17

CHAPTER 2

REVIEW OF LITERATURE

As water harvesting is a very old tradition and has been used for

years, several techniques have been developed so far. Extensive literature is

available on RWH with respect to various methods, its impacts on

groundwater quantity, quality and its modelling. Literature related to the

various methods of recharge estimation, applications of remote sensing and

GIS in artificial recharge, studies on groundwater modelling, