejunuvation. The following are inferred from these results representing one summer and one

winter month.

Adayar

The pH, total suspended solids and ammonia are within the tolerable limits, in the upstream

side before it enters city limit. At Kotturpuram and Thiru.Vi.Ka Bridge locations, the values

of total dissolved solids, chlorine and chemical oxygen demand are high. In general during

summer months the Electrical Conductivity and BOD values are high since there is no flow.

Cooum River

The values of pH, total suspended solids, ammonia, chlorides are within acceptable limits,

especially in the upstream side, before it enters city limit. At Binny Road junction, the total

dissolved solids are very high. BOD and COD values are very high indicating high degree of

pollution. The Electrical Conductivity values are on the higher side.

Buckingham Canal

In this case also as in Adayar and Cooum rivers, the BOD, COD and total dissolved solids

and EC values are more than above the acceptable limits.

Otteri Nallah

The BOD, COD and EC values are high during summer months.


Chennai River Basin

Generally the quality of all the inland surface water streams is showing a highly polluted

nature during summer months probably due to the absence of flow in the streams. The

monsoon flow and the tidal actions during the winter months are helping in bringing down

the selected parameters indicating lesser pollution.

Groundwater Quality

The groundwater analysis data of the Chennai Basin reveals that in many parts of this basin

the quality of groundwater is not potable, exceeds the permissible limit and the salinity in

terms of TDS values > 750 ppm. In the Chennai Basin areas it varies from 400 to 7000 ppm,

SAR Values varies between 1.00 the minimum value at Mappedu and the maximum value of

25.00 at Navatikulam of Kanjeepuram Taluk. In the major part of the basin, the water is of

the Sodium Chloride type as the main composition of water is sodium and chloride.

The groundwater quality as observed in some of the domestic wells and borewells

around Madhavaram, Manali, Ambattur, Pallavaram and Chrompet areas are not potable due

to the discharges of industrial effluent. By discharging the sewage accumulated from the

Chennai City and its environment into the areas around Pallikkaranai, Ogium Duraipakkam,

Perungudi, Nesapakkam, Kodungaiyur, Velacherry and etc the area around not only get

polluted and contaminated, the entire groundwater were not potable and unsuitable for any

purposes. The wastewater from industries, which is around 37.50, MCM are allowed into

rivers and streams, running within the basin cause surface water and ground water pollution.

The quality of water in the Chingleput Taluk is generally good except near

Vengaivasal. The water quality from Tambaram to Ponneri is within permissible limit of an

EC value of 2250 Microsiemens/cm, except in some of the wells observed. The quality of

water in the western side of Chennai city is also good in nature except in a few places at

Thiruvallore and Sriperumbudur.

The water quality around Arakonam Taluk is also good. The water quality is poor

near Walajapet in Vellore District. Generally the water quality in the Chennai basin group is

good except in a few places. The general fall of groundwater level in Chennai basin group

was observed to be 2 to 4 m for 10 years and 20 years respectively. It is observed that the

Chennai basin group is predominantly sodium chloride type.

The ground water available in Chennai basin group is free from iron and fluoride. The

nitrate content is seen in groundwater in the areas near Arakonam. Around Pallipet and

Arakonam, total dissolved solids, magnesium, sulphates, chloride contents and total hardness

are beyond acceptable limits. In several places the sodium content is on the higher side. A

trend of increased value of sodium is observed during the pre monsoon period.


Chennai River Basin

Throughout the basin generally the ground water is fit for irrigation except around

Arakonam, Pallavaram, Gummidipoondi and Poonamallee. Out of the 27 blocks falling under

this basin seven are classified as over exploited, three as critical, fourteen as semi critical and

the remaining three as safe blocks according to the study made in 2003 (GWREC NORMS)

based on the present levels of exploitation as against the recharge.

The corresponding figures during 1997 were seven, two and eighteen respectively.

Some of the blocks previously catregorised as gray were reclassified as critical, semi critical

and safe. Thus caution is needed in exploiting groundwater in these areas to prevent possible

ground water mining.

Sea Water Intrusion:

The Seawater Incursion Study conducted by the State Groundwater Wing of the

Public Works Department in the Mouthambedu - Minjur – Panjetty and Beasant Nagar –

Thiruvanmiyur – Kottiwakkam- Injambakkam areas of this basin indicates that the seawater

incursion takes place between 7 to 13 km from the seacoast in Minjur areas and around 1 to 4

km in the other areas. Seawater intrusion is noticed around Minjur belt, north of Chennai. A

study is being done in and around Minjur since 1969 to 2000. The aquifers are tapped for

Chennai city water supply. The study was conducted by Ground Water Wing (SG&SWRDC,

WRO) of PWD by arranging 20 sets of Pieziometers consisting of 52 observation borewells

and 11 production wells. Isotope geochemical techniques were also used during 1983-85. The

sea water-fresh water interface has moved from 4-9 km. from the coast in 1987 to 6.5 km.

during 1992 and the interface is further advancing to 13 km as on date.

The Electrical Conductivity value of water in the Pieziometers went even upto 96,000

microsiemens/cm (may be due to salt pan activities). In the adjoining Thiruvanmiyur area in

South Chennai, there is lot of extraction of ground water for city water supply. In these areas

the seawater intrusion takes place more than 0.5 to 1 km from the seacoast. As there is cause

for alarm in respect of seawater intrusion in this area, caution is needed to avoid ground water

mining. Necessary remedial measures like restrictions on ground water pumping, stipulations

on building construction for leaving open space for ground water recharge etc, may be

effected to avoid damage to ground water aquifer. During July – September 2004, a

reconnaissance survey regarding insitu water quality were done in and around Chennai

Metropolitan Area, apart from the collection of water quality data by various Government


Chennai River Basin

agencies. A map showing the Electrical Conductivity values for different geological

formation is drawn.

3.15 Environment Impact assessment on Water Resources by Development Sedimentation of Reservoirs

Poondi reservoir with a capacity of 77.91 MCM (2,753 Mcft.) was built across

Kosathalayar in 1945 to supply drinking water to the city of Chennai. Now it is proposed to

raise the FRL of this reservoir by 0.60 m and bring the capacity of the reservoir to 97.98

MCM (3,460 Mcft.). A portion of the catchment area for this reservoir falls in Andhra

Pradesh limits. A study of siltation of Poondi reservoir over a period of 40 years from 1944 to

1983 by PWD revealed that the average annual rate of silting is 0.298% of the reservoir

capacity and the annual rate of sedimentation over the drainage area is 0.031 MCM/sq.km.

Soil Salinity Problem:

Due to indiscriminate drawal and use of ground water, along the seacoast, seawater

intrusion has started, resulting in occurrence of problem soils. In such soils cropping has been

found uneconomical. These problem soils areas may be clearly identified and farmers may be

asked to adopt, soil test-based recommendations for saline and alkaline resistant crops.

Water Logging Problems

Some pockets of Chennai city is prone to water logging during Northeast monsoon

and the flood water would get drained into river running within the city. These floodwaters

could not be drained into the sea as the sea will be at high water level during the monsoon

period and the river is also at high flood level during same period. The cross sections of the

city waterways may be properly maintained to carry the drainage water of the low lying area

and must be made capable to discharge into the sea, the moment sea water level reaches low

tide level.

Coastal Erosion

Due to the formation of Chennai Harbor in 1890, North of Cooum river mouth,

resulted in the obstruction to the littoral drift activity. The accretion on the south of Cooum

mouth resulted in the formation of Marina beach. In the north of Chennai Harbor, erosion

features were predominant during Northeast monsoon period.

The jetties obstruct the littoral drift and cause the formation of Marina Beach in the

southern side and erosion on the northern side. Since 1912, the Royapuram site has been and

still continues to be an ever-eroding zone. The development activities in the form of


Chennai River Basin

construction of Chennai Port affected the stability of this shoreline. Permanent remedial

measures against sea erosion in north Chennai coast have to be evolved and implemented.

High rise Buildings

The high-rise buildings, as flat, both for residential and commercial purposes are

springing up in almost all parts of the city and even extending in MMDA limits in the

suburban areas. The vertical expansion, in view of the scarcity of land area will increase the

residential facilities with consequent effects on the water supply and drainage facilities. The

existing water supply mains, sewage disposal pipes are designed for a population that existed

decades earlier. Deterioration of pipes due to corrosion is expected. A study is to be taken on

the existing facilities with regard to drinking water supply mains, sewage disposal pipes;

storm water drains to cater to the existing pressures of population and for the population

growth expected. In the areas within the limits of CMDA, care has to be taken on the

arrangements for sewage disposal and storm water drains.

The CMDA should be strict while giving approval for the multistory construction of

building within the city limit, especially by calculating the feasibility of carrying capacity of

sewage load, drinking water supply, electrical power generation limit, and etc.

Flushing of city drainage courses

Chennai city is traversed by four waterways viz. Adayar, Buckingham canal, Cooum

and Otteri Nallah. These water sources have become an eyesore due to discharge of sewage,

industrial wastes and slums that have come up along these waterways. In Adayar,

Buckingham canal, Cooum river and Otteri Nallah, there are about 228, 128, 343 and 66

infalls points respectively, comprising of effluents from industrial discharge, commercial

sewage treatment plant, pumping station, storm water outfalls, slums etc. The city is now

provided with fullscale biological sewage treatment plants designed to carry 262 MLD that is

within the quantity of sewage currently generated. These treatment plants are constructed in

four locations viz. Koyembedu - west (34 MLD) Nesapakkam - southwest (23 MLD)

Perungudi - south (45 MLD) & Kodungaiyur -North (160 MLD). This has to be projected to

the future estimated demand of around 400 MLD, all inclusive of Chennai city - 310 MLD,

recently laid sewage lines of Alandur, the proposed underground sewage systems to

Tambaram, Pallavaram, Ambattur and the newly formed Municipalities like Ullagaram, etc.

3.16 Water Resources Available, Supply, Demand & Sewerage DisposalChennai Basin covers Chennai City (Chennai District) and parts of Thiruvallore,

Kanjeepuram and Vellore districts. The urban and rural population figures in each of these


Chennai River Basin

four districts covered by this basin were collected from the Statistical Department. The

population as per 2001 census of this basin is 8.43 million. Out of this 6.39 million live in

urban areas and the 2.04 million live in rural areas and the percentage work out to 75.80 %

and 24.20 % respectively. The birth rate and the death rate in this basin are 20 per 1000 and 8

per 1000 respectively as per 2001 census.

The literacy rate is 71.85 % for male for 56.50 % for as against state percentage

literacy rate of 74.88 % for male and 52.29 % for female. Based upon the projected annual

rate of growth of 2.04% the future population for both urban and rural areas for 2004 will be

8.89 million, out of which urban population will be 6.77 million and rural population will be

2.12 million. In general water requirement of this basin constitutes various sector and user

groups such as domestic, agricultural, livestock, industries, recreational and environmental

activities and power. The total water requirements for each sector were assessed for the year

2000, 2005, 2020 and 2040 and were furnished below. Table No: 20 – Projection of water requirements for various sectors in MCM.

S.No. Sector 2000 2005 2020 2040 Remarks

1 Domestic 235 260 350 4252 Agriculture 2900 2600 2400 22003 Livestock 40 40 40 40


125 160 260 400

5 Tourism, Recreation, Amusement parks and other Environment Aspects

30 30 30 30

6 Power 22 25 28 31

7 Total 3352 3115 3108 3126

Note: - The water requirement works out especially for agriculture, has been assessed based

on the anticipated implementation of better Watershed Management and Conservation

Techniques, as suggested above.

More over when compared to the demand of the previous years, most of the surface

water used for irrigation were diverted to domestic drinking water need and also due to the

implementation of changing of cropping pattern by many of the landholders, because of the

non availability farm labourers at cheaper cost, the irrigation water requirement has been

reduced considerably. Also side by side most of the irrigated land were recently be converted


Chennai River Basin

into major industries and industrial complexes, domestic – housing development (both by

Government Housing Units and by Private entrepreneurs) and Recreational – Amusement

parks, the net water requirement were assessed according to the prevailing and future

expansion anticipated, since this basin has got a peculiar setup, viz comprising of Major cities

and towns.

The present demand for these sectors as on 2004 were as follows (in Million Cubic

Metres): They are Domestic: 260 MCM; Agriculture: 2,600 MCM; Livestock: 40 MCM;

Industries: 160 MCM; Recreation & Environment: 30.00 MCM and Power: 25 MCM. The

total water requirement for various sectors of this basin works out 3115 MCM.

The total water potential available inclusive of all, such as surface water, diversion of

water from Palar, Veeranam and Krishna and the groundwater resources of this basin and

diversion of groundwater from Palar were workout 2431.22 MCM.

Firstly, since 1991 or slightly even before, the Chennai Basin is a deficit basin. This

force the Government machineries more especially during unprecedented drought years and

failure of monsoonal years, to divert the maximum available groundwater resources available

in the northern part of the Chennai Basin to meet the drinking water demand of the Chennai

City people who has no moral right to claim legitimately, since almost more than 40% of the

occupants are illegally constructing their dwellings more than the permitted limit.

The city, by these unprecedented growths is in a grip of water scarcity and in recent

years the scarcity is becoming acute. Normally water scarcity for the Chennai city and its

environment will occur only during very severe drought, especially during failure of

monsoon season, below 20 to 30% of the normal annual rainfall years. But due to the vast

unimaginable expansion and all type of water need, the scarcity in water for Chennai city is

continue since 2001 onwards even though the rainfall is not deficit. That is why the

Tamilnadu Government along with the Andhra Pradesh Government is implementing the

Krishna Water Supply Project. The ultimate aim of importing 340 MCM (12 TMC) of water

from Krishna River is to meet the requirement of Chennai Metropolitan area for the projected

population of 2001 AD through river Pennar and delivering it at Poondi Reservoir for

distribution through Sholavaram, Red Hills and Chembarambakkam lakes.

In the initial stage 3 TMC of water is proposed to be supplied from 1996 onwards and

will be stepped up gradually. In addition to this, new Veeranam Water Supply Scheme is

formulated by Tamilnadu Government to draw 2.3 TMC of water from Veeranam tank in

Cuddalore district situated at a distance of 230 km from Chennai.


Chennai River Basin

Secondly, apart from the unimaginable population growth on one side, during the year

1991, the Government of India announced the new industrial policy in order to accelerate the

growth of industries all over the country. Subsequently, in January 1992 the Government of

Tamilnadu launched its new industrial policy at State Level. The policy seeks to provide

conducive atmosphere for the development of large and medium industries and for

stimulating the growth in small-scale industries. Due to the priorities given by the

Government, various industrial developments took place especially within the Chennai

Metropolitan Area, which also consumes large-scale water resources to meet their industrial

and domestic demand. To meet the industrial water demand, as a policy of the Government,

they forced to divert the water from its reserve previously allocated to drinking water. Viz.

Diversion of water to Ford India, Hyundai and etc. When we consider the economy, social

improvement and provide employment opportunities, these developments were unavoidable.

This short gap can be overcome by changing of cropping pattern or by reducing the

net irrigated area; a negligible quantity of irrigation water can be diverted to meet this

demand. Thirdly, while we expects a marginal increase in industrial growth, to meet the

power supply for these industries, there is a gap in power generation, which force the

government to take effective steps in the production of power generation, which also

consumes more quantity of water resources in various heads. The new schemes formulated

in this power sector by the government of Tamilnadu, especially the execution of the

following new schemes such as North Chennai Thermal Power Project Stage I, each of 210

MW of three units, Stage II of 500 MW, Stage III of each of 500 MW of two units and the

Basin Bridge Gas Turbine Plant each of 30 MW of four such units, all these power sectors

requires huge quantity of raw water from the Kosathalayar and Cooum basin, apart from the

cooling water which they drawn from the sea.

These are the main factor, which affects the regular city water supply apart from the

shortages due to monsoonal failures. The surface water potential available in this basin were

fully utilised by all sector to their might. In this surface water potential about 90 % of the

water is being consumed by agriculture only. But the general overall efficiencies of this

sector are only 30 % to 40 %. Vide various storage levels of all reservoirs enclosed.

3.17 Alternatives For Meeting Future NeedsShort Term

The surface water potential of this basin group has been almost utilised in full. The

maximum quantity of surface water, i.e., about 90 % is consumed by agriculture. But the


Chennai River Basin

general over all efficiency of this sector is 30 to 40 %. So, even if about 10 % of this

consumption could be reduced, it would result in considerable savings and the quantum of

water could be spared for other purposes. The following short-term measures are suggested

for reducing the consumption of water for irrigation.

Equitable distribution of irrigation water by better water management. Improving the

performance of the existing irrigation systems by suitable structural measures. In modern

water management, drip and sprinkler irrigation play a major role in effective use of the

precious water to the crops and orchards which not only increase the irrigation efficiency but

also the yield. There are also other added advantages apart from the above two. So the

Government of India have played an important role in popularizing the micro irrigation

method from the Sixth plan onwards- by way of allotting funds to different States and giving

subsidies.

Though India occupies seventh position with 70859 ha under drip irrigation, it has to

go a long way to bring more land under drip and sprinkler irrigation. Hence, steps should be

taken to increase the land many fold so that better production per unit of water can be

achieved.. In this respect initially farmers and agriculturists may educate accordingly to

implement the better water management techniques to reduce the quantum of water usage

considerably thereby around 20 to 30% of the surface water utilisation can be reduced. At the

first instance drip irrigation can be taught and forced to adopt the Mango and coconut groves,

orchards and horticulture purposes, which alone occupies 25 % of the irrigation needs.

By adopting better Watershed Management Techniques – such as Conjunctive use of

surface and ground water wherever possible, especially where people utilise only surface

water where there are copious groundwater potential also available. These potential areas

were to be earmarked and government and agricultural department officials should take this

issue as a prime one and try to implement the utilisation of Conjunctive use of surface and

groundwater utilisation for wet crop. Only irrigating wet crop such as paddy and sugarcane

occupies more than 40 to 50% of the surface water potential. Hence much care should be

given in this respect to reduce the utilisation water resources, so that the saved water can be

diverted to drinking water requirement of the Chennai city people. Adopting better

agricultural practices such as crop rotation, changing of cropping pattern, raising garden

crops and other less water consuming crops.

Long-Term

The following alternatives are suggested for sustainable water resources development

in this basin. Construction of additional reservoirs in Chennai Basin to store water for


Chennai River Basin

Chennai water supply, on the initiative of the then Prime Minister of India in February 1976,

the States of Andhra Pradesh, Karnataka and Maharashtra agreed to spare 15 TMC of water

(each 5 TMC) from their share of Krishna water for drinking water supply to the city of

Chennai. Following this, the Tamilnadu Government entered into an agreement with the

Government of Andhra Pradesh on 18.4 1983 for the implementation of this joint project for

the drawal of 15 TMC of water from Srisailam reservoir across river Krishna. As per this

agreement Andhra Pradesh Government will deliver 12 TMC of water per annum (excluding

3 TMC as losses in transmission) at Andhra Pradesh-Tamilnadu border for Chennai Water

Supply and this will be received in the following manner. From July to October: 8.00 TMC

and From January to April: 4.00 TMC. Out of 8 TMC of water received during July to

October, 4 TMC will be utilised for drinking water supply at the rate of 1 TMC per month

(930 mld) with the available drawing facilities.

Hence, by the end of October a balance quantity of 4 TMC of Krishna water will be

available and necessary storage space to this quantity is to be provided. For creating

additional storage facilities the following proposals were formulated and executed and all

works were completed as on date in the 1st phase.Table No: 21 - Details of Works Proposed with their capacity.

S.No. Details of Works Proposed Capacity in Mcft.

1 Raising the FTL of Poondi reservoir by 0.6 m 710 Mcft2 Raising the FTL of Red hills tank by 0.6 m 450 Mcft3 Raising the FTL of Chembarambakkam tank by 0.6 m 525 Mcft

Total 1685 M.c.ft

For storing the balance quantity of 2315 Mcft it is found essential to create atleast two

reservoirs in Kosathalayar river basin or elsewhere. Out of the two reservoirs required, one

with a capacity of 1000 Mcft is proposed near Thirukkandalam village and another reservoir

at Ramanjeri with the same capacity of 1000 Mcft. Now works were taken up for detailed

investigation. The scheme proposed near Thirukkandalam village was to be taken up for

execution under phase II of Krishna Water supply project. As per the instructions of the Chief

Engineer, Krishna Water detailed investigation was taken up. The villagers of Guruvoyal and

surrounding villages have objected to this proposal since a vast area of wet lands together

with habitated houses, temples, brick kilns, pump sets etc. are coming under the water spread

area of the proposed Thirukkandalam reservoir and finally the proposal was dropped.


Chennai River Basin

Alternative proposals were suggested to go in for storing the flood flows of Araniyar

river water in Vadamadurai, Vengal and Kadarvedu tanks, which are irrigation tanks. The

suggestions were examined by the Executive Engineer, PWD, KWSP Division, Ambattur and

it is proposed to store additional water in the above three tanks by drawing surplus flood

water from Araniyar river through an anicut proposed at Kalpattu village and water from

Kardaleru- Poondi canal above Rajan Odai. In order to augment one TMC of water in lieu of

Thirukkandalam reservoir it is proposed to modernise the Vadamadurai tank, Vengal tank

and Kadarvedu tank. By doing this, water can be stored to the tune of 0.913 TMC in

Vadamadurai tank, 0.250 TMC in Vengal tank and 0.107 TMC in Kadarvedu tank. The total

existing capacity of these sources is 266.00 Mcft and capacity after modernisation will be

1270 Mcft. The total irrigation resources to the crop of these three tanks is 266 Mcft. Hence

balance available for Chennai City water supply works out to 1004 Mcft.

The following are the proposals to be implemented at a total cost of Rs.134 crores.

i. Construction of an anicut at Kalpattu village with head sluice, across

Araniyar to divert flood flows.

ii. Improvements to the existing channel for a carrying capacity of 1500 cusecs

with regulator arrangements.

iii. Raising the FTL by 0.6 m and deepening etc. of Vadamadurai, Vengal and

Kadarvedu tanks.

iv. Interlinking the tanks by canals.

v. Excavation of a canal with capacity of 500 c/s.

vi. Kandaleru Poondi main canal above Rajan odai off-take to Vadamadurai tank.

Extension of a new canal for letting down 1200 c/s of water from Kadarvedu

tank to Kosathalayar River above Tamarapakkam anicut.

Irrigation efficiency should be stepped up in stages and brought upto by better

Management.

Tank irrigation system plays a major role in Tamilnadu agriculture and about 30% of

the irrigated command area comes under tank irrigation system. But at present, the

overall efficiency of tank irrigation system is very low and it ranges from 30 to 40%.

In order to increase the overall efficiency of tank irrigation system, modernisation of

tanks under EEC assistance was sought for. Accordingly 205 tanks under phase I and

296 tanks under phase II in about 13 districts were selected. The works in phase I are

completed and the works in phase II are almost nearing completion.


Chennai River Basin

This helps in conserving the limited water stored in the tanks, using it in the most

efficient manner and distributing equitably for increasing the productivity of irrigated

agriculture. In the completed modernisation works, it has been found that the overall

efficiency has been increased from 45 to 60%. Hence possibility of rehabilitating the

tanks in a phased manner has to be explored and executed by getting assistance from

internal as well as external financial agencies.

• Industrial and municipal wastewater should be treated and reused.

The concept, namely the value of the produce obtained per unit of water consumed

should be introduced. Accordingly the sector demands have to be readjusted.

• Less water consuming industries should be encouraged in places water scarcity areas.

• Desalinisation of seawater especially for major industries and as well as for domestic

consumption should be planned and encouraged.

3.18. Environmental PlanningIndustries

In Chennai basin group, the Government have imposed a total ban insetting up of the

highly polluting industries (vide G.O.Ms.No.213, Ministry of Environment (Ec-1) department

dated 30.3.1989) within 1 km. from the embankments of the water sources like

Chembarambakkam tank, Upper supply channel (Poondi to Sholavaram) and lower supply

channel (Sholavaram to Red Hills). The wastewater from industries allowed into rivers and

streams, running within the basin is around 37.50 MCM. This water causes both surface and

ground water pollution. The industries may be directed to enforce strict adherence to the

norms of treatment for trade effluents and to recycle water wherever possible for secondary

and tertiary uses. The Government should arrange finance if needed and time should be

stipulated for the construction of a treatment plant.

Sewage Disposal.

The river courses get polluted within Chennai city limits due to letting of sewage and

drainage waters by slum dwellers, private parties, etc and also some industrial partly treated

or untreated wastes. The quality of water in these water ways get deteriorated and also foul

smell emanates from the waterways. Severe pollution is caused by raw domestic sewage and

industrial wastewater. The civic bodies have to follow the norms for sewage treatment.

Sewage treatment plant may be installed in all major towns covering slum areas in the basin

before they are let down in the river courses. Chennai city is traversed by four waterways viz.

Adyar, Buckingham canal, Cooum and Otteri Nallah. The water resources here become an


Chennai River Basin

eyesore due to discharge of sewage, industrial wastes and slums that have come up along

these waterways. The following table provides information’s on the number of infalls in the

waterways source wise, break-up details on industrial, commercial sewage treatment plant,

pumping station, storm water outfalls.

Table No: 22 – Total Number of in falls sources wise in the Rivers.

S.No Description Industrial discharge

Commercial

Sewage treatment

plantPumping Station

Storm Water Outlets Slums Total

1 Adayar 20 38 1 4 148 17 2282 Buckingham 14 21 1 9 64 19 1283 Cooum 18 270 1 2 28 24 3434 Otteri Nallah 13 3 0 2 43 43 66

In Chennai city the capacity of the existing sewage treatment plants are inadequate to

meet today’s total sewage generated and should be increased. The Government has provided

adequate funds for Chennai cities to the towns for the sewage treatment plants. As adopted in

Chennai city, for example at Kodungaiyur, Nesapakkam, Perungudi, the treated sewage may

be utilised for cultivation of crop varieties in respect of the places in this basin, wherever

possible. The city is now provided with full scale biological sewage treatment plants designed

to carry 262 MLD that is within the quantity of sewage currently generated. These treatment

plants are constructed in four locations viz. Koyembedu - west (34 MLD) Nesapakkam -

southwest (23 MLD) Perungudi - south (45 MLD) & Kodungaiyur -North (160 MLD). It is

estimated that about 5000 to 10000 c/s for shorter durations (3 hours to 1.5 hours) is needed

to flush the stagnating waters of Cooum and Adayar. This has to be projected to the future

estimated demand of 400 MLD, all inclusive of Chennai City (310 MLD) balance, recently

laid sewage lines of Alandur and the proposed underground sewage lines covering Ambattur,

Pallavaram, Tambaram and the recently formed Municipalities of Ullagaram –

Puzhuthiwakkam, and etc.

Recently, the CMDA in coordination with the Irrigation Wing of the Public Works

Department has cleaned the Adyar waterways 43 km stretch from Chembarambakkam Lake

to the tail end and only a small portion is left out and it is under completion stage. Similar

schemes are under consideration with the government to clean the waterways of Otteri

Nallah, Mambalam Canal, Buckingham Canal and Cooum with foreign assistance.

Recycling of Waste Water

Reclamation of sewage for reuse is a major positive step contemplated recently by


Chennai River Basin

Government. Two major industries viz., Chennai Fertilizers and Chennai Refineries have

installed tertiary treatment plants for polishing of the secondary treatment sewage of

Kodungaiyur treatment plant for necessary non-essential requirements within the industry.

These plants are designed for a capacity of 11 and 22 MLD respectively. Large extent of

sewage grass farming with the treatment plant effluent is adopted. New sewage farming is

being replaced gradually by long-term teak plantation to improve the environmental status.

The Government is also negotiating a proposal with the Government of Japan for installation

of sewage reclamation plants to take care of bulk of the sewage quantity they would be

generated within the city in the near future. Implementation of this proposal will ensure

environmental protection of the waterways from sewage pollution. The city is now provided

with fullscale biological sewage treatment plants designed to carry 262 MLD that is within

the quantity of sewage currently generated.

These treatment plants are constructed in four locations viz. Koyembedu - west (34

MLD) Nesapakkam - southwest (23 MLD) Perungudi - south (45 MLD) & Kodungaiyur -

North (160 MLD). This has to be projected to the future estimated demand of 400 MLD, all

inclusive of Chennai city 310 MLD, recently laid sewage lines of Alandur and the proposed

underground sewage lines for Tambaram, Pallavaram, Ambattur and Ullagaram.

3.19 Control of Sand Quarrying

Excess quarrying of sand from Cooum river near A.N.Kupam Anicut, has resulted in

the washing away of the anicut portion in the right hand side and also disturbances in the

remaining portions of the anicut. As per the Government Order No 957 PWD dated 29.5.72,

the poromboke lands within a radius of 300m both on the U/S and D/S side of the water

supply head works (Irrigation structures) located on the river banks are prohibited lands for

removal of sand by private parties, and the G.O. should be strictly followed to prevent sand

mining effects. Except for silica sand, the coastal belt is not rich in mineral resources. Now

the Government of Tamilnadu controls the sand quarrying by taking the control and regulates

them judiciously. Now the Government owned Pubic works Department itself is quarrying

sand at specified spots, accumulated that quarrying sand and distribute to the public at an

economic rate. This is welcome sign for improving the groundwater storage in one-way or

other. The mineral resources that occur include silica sands, lime shells, and salt and beach

sands. Silica sands, white to grey in colour, form the geological horizon along the entire East

Coast from Chennai to Injambakkam, of this basin and continue still beyond south along the

seacoast upto Pondicherry. The silica sand deposits, estimated to be around 11 million tones


Chennai River Basin

are suitable for glassmaking and foundry purposes. Apart from the varieties of silica sands,

lime shells occur in the Pulicat Lake area and private users are using these.

3.20 Flood, Drainage and Drought ManagementThe Chennai Basin group consists of a portion of Araniyar Basin, Kosathalayar Basin,

Cooum and Adayar basins. Also Buckingham canal which was a source of navigation

previously is running parallel to the coast line for about 58 km length in Chennai Basin limit.

The above rivers and canals function as drainage courses in this basin. The Otteri Nallah,

which runs for a length of 11 km, is also a drainage carrier of Chennai Basin and it discharges

into Buckingham canal near Basin Bridge. During the years of 1943, 1976 and 1985 this

basin experienced heavy floods and damages due to cyclonic effects. The prevalent

encroachments and obstructions in the water ways are the main causes for flooding of

Chennai City and maximum relief can be achieved only by clearing the above obstructions.

The Chennai Basin group area does not fall under the category of drought prone area

as identified by the Central Water Commission. The average annual rainfall of 1131mm in

this basin is more than 1000 mm, the limit fixed by the irrigation commission for identifying

drought prone areas along with other criteria. However, droughts are frequent in the basin due

to failure of monsoon. The Metropolitan City of Chennai was in the grip of severe drought

between 1947 to 1954, 1968, 1972 to 1975, 1982, 1983, 1987, 1992, 1997 and 2001 to 2004.

The drought during 1992 and three consecutive years since 2001 to till date, the

drought were so severe and maximum that domestic water supply through pipeline in the

entire city of Chennai was stopped and measured quantity of water was supplied through

tankers. During these drought periods, the groundwater mainly available in the Chennai Basin

Well Fields and the Neyveli Aquifers were the only source safeguard the city water supply.

Drought Control Measures

Short Term Plan

Operational methods of surface reservoirs i.e. using special storage spaces exclusively for

Drought needs.

Conjunctive use of surface and ground water

Rain fed agriculture management by improved varieties and agronomic practices.

Increasing soil intake and soil water storage and Controlling evaporation in water bodies.

Land use regulation to minimise water use during droughts.

Changing over from traditional agriculture to pasture or grass land, fruit farms and

vegetable gardens according to the Availability of water resources in the area.


Chennai River Basin

Demand reduction strategies, viz. change in crops & cropping practices, domestic water

use.

Long Term Plan

Effective utilisation of ground water storage reservoirs including recharging.

Inter basin and intra basin transfers.

Improving conveyance efficiency by minimizing on way losses by lining the system.

Use of soil conservation measures for increased water yield.

Run-off harvesting structures.

Improved methods of irrigation.

Desalination of seawater for domestic and industrial purposes.

Improved water conservation practices, like recycling of water for industrial purposes.

3.21. Laws, Regulations and Institutional ElementsAll the general laws and regulations pertaining to water policies, environment and

pollution control, sand quarrying, drawal of water for various purposes are applicable to this

basin. There are ample numbers of rules, laws, acts and circulars from various departments

were framed so far, regarding surface water and groundwater, sand quarrying, setting up of

various types of industries, aquaculture, fishing, agricultural development due to Government

policies on Green Revolution, etc. Government then and there have to enforce strictly by

governing all aspects where there is a violation or deviation takes place. There are adequate

Acts and Laws regarding sand quarrying, regulation on water supply and utilisation both for

surface and groundwater. Apart from it there are adequate Acts and Laws regarding water

pollution, air pollution, noise pollution, forestry, aquaculture development, fisheries,

protection of flora and fauna, mangrove forests, agricultural sectors, public health, animal

husbandry department, salt corporation, farmers section, etc. Violation or deviation in any

one of these sectors will either directly or indirectly affect the surface and groundwater

recharge, exploration, exploitation, conservation, planning, development and management.

The Government Tamilnadu issued orders to regulate the sinking of wells and

borewells and also regarding usage the surface water and groundwater vide two acts

enclosed. However it has not been strictly enforced till date. Apart from it these issued

government orders should be modified so that there is no defaulters.

To regulate these things the following can be adopted strictly: -


Chennai River Basin

i) All the wells, tubewells and borewells located within the Tamilnadu limit intended for

any purposes should be registered by filling in the Proforma published in all leading

daily newspaper within 30 days of notice, failing which necessary civil and criminal

action will take place, including penalty of Rs. 10,000 or rigorous imprisonment for

one year or both, irrespective of locality or cast or creed or religion.

ii) The details of the groundwater structures whatever may be present condition, it

should be mentioned in the application itself. If any of the columns left out unfilled,

appropriate reasons should be substantiated.

iii) The river, tank, water bodies, groundwater resources and the marine environment

must be fully protected from pollution of any suit. Even the existing industries

constructed and developed before the implementation of the Pollution Control act

should be brought under control and should allow to function till all formalities were

completed.

iv) The wells or borewells constructed should be used only for the purpose for which it

has been constructed and no commercial activities can be undertaken.

v) If any wells or borewells constructed were used for other purposes intended for the

purposes it was constructed, under groundwater violation act, the concern person will

be liable for prosecution and suitable civil and criminal action.

vi) For drilling of borewells or wells, necessary permission should be obtained from the

authorities concerned and wells or borewells should be constructed only by deploying

Registered Contractors under the authorities concerned. All the Rig Owners and

Drilling Contractors should register their operation within their district concern and

their movement has to be regulated. While drilling operation, a board containing the

details about the borewell drilled, authorities concerned, rig owner with their

registration details and official permission obtained should be provided at the site and

after completion of the borewell necessary completion certificate to be obtained from

the concerned authorities before commissioning of the borewells.

vii) Similar laws and rules can be framed to control the sinking of wells and borewells

should be enforced; otherwise mining of groundwater cannot be controlled.

viii) Any developmental activity to be controlled, watched, then allow to function if it does

not affect the present scenic beauty and to preserve while expansion.

ix) Water intensive activities should not be encouraged, considering the heavy demand

for the limited surface and groundwater reserves in the area, for sustainable

development, Even the existing water intensive industries should be forced to


Chennai River Basin

purchase the city or municipal sewage and has to be treated to meet their industrial

demand. Only for specific drinking or for their housing domestic need they should be

allowed to extract either surface water or groundwater with need based quantity only.

x) The developmental activities should be such as to provide employment opportunity to

the local population, which is fairly unskilled, since these things alone will improve

the socio economic and welfare of the downtrodden, uneducated village people.

Whatever may be reservation provided in the Act for suppressed class people, till date

nothing has reached the real suppressed class people lives in villages.

xi) Only those comes under creamy layers, so called suppressed people lives in cities and

town, who were really enjoying all benefits provided to those who were really

suffering till now, should allow those who don’t have opportunity to understand what

privileges they are entitled and how to get these privileges for which they are entitled.

Only then there is a meaning in achieving “Sustainable Development” in India.

4. CHENNAI METROPOLITAN DEVELOPMENT AREA

4.1 Location and Extent.

This Chennai city is located at approximately 13° North latitude and 80°30' East

longitude, on the famed Coromandel Coast of the Bay of Bengal. Chennai is the fourth

largest city in India, after Mumbai, Kolkatta and New Delhi, the national capital. The city

derives its twin names of Madras and Chennai from the two names associated with the piece

of land on which Messieurs Andrew Cogan and Francis Day opened a 'factory' for the British

East India Company in the 17th century. Area shown vides Plat No: 16.

Today, Chennai covers 174 sq km (approx. 67 square miles), the territory running for

approximately 20 km along the seacoast. The city is about 13 km at its widest. From the

capital of Madras Presidency, which included Tamil, Telugu, Malayalam and Kannada

speaking areas comprising most of South India- the composite Madras state in the post-

Independence era-is now the political and financial headquarters of Tamil Nadu, the

exclusively Tamil-speaking state in the Union of India. The greater the power that came to

vest in the Britishers in the 100 years preceding Independence, the greater did the attraction

become, contributing greatly to the growth of the city, and the spurt in its population.

Demographically too, the city has experienced considerable change. The first scientific

census of the city was taken in 1871. A population of 3,97,552 was recorded for the eight

municipal divisions of the city, which at the time covered an area of 27 sq miles.


Chennai River Basin

The urban agglomeration, with a population of 42.16 lakh (presently 45 lakhs) -

Chennai city and 65.0 lakhs (presently 70 lakhs) – Greater Chennai Metropolitan area based

on 2001 census, now forms a thriving modem metropolis with flourishing industrial suburbs,

accounting for a fifth of the total urban population of Tamil Nadu. Yet, despite all its modem

growth, metropolitan Chennai still remains true to much of its fascinating historic past, a

legacy that is most clearly illustrated in the water distribution system of the city.

Until the nineteenth century, Seven Wells, even now found opposite the Stanley

Medical College Hospital, was the city's primary source of water supply. The Seven Wells

Government Water Works, a scheme executed in 1772, was the city's first organised water

supply, though initially it was meant only for the Fort area. The wells, which were ten and not

seven in number, supplied 1,40,000 gallons/day and showed no signs of exhaustion even a

century later. The wells are no longer in existence today, but the original site retains its

connection, with the civic amenities being the home of a pumping station. Before Seven

Wells, drinking water for the Fort used to be carted from other wells.

Another notable feature within Madras is the Buckingham Canal a length of 418 km

out of which 161 km runs through Tamilnadu and 90 km of it in the Madras Basin, cuts in

1806. It is in fact only two parts of a four-part canal, which is one of the longest canals in the

country. Originally used for navigation, even up to the 1950's, it has now unfortunately

become rather an unsightly and highly polluted dumping ground for municipal and other

wastes. Other waterways in the Madras area include, Cooum, the Adyar and the Otteri

Nullah, a rivulet joining the Buckingham Canal just north of the Basin Bridge and

Mambalam Canal, which also now serves as an open drain for that part of the city. At present,

the city consists of four municipalities, 23 town Panchayat (now recently revised), five

satellite townships and a few outlying villages (all are recently revised). The city area is 174

sq km and the metropolitan area 1,166 sq km. The terrain is generally low-lying and flat with

an average slope of less than 1/1500. Most parts of the city are within four to five metres

above sea level. According to the 2001 Census, the present population is 64,21,985 in

Chennai agglomeration and 48,41,396 in city proper. Providing protected water, drainage and

sanitation for this population and the industries is a problem of immense proportions.

4.2 Physiography

Physiographically the Chennai Metropolitan Area can be divided into three units viz.

they are of Southwestern mountainous terrain gently sloping towards east and southeast,

Central elevated terrain and Eastern coastal plain. This part is the southern tip of the

Kosathalayar having Cooum and Adayar are the two rivers drain the area. Cooum and Adyar


Chennai River Basin

rivers mostly flow from west to east originate from surplus courses of Cooum tank in

Thiruvallore Taluk and Chembarambakkam Tank in Sriperumbudur Taluk, with a man made

artificial Buckingham canal runs from north to south. All these two rivers stretching from

west to east confluence with Bay of Bengal in the East. Vide Plat No: 17.

The length of the Adayar River is 43 km from its origin to the sea. It just starts as two

small streams beyond Tambaram and assumes the proportion of a river only after the

confluence of the surplus course of Chembarambakkam tank near Thiruneermalai. The

catchment of the river is about 860² Km of which about 300² Km lie in Chembarambakkam

sub basin. The Maximum elevation is around 320 m above m.s.l. (Thiruneermalai,

Pallavaram and Kadapperi Hills) and minimum elevation is 5 to 15 m above mean sea level.

There are many number of big tanks situated in the Chennai Metropolitan area. They are:

Sholavaram, Red hills and Chembarambakkam and small lakes such as Velacherry lake,

Chittalapakkam lake, Madipakkam lake, Thiruneermalai lake, Ambattur lake, Padi tank,

Purasawakkam tank and Madhavaram tank.

Except the Chembarambakkam tank and Thiruneermalai tank, there is no direct

command area for any of these tanks. These water bodies were useful in meeting the

drinking water needs of the Chennai Metropolitan Area, irrigation and for many number of

industries located around Chennai city and its urban agglomerate. All the drainages of the

study area are almost flow from west to east and ends in Bay of Bengal. The main study area

of Greater Chennai is more or less lays on the East Coast, hence the plain to gentle and the

Coastal Physiography only occurs. The trend of coast is more or less uniform throughout the

length of the study area. However broken natures in the trendline forms small parts and

fishing point's etc. Normally the coast spreads 750 m to 1000 m towards west from the tidal

points with coverage of sands and sandy clay materials. In coastal area of the study, more or

less plain topography is seen.

Small beach ridges and sand hillocks are occurring in and around the coastal belt near

Adayar estuary and extend upto Injambakkam. Sea erosion prone, broken coasts are

observed in Thiruvottiuyur to Ennore area. In Inland, topography, smaller hillocks and

elevated social forests were present. The maximum and minimum elevations of the study area

are between 2 to 15 m in the coastal plain, 10 to 25 m in the central region and more in the

hills of Thiruneermalai, Pallavaram and Kadapperi Hills. Apart from these small hills and

hillocks, certain elevated upland and reserve forests, which covers a small area mostly on the

northwest and west. The nominal topography is generally slopping towards the East and

Southeast. The general trend of dipping ranges from West to East. The Hydraulic gradient


Chennai River Basin

and the flow lines of ground and surface water are towards east, the sea. They’re some small

hills and hillocks also lie just near Pallavaram, Thiruneermalai and Tambaram, leaving the

major hills and hill ranges lies on the northwestern and western part of the Chennai basin.

4.3 Climates and Rainfall

Chennai is located in one of those drought-prone areas. Chennai belongs to a tropical

climate with a mean annual temperature of 30°C. The climate of the region is dominated by

two monsoons caused by the thermal contrast between land and sea. Monsoon climates are

characterised by clearly marked seasons with specific types of wind and weather. In Chennai,

the weather patterns are dominated by the Northeast monsoon, which normally occurs during

October-December. Most of the heavy rainfall in the Northeast monsoon is associated with

clear synoptic system of depression and cyclones, with nighttime rainfall being most

common. Diurnal variations in temperature are moderated by coastal influences. The

Northeast monsoon rains dominate most of the low-lying alluvial and coastal plains of

Greater Chennai. Though its influence is invariably erratic but failure of rains is not common.

Here, the climate is characterized by steady, dependable seasonal precipitation.

However, according to a study by the Centre for Water Resources, Anna University, Madras,

the Southwest and Northeast monsoons show a compensatory behaviour. In years above

normal and predominant Southwest monsoon rainfall, between June and August, the

Northeast monsoon is either deficient or almost absent. Similarly, if the contribution from

Southwest is below average, a better Northeast monsoon can be expected. However details

about the rainfall patterns were discussed in the previous para itself.

The hottest and driest period of the year is from April to May, when daytime

temperatures may reach 45°C. During this period, temperatures rarely fall below 25°C even

after sunset. The lowest temperatures occur during December and January, when an average

of 25°C is recorded. Humidity also varies according to the season. June (65 per cent relative

humidity) is the least humid month and November (80 per cent relative humidity), the most.

Table No: 23 - The mean monthly temperature, rainfall and humidity of MadrasFor 1987 figures for a typical year.

S.No. Month Temperature in º C Rainfall in mm Humidity in %1 January 24.8 28 772 February 26.1 7 743 March 28.2 9 734 April 30.4 17 735 May 31.9 45 656 June 31.9 51 607 July 30.4 97 638 August 29.9 123 68


Chennai River Basin

9 September 29.4 120 7210 October 28.1 285 7911 November 26.1 343 8112 December 24.9 135 80

(Source: Murugan el al, 1993).

Rainfall Theisen Polygon with Isohyets drawn for greater Chennai vides Plat No: 18.

4.4 Geology Geologically, the site of Chennai is of recent origin. Formally, the entire area formed

part of a shallow sea. The elevation generally ranges up to 30 m in the west, starting from the

sea level in the east. Four 'cycles of erosion' in this area have given rise to a complex

assemblage of fluvial, estuarine and marine deposits. Geomorphic evolution and morpho-

structural analyses cited by Subrarnanian (1974) suggest that geotectonic activity during the

Quaternary Period had resulted in marine regression and large-scale, changes in the migration

of river courses. The Quaternary deposits are the only lithological-units and are to be found

over most of the area. Black and gray clays and sandy clays full of marine shells can be seen.

The fact that these shells are all of species now found living in the Arabian Sea prove

the recent age of these beds. The Quaternary deposits consist of boulder beds, laterites and

alluvium deposits. Generally in hard rock domains, higher weightages are given to the

geomorphic units, Lineament density, and thickness of weathered and jointed zone and soil

characteristics. In the sedimentary formation geology and soil characteristics are given higher

weightage. In general the runoff during monsoonal seasons are said to be on the higher side

within Chennai City limit of 173 square kilometer area as compared to the rest of the urban

agglomeration. The built up area has occupies more than 70 to 80 % of the net area available

for building construction apart from the common passages and major city roads. Mostly all

the roads were paved fully and even the rest of it was fully covered leaving no space for

direct percolation.

Table No: 24 - The geological formation encountered in the Chennai Metropolitan Area along with their groundwater conditions.

S.No Group System LithologyAquifer

Characteristics

1. Quaternary Recent –Sub-recent

Soils, coastal /river Alluvium (sand & silt), Black Clay

Moderate to good porous aquifer system

2. TertiaryCuddalore S.St (Eocene to Pliocene)

Sandstone & and shale Moderately porous Aquifer.


Chennai River Basin

3. MesozoicUpper Gondwana (Sriperumbudur Beds)

Sandstone and siltstone; Grey shale; Black shale.

Less Porous aquifer.

4. Azoic ArchaeanCharnockites, Granites, Gneisses. Fractured Aquifer.

The hydrogeological setup of Chennai Metropolitan Area and the sub surface

formations are classified into six different aquifer zones

A Coastal Alluvium followed by crystalline rock.

B. Alluvium followed by Tertiary S.St and Crystalline rock.

C. Alluvium followed by Tertiary S.St, Gondwana Clay and Hard Silt Stone.

D. Alluvium followed by Gondwana Clay, Clay stone and Silt Stone.

A. River Alluvium followed by crystalline rock.

B. Crystalline rock with thin Top Soil Cover.

The Geological Map of Greater Chennai showing the locations of observation wells were

drawn and appended vide Plate No: 19.

For hydrogeological aspects the Greater Chennai are categories as follows.Groundwater Aquifer Zones in Chennai City and its Surroundings A Coastal Alluvium followed by crystalline rock.

A thick coastal alluvium of sands and clays followed by crystalline rock, encountered

around the entire Coastal Stretch of 5 km from east, from Royapuram in the North to

Duraipakkam in the South.

B. Alluvium followed by Tertiary S.St and Crystalline rock.

A thin coastal alluvium followed by Tertiary & Crystalline formation, encountered

around Thiruvottiuyur west, Royapuram, Vysarpadi, Erukkanchery, Georgetown,

Park town, Sow carpet, Chindadripet, Mint, T.Nagar, Nungambakkam Vepery,

Kilpauk, Theynampet, Nandanam, Gopalapuram, Royapettah, Thousand lights.

C. Alluvium followed by Tertiary S.St, Gondwana Clay and Hard Silt Stone.

A thin River alluvium followed by Tertiary & Gondwana formation, encountered

around Paady, Sembium, Madavaram, East and West Annanagar, Choolaimedu,

Shenoy Nagar, Arumbakkam, Perambur, Purasaiwakkam, Ayanavaram, ICF Colony,

Villivakkam, Madavaram, Avadi, and around Northwest.

D. Alluvium followed by Gondwana Clay, Clay stone and Silt Stone.

A thin River alluvial mostly clay with sand lenses at the top followed by Gondwana

claystone or siltstone, encountered around Koimbedu, Westmambalam,


Chennai River Basin

Kodampakkam, Vadapalani, Ashoknagar, K.K. Nagar, Saligramam, Alwarthirunagar,

Virugampakkam, Valasaravakkam, Porur, Poonamalle and upto Thirumzhisai.

E. River Alluvium followed by crystalline rock.

A thin River Alluvium followed by crystalline rock, encountered around West

Saidapet, Saidapet, Nandampakkampart of Ramapuram, Mogaliwakkam,

Chinnamalai, Kotturpuram, Kottur Garden, Kottur, etc.

G. Crystalline rock with thin topsoil cover.

A thin top soil cover followed by crystalline rock Archaean formations were

encountered around St. Thomas Mount, Guindy, Alandur, Ramapuram, Chrompet,

Meenampakkam, Pallavaram, Tambaram, Selaiyur, Rajakeelpakkam, Ullagaram,

Medawakkam, Keelkattalai, Madipakkam, Puzhuthiwakkam, Adambakkam,

Taramani, Velachery, Pallikaranai, Nanganallur, Tambaram, Rajakilpakkam,

Mambakkam, Perungalathur, Vandalur and upto Kelambakkam road.

Source: Data collected from Chennai Rig Owners Association, various drilling agenciesand from CGWB., PWD (GW)., CMWWSSB and other departments. Map showing the Hydrogeological Zone with recharge areas enclosed in Plate No: 22 A. 4.5 Landuse

In this basin where Chennai Metropolitan City occupies most of the areas, the

pressure for land is mainly from all sectors like housing, industries and only very few

occupies for irrigation, which slowly vanishes once for all within peripherals of the city limit.

The geographical area of the Greater Chennai Metropolitan Limit is 1,13,400 ha. The

classifications of the land of this Chennai Metropolitan Area are grouped and are as follows.

Even though before conversion of these parts of land into urban development, there are many

areas were put under the intensively irrigated area, the sparsely irrigated area, land covered

under water bodies, wasteland, forest cover, thorny bushes and scrubs, area already occupied

by urban development, temple land, small ponds, river, channels, highway, major district and

town roads, playgrounds, industrial area and etc. But now the Chennai Metropolitan

Development Authority has classified these parts of Chennai Metropolitan Area during 1996.

The Proposed Landuse Map – Master Plan 2011 - Draft, prepared by and issued by

Member Secretary, Chennai Metropolitan Development Authority vide. M.M.D.A. Drawing

No: M.P. No: 4/95 dated 24th June 1996 has classified and categories the entire land as

follows. The map showing these boundaries of listed classification were shown in the map

enclosed for reference and guidance, which will be a self-explanatory. No separate notes

required for this. Area specified for: Commercial, Hazardous Industries, Hilly Area,


Chennai River Basin

Institutional, Open Area, Residential, Non-Urbanisatioonal, Urbanisatioonal, Industrial /

Industrial Special, Open Space & recreational, Cantonment, Forest, Vandalur Area, Guindy

Park Area and Water Bodies. Leaving these specified areas, this map also shows the existing

and proposed National and State Highway, ring roads, city interconnecting roads, Railway

Track, important locations and etc. Vide Plate No: 19 & the present land use Plate No: 20.

4.6 Surface water resourcesChennai City and its suburban areas are supplied by four major waterways, together

supplying 250 MLD of water 200 MLD is a more conservative estimate working out to a

meager 50 litre per capita per day (lpcd), all transported from the Chennai Basin only.

Table No: 25 – Major Rivers flows into Greater Chennai Area & Chennai Basin

S.No. River Length in km. Sub Basin Area in Sq. Km.1 Araniyar 66.4 7632 Kosathalayar 110.0 32403 Cooum 66.50 6824 Adayar 42.0 857

Source: River Basin Study of Chennai Basin Group – Annual Abstract, Institute for Water Studies, Tharamani, Chennai 600113, Report Nos.: 3/95 – May 1995.

The surface run-off from the Kosathalayar, Nagari and Nandhi rivers, as also a

recently cut diversion of the Araniyar constitutes the major portion of the surface water

supply. In most years, these rivers flow only during the Northeast monsoon period and this

surface water is stored in the three reservoirs at Sholavaram, Red Hills and Poondi. The main

contribution of the Southwest monsoon, which is less dominant in Chennai, is to raise the

groundwater level. Collectively, they have a total capacity of 180 Mm³. Table No: 26 - The capacities of these reservoirs are shown below.

Surface water Storage SystemReservoir Capacity in million cubic metres Catchment Area in Sq. Km.

Poondi 77.20 1968.4Sholavaram 22.97 2850Red Hills 80.65 59.57

Source: Murugan et al, 1993:6

The three reservoirs are located approximately 20-50 km to the northwest of the city.

From Poondi, water is carried to Sholavaram lank through a lined canal up to

Tamaraipakkam, and then through the unlined upper supply channel. From Sholavaram the

water is conveyed to the Red Hills reservoir through the lower supply channel. During floods,

water from Poondi reservoir flows through the Kosathalayar River into the Tamaraipakkam

anicut, where a portion of water is diverted to Sholavaram through the upper supply channel.

The Red Hills is the terminal tank for the surplus water in the system. Another surface water


Chennai River Basin

source in the Madras Basin is Chembarambakkam reservoir, an irrigation reservoir with a

storage capacity of 88 Mm³, located 26 km southwest of the city. The main crop in the area is

rice. Sugarcane, banana, betel leaves and groundnuts are also grown in some places.

Due to urbanisation and industrialization, the area of the croplands has been reduced,

and as a consequence the irrigation water requirements too have been decreasing

significantly. During the non-monsoon period, the reservoir levels fall as the stored water is

drawn to supply drinking water to the city. The reliable yield of the existing surface sources,

excluding the Arani diversion based on the inflows in a 20-year period from 1969 to 1988, is

only 148 mld (vide. UNDP project IND/86/011). In practice, the draw-off from the reservoirs

has been more than the estimated reliable yield in some years, but less in others. Drawing

more than the reliable yield when water is apparently available reduces the carry over storage

for the following year. If the monsoon rainfall is also below average that year, there may not

be enough water in storage at the start of the year to maintain the supply at full draw-off until

one more monsoon. For instance, on January 1, 1993 the total storage of the Red Hills,

Sholavaram and Poondi reservoirs was only 48 Mm³ while the storage capacity is 180³ Mm.

The storage level at the beginning of 1992 was near this maximum capacity (178

Mm3). The following gives the actual storage of Red Hills, Sholavaram and Poondi

reservoirs from 1978 to 1993. Storage position of the four major reservoirs earmarked

for city water supply scheme from 1945 to till date is furnished vide Statement no: IX.

Table No: 27 – Storage Position since 1978 to 1993.

Observed Storage in Different Years.Year Storage (Mm³) Year Storage (Mm³)1978 177 1986 1521979 169 1987 421980 178 1988 641981 106 1989 721982 103 1990 621983 35 1991 1091984 85 1992 1781985 104 1993 48

Source: 'Alternate Day water supply' The Hindu. Jan. 2, 1993.

Due to shortages, alternate day water supply was resorted to in 1983, from February

to September and then also in January 1994. In July 1993, the Sholavaram and Poondi

reservoirs recorded 'dead storage', when there was in fact no surface water within these two

reservoirs. During these periods of rationing only 227 MLD was provided on alternate days

or only 113.5 MLD/day. This was significantly lower than the normal daily supply of 212


Chennai River Basin

MLD. The storage of these three reservoirs was totally dry as on date, even though alternate

days water supply restored since two years. Now there is no water supply through pipelines

from 2001 – three years. Water is being supplied through tankers to an amount of 205 MLD.

As population grew the city population has reached close to a million, nearly double

the size at the turn of the century - an additional reservoir was constructed at Poondi across

the Kosathalayar. Raising the total surface storage capacity from 100 million cubic meters to

180 million cubic meters- there was no addition to the storage subsequently. The progressive

reduction in the use of eri waters for irrigation must however have meant some increase in the

supplies available to the city. The amount of surface water effectively available to the city

population was, remains, considerably less than the storage capacity of the reservoirs. Apart

from the fact that actual storage, being a function of rainfall in their catchments, is variable

from year lo year and even within a year, an estimated 35 to 43 % of stored water is lost due

to evaporation and seepages from the reservoir. Substantial amount is also lost due to seepage

through the tank bed and in channels linking the three storages. The precise magnitude was

unable to be estimated correctly.

A further constraint is imposed by the volume which the water works is equipped to

handle for distribution. The handling capacity of the system has progressively increased. By

1951 it had reached 190 mlpd and the 'safe yield' for distribution to 200 rnlpd. It remained at

that level through the next two and half decades. It was only in 1995 the capacity of the water

works was increased to 300 mlpd to enable it to handle the additional supplies expected from

the Teluguganga project. In general during most of the years only half of its quantity only

available.

On the basis of statistical analysis of data over a 35 -year period, the supply likely to

be available in 8 out of 10 years is estimated at 162 mlpd. The inter year variability in storage

and supplies shows that capacity of 1.25 bcft in January - 1983 to 6.7 bcft in 1999; and the

minimum level during the year (which occurs in different months each year) ranging between

ZERO in 1987 and 3.4 bcft in 1996. The mean storage level ranged between 0.8-bcft inl983

to 4.4-bcft in l995. Maximum storage and mean storage are strongly and positively

correlated.

The correlation between storage and volume delivered, though positive, is not as more

effective, due to so many losses. The average daily supplies from surface sources ranged

from 140 mlpd in 1987 to 400 mlpd in 1999. The ratio of supplies to storage also shows a

tendency to be higher when the level of storage is high but the relation is not tight. The data

on Daily Water Supply Distribution to Chennai City and its environments and the combined


Chennai River Basin

monthly storage capacity of all reservoirs during a period of 30 years, shows that there is an

average supply of 150 to 160 mlpd was achieved and commissioned since then. Very rarely

the daily water supply has touches a peak high of more than 400 mlpd (during 1999).

Due to prevailing unprecedented severe drought and continuous failure of monsoon

since three consecutive years the City Water Supply Scheme has had enough changes in the

public distribution of water supply domain. Initially for sometime it was introduced alternate

days of water supply by reducing the quota for each dwellings through pipe lines was,

subsequently that too, was dispensed with.

Installation of individual water tanks in each and every locality were provided, and

then water supplies were made through water tankers at regular intervals of time. Here, the

question of supplying water at the specified rate is not possible and cannot be accountable

except how much quantity was transported within the Chennai City every day to cater the

minimum need.

The city water supply demand / supply from the year1901 to 2001 and the

projected demand upto 2021 are furnished below.

Table No: 28 - Madras City - Decadal population growth, Water demand,Water availability and allocation

S.No. Year PopulationIn million

Water demand In mld

Water Availability

Water Supplied City Supply

City Ind. Tot. City Ind. Tot.1 1901 0.54 110 110 110 2032 1921 0.56 110 110 110 2003 1931 0.58 110 110 110 1894 1941 0.74 110 110 110 1555 1944 0.86 110 110 110 1286 1951 1.42 200 200 200 1417 1961 1.73 200 200 200 1158 1971 2.47 200 200 200 819 1981 3.28 * 293 240 53 293 73

10 1991 4.034 ** 348 275 73 348 6811 2001 4.977 801 170 971 *** 805 535 140 675 10712 2011 6.046 997 330 1327 805 535 140 675 8813 2021 7.000 1217 330 1547 **** 1367 770 300 1070 110

Source: International Symposium on Strides in Civil Engineering 1993. (“Reuse of Wastewater” by S.Nambi Ayyadurai); *, **, ***, **** Water availability inclusive of surface water and groundwater, resources from Teluganga and other urbanized means.


Chennai River Basin

The table shows that the demand / supply was not achieved till date. Subsequently,

since 2001 onwards, due to failure of monsoons and prevailing drought conditions through

out the state, the water supply through pipeline disrupted and supply was made through only

tankers. Here the supply of water through tankers mostly constitutes groundwater pumped out

from wells and tubewells located all around Chennai city and also surface water obtained at

our border through Teluganga Scheme on very few occasions.

Apart from the normal pressure developed through failure of normal monsoon affects

the regular water supply to the Chennai City, the pressure developed through other means

like increasing of houses and multistory apartments which is unaccountable and in multifold,

when compared to the resources availability, the public distribution system gets paralysed.

Also in many places the groundwater becoming saline due to lowering of water levels below

mean sea level, resulted for seawater incursion. In certain places due to local pollution, the

present groundwater gets contaminated, resulted for expecting government machineries to

meet their demand. Moreover, till the nineteen seventies, the city's public supply system

depended exclusively on surface water.

With capacity remaining constant, and population increasing, per capita availability

from the system fell from 140 lpcd in 1951 to 80 lpcd in 1971. At the same time the public

system was under pressure to extend the distribution system to areas with poor access or no

access at all to the public water supply. Meanwhile to meet the local requirement TWAD

Board, through their Rural water Supply Schemes, drilled many number of borewells in the

outskirts and installed both power pumps and hand pumps of India Mark II to meet the local

demand then and there to minimise the pressure in supplying water through tankers. This led

to the installation of public taps; installation of bore wells fitted with hand pumps and large

sized tanks to store metro water in the poorly served areas.

All of which must have helped to ensure more equitable distribution of dwindling per

capita availability particularly in times of scarcity. The resulting squeeze on the supply must

have been borne more by areas and population segments which benefited from relatively

abundant supplies in the past This squeeze is reflected in lowered pressure in the distribution

network, smaller and more irregular supplies from the public system. This prompted the

government, through Metro water, to take a series of steps to arrest this trend and in course of

time, increase the per capita supply through the public system to a growing population. The

Government at the first instance as a war footing steps, quicken the implementation of the

New Veeranam Scheme and commissioned the scheme after laying the 228 km pipe lines

from Veeranam Lake to Chennai City upto Chembarambakkam.


Chennai River Basin

Since unfortunately there was no enough storage in the Veeranam Lake, as a war

footing, Tamilnadu Water Supply and Drainage Board have drilled nearly 45 deep borewells

in the Neyveli – Panruti Cuddalore Sandstone – Tertiary aquifers and pumped out the

groundwater from these borewells through the Veeranam pipelines to the Chennai city. The

timely laying of pipe lines anticipating the monsoon will vigorous and incase if Veeranam

gets adequate resources, it can be pumped out to Chennai. Even though there was no

expected monsoonal rains arrives, however by drilling deep borewells, through the timely

completion of laying of pipe lines, these groundwater’s has allows to flow through the new

Veeranam pipe lines. This groundwater reaches Chennai at Chembarambakkam point and

filled through tankers and meet out the demand to a considerable extent. This itself has

achieved a target of around 80 million liters per day, vide. Hindu during July & September

2004. Presently since the Veeranam Lake through the abundant rainfall in the catchment

areas overflows, around 180 million litres of water per day is being pumped through these

pipelines to the city drinking water need. In the meanwhile the Government take a series of

steps to meet the demand through different strategies.

They are (1) augmenting supplies from surface sources; (2) increased exploitation of

groundwater, (3) measures to augment ground water recharge and (4) measures to check

over exploitation of groundwater. A number of schemes to de-silt the three storages were

taken up during the 1980s; Water rights of farmers with irrigation rights to water from the

Eris were purchased. In 1993 and 1999, some water from Chembarambakkam was diverted to

meet the city's needs. By 2001 expected supply from local surface sources is placed at around

247 mlpd. Government has speed up of bring waters from Veeranam lake, some 228 km to

the south of the city through a pipeline was sanctioned, commissioned and completed under

war footing as mentioned earlier.

The concept of Teluganga Project if materialized fully, it will be a great boon to

Chennai, not only to Chennai City people and its suburban, to a certain extent industrial and

irrigation demand can also be meetedout. After protracted negotiations, an agreement was

reached in 1976 whereby the three riparian states Andhra Pradesh, Maharashtra and

Karnataka, the riparian states of Krishna river, agreed to the diversion of 12 TMC to Chennai

with the Tamilnadu government bearing the costs of the works involved.

In the event, continuing controversies over the claims of Rayalaseema farmers to

irrigation water from the proposed canal delayed the implementation of the project. The first

stage, commissioned in 1996, was expected to bring 5 bcft (equivalent to 380 mlpd) from the

Srisailam reservoir cross the Krishna through the Somaseelam reservoir on the Pennar and


Chennai River Basin

subsequently through an open channel to Poondi, Special canals have been constructed to

carry TG water to the three city storages and to increase the storage capacity of these

reservoirs by about 35 mcm (20 mcm in Poondi and 15 mcm in Red hills). The capacity of

the city water works were already increased to store these supplies anticipated through

Teluganga Project.

Two new reservoirs at Ramancheri and Thirukkandalam with a capacity of 61.5 mcm

are to be constructed. The second stage is expected to give and extra 7 bcft at zero point by

2011. The water is to be drawn during July-October and January -April during which storage

levels in the city reservoirs are low. TG waters began to arrive in 1996; 2.8 bcft were

received in 1997 and 1998; 1.8 bcft in 1999 and 6.5 bcft during September 2000 and May

2001. The increase in the supply due to TG in the city storages will however be considerably

less than receipts at zero point because of seepage in channels and other losses en route. It is

estimated that 5 bcft at zero point will add 1.5 bcft in the reservoirs. The Surface water

Resources available combining all these resources were around 1113 MCM. All these total

assessed Surface Water Potential itself is a big question.

Normally all assessment were done based on certain observed secondary level data

with the scientific coefficients. These scientific coefficients will hold good under certain

hydrological, hydrogeological and hydrometeriological conditions only. The methodology

adopted has to be refined according to the prevailing hydrological, hydrogeological and

hydrometeriological conditions. Then only water budgeting can be done properly.

Hence the assessment of Surface Water Potential through the 75 % of Rainfall

Dependability in the 174 square kilometer area, and the whole of the Chennai Metropolitan

Area of 1,166 square kilometer, has to be refined. The total Surface Water Potential assessed

through 75 % rainfall dependability of the Chennai Basin covering an area of about 5542

square kilometer is 784 MCM. Out of this the Chennai Metropolitan Area occupies 1,166

square kilometer, which alone has to contribute around 165 MCM, which has to be corrected.

This will affect the Water Planner to do Water Budgeting based upon these figures.

4.7 Ground water resources

It is this inadequate availability of fresh water from surface sources, caused by

inconsistent rainfall patterns, indifference to maintaining low-capacity reservoirs such as

tanks and the undependable estimation of population-growths in the city that has focussed the

attention on other sources of fresh water in recent years. If one involved the diversion from

other surface sources as in the Telugu-Ganga and Veeranam projects, another related to

extraction of ground water, replenished through seepage with every downpour though not in


Chennai River Basin

quantities adequate enough to meet the demands, and not to the full possible extent of

exploitation.

Traditional dug wells and borewells on the domestic household front have been

numerically strengthened with the digging of many more on the dried-up riverbeds.

Elsewhere too, where ground water reserves are found to be plentiful, there too wells have

been dug up along the aquifers. Only, in recent years, the over- exploitation of ground water

in both sites, and also inadequate replenishments, have taken the water table far below the

traditional well-digging mechanism. Deep borewells are sunk in these places to extract

ground water.

All this also involves property rights over ground water, which, mainly for the benefit

of private tanker operators, has been codified as law. The ground water system, an

underground lake or stream that also incidentally contributes to the overland flow through

seepage into channels, is determined by a number of factors. Precipitation is obviously of

central importance. However, the degree of infiltration is greatly influenced by the

permeability of soil and parent material, which increases the groundwater storage.In 1978 a separate governmental agency was formed to look after the water supply and sewerage

system of Madras city. The Madras Metropolitan Water Supply and Sewerage Board (MMWSSB) or Metro

water for short, was set up by the Tamil Nadu Government under a separate legislation (Act No.28 of 1978),

thus taking over the well-fields system of the Public Works Department (PWD) and also the ground water

system. This system comprises wells at Tamaraipakkam, Panjetty and Minjur, with a designed yield of 90 Mm³.

Originally, 83.5 Mm³ of this yield was designated for local industries in North Madras. A provision was made

for the diversion of the waters to the city supply schemes, but only in an emergency. But thanks to the ever-

increasing demand of the city, this diversion has become a permanent augmentation feature, thus curtailing

water supply to the industry district in the North Madras region. This favour in respect of the domestic

consumer has been clearly illustrated in times of acute shortage as in 1983, when some industries were asked to

close down temporarily to satisfy the drinking water needs of the city population. In addition to these three well

fields, other well sites were added more recently. Viz Poondi and Kannigaipair, certain wells located at

Injambakkam, Palawakkam etc were too linked with.

Table No: 29 - Capacity of ground water Various sourcesName of Source Designed Yield (Mld)

Tamaraipakkam 29.25Panjetty 36.0Minjur 24.75Poondi 27.0Floodplains 13.5Kannigaipair 13.5South Madras Aquifer 6.8Total 150.80


Chennai River Basin

Note: The reader should note that the figure of 150 MLD is the total capacity. An alternative study by Selvakumar 1993) gives a mine conservative 123.1 MLD which can safely be the yield from these ground water sources. Adapted from Somasundaram et.al.1993.

Table No: 30 - Safe Yield from difference Source (Groundwater & Surface Water)

S.No. Source Safe Yield1 Poondi, Red hills and Sholavaram (surface water) 200 MLD2 Araniyar – Kosathalayar well Fields 151 MLD`3 Southern Aquifers 10 MLD4 Wells in Urur, Thiruvanmiyur, Porur and Kattupakkum 20 MLD5 Municipal wells within city 5 MLD6 Tubewells and Hand Pumps 50 MLD

Total 435 MLD

Source: Master plan for Madras Metropolitan Area – 2011, draft report prepared by the Chennai Metropolitan Development Authority, July 1995. (A.M.M. Report)

Even though most of these groundwater Resources are lying outside the limit of

Greater Chennai Metropolitan Area, these resources were in one way or other transported

through network to meet the drinking water demand of the Chennai City only. Ground water

sources were thus exploited during 1983-86, based on an United Nations Development

Programme (UNDP) study, Poondi (27 MLD), Floodplains (13.5 MLD) and Kannigaipair

(13.5 MLD) well-fields, among others, with World Bank Funding. A total of 68 wells in

these areas are designed to yield 54 MLD. The southern Thiruvanmiyur-Covelong aquifer,

developed by the Government owned Tamil Nadu Water Supply and Drainage Board

(TWAD) and taken over by Metro Water, yields 6.8 MLD. Another 27 MLD of water is

drawn from the Southern Aquifer, which lies along the coast to the south of the Adyar River.

However, the latter generally supplies water to areas within the metropolitan area. In

addition, water is also drawn from household wells within the city, largely by India Mark II

hand-pumps, shallow tube-wells and pumps, all accounting for 50 MLD. The UNDP studies

show that the contribution of ground water to the reliable yield is appreciably less than the

installed pumping capacity.

Thus while the estimate totals 151 MLD, only 60-80 per cent reliability can be

achieved. This is because, after several years of low recharge, water levels depleted

considerably, leading to reduce outputs. In addition, water levels have gone down below-the-

suction level of the pumps in some well fields. Likewise, poor yield in wells due to

fluctuations in water level; down-time caused by the too frequent failure of pumping units,

power failure and transmission losses, also account for the lower reliability level of ground

water sources. It should be noted, however that local farmer pumps far more from the Araniar


Chennai River Basin

Kosathalayar aquifer than Metro Water. Schemes are underway to improve the ground water

levels in the well fields area. Five check-dams across the river Kosathalayar are constructed

to impound floodwaters during monsoon periods, which otherwise passes into the sea. These

check dams are confined to the areas of the middle four well fields Tamaraipakkam,

Floodplains, Kannigaipair, and Panjetty. There are doubts that the impounding of water

through these check-dams may restrict ground water flow towards Minjur Well-fields, which

is also in the same Kosathalayar basin. If this is proved true, this may result in a lowering of

the water level at Minjur well-field, thus inviting further seawater intrusion. The combined

effect has been a steady fall in the level of the city's ground water table. The situation has

been worsened still by continued road development and paving concrete over the side ways

inside apartment considerably reduced the seepage of surface water during rains accelerating

the rate of runoff to the sea, thus exacerbating the water shortage.

4.8 Hydrogeology

The top river alluvium of the main river of Kosathalayar plays an important role

followed by Tertiary sandstone was the vital aquifer zone of Kosathayar basin. These aquifer

zones comprises of thick top river alluvial sand with clay loams between 60’ to 70’ below

ground level with a thick sands, clays and friable medium to coarse grained sandstone

encountered between 70’ to 130 / 150’ below ground level. In northwestern and western part

Gondwana siltstone / claystone / yellowish clay / black clay or grit as a contact zone.

In the center part of the Greater Chennai Metropolitan Area, around Cooum and

Adyar river area certain alluvial bed were noticed and groundwater aquifer zones fetch some

good quality of groundwater. Now due to unpredicted rainfall and over drawal of

groundwater these alluvial aquifers are totally dry and from it there is no copious amount of

groundwater available for extraction. Moreover the areas around coastal belt viz. Triplicane,

Mylapore, Adayar, Thiruvanmiyur and Beasant Nagar, due to over drawal of groundwater,

the groundwater quality became saline unsuitable for drinking purposes. The recharge and

storage of water underneath the surface are due to the rainfall and the hydrogeological

conditions such as aquifer, flow, discharge and existence occur due the existence of these

three rivers only.

Mainly these aquifer zones were concentrated and flanked by three rivers of

Kosathalayar, Cooum and Adyar having different aquifer thickness varies from ground level

to 130’ below ground level. These aquifers around Karnodai Bridge, Red hills, Perambur,

Royapuram, Thiruvottiuyur, Kilpauk water works, Kelly’s, Vepery Purasawakkam, etc had

moderate groundwater aquifer zones. The water level has gone down below 40’ to 70’ these


Chennai River Basin

zones were not yielding heavily nowadays. Due to continuous extraction of groundwater by

indiscriminate sinking of wells and borewells seawater incursion occur around areas near

Triplicane, Mylapore, Santhome, Adyar, Beasant Nagar and Thiruvanmiyur. These shallow

aquifer zones were encountered between 40’ to 70’ in the north, northeastern, eastern and

southeastern region especially near the riverbed and its environment.

The alluvium, parting more recharges of groundwater than Tertiary Sandstone or rock

environs. The recharge and storage of water underneath the surface are due to the rainfall and

the hydrogeological conditions. From the hydrogeological point of view, it constitutes a very

good water bearing zones. Its deposits consists of top reddish / reddish brown sandy soil, /

sandy clay, gravelly soil, boulder bed of unconformity formation, kankar, highly weathered,

weathered, fractured, jointed and highly sheared zones, whose thickness varies from 40' to

200’ (12m to 60 m) below ground level.

There are many number of drinking water borewells drilled by Metro water Agency,

and borewells drilled by private agencies around Palawakkam, Duraipakkam and

Injambakkam meet the drinking water requirement of certain pockets. Now as on date the

yield from these borewells reduced and not even sufficient to cater the local requirement.

The depth of these borewells varies from 40’ to 120’ below ground level and the yield varies

from 40 to 700 litres per minute.

Present day, the number of tubewells drilled by every individual house owner and flat

owners, for all purposes may workout around 58,000 to 70,000 in the entire coastal Alluvial

zone only. (Based on A Registers maintained by Revenue department, since some of the

shallow borewells were abandoned or said to be dry or not functioning due inadequate water).

Other than these tubewells there are many number of shallow tubewells spread over south of

Adyar, where a thin river alluvium followed by crystalline rock met with. River alluvium

followed by Gondwana Sandstone encountered, in the areas around Anna Nagar, Vadapalani,

Porur, Valasarawakkam, Poonamallee, etc. Though these aquifers were not so much

potential as compared to the alluvial terrain of Araniar and Kosathalayar, many number of

wells and borewells spread over, were yielding between 20 to 50 litres per minute. Mostly

these borewells were shallow ranging between 100’ to 200’ below ground level.

This is not the case as on date since most of these borewells were over exploited leads

to drying up of most of the borewells. Even though it constitutes thousands and thousands of

wells and borewells housed not less than one or two for every individual house, the yield is

very much limited due to lack of proper recharge factor. Mostly city areas are either occupied

by constructed buildings or by road or by concrete paved areas. Hence there is no enough


Chennai River Basin

space to allow the rainwater percolate into the ground. Only the baseflow water through other

means being extracted till now and gradually gets reduced. Now the entire dynamic

groundwater reserve are fully evacuated and as on date wells and borewells yield, are being

tapped from the static reserve. This is the reason that, even though normal monsoonal rains

occurs, there is no sufficient raise in groundwater levels noticed. As such mining of

groundwater took place within the Chennai Metropolitan City.

Except in one or two areas, in rest of the areas, groundwater levels never retain the

original position. Infact every year there is a decline in water level at the rate of 1.6 to 2.5 m

per annum. This is resulted for lowering of water levels beyond 6 to 18 m below ground level

even during monsoonal season. Similarly in Gondwana region, viz in areas around Anna

Nagar, Koyembedu, Mogapair, etc it is still worst, like even during monsoonal season the

recuperation took more than 24 to 48 hours duration.

Refer the water level contour map generated through the observations made

during September 2004 and for six years from January 1998 to December 2003. Vide

Plate Nos: 13, 14 and 22.

As we comes to hard rock terrain, which occupies the rest of the areas, the highly

fractured and jointed formations with good amount of groundwater flow encountered were

very few only. In general these shallow and deep borewells were yielding between 20 to 200

litres per minute during since 1990 and due to indiscriminate sinking of deep borewells at

very closer intervals, which is the only water sources to meet the water demand for the fast

growing apartment cultures within Chennai city since for the past 10 years, the yield from

these borewells were very well reduced to 10 to 50 litres per minute and also in most of the

areas, continuous pumping is not possible. Nowadays, in the Chennai city areas, most of

these borewells were fitted with compressor motor by removing the submersible pump and

jet pumps. These compressor motors were very well suits for shallow and deep borewells,

for continuous pumping, even though there is no sufficient recuperation-taking place.

Nearly 50 to 60 % of the existing borewells there is no water or extracting water less

than 500 to 700 litres in a day. In most of the borewells, the hard crystalline basement

encountered within 110’ to 150’ below ground level and in that area, the water level also goes

below 40’to 50’ below ground level. In certain areas, where the fractures and joints

encountered between 45’ to 150’ / 200’, borewells are prominent with yield ranges between

30 to 70 liters per minute for a continuous pumping of more than 4 to 6 hours duration. Based

upon the drilling data obtained from various rig operators, as on date daily by deploying

around 50 to 70 rigs available at Chennai (both owned rig and hired rig from Salem and


Chennai River Basin

Namakkal area) around 100 borewells are being drilled within Chennai Metropolitan Area to

a depth varying from 130’ to 250’ bgl. Very rarely people go beyond 300’ bgl.

Among these drilled borewells 50 % of it were said to be totally dry and there is not

even traces of water bearing zones. In 25 % of the borewells, by installing compressor pump,

one borewell can yield between 400 to 1000 litres of groundwater in a day throughout. In 20

% of the borewells by installing compressor motor, they can extract around 2000 to 4000

litres of groundwater in a day. Only 5 % of the borewells drilled can extract around 4000 to

7000 litres of groundwater, rarely upto 10,000 litres for jet pump. This is the present

condition. In very few locations, where the fractures and joints encountered beyond 200’ to

300’, deep borewells are located but however the groundwater yield are only 40 to 60 liters /

minute for only 5 to 6 hours / day of pumping.

The average depth of the open dug well varies from 30’ to 50’ below ground level and

the borewell varies from 10’ to 300’ below ground level. In certain areas deep borewells

were drilled and depth were ranges from varies from 200’ to 400’ below ground level, but

there is no appreciable yield noticed from these borewells. The detailed Hydrogeological

mapping and based on the borewells drilled by various agencies, it is ascertained that there is

no good potential aquifer zone beyond 300’ below ground level. Hence drilling of borewells

beyond these depths will be mere waste. It is nothing but increasing the storage and cannot

able to increase the yield or recuperation.

The saturated zone generally below 300’ is very rare and mostly they are not yielding

copious amount of groundwater, except one or two yielding borewells. The winter water level

varies from ground level to 10’ to 20’ in the borewells located in the sedimentary terrain and

from ground level to 15’ below ground level in the borewells located in the hard crystalline

terrain. The recuperation time varies from 4 to 8 hours for normal years. It is slightly vary

during below normal rainfall years and drought years. The summer water level varies from

20’ to 40’ below ground level and the recuperation time varies from 12 to 24 hours in

sedimentary terrain. Sometimes it goes beyond 36 to 48 hours during below normal rainfall

years and during drought years. In one or two borewells the water level goes below 45’ to 80’

below ground level due to continuous large-scale extraction of groundwater.

Normally groundwater extraction is being done mainly for domestic purposes within

the Chennai city and its suburban areas except most of the wells in the area around

Kosathayar intended for irrigation purposes. In the areas around Thiruneermalai tank,

Kundrathur, Kovilambakkam, Nemmelicherry, Hasthinapuram, Chittalapakkam,

Mambakkam, Madambakkam Padappai, Manimangam, Poonthamallee, Thirumazhisai,


Chennai River Basin

Oragadam, Perungalathur, etc there are some lift irrigation practices are continued, mostly

done by open wells only. Only in the Kosathalayar River upstream near Mannur Koot road,

Avadi, and areas just south of Kosathalayar tubewell irrigation are continued.

In these areas, lift irrigations are prominent rather than surface water irrigation

practices. In very few borewells inventoried, bedrock has not been met with and those

borewells can be deepening further to increase the groundwater withdrawal. The aquifer

zones are mainly top sandy, kankar, and highly weathered, weathered, fractured and jointed

granetic gneiss / Charnockites with quartzite and feldspar intrusions. Groundwater recharge

in this area is mainly due to direct infiltration of rainfall; return flow from the nearby-

irrigated field, especially located on the western, northwestern side, northern and eastern side

between the rivers of Kosathalayar and Cooum.

Also some seepage from the rivers, canals and water bodies like tanks are helps to

increase the groundwater recharge. The elevated areas such as northwestern, western and

southwestern part of the area around, the surface runoff are more during rainy season, which

naturally drains into the investigated area both in surface and as well as in sub surface. In

certain areas covered by outcrops and surface exposures (Pallavaram, Thirusoolam,

Kundrathur and Thiruneermalai) scope of groundwater development is freak in those areas.

In general each borewell located around the peripherals of the investigated area,

located just south of Kosathalayar riverbed, can irrigate 2 to 3 acres of wet crop during

monsoon and one dry crop during non-monsoon season. In ayacut areas, (Lower River Basin

Area) either one or two wet crop such as paddy or one wet crop of banana / sugarcane whose

time requires for harvesting a minimum of 11 to 12 months, and or one wet crop with one dry

crop and or two dry crops are being irrigated mostly in this area. The seepages from the rivers

and canals workout 1.2mm / day and from tanks workout 2.2 mm / day. It also depends upon

the number of day’s water available or flow on it. The seepages from the irrigated paddy field

will be of the order of 16" per crop, around 31” from the banana or sugarcane and for dry

crop it varies from 9" to 12" per crop.

Losses due to evaporation and sub surface base flow will roughly be about 10% of the

total annual recharge. Since there is continuous vast areas put under irrigation practices,

intensive irrigations practices were not prominent except in one two pockets. Hence the

seepages from water bodies, canal, streams, river, and etc are not substantially increases the

groundwater levels. The return flow from these fields also restricted very much, which also

set another part of groundwater recharge. Similarly in the non ayacut elevated terrain certain

dry crops were irrigated using lift irrigation, there the seepages from water bodies, canal,


Chennai River Basin

streams, river and etc especially during non monsoon summer season is meager except the

return flow from the applied water which also considerably very less.

Since the average number of rainy days in a year is only 56 to 69 days, out of which

more than 40% of the rainy days, rainfall occurs between 5 to 10 mm, it has no significant

effect regarding the recharge of groundwater through rainfall precipitation, during non-

monsoonal seasons. There is no legislation in controlling the sinking of open wells or

borewells, which may be one of the reasons for the depletion of groundwater levels. Within a

span of four to five years, there is an increase of more than 35% of drilling of deep borewells

of the order of 150' to 200' bgl and installing compressor pump for continuous pumping of

groundwater to meet the domestic requirement, since there is no pipeline water supply by

Chennai Corporation which was dispensed with since two years.

Availability of water through either by corporation or by private water tankers at the

required time is very difficult, people either by any means try to get water through borewells,

which is the main cause for the increase in number of borewells within the Chennai city to

three to four fold within a span of three to four years. This is the main cause of depletion of

groundwater levels and contamination of groundwater in some of the existing borewells.

Unless proper groundwater legislation is not introduced and strictly enforced, lowering of

water levels cannot be avoided, this leads to drying up of open well and shallow borewells.

This is the main cause of occurring seawater incursion in the areas around Triplicane,

Mylapore, Santhome, Adayar, Beasant Nagar and Thiruvanmiyur. Slowly the groundwater

quality around Palawakkam, Duraipakkam and Injambakkam were also becoming saline

when compared to the groundwater of previous years. Vide groundwater level contours

and groundwater quality contour maps drawn for both Chennai Basin & Chennai

Metropolitan Areas separately.

In our state, Groundwater Extraction has been regulated by legislation and an Act was

issued which is a positive step to improve and to preserve the groundwater reserve to an

extent. However it has not been enforced strictly. In the recent years many wells, whose

depth varies from 30’ to 50’ depth and borewells varies from 100’ to 160’ bgl are drying

fastly and unused. On most of the occasions, the Compressor Pumps installed in the

borewells were running idle which consumes more quantity of electrical energy spent

unnecessarily. If this conditions continues and if there is no control of drilling of borewells,

there is every possibilities of depletion of groundwater levels and totally evacuate both

dynamic and static groundwater reserve of the aquifer system. To avoid this stage spacing

between borewells and duration of pumping has to adopt strictly. We analyse the


Chennai River Basin

groundwater levels for the recent two to three years in the areas around South of Saidapet and

upto Tambaram. In these areas there are mushroom type of development flats took place.

The available water bearing zones in the crystalline basements were only between

ground level to 30’ to 40’ depth maximum, during monsoonal rainfall periods, mostly this

thin secondary porosity aquifer zones were saturated fully within a month’s rainfall especially

during October - November itself. We have done enormous Geophysical Resistivity Survey

in these areas and drilled many number of borewells. In all these borewells the top weathered

and minor jointed zones were alone encountered and the groundwater in these zones were

very well saturated during every years annual monsoonal rainfall. The fractured and jointed

zones beyond 40’ are very much restricted. Only 10 of 100 borewells drilled, fractured and

jointed zones at deeper levels encountered, that too a maximum of 100’ to 130’ bgl.

Very rarely borewells drilled beyond 150’ were yielding more quantity of

groundwater. It is a well-known fact that there are no potential aquifer zones encountered in

these crystalline terrains beyond 300’ bgl. These groundwater potential in these top zones

were more or less sufficient to cater the needs of the population of dwellings as on date, jus

before one or two years, and due to the multifold increase in the construction of apartments in

these areas, the groundwater available from these thin aquifer zones were insufficient to meet

the entire demand every year since 2002. This is the reason since two years what ever may be

monsoonal rains receive by these wells, they are unable sustain to meet the additional

requirement throughout the years. This causes of depletion of some of the existing open wells

and borewells are dry during June – July itself, where the aquifer zones extended only upto

25’ to 35’ bgl before the onset up monsoon. If there is any unusual summer rain or early rain

during southwest monsoon receives, only during those years these wells get charged to a

certain extent and withstand till the regular monsoon commenced vigorously.

The saturated zones in those wells and borewells extend beyond 35’ to 50’ / 60’ were

alone capable of yielding some quantity of groundwater for 20 to 30 % of the houses. It is

noticed during rainy season, in most of the open wells and borewells the groundwater levels

in these open wells comes to ground level even during first spell during October – November

and subsequent rains were mere waste and goes as a runoff since there is no enough saturated

fractured and jointed encountered beyond 40’ to charged fully. That is why all the rainfalls

after November were goes as a runoff. After the rainfalls were over, since January onwards,

slowly the groundwater levels gets depleted and totally most of the wells and borewells were

dry since May – June onwards. Very rarely, in those wells and borewells fractures and joints


Chennai River Basin

developed beyond 40’ to 70’ or still beyond, that occurs only in 10 to 20 % of the wells only,

were able withstand and extract to a minimum requirement of three or four houses.

Refer observations of borewell survey conducted during April – September 2004;

vide Appendix - Statement IV enclosed. In total there are around 3.2 lakhs of wells and

borewells located within the Greater Chennai Metropolitan Limit deployed for drinking water

requirement. As there is no sufficient rain normally after January to June except 10 to 20 %

of the wells and borewells, totally the entire crystalline aquifer zones were totally dry. This is

the present scenario of present day stages of groundwater development taking place in these

regions as whole. Even though rain falls over the surface over and above the normal

monsoonal rains, there is no sufficient zone of saturation available in the secondary porosity

aquifer zones of hard crystalline terrain due to devoid of joints and fractures extend beyond

25’ to 40’ bgl. This is not the case in the other part of the Chennai Metropolitan Area.

Since the thickness of the sedimentary aquifer zones were extended and the porosity,

permeability and specific yield of these aquifer zones are more when compared to the

crystalline terrain. This is the fate of the various hydrogeological conditions encountered in

the Chennai Metropolitan Area. Even though rainwater techniques were implemented, the

type of techniques implemented in these regions was not helpful to accommodate more

quantity of rainwater during rainy season. Other special type rainwater harvesting structures

were to be introduced specifically for this region. In general Rainwater Harvesting

Techniques is a site specific and there should six types of rainwater-harvesting techniques

should be implemented covering the Chennai Metropolitan Area, which has six different

hydrogeological conditions were encountered. When we compare the groundwater levels and

groundwater quality observed from these wells located within the Chennai Metropolitan Area

during September 2004, it is known fact that the groundwater levels were still lowered during

September 2004 when compared to the groundwater levels observed during January 1998 to

December 2003. Similarly the extraction from these crystalline aquifer zones was

considerably reduced to one third of what we extracted during 1990 to 2000 periods. Keeping

this in mind the mining of groundwater from these three aquifers should be dispensed with

immediately.

Last but not the least is to solve this issue it is wise enough to go in for collection of

all sewage wastewater generated within the Chennai City, bifurcate into two distinct category

as partially polluted and fully polluted and by treating these wastewater, the treated water can

be used to meet the 50 % of the City requirement. Regarding the other ways and means to

solve these sensitive issues, this has been very well discussed in the subsequent column of


Chennai River Basin

this report. The groundwater quality in general potable and suitable for all purposes.

However some significant groundwater polluted zone has been noticed in the study area,

which has to be carefully governed. To have a detailed study regarding the geochemical

characteristics of the groundwater at various stages, water samples were collected at different

places at different depths to understand the spatio temporaral variations of groundwater and

were discussed. The present day map showing the various features viz. Administrative setup

map, rainfall Isohyets, Landuse, Geology, Hydrogeology, Groundwater levels and

groundwater quality for Chennai Metropolitan Area were drawn and appended for reference.

4.9 Surface Water and Groundwater Potential assessment.

Regarding surface water potential available as on date supplied is a transported water

from the reservoirs of Poondi, Sholavaram, Red hills and Chembarambakkam, except the

Poondi all the three reservoirs were located within the Chennai Metropolitan Area limit,

though not located within the Chennai City limit. However their catchments were located

away from the Greater Chennai Metropolitan Area.

Based on rainfall dependability of 75 %, the anticipated surface water resources

accumulated within the Chennai Metropolitan Area of 1,166 sq. km is around 165 MCM.

However the capacity of three reservoirs located within Chennai Metropolitan Limit after

being raised recently was Red Hills – 93.46 MCM, Sholavaram – 25.30 MCM and

Chembarambakkam – 103.23 MCM. These reservoirs were normally gets surface water from

their catchment areas located on the western, northwestern and southwestern sides. The

surface water accumulated from the Chennai Metropolitan limit has no direct influence

regarding the filling up of these reservoirs annually. No way these two were interrelated.

Hence the total Surface Water generated and filled within the Greater Chennai

Metropolitan Area is around 387 MCM.

Regarding groundwater point of view normal estimation of Groundwater Recharge

deployed for other watersheds based on GWREC Norms cannot be deployed since most of

the suburban areas were covered fully by constructed buildings, roads, highways, industrial

units and etc for the Chennai City Limit of 174 square kilometer area. For rest of the areas the

block wise groundwater potential estimated through GWREC Norms 1997 and projected to

as on January 2003 was taken into account with percentage of area covered within the


Chennai River Basin

Greater Chennai Area. For the Chennai City limit Normal method of monsoonal recharge

techniques cannot be used for the estimation of groundwater recharge. Moreover total

cropping area with cropping pattern, well census data etc are not available, the NABARD

Adhoc Norms introduced for non-ayacut elevated terrain, which is more or less some extent

hold good, was employed to estimate the total Groundwater Potential of this Chennai City

Limit.

To demarcate the recharge area the Greater Chennai Metropolitan Area is sub divided

into six hydrogeological zones, which was mentioned earlier. The available data on total

geographical area, water level fluctuation, monsoon and non monsoon rainfall, specific yield,

return flow from the limited ayacut and non ayacut dry land wherever occur, seepages from

water bodies for minimum number of days, etc are used for the estimation of monsoon and

non monsoonal groundwater recharge of each of the hydrogeological area.

However correct assessment regarding groundwater extraction could not be estimated

due to the non-availability of either area irrigated with all other relevant details or normally

assessed through groundwater extraction details through well census, both are not available.

Anyhow groundwater extraction was estimated roughly with the figure of well census

available from Statistical Web Site.

The rough estimated groundwater recharge might be as follows: The total area

available for groundwater recharge is 1166 sq km or 1,16,600 ha. The normal average total

annual rainfall is 1300 mm, average of three rainfall stations roughly. The block wise

groundwater potential available both separately for monsoon and non-monsoon seasons were

estimated. Regarding draft estimation correct well census details are not available however

the data available in the Statistical Department Well Census data was utilised. For water

demand for domestic purposes the methodology adopted by TWAD Board and CMWSSB

unit coefficient earmarked for rural and urban development with the density of population per

square kilometer was considered for estimation. Similar procedure regarding domestic and

industries demand for 25 years has also projected as adopted in the Chennai Basin. The

estimated overall groundwater potential available in the Greater Chennai Metropolitan Area

through the blocks covered is around 324.243 MCM per annum. The statement showing the

block wise groundwater recharge, draft, domestic and industries demand for another 25 years

the stages of development were shown vide Statement No: VI A.

Even though there is no adequate surface water storage available in the four major

reservoirs as on date, only with this available groundwater, we are able to manage and extract

some quantity of groundwater through not less than one lakh number of wells and borewells


Chennai River Basin

located in our city dwellings, which also quench our thirst to a considerable extent as on date

apart from the water supplied through water tankers.

Nowadays demand for water increased in multifold due to various reasons, which is

unaccountable. But one thing we have to appreciate and put into record, the timely action

taken by the government for the implementation of the new Veeranam Water Supply Scheme

(even though Veeranam Water does not reach, some groundwater were transported through

these pipelines laid for this purposes, serve its need), mandatory and forcing the people of

Tamilnadu to implement the Rainwater Harvesting Techniques, though not executed properly

by the public, were really enjoying some benefits through these resources, which alone

quench our thirst when we really need water for minimum requirement. Otherwise we all

citizens of Chennai City might be starved and die for water during this unprecedented

drought season.

4.10 Ground water legislation

The Groundwater Quality in the Araniyar-Kosathalayar basin is well within the

national standards for drinking purposes. However, due to continuous extraction of

groundwater nearby the coast, say within 10 km width, the groundwater quality is poor in the

Minjur area, because of saline water intrusion in the Minjur Aquifer. In the Cooum basin, a

parcel in the northwestern region also has brackish ground water. The area south of Cooum

River generally registers better quality water. Where the water has been saline or brackish,

the over-exploitation of ground water was found to be the chief cause. Following clear

evidence of sea water intrusion into the Minjur Aquifer, the Tamil Nadu Government realised

the necessity of saving the coastal aquifer and other ground water potential zones in and

around the city "The Madras Metropolitan Ground Water (Regulations) Act, 1987" was

passed, and came into force from December 15, 1988 with supporting rules and regulations,

to combat the indiscriminate withdrawal of water by local agencies, covering 305 villages

falls within the Chennai Metropolitan Area (was latter amended from 285 to 305 villages).

With the introduction of the legislation the water drawers were compelled to conform to its

provisions. This includes the provision of full details of quantities drawn and that, which was

proposed for future use.

Ultimately, surface storage should be able to supply most annual water requirements

for the city. The ground water reservoirs, generally many times large, can be retained

primarily for cyclic storage covering a series of years having abnormal precipitation. Thus,

ground water levels would be lowered during a cycle of dry years, and raised during the

ensuing rain rich period. The well fields of the Araniyar-Kosathalayar basins as well as other


Chennai River Basin

designated groundwater areas were brought under the control of Metro Water Authority. At

that time most of the wells taken over by Metro water from Tamaraipakkam, Panjetty and

Minjur fields was reserved for industries in north Madras. Much larger quantities are said to

be drawn by farmers of the area for irrigation.

Over a time an increasing proportion of this amount has been diverted for domestic

use so much so that several industrial establishments are forced to look for alternative sources

of supply - mostly private wells. It is a fact that the take-over of these well fields did not

augment total supplies but only redistributed available supplies from the private sector to the

public system. Much later, Metro water also adopted a policy of insisting on industries using

treated sewage for part of their needs.

4.11 Water Quality and Pollution

In today's situation, even fresh rainfall tends to be polluted as it drags down with it

suspended particles in the air. No water is really free of pollutants; the distinction is more a

matter of degree. In terms of pollution, the factors may be conceptualised into a number of

inter-linked categories, viz. precipitation, surface water (rivers and lakes) and ground water.

If at the instant of formation, precipitation is very pure, having its origin in the massive solar

distillation process of the hydrologic cycle, the purity of water deteriorates rapidly, as the

falling rain accumulates dissolved chemicals and particles from the atmosphere, caused by

natural phenomenon or human activities, such as industrial operations and automobile

exhausts. This also holds true of surface waters such as Streams Rivers, and Lakes. Only that

in standing waters as in lakes, reduced velocity and turbulence also allow much of the

particulate matter entering through river waters to settle, thereby lowering the quantity of

suspended solids in the lake.

Reduced turbidity and the relatively long retention times in lakes also generally

encourage the growth of iquatic organisms. One general misconception is that the ground

water is comparatively pure. While true in some cases, ground water mostly retains the

chemical content of the surface water in the area. Natural filtration through great depths of

soil –generally emoves most suspended materials, including turbidity and bacteria.

On the contrary, however, the slow movement increases opportunities for the water

ontacting and dissolving chemicals present in the soil. Ion-exchange reactions, where those in

the soil replace chemicals in the water, are an important process for consideration. This may

dramatically raise or lower the quality of the available ground water. Studies indicate that


Chennai River Basin

around 60 % of ground water in Chennai contains abnormally high levels of dissolved solids,

bacteria and or chemicals. The high concentration of Total Dissolved Solids is most probably

due to the seepage of sewerage from the waterways into the ground water. Water in some

areas is entirely unfit for drinking either because of high mineral content or due to the

presence of bacteria.

Studies also show that the ground water in Chennai has higher salinity than the ideal.

Unfortunately, in urban aquifers it is often difficult to determine the process by which this is

caused. Household waste, tannery effluent, and engineering works effluent are all sources of

Chlorine (Cl¯) and Sodium (Na +), building wastes, household water, power station waters,

and tannery effluent are also sources of calcium and sulphate ions. In a city like Chennai,

these sources invariably combine to form a complex pattern of inter-related sources; ranging

in character from the small and numerous, to the large and diffuse.

The major source is almost certainly biological wastes. Clearly, there is a danger to

infants from such waters. Even more important are the other unanalyzed inorganic and

organic chemicals and microorganisms which might have entered the ground water system.

Fluoride concentrations are also below permissible / desirable levels, and the waters are

mostly saturated with calcite and dolomite deposits. River water quality is also very poor.

They contain no dissolved oxygen (02), but have a high Biological Oxygen demand (BOD).

Ammonia (NH4 +) concentrations are invariably high, as are concentrations of nitrates

(N03¯) and trace metals. Ground waters are almost as badly polluted. Particularly notable are

the concentrations of As +, Hg +, Pb +, Cd + and Cr +, which are well in excess of Indian

standards. The aquifer is apparently incapable of absorbing sufficient metals under the

prevailing pH and chlorine conditions. The source of the pollution is, as in many other parts

of the world, almost certainly a combination of inadequate sanitation and industrial discharge,

spillage or dumping.

If the inadequate supplies of ground water mean that the restricted movement causes

only slow pollution, the reverse is also true in areas already polluted. There the cleaning and

clearing also take an unusually long time, often years. Chennai City has a wide range of

industries, from large-scale tanneries, textile factories and motor assembly plants, to roadside,

one-man vehicle repair shops. Some wastes are disposed of through the sewerage system or

through the surface watercourses. But many such small premises do not, have access to any

disposal system and they allow wastes to soak into the ground. In a recent incident, the

cyanide contamination of a surface watercourse led to the death of several buffaloes, and it is

almost certain that industrial contaminants can enter the local aquifer, either through the


Chennai River Basin

surface water bodies or directly through infiltration. The pollutants range from metals and

other inorganic species to industrial organic compounds. One major environmental problem

of the city has for long been the units that process hides and skins, located around suburban

of Chennai city.

These are located around Madhavaram and suburban areas of Rathinamangalam near

Vandalur, Pallavaram, Chrompet and Pammal. Until recently, they had been without any

effluent treatment facilities for over 100 years, their discharges wreaking havoc on the

environment. After much persuasion by the United Nations Industrial Development

Organisation and the State Pollution Control Board and other such agencies, 102 tanners in

the area recently installed a common effluent treatment plant. These are now designed to

handle about three million litres of effluents a day and will hopefully go some way in

rectifying this long-standing pollution problem.

However the Total Dissolved Solids of Groundwater in these regions varies from

6000 to 12,000 ppm since most of the aquifer zones were enriched with high salinity of

groundwater which yet top be diluted and leaches into the baseflow during monsoonal

season. In addition to that all these effluent treatment plant were reducing the other chemicals

and reduces the colour but whereas the Total Dissolved Solids never reduced within the

permissible limits. Some of the water samples tested insitu during April – September 2004

shows there is no significant improvement in water quality changes in these polluted areas.

Before the mid 1970s, the waterways in Chennai were reasonably clear. Subsequently, with

ever-increasing discharge from factories and households, decay became all too evident. The

Cooum, which originates near Kaveripakkam in Vellore district, winds its way through more

than a dozen towns before entering Chennai city. While the quality of water before entering

the metropolis is tolerable, the pollution becomes acute once it enters the city's suburban

limits. The Adyar, contains a lot of effluents from the tanneries en route, apart from the

contribution of domestic waste.

The Buckingham Canal remains a clear waterway until the Pulicat Lake on the

Andhra Pradesh-Tamil Nadu border. Its pollution starts at the industrial suburbs of Chennai

until it has been reduced to a drain near the Chennai Central station, where the Railways has

taken over a stretch of the canal for platform extension. Earlier, pollution of the rivers was

not much of a problem due to the flushing of the river by seawater during high tides. This

natural process has also suffered, following the formation of sand bars at the mouth of the

rivers, depriving the waterways of this natural process.


Chennai River Basin

The Groundwater Quality Map Plat Nos: 14 & 22 showing the TDS values generated

by observing the insitu water samples at site during July – September 2004 and also the

results obtained from various user agencies for the period from January 1998 to December

2003 was drawn and appended.

4.12 Impact on Environmental problems

As if this is not enough, the drainage system, laid in 1914, and the sewerage lines, first laid in

1890, have not kept pace with the 20-25 per cent decadal growth in population, resulting in

the clogging of waterways and the consequent increase in pollution. The water supply system

itself is often blamed for the cyclic outbreak of epidemics in the city. Studies show that about

2,000 tones of garbage are generated in the city daily. Debris accounts for another 500 tones a

day. Although the city's Municipal Corporation claims that 7,185 sanitary workers clean 85 to

95 per cent of the garbage, many parts of the city appear to be perpetual refuse-sites leaving

the Adyar, Cooum, Otteri Nullah and the Buckingham Canal little better that sewers.

The city sewerage system is similarly over-loaded, along its 1,849 km lines in 8,946

streets, with multiple pumping stations at 102 locations, to offset the flat nature of the terrain.

In 1991, about 86 per cent of the total city area was covered by the sewerage system with

another six percentage points added in another three years Two of the five sewerage

treatment plants and 14 sewerage pumping stations are being modernised. While hut-dwellers

too have no access to sewers for waste disposal, Chennai also has a substantial population of

oxen, cows, and buffaloes, which too contribute to the sewerage problem. This, apart from

the 18,223 families living on the pavements and 35,450 families with a total population of 6-

7 lakhs living in slums along the four waterways, as shown by a study of the Tamil Nadu

Slum Clearance Board (TNSCB), in 1992/93. In all cases, there is a contribution of organic,

bacterial species and inorganic wastes to the aquifer. They use the waterway, or whatever

remains, as a drain, or sewer. The main water-borne diseases that break out frequently

include enteric fever, hepatitis, acute diarrhea-based diseases and tuberculosis.

The cholera epidemic in 1987 claimed over 70 lives, while a more virulent and varied

strain of the bacteria, which struck in 1992, claimed 13 lives. In both instances, lack of

chlorine in the water was found to be the cause. However, it has been found that increased

chlorination does not kill the polio virus, also endemic within the city Chennai, is also

plagued by a high incidence of malaria and filariasis, both transmitted by mosquitoes

rendered chemically-resistant by the indiscriminate spraying of pesticides and insecticides.

In this context, one should know that many voluntary organisations, in coordination

with the Chennai Corporation, have made many efforts to help check the degradation of the


Chennai River Basin

city's environment and improve sanitary conditions. The valuable contribution from such

Exenora International and others has played an important role in controlling the pollution.

4.13 Water Conservation & Management Resource management especially for Water Users for Domestic purposes have a

significance view on the growing population and simultaneous increase in water needs of the

people. Spasmodic rainfall adds a challenge to the efforts of proper utilization of the resource.

Vagaries of nature may apparently seem to cloud the results of artificial recharge structures.

A bad rainfall year for example after adopting conservation practices in an area effectively

nullifies shortage in storage of reservoirs. Analysis of long-term water level fluctuations

combined with rainfall data, and the net surface water potential available doesn’t give

meaningful and statistically significant results, especially for Chennai City and its suburb.

Whereas this long-term measurement on irrigated area on watershed basis, plays a significant

role since the areas are open and not covered artificially by any means.

Hence, lot of perseverance and patience is required before the fruits of conservation

can be seen. First and foremost important is, water supplied irrespective category and

irrespective of quantity should be charged according to the usage. Anything which gives free

of cost cannot be controlled by any means. Even the water extracted from the ground

including small houses and huts should be metered and charges to be levied, similar to

Electricity charges levied. There can be some varieties of tariffs, according to the type of

usage, but irrespective of usage and purposes it should be charged. Then only any planning

and budgeting can be done for the future need. While enforcing the water charges according

to the usage, irrespective of purposes whether it is for drinking, domestic, irrigation,

industries, etc. a full proof system has to be evolved to avoid corruption and malpractices or

not to tamper the meter, which our Tamilnadu peoples were well versed. Here the design of

water meter pose a very big problem, since in our Chennai city water is not flowing in the

pipe lines at regular discharge rate.

Sometimes due to water scarcity the government has supplied water through pipeline

only on alternate days also at stipulated time intervals. This causes so many problems with

the meter reading. The meters installed do not take into account the real usage, whereas it

shows only wrong measurements. To avoid this the water rate can be levied at a fixed rate

based on the number of people, viz. less than five members, between 5 to 10 members and

etc. For flats and apartments, even though one or two connections were provided for the

whole units, water charges were to be levied according to the number of flats / apartments


Chennai River Basin

and also based upon the total number of peoples lived in each flats. If they maintain any lawn

and etc that too should be charged. Any defaulters to be penalized during subsequent months

similar to electricity system. Secondly, an awareness programme can be organised between

the existing and also the newcomers on varieties of water saving technology. Various

scientific inventions are available as on date especially for taking bath, washing cloths using

washing machines, toilet flushing, cooking vessels cleaning and floor cleaning, etc which all

consumes 80 % of the total quantity of water utilised daily by all houses both within the city

or outside. Thirdly the existing water supply and sewage pipelines laid within the Chennai

City limit are more than thirty to forty years old and the dimensions are inadequate to fulfill

the need of the existing density of population living in each areas and each street. All these

pip lines have to modified and replaced immediately. Though it involves huge expenditure it

is unavoidable, since when water managers are planning to do budgeting how the water crisis

can be solved, unless these measures were not improved and undertaken side by side, the

planning evolved by planners will become a colossal waste.

While planning for laying new pipelines both for water supply and sewage, for both

these purposes two separate pair of pipelines was to be provided. For supplying water, it

should be bifurcated into two, one for supplying potable water drinking and cooking purposes

and the second one for bathing and toilet purposes. Similarly while laying pipelines for the

collection of sewage purposes, two separate pipelines were to be provided, one for the

collection of toilet flushing water collection and the second one for the collection of

bathroom, washing and other kitchen wastewater generated. All these collected sewage can

be collected and can be treated fully so that the treated wastewater can be reused for bathing

and toilet purposes again. In this way around 400 million litres of water can be reused daily

and can be meeted the 70 % of the daily requirement from these quantity itself, the daily

requirement of 650 MLD of potable water can be reduced to 250 to 300 million litres, which

can very easily be achieved and full filled.

Interconnecting all major cities can evolve similar treatment techniques and towns

and treatment can be done in faraway upland places, where the groundwater is scarce and

available at deeper levels. Naturally the capital costs involve are heavy and tremendous

political will is required to undertake such a huge project within the urban area. It is only a

one-time investment and the recurring expenses are very low, when compared to the other

technology of Desalination of Seawater or transporting of groundwater or surface water

through tankers from faraway places continuously for years together.


Chennai River Basin

Water resources were very well consumed by many numbers of major industries apart

from Madras Refineries Limited and Madras Fertilisers Limited, who were purchased the

Metro Water Sewage and recycled water for their raw water purposes. Similarly pure potable

water were used by Ford India Limited, Hyundai Motors Limited, Ennore Thermal Units,

Basin Bridge Gas Turbine Project, Kalpakam Atomic Power Reactor Unit, and many number

unaccountable industries consume huge quantity of groundwater and surface water for

running their respective industries daily. The quantity of supplying of potable water or

extraction of groundwater by these industries either within their campus or outside where can

be controlled and minimised by supplying the treated sewage water of the Chennai

Metropolitan Development Authority at cost basis, so that the quantity of supplying or using

the potable water can be minimised and saved. These saved quantity of water resources can

be substituted for other primary drinking water need of the Chennai City or suburban people.

Presently supplying water for the various industrial estates run by TIDCO, SIPCOT and

others industrial sectors etc can also purchase these treated sewage at cost basis from Chennai

Metropolitan Sewage Authorities concern.

They can fulfill their portion of the industry requirement from these resources instead

of allowing them to extract their own resources or supplying them from the general pool.

This is one way or other saving the water resources at the source point, and at the same time

reducing the burden of discharging the treated sewage wastewater into the ground directly. A

portion of it can also be used for irrigation purposes at cheaper cost for poor farmers who

have land at the peripherals of the coastal agglomeration where there is no sufficient water

available for irrigation. By discharging these sewage waste into the groundwater system

directly instead of through other means, by treating partially, will contaminate the entire area

as a whole and as well as the groundwater aquifer system. This will increase the intensity of

pollution to nearby areas and after two or three decades, there is no enough groundwater

potential in the vicinity for safe extraction.

If these technologies will not adopt in the near future, whatever may be the water

resources gathered and augmented, the multifold increase in water demand by various sectors

cannot be fulfilled under any circumstances. Diverting the irrigation water by purchasing

their rights to meet the domestic water supply may be fruitful for time being, but however it

will create lot of other problems. Also continuous pumping of groundwater, now doing as on

date, reflect the depletion of water levels beyond the dynamic reserve leads to water mining

in upland areas, which has not be replenished even during above normal rainfall years and in


Chennai River Basin

the coastal agglomerations the groundwater quality becoming saline and contaminated

aquifer fully, which becomes unsafe ever.

By implementing the treatment of sewage water for recycling purposes, considerable

amount of pumping of groundwater can be curtailed. The requisite amount of potable water

can very well be meeted out from the available surface water resources itself, instead of

pumping of groundwater from the well fields, by forcing the farmers in augmenting their

irrigation rights. Groundwater can be preserved for sustainable development. Before planning

for sewage treatment, first the Chennai Metropolitan Water Supply and Sewage Board, who

are real affecters and responsible for the supply of water to the city peoples, first estimate the

total quantity of water demand for the entire population of Chennai Greater Metropolitan

Area as a whole.

Initially for the present day population, then projected to the anticipated growth for a

span of not less than 40 to 50 years duration, both for the total domestic requirement

separately for drinking, bathing and other purposes and toilet flushing and gardening,

similarly for the anticipated sewage and other waste water generated from each house

holding.

This has to be assessed area wise, division wise along with the infrastructure facilities

available as on date like width of the road and their length. Then only proper planning can be

done. For this it is a really useful to create a GIS computer model for various user

requirement and demand input and finding out the solution. Finally finding out cheaper ways

and means of Desalination of Seawater for domestic purposes. Even though there are various

advanced techniques were available as on date, the initial investment cost for setting up of

these units and their running expenditures were uneconomical for countries like India,

especially Tamilnadu.

4.14 Merits and demerits of Installation of Desalination System for Seawater.

The two main technologies for desalination are based on heating water to a vapour,

then condensing it to yield fresh water i.e. distillation. The other technology utilises reverse-

osmosis, in which, ions migrate across a semi-permeable membrane in such a fashion that

concentration, pressure and other physical parameters remain the same across the membrane.

In the first process, the energy source becomes critical. It should be relatively cheap,

easily available and easy to handle. Normal candidates are fossil fuels. In the second process

high pressure pumps are utilised which consume tremendous quantities of power and also the

semi-permeable membrane does not have a long life. Reverse osmosis needs electricity, while

distillation needs heat. Vide statement enclosed regarding units installed within Chennai City.


Chennai River Basin

4.15 Economic Resources, Feasibility and Pricing of Water

This section considers the role and implications of assigning economic value to water

resources to bring about such optimisation. In pursuing the concept of sustainable

development, economists have widely discussed the discrepancies between the discount rates

of individual 'units', be they households or firms, and the optimum discount rate for society.

(For example, see D. Pearee, 1995). The implicitly higher discount rates of individuals,

because of their short- term vision, has led to the collective usage of natural resources that is

invariably unfavorable for society in the long-term.

To combat such shortcomings, environmental economists have stressed the

importance of 'rational' pricing measures that reflect the true cost of a natural resource in

society. For common property resources, such as air and water, mismanagement due to

inadequate pricing policies is a common phenomenon, as is over-utilisation (See Hardin's

portrayal of the Tragedy of the Commons, 1968). In the context of water-resource provision,

costs should, therefore, include those incurred through water storage, treatment requirements

and distribution to the population. Further, the environmental costs of water pollution and

declining water availability should also be factored into the fiscal equation.

In a recent study on water- pricing, World Bank experts suggested that such measures

would ultimately lead to a more efficient use of water by the population (The Indian Express,

August 8, 1995). It is under this premise that wasteful practices, such as allowing taps to run

unnecessarily, storage tanks and pipe-works to leak and water sources to become polluted,

might be discouraged. Conceptually, the provision of appropriate water-pricing policies

would appear to come some way to addressing the present problems of mismanagement and

misuse. The question may arise for pricing the water. It is very difficult on various reasons to

measure the exact quantity like non-functioning of water meter due to air lock and will not

function when it operates.

To avoid these operational systems, it is wise enough to price the water on the basis of

type of house, viz. independent, flats or undivided joint family housed in one single big

house. A house may be well defined in this respect. Say at the rate of 80 to 100 litres per day

per person for five members a maximum for one-house, charges to be levied monthly or once

in six months at the flat rate irrespective quantum they consumed. It is a fact that most of the

upper class people use this drinking water for cleaning their cars; floors and some were used

for gardening purposes. For large apartments, row of houses in one single campus, or houses

like bungalows and having with gardens etc. these water users can be identified and water

meters can be installed and can be charged according to the water consumption basis. Even


Chennai River Basin

though some of this water is inevitably wasted, let them pay for their usage rate. During acute

water scarcity periods, fixing the maximum limit irrespective of their usage can either control

these higher water consumption groups or temporarily their connections can be dispensed

with. They can be restored when normalcy occur, without asking them to pay for

reconnection charges.

In addition, one must acknowledge that policy implementation challenges are not

simply confined to the domestic sector. Industry in Chennai is increasing at a phenomenal

rate, and hence non-domestic demand poses a significant challenge to the suppliers. In some

cases, industries have been forced to undertake their own initiatives, In the North Madras-

Manali industrial-belt, for example, two industries, namely Madras Refineries Ltd. and

Madras Fertilizers Ltd., actually purchase sewage from Metro water and treat it themselves in

sewage treatment plants. These isolated cases should be encouraged to adopt by other

industries who were consuming huge quantity of both surface water and groundwater like

Ford India Limited, Hyundai Motors, Ashok Leyland, ICF and Power Sectors, to acquire the

city sewage and go for installation of treatment plant within their premises.

5. Water Resources Potential, Demand, Evaluation and Solution Based on the above detailed study the total overall Surface water and Groundwater

Potential of the Chennai River Basin and Greater Chennai were summarized below, along

with methods of adopted for assessment. The total Surface Water Potential estimated through

75% Dependability Rainfall of the Chennai River Basin covering 5542 square kilometer area.

5.1 Water Potential Of Chennai BasinSurface Water Potential Assessment: -

The total Water Potential of the Chennai Basin was as follows: -

Surface Water Potential through 75% dependability of

Southwest Monsoon season : 248 MCM

Northeaster Monsoon season : 422 MCM

Transition Periods : 114 MCM : 784 MCM

Surface Water transported from

Palar through Palar & Poiney

Anicuts for the 215 tanks : 122 MCM : 122 MCM

Krishna Water Anticipated : 340 MCM : 340 MCM

Veeranam Water : 65 MCM : 65 MCM

Total Overall Surface Water Potential Available: 1,311 MCM


Chennai River Basin

Groundwater Potential assessment: -

GEC – 1997 Methodology Recommended by Government of India: -

The revised methodology – Groundwater Resource estimation Committee – 1997, as

recommended has incorporated number of changes compared to the recommendation of

groundwater estimation Committee – 1984 in this methodology.

Watershed has been recommended as the assessment unit in hard rock areas.

Groundwater assessment has to be made separately for non-command and command

areas and areas of poor quality have to be treated separately.

Groundwater recharge has to be assessed separately for non-monsoon and monsoon.

An alternative methodology has been provided for estimation of specific yield based

on application of groundwater balance in dry season, which would be applicable in

the non-command part of hard rock areas.

Norms for return flow from irrigation are now based on the source of irrigation i.e.

groundwater or surface water, type of crops and depth to water level below ground

level.

Groundwater levels have been made an integral part of groundwater assessment and

categorization of areas for groundwater development is now based on the stage of

groundwater development and long-term trend of ground water levels.

Allocation for domestic and industrial water supply is now recommended based on

population density and relative load on groundwater for this purpose.

Computation of Groundwater Resources based on GEC – 1997 Methodology

In Tamilnadu, the data in respect of different parameters and variables are not readily

available to carry out the computations on watershed basis as recommended in the GEC –

1997 methodology. The requisite data has to be collected at village level and the same have

to be compiled to arrive at the computations for each watershed. The State Ground has

already taken up this work of data collection and Surface Water Resources Data Centre,

Chennai and it may take some time to complete this task. Hence, the computations have now

been carried out with block as the assessment unit and in the absence of data on command

and non-command areas they have been estimated together and then proportionately

allocated.

(a) Groundwater Draft Computation

Groundwater draft is computed using both crop water requirement and unit Draft method.

i. Groundwater Draft computation using crop water requirement.


Chennai River Basin

Groundwater draft has been computed on the basis of cropping pattern. The crops

have been grouped under categories of paddy, non-paddy and banana and sugarcane. The

average water requirement of 1.09 m, 0.53 m and 1.70 m has been allotted for the categories

given above. The data on cropped area during monsoon and non monsoon is not available and

hence the segregation of monsoon draft and non monsoon draft have made on pro-rata basis

with the electricity consumption measured at sample points by TNEB as guiding factor. The

data on cropped area for each block is available for 1997 – 98 and prior to that the data is

available only on taluk level and hence the data of 1997 – 98 has been assumed for the

previous years also.

ii. Groundwater draft computation using unit draft of groundwater structures.

Department of Economics and Statistics, Government of Tamilnadu have compiled

the well census data for each block from the Block Profile on Irrigation Statistics Published

for the year 1997 – 98 the unit draft figures have been assumed within the recommended

range given in the GEC – 1997 methodology and the draft has been computed on the basis of

unit draft and number of structures. The unit draft for different structures used in the

computation is given below:

Dug Well 0.7 Ham

Borewell 1.0 Ham

Dug Cum Borewell 1.0 ham

Tubewell 2.0 Ham

Though, periodic updating of wells in use is being made by Government of

Tamilnadu, the unit draft assumed may no\t be valid in many drought prone pockets due to

limited saturation thickness of the aquifer. On the other hand, the cropped area and its water

consumption can be taken as more realistic. Therefore, whenever the sustainability of yield in

abstraction structures is visualized, viz. deltaic region, the draft from number of abstraction

structures are accounted for final computations while in other areas, crop water requirement

is taken for computation of groundwater draft.

(b) Return Flow from Groundwater Irrigation

Crop water requirement has been calculated on the basis of cropped area and average

water requirement. Return flow from the groundwater irrigation has been computed on the

basis of the percentage as given in the methodology in relation to depth to water level in the

irrigated area. The return flow from groundwater irrigation computed for 1997–98 have been

assumed to be the same for the previous years also.

(c) Base Flow Computations


Chennai River Basin

In Tamilnadu it has been assumed, as “NIL”, as very few rivers are perennial.

(d) Parameter computations

The specific yield computed on the basis of water level fluctuation during non-

monsoon period as given in the methodology appears to be unrealistic, as water level

fluctuations measured in the wells do not correspond to the response from other variables.

Hence, a realistic specific yield value has been assumed for each unit of computation. In the

earlier computation, the specific yield values have been assumed taking into the consideration

of major rock type. However, if the percentage of different rock types is near equal in a

block, then the resource computed may not be realistic.

In case of segregation of crystalline and sedimentary rocks, the percentage of each

category may be separated for each block and weighted average may be assigned for

parameter values, as the factor of geology comes into picture only in the computation of

rainfall recharge and weighted average takes care of that factor. However, the formation

becomes more clayey towards the coast in selected areas and hence the values have been

arrived at considering the local hydrogeological conditions.

Specific Yield:

Crystallines : 1.5 5

Sandstone : 3.0 %

Alluvium consisting of clay, silt and sand admixture: 12 – 22 %

Infiltration Factor

Crystallines : 8 %

Sandstone : 12 %

Alluvium consisting of clay, silt and sand admixture: 5 – 12 %

(e) Canal Seepage Computations

The canal length, wetted perimeter, days of flow (monsoon and non monsoon) and the

seepage factor given in the methodology have been used to determine the seepage from canal

for monsoon and non-monsoon period separately. The data on canal details have been

assumed to be the same as there will be little change in the functioning of a canal.

In areas of shallow water levels, the canal seepage is sometimes over estimated, as the

storage space is not available. GEC – 1997 has suggested that seepage factor can be suitably

reduced in case of shallow water level areas or water logged areas, which is the case during

the release of water in the canal and the factor has been reduced accordingly and canal

seepage has been computed.


Chennai River Basin

(f) Seepage from Tanks

Water spread area; days of water availability (monsoon and non monsoon) and

seepage from tank given in the methodology have been used to determine the seepage from

tanks for monsoon and non-monsoon separately.

(g) Seepage from Check Dams / Nalas.

It has been assumed as negligible in Tamilnadu.

(h) Return Flow from Surface water Irrigation

The data on cropped area has been grouped into paddy and non-paddy. An average

water requirement of 1.0 m and 0.53 m has been assumed for paddy and non-paddy crops.

The crop water requirement has been worked out and the return flow from the surface water

irrigation has been computed on the basis of percentage of applied irrigation water. The

return flow from surface water irrigation computed for 1997 – 98 has been assumed to be the

same for the previous years also. In certain areas, the recharge from return flow from

irrigation is not considered for recharge during monsoon season, as the formation gets

saturated with recharge from rainfall, seepage from canal, etc. and the recharge from return

flow from surface water irrigation may be flowing out as rejected recharge.

(i) Allocation for Domestic and Industrial Purposes

The population density (thousand per square kilometer) fractional load on

groundwater for domestic purposes and area (square kilometer) has been used to determine

the domestic demand. The data on actual fractional load is not available for each block and

TWAD Board And CMWSSB, which are responsible for water supply, furnished that in

general the share of groundwater (loads on groundwater) for domestic water supply in rural

and urban area is taken as 0.7 and 0.3 respectively. In hilly areas the load is taken as 0.3.

Accordingly, the allocation f9r domestic and industrial purposes have been computed.

(j) Computation of Resources

The recharge during monsoon was computed, after normalization of rainfall recharge.

The annual recharge, net groundwater availability, potential for future development and stage

of development have been computed as suggested in the Groundwater Resources Estimation

Methodology – 1997. The long term trend during pre monsoon and post monsoon water

levels in National Hydrograph Stations of Central Ground water Board and Observation wells

of State Ground and surface Water Resources Data Centre, Water Resources Organisation in

Public works Department, Government of Tamilnadu has been used.

(k) Estimation of Groundwater Potential in accordance with the Methodology

recommended by Groundwater Resource Estimation Committee.


Chennai River Basin

The area wise / block wise groundwater potential and utilisable groundwater resource

was calculated as per the recommendations of Groundwater Resource Estimation Committee

– 1997. The block wise groundwater potential details as on January 1998 and January 2003

which is shown in the Statement No: VI. The total Dynamic groundwater resource for the 26

blocks covers within the Chennai Basin area were computed and then it has been recalculated

percentage wise depends upon the area occupied within the basin for each block for the

whole Chennai Basin. It consists of total dynamic groundwater resource, the net annual

groundwater availability, gross draft for irrigation, domestic and industrial demand,

allocation for domestic and industrial demand for the next 25 years and the net groundwater

availability for future irrigation.

Groundwater Potential of the Chennai Basin based on GWREC : 1119.39 MCM

(Block wise Groundwater Potential assessments vide Statement No: VI)

Groundwater drawn from Palar through Infiltration Wells : 0000.83 MCM

Sub Basin wise details are furnished below for reference.

S.No. Name of theSub Basin

Utilisable Groundwater Recharge in

MCM

Net Groundwater

Draft in MCM

Balance Groundwater Potential in

MCM

Percentage of development

1 Araniar 140.49 69.10 71.39 49.182 Kosathalayar 549.99 448.66 101.33 81.573 Cooum 206.70 148.28 58.42 71.344 Adayar 222.21 102.82 119.39 46.27

Total 1119.39 768.86 350.53 68.69

Block Wise Groundwater Potential Estimated was appended vide Statement No: VI.

Categorisation

The units of assessment can be categorised for groundwater development based on the

stage of groundwater development and the long-term trend of pre and post monsoon

groundwater levels. The following categorisation proposed by GEC – 1997 Norms based on

these two factors.

(a) Safe areas with potential for development.


Chennai River Basin

i. Areas where groundwater resource assessment shows stage of groundwater

development at 70 % or lower, and there is no significant long term decline of

pre or post monsoon groundwater levels.

ii. Areas where ground water resource assessment shows stage of groundwater

development more than 70 % but less than 90 5 and both pre and post

monsoon groundwater levels do not show a significant long-term decline.

However, in these areas, caution may be exercised in planning future

development, with regard to quantum of additional groundwater withdrawal.

(b) Semi critical areas for cautious groundwater development.

Areas where groundwater resources assessment shows stage of groundwater

development more than 70 % but less than 90 %, and either pre monsoon or post monsoon

groundwater level shows a significant long term decline.

(c) Critical Areas.

i. Areas where groundwater resource assessment shows stage of groundwater

development more than 90 %, but less than 100 % and either pre monsoon or

post monsoon groundwater level shows a significant long term decline.

ii. Areas where ground water resource assessment shows stage of groundwater

development less than 100 %, but both pre monsoon and post monsoon

groundwater levels show a significant long term decline.

iii. Areas where ground water resource assessment shows stage of groundwater

development more than 100 %, but either pre monsoon or post monsoon

groundwater levels does not show a significant long term decline.

(d) Over Exploited areas.

Areas where groundwater resource assessment shows stage of groundwater

development more than 100 % and both pre and post monsoon groundwater levels show a

significant long term decline.

Accordingly, the categorisation is made on the basis of long-term water level trend

and stage of development. The long-term trend of groundwater levels is not available for

some blocks. Further, it is also noticed that the stage of groundwater development has exceed

100 % while groundwater level trend does not show a decline trend. Similarly, the stage of

development is less than 70 % but the groundwater level trend shows a declining trend. The

anomalies noticed can be attributed to the non-representative wells being monitored and also

the change in groundwater development scenario with increased hand pumps, piped water

supply schemes and local groundwater mound (high) in human settlement. The validated


Chennai River Basin

database will alone eliminate such anomalies in the subsequent assessment. However, in the

present estimation work, where such anomalies have been noticed, considering the actual

stage of groundwater development in the absence of long-term water level trend has carried

out the categorisation. Further, in case of declining water level trend and stage of

groundwater development less than 70 %, the blocks have been categorised as semi critical.

Total Groundwater Potentials available as on 1st January 2003 : 1120.22 MCMT

Total Water Potential as on 1st January 2003 Settlement : 2431.22 MCM

The annual Groundwater Potential of the Chennai Basin, as per the Groundwater

Estimation Committee Norms works out 1,119.39 MCM. The water drawn from Palar River

through infiltration wells annually to meet the drinking water requirement of Pallavaram,

Alandur, Tambaram, Pammal and Vandalur were account for 0.83 MCM. Hence the total

annual groundwater Potential workout 1,120.22 MCM annually. Out of the 26 blocks covered

in this Chennai Basin the Groundwater Potential Available for further development were

categorized by GWREC Norms 1997 assessed as on January 2003 (vide Statement VI) and

also the abstract is furnished below:

Chennai City Agglomeration. (Over exploited)




Blocks safe.


blocks


Out of the 26 blocks (either partly or fully) covered in this Chennai Basin, the stages of

groundwater development groundwater as on January 2003 were, 7 blocks over exploited, 3

blocks critical, 13 blocks semi critical and 3 blocks were safe. It is seen that as on date there

is very minimum quantity of groundwater available for further development. (Statement: VI)

Assessment of Present and Ultimate requirement of Groundwater for Domestic and

Industrial uses:

As per the National water Policy, requirement for domestic water supply is to be

accorded top priority. This requirement has to be based on population as projected to the year

2025, per capita requirement of water for domestic use, and relative load on groundwater for

urban and rural water supply. The empherical relations recommended in the methodology are


Chennai River Basin

applied for the computations. The data on actual practical load is not available for each block.

The CMWSSB and the TWAD Board, which is responsible for water supply, assessed in

general the load on groundwater for domestic water supply in rural and urban area is taken as

0.7 and 0.3 respectively. In hilly areas, the load is taken as 0.3. Accordingly the allocation for

domestic and industrial needs have been computed.

Estimation of Groundwater Resources as on January 2003.

Groundwater Resources have been computed as on January 1998 and it has been

suggested by the State Level Working Group to update the estimates to January 2003. Net

groundwater availability is assumed to be the same and ground water withdrawal has been

projected on the pro-rata basis. In computation of stage of development, groundwater draft

for all purposes is to be considered. The allocation for domestic and industrial purposes at

year 25 has been considered as domestic draft. In case of projection of irrigation draft, a

uniform rate of 0.6% has been assumed in earlier computations. However, it was felt that the

groundwater development in different categories of the blocks will not be the same and

groundwater development will be least in the already over exploited block due to restriction

on bank financing. Accordingly the block categorised as on January 1998 has been taken as a

guiding factor to allocate different growth rate as given below.

S.No. Block Categorised as on January 1998 Growth Rate in % per year.

1 Safe 0.4

2 Semi Critical 0.3

3 Critical 0.2

4 Over Exploited 0.1

The long-term water level trend data for the period 1989 – 98 has been considered for

categorisation of blocks as on January 1998. In the projection of estimates to January 2003,

the long-term water level trend data for the period 1994 – 2003 has been considered. A

summary of the statement has been provided in the Statement No: VI. A perusal of the

statement VI shows that in general there is an increase of 1 to 3 % in the stage of

development on projection to January 2003.

Number of blocks falling under different categories was furnished

Chennai City Agglomeration. (Over exploited)




Blocks safe.


Chennai River Basin


blocks


Out of the 26 blocks (either partly or fully) covered in this Chennai Basin, the stages

of groundwater development groundwater as on January 2003 were, 7 blocks over exploited,

3 blocks critical, 13 blocks semi critical and 3 blocks were safe. It is seen that as on date there

is very minimum quantity of groundwater available for further development.

The over exploited blocks and the critical blocks require extensive groundwater

conservation techniques – rainwater harvesting and artificial recharge for improving the

groundwater storage. Regarding the coastal blocks located in the Chennai Basin, most of the

areas around 2 (south of Chennai near Injambakkam) to 13 kilometers (area around Minjur

and Mouthambedu) from the sea coast, the groundwater are fully saline due to sea water

intrusion or by saltpan activities or by natural means, which also requires water quality

improvement programme. About 10 blocks are falls in these categories regarding the Chennai

Basin, which requires special attention by the Water Managers and Water User Groups.

Conservation and judicious management of groundwater resources is the prime need of the

hour and also for the coming years so as to make the Chennai Basin to attain self-sufficiency

in the water resources sector.

5.2 Water Potential Of Greater Chennai Metropolitan Area.Based on the above detailed study the total overall Surface water and Groundwater

Potential of the Greater Chennai Metropolitan Area was summarized below, along with

methods of adopted for assessment. The total Surface Water Potential estimated through 75%

Dependability Rainfall of the Greater Chennai Metropolitan area covering 1166 square

kilometer area.

The total Water Potential of the Chennai Basin was as follows: -

Surface Water Potential through 75% dependability of

Southwest Monsoon season : 52.20 MCM

Northeaster Monsoon season : 88.80 MCM

Transition Periods : 24.00 MCM : 165 MCM

Surface Storage of the three Major Reservoirs located within the Chennai Metropolitan Areas

Redhills : 93.46 MCM

Sholavaram : 25.30 MCM

Chembarambakkam : 103.23 MCM : 221.93 MCM


Chennai River Basin

Even though the catchment areas of the above three major reservoirs were located

outside the peripherals of the Greater Chennai Metropolitan area, three reservoirs were

located within the Chennai metropolitan area.

Hence the Total Overall Surface Water Potential Available: 387 MCM / annum

Groundwater Potential of the Greater Chennai Metropolitan Area was estimated through

Adhoc Norms based on Water Level Fluctuation method suggested by GWREC1997

assessed for the blocks either part or full is: 324.243 MCM vide Statement No: VI (A)

Hence the overall Water Resources potential both of surface water Resources and

Groundwater resources of Greater Chennai Metropolitan Area is: 711 MCM / annum

Note:

1) The total Surface Water and Groundwater Demand were estimated and were

furnished separately in the report itself.

2) By treating the Sewage collected to a tune of around 310 MLD can be reused to meet

the balance water requirement of the Greater Chennai Future demand.

3) Irrigation, Industrial and Livestock demands of this Greater Chennai Metropolitan

Area has to be assessed before budgeting the water resources availability, so that all

sectors has to be provided water adequately, depends upon their merits and necessity

and not based on their numerical values and demands.

4) The same methodology has to be adopted similar to Chennai river Basin for the

assessment of both surface water and groundwater resources of the Chennai

Metropolitan area. Regarding assessment of groundwater potential for Chennai City

limit, it was done based on Water Level fluctuation and Specific yield. Hence the

overall assessment on water resources has to done by conducting detailed

investigations inclusive well census, pumping tests and other refined methods.

For the assessment of Groundwater Potential for the Chennai River Basin and for the

Greater Chennai Metropolitan area, the latest Well census, Irrigated area with cropping

pattern and other extraction details are very much essential before these areas were bifurcated

into watershed wise. Presently Groundwater Recharge Assessment were done Revenue

division – Block wise, but however it has to be refined and reassessed based on mini water

shed wise for getting more accurate results. Now data is not available and also the area has

not been bifurcated into watershed wise. For the groundwater assessment latest, groundwater

aquifer parameters by conducting pumping test hydrogeological zone wise, infiltration rate of

different soils encountered in each and every watershed wise, permeability rate etc has to be

estimated before assessment.


Chennai River Basin

Whatever may be methodology adopted within the Chennai City Limit covering 174

square kilometer area which were mostly occupied by constructed buildings, paved roads,

gutters, sewage lines, storm water drains, and etc assessment of groundwater potential cannot

be done more accurately. Only Adhoc Norms can be adopted. However for the remaining

areas covers within the Greater Chennai Metropolitan area, assessment can be done as

suggested by GWREC 1997 Norms. It is a known and accepted fact that the overall water

resources availability of the Greater Chennai Metropolitan Limit will always be a deficit

basin when compared to the growing population, moving population, industrial growth,

livestock increase and other tourism related activities. This area requires transportation of

water resources either fully from the Chennai Basin or from the neighbouring river basin to

meet the demand.

In this respect adequate precautionary measures can be strictly enforced now itself

while issuing permission to allow for growth or expansion in each and every aspect

considering the shortage of water resources availability. The total Water requirement of the

Chennai river Basin were estimated based on census and other needs and were furnished in

the Para 3.9 were again furnished below for easy reference. There is only a shortfall of

around 34 % of the total water requirement can be solved by implementing recycling waste

water generated in all fields.

Since most of the irrigated land were recently be converted into major industries and

industrial complexes, domestic – housing development (both by Government Housing Units

and by Private entrepreneurs) and Recreational – Amusement parks, the net water

requirement were assessed according to the prevailing and future expansion anticipated, since

this basin has got a peculiar setup, viz comprising of Major cities and towns. Total water

requirement of this basin by various sectors Viz. domestic, agriculture, livestock, industries,

tourism, power and etc has been assessed for the years 2000, 2005, 2020 and 2040 and are

furnished below. The total water requirements furnished below were in MCM for each sector.

S.No. Sector 2000 2005 2020 20401 Domestic 235 260 350 4252 Agriculture 2900 2600 2400 22003 Livestock 40 40 40 40


125 160 260 400

5Tourism, Recreation, Amusement parks and other Environment Aspects

30 30 30 30


Chennai River Basin

6 Power 22 25 28 317 Total 3352 3115 3108 31268 Total water Potential 2027 2432 2432 24329 Water Deficit in MCM -1325 -683 -676 -694

10 Water Deficit in Percentage 39.53 22.93 21.75 22.20

Since most of the irrigated areas are being converted into industries and settlements, the

irrigation demand will simultaneously gets reduced which can be compensated to meet the

other demands. Otherwise either by changing cropping pattern or by modern improved

method of irrigation practices as suggested in the other columns, water requirement for

agricultural purposes if reduced to 90 % of the requirement and minimized by another 10 %

by conversion of agricultural land for industrial or housing purposes which can spared totally

around 440 MCM, which will be sufficient along with the water generated from recycling of

waste water generated and for balance desalination of seawater can be substituted. While

issuing licenses to new industries, they have to be forced to undertake recycling of

wastewater by buying wastewater from the City Corporation Sewage and to meet the balance

of water by installing desalination plant. They should not be allowed to utilise either surface

water or groundwater except for their minimum barest requirement and if this has been

adopted water demand can be solved easily without transporting water from other basins.

Note: -

i. Surface Water resources were assessed based on 75% dependability of annual rainfall

observed through various rainfall stations falls within the river basin. However the

correct methodology to be adopted was based on Daily rainfall with respect to rainfall

– run off Rainfall Frequency Analysis by Preparing Relief Map and Morphotectonic

maps of the river basin. Storages of the reservoirs were too assessed by taking correct

measurements including the present capacity with number of fillings and discharges

periodically. Rainfall – Run off – frequency analysis with Unit Hydrograph for all

Rainfall Stations with the areas of influence has to be done and has to be marked

before analysis. The same methodology has to be adopted for the latest 5 to 7 years

with the recorded daily rainfall with more number of rainfall stations for frequency

analysis. Assessment through 50 % and 75 % dependability is only an Adhoc method

of assessment of surface water potential, which method was deployed at present.

ii. Groundwater Potential was estimated based on GWREC 1997 Norms, but the well

census is not accurate. This has to be refined based on 2004 well census to have the

estimation correctly. The entire 1166 square kilometer area has to be bifurcated into


Chennai River Basin

mini watershed basis. The same watershed methodology suggested by GWREC

Norms 1997 has to be deployed for this area also. Also each village area falls within

the basin has to be assessed correctly instead of taking percentage of area of

respective blocks. The specific yield values, other recharge factors regarding potential

recharge, return flow from the irrigated field, return flow from the surface water

irrigation, seepage from the water bodies, etc which were normally taken into

consideration for groundwater recharge factors as inputs of groundwater recharge

does not hold good while assessing the groundwater recharge for the Greater Chennai

Metropolitan Area, since intensive irrigation activities, traditional irrigation practices,

irrigation of two wet crops in an year through surface water irrigation, etc are

uncommon. Regarding draft assessment unit draft per irrigation structures, viz wells

and borewells adopted for the assessment of groundwater draft utilised for irrigation

wells cannot be deployed for domestic wells / borewells, since this area constitute too

many number of wells and borewells used for drinking water need for the city

population. The well and the population density is also too much which cannot under

pro-rata basis. Hence while estimating the surface water potential using rainfall

dependability method and the estimation of groundwater potential and draft using

GWREC Norms 1997 has to modified and refined according to city environment.

6. RecommendationsThe opportunities to improve the fresh water supply situation in the city are very few.

These recommendations are chosen for their simplicity of implementation. They do not

constitute the only set of solutions, but from the analysis of the data and experience gained,

represent the most pragmatic methods of reducing the demand for water while ensuring the

greater availability of the most precious of resources. Saving and conserving of water

irrespective utility must be adopted as a principle by each and every citizen thinking that “By

Saving Water, They are Saving The Nation” as a whole.

6.1 People's participation

A campaign to encourage people to practice water-conservation and attempt ground

water recharge (mainly targeted at women) on the lines of the Polio Plus immunisation

campaign would be the best form of public participation to ensure sustainable fresh water

supply within the city. Given the long-term implications for the future generations,

educational institutions and school children could be targeted as they also invariably

influence, their mothers in particular-apart from taking it with them as they grow. Non-


Chennai River Basin

domestic sector initiatives providing fiscal incentives for reusing wastewater, and promoting,

identifying and propagating water saving technologies can reduce the demand for water. Data

regarding the various stages of surface water and groundwater development has to be

published, widely announced to among agricultural sectors, Water User Groups and

Industrial Sectors so that every individual should aware how much they are able to save so

that how much they are keeping the water resources reserve for the future generation, as a

forerunner for “Sustainable Development”. In this respect all Government, Quasi

Government, Educational Institutions and NGO’s who are dealing the water resources

assessment and its allied studies should share their knowledge and findings, so that repetition

of same works can be avoided.

6.2 Use of surface water

The use of surface water should be guided by the principle that any excess available

must be instrumental in reducing ground water usage. Implementation of better Participatory

Watershed & Irrigation Management and Conjunctive use Techniques, forming of Water

User Groups, improved irrigation systems, changing of cropping pattern depends upon

monsoonal changes instead of adopting the traditional practices, Water Harvesting

Techniques, etc should maximized to reduce the utilisation of water resources and also reduce

the runoff, so that the surface water collected can be make use off for other primary uses.

6.3 Water storage

Aquifers must be viewed as storage systems, and all initiatives to augment the ground

water availability must be encouraged and supported. While preserving the groundwater

availability for sustainable development, care should be taken not to contaminate or pollute

the existing groundwater aquifer. Specifically, the following activities could be taken up by

the organisations mentioned in brackets: Renovation of temple tanks, cleaning of waterways

and adoption of low-cost rain water harvesting/storage systems and water treatment systems

for ground water recharge at a domestic-level. For domestic purposes where the saturation is

very less and the thickness is very minimum, roof water / rainwater harvesting can be done

by ground level storage system by constructing sump below each of their houses in their

respective basement itself, so that the harvested water can be used to meet their daily

requirement after proper purification. This was the case in most of the countries. This type of

constructing the water sump below the basement to a certain extent prevents the houses from

damages caused by earthquake to a certain extent.

6.4 Pricing water


Chennai River Basin

Water metering - There is an immediate need for accurate cost-effective water meters

that can be used for the intermittent supply system now in vogue in Chennai. This has to be

identified and propagated and Charging for water for their use has to be implemented and

should be mandatory for all. Collection of water charges should be enforced strictly. There is

a proverb, that anything gets free, it does not have any value or the consumptions cannot be

controlled. Unless if the beneficiaries pay and incur some monthly expenses, then only they

feel how to conserve the precious water. Previously the water resources were enormous but

whereas the beneficiaries were very less, that is why nobody feels any difficulty.

On those days, back to year 2000 and before, in street tapes, water was flowing round

the clock, since mostly people will remove the tapes, and mostly all these pipelines were

without tape. The water will pour over the street and wet the entire area. This is the case.

Presently since three years there was no water available in the reservoirs, which were said to

be dry or have very few quantity, there was no public water supply through pipelines.

Chennai peoples were completely forgot about the pipeline water supply. They really depend

upon the water supply through much number of hand pumps or by water tankers. Now there

are many pots surrounded by Hand pumps and peoples were standing on the Queue and all

the tapes were closed tightly. People will realise the importance of water only when there is

scarcity or demand, see today’s affair. As on date water is costlier than milk. Unless the

supply has been regulated at the cost basis nothing can be controlled.

6.5 Groundwater Control and Regulation

Based on the Model Bill prepared by Government of India to regulate and control the

development of groundwater in the States, The Tamilnadu Groundwater (Development and

Management) Act, 2003was prepared and enacted in the 12 th Legislative Assembly of

Tamilnadu in the month of March 2003. This acts extends to the whole State of Tamilnadu

except the notified areas to which Chennai Metropolitan Area Groundwater (Regulation) Act

1987 is in force. In view of the greater exploitation of groundwater, it is most important to

adopt a regulatory measure by enacting Groundwater Legislation.

This act exempts the Domestic Wells with 1 HP Motor, wells sunk by State and

Central Government for Scientific study and Wells sunk by small and marginal farmers of

Tamilnadu. Apart from various provisions for control, regulate and safeguard the

groundwater resource of Tamilnadu, it also covers the management aspects of groundwater.

State Groundwater Authority will be constituted soon to implement the Act.

To observe the Groundwater Discipline, spacing norms have been prescribed based on

the guidelines issued by NABARD (National Banking for Agriculture and Rural


Chennai River Basin

Development) for adoption between any two minor irrigation groundwater abstraction

structures – wells for development of groundwater for availing institutional finance. It has

been decided to enforce spacing criteria for sinking wells in all the areas and along the river

courses to avoid mutual interference between the wells. The following spacing norms have

been adopted for issuing groundwater clearance for irrigation, domestic, industries and for

minor irrigation schemes.

Spacing Norms to be adopted for issuing Groundwater Clearance.

S.No. Spacing Between Distance not less than

1 Two Dug Wells 150 m

2 Two Shallow tubewells, Two filter points, Two dug-cum-borewells 175 m

3 Two medium tubewells 600 m

4 Two deep Tubewells 600 m

5 Medium tubewells and deep tube wells 600 m

6 Shallow tubewells and Medium tubewells 390 m

7 Dug well and medium tubewell 375 m

8 Dug well and deep tube well 375 m

The above norms have to be adopted strictly when groundwater clearance issued before

allowing the farmers or industrialists to sink the wells or drill the tubewells.

However, the Act not yet implemented since the authorities concerned is not yet

constituted. It means as such there is no legislation in controlling the sinking of open wells or

borewells, which may be one of the reasons for the depletion of groundwater levels. Within a

span of four to five years, there is an increase of more than 25% of drilling of deep borewells

of the order of 150' to 200' below ground level and installed higher horse power submersible

motor, since the electricity is free for farmers. This is the main cause of depletion of

groundwater levels and lowering of irrigating area per well. Unless the groundwater

legislation now implemented was not executed effectively, lowering of water levels cannot be

avoided, this leads to drying up of open well and shallow borewells. This is the main cause of

occurring seawater incursion in the Minjur Aquifer zone upto 13 km from the seacoast.

6.6 Present Scenario of Groundwater Structures

In the recent years many wells, whose depth varies from 12 m to 15 m are drying

fastly and unused. The quantum of extraction of groundwater, say about 1,00,000 liters in two

or three hours in a day on earlier days, has been pumped and are being extracted through two

or three borewells in more than 6 to 10 hours of pumping in a day as on date. This resulted


Chennai River Basin

not only for huge expenses for extraction (there is no significance increase in the crop value

since the power supply is given free of cost to the farmers) but also affects the electrical

power utilisation.

More quantity of electrical energy has been spent unnecessarily, since the electricity

is free for agricultural sector. If this conditions continues and if there is no control of drilling

of borewells, there is every possibilities of depletion of groundwater levels and totally

evacuate both dynamic and static groundwater reserve of the aquifer system. To avoid this

stage spacing between borewells and duration of pumping has to be adopted strictly. In recent

years many shallow borewell are defunct and abandoned due to indiscriminate sinking of

borewells. It is a well-known fact that during previous years drought during 2003, the

irrigation rights of pumping of nearly 164 borewells located in the three well fields were

acquired from farmers to meet the drinking water demand of the city supply.

These borewells were continuously pumped and as on date most of these borewells

were now yield less than half the quantity of previous years yields, and some were totally dry

and unused. Apart from these borewells, some of the shallow borewells nearby these were

also said to be dry or their yield gets reduced considerably. Similarly, these years too, during

2004 the irrigation rights of farmers pertaining to holders of more than 208 borewells (located

within the Well fields of A & K Basin - vide Metro Water Web site & Hindu dated 12 and

26th September 2004) were acquired.

These 208 borewells are being extracted fully to a tune of around 12 MLD to meet the

drinking water demand of the city people. The yield from these borewells were also gets

reduced. It is seen from the newspaper daily, dated 17 th September of “Dinamalar”, farmers

and village peoples and peoples from Self Help Groups were agitated in pumping of

groundwater from these borewells to transport to Chennai City, stating that their tube wells

were becoming dry due to transportations of groundwater. These mining of groundwater from

these aquifer zones will long last only for few years, since if anybody do dating of

groundwater, these groundwater reserves were of decades old static reserve. If this much

quantity of groundwater were utilised for irrigation purposes mostly around 40% of the net

extraction will goes into the ground as return flow from the applied water. But here in this

case, since this extracted groundwater were taken away from the area through water tankers

to meet the drinking water need of Chennai people, the irrigation activities were standstill.

The top zone becoming very compact, does not allow faster rate of precipitations

during rainy season and in due course the entire aquifer zone becoming dry. This leads to

almost the entire well fields becoming dry in course of time. Once the groundwater levels


Chennai River Basin

goes below the dynamic reserve and mining of groundwater took place from the static

reserve, replenishing of groundwater levels to the previous years will not took place whatever

may be the subsequent year rainfall, even if there is a flood occur, since these evacuated

groundwater reserve were decades old. The replenishment of the losses of these groundwater

resources is not a nightmare to replenished within over a period of one or two years of

rainfall. The study made since 1966 to till date will reflect the correct picture about the

various stages of groundwater extraction in the five well fields of Araniar – Kosathalayar

Basin.

6.7 Immediate Remedial Measures to solve the water Problems

Hence instead of drilling additional borewells other alternates can be rethinking twice.

Last but not the least, to solve this issue, following are the immediate step suggested. It is

wise enough to go in for collection of all sewage wastewater (estimated around 262 MLD,

and around 310 MLD if collected fully during normal water supply periods) generated within

the Chennai City. The sewage water generated within the Chennai Metropolitan Limit is to

be bifurcated into two distinct categories as partially polluted and fully polluted at the

collection point it and by treating these wastewater, the treated water can be used to meet the

50 % of the City requirement. Regarding the other ways and means to solve these sensitive

issues, this has been very well discussed in the subsequent column of this report. If

implemented the water crisis as on date can become a water problem.

7. Conclusions.This study is only a macro level survey highlighting the importance of water, its

availability, and its condition as on date and its demand in future. To assess the water

resources availability, present utilisation and balance for future demand very accurately, it is

very much essential to study in the following aspects:

An elaborate detailed micro level insitu study of the entire Chennai Basin including

the catchment’s areas falls in Andrapradesh, compilation of all secondary level data,

reports furnished by various agencies till date in this basin, collection and compilation

of all well census data (recently very well documented by the State Groundwater

Wing of the Public Works Department), so that how much quantity of surface water

through rainfall obtained from the Chennai Basin (Relief Map has to be prepared for

the entire Chennai Basin followed by rainfall frequency analysis for more than 30 to

50 years is essential regarding this) and the Groundwater Recharge available and also


Chennai River Basin

actual utilisation of both surface water and groundwater and the balance for future

demand.

Assessment to be done regarding the surplus availability of surface water through

Palar Anicut and Poiney Anicut to various systems tanks located within the Chennai

Basin, based on a detailed study in Palar Basin also.

Assessment to be done regarding availability of subsoil water from River Galleries

and Collector Wells constructed in various spots in Palar River Bed, till now

supplying water to Tambaram, Pallavaram, Alandur Municipalities, Maraimalar

Nagar Township, Ford and Hundye Car Projects, and other industrial sectors, etc.

Assessments to be done regarding the assured availability of Krishna Water through

Telugu Ganga Project from Andrapradesh, vide agreement made.

Assessments to be done regarding the permanent availability of water resources from

Neyveli Aquifer and Veeranam Lake without affecting their requirement for both

drinking and irrigation need, and also not depleting the water levels.

Detailed Feasibility studies regarding Recycling of wastewater for potable or for other

industrial or suitable irrigation purposes.

Feasibility studies regarding installation of Desalination Plant wherever possible, by

economic means.

Identification of feasible areas for the construction of additional reservoirs, lakes,

recharges pond, etc for the collection of surface water and for drilling borewells.

These surveys should also focus on the total generation of wastewater in all respect

and also to examine various aspects of recycling those generated wastewater to the utmost

extent without wasting a drop of water anywhere at any point. Similar studies simultaneously

can be conducted in Palar basin also since these two basins geographically can be connected

as an interdependent basin so that these two rivers can be interconnected as a trial basis

regarding the impact on inter linking of rivers in Tamilnadu State as a prelude in interlinking

of rivers in India as a whole. It is also seems to be very much essential to estimate the correct

picture depicting the various stages of water resources development.

These should cover viz. Where we were? Where are we? And where we will be?

Regarding our water resources in Chennai City and its environment. It is the boundan duty of

each and every one, and should aware how we get water for our need every day, and unless

everyone realise, it is very difficult to control the utilisation of water in each every point.

Even saving a drop a second by everyone will make an ocean. Finally last but not the least


Chennai River Basin

elaborate study with the collection of more primary level data will alone solve the crisis

followed by creating awareness among the people.

All the views expressed in this report are of the authors of Mr. K.R.Sivaraman and Dr.

S. Thillaigovindarajan, Water Resources Consultants, who were Retired Senior

Hydrogeologists of the renowned Groundwater Wing of Public works Department,

Government of Tamilnadu who were associated for more than 35 years of field experience in

the Water Resources Assessment. The authors along with their counterparts were associated,

either directly or indirectly in various types of field works regarding the collection of field

data to know the stages of water resources development as on date and also for the

preparation of a detailed report on the macro level study within six months duration. This

report need elaborate refinement, regarding validation of most of the secondary level data,

ground truth regarding certain Thematic Maps derived from IRS I D Landsate Data of

January 1998, present conditions and their yield of the borewells drilled by the erstwhile

UNDO, GWD, TWAD and CMWSSB, assessment of surface water and groundwater

potential, utilisation and balance by using the Landuse data (as suggested by GWREC Norms

1997) for further development by conducting a detailed micro level study subject to the

availability financial resources and time. The author also wishes to offer comments from all

segments who are dealing and associated as stakeholders with the Chennai River Basin.

K.R. SIVARAMAN & DR. S. THILLAIGOVIDARAJAN.


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Chennai River Basin Micro Level Report - Rainwater … · Web viewProblems should be described using systems terminologies: entities, attributes, levels, and interrelations. The nature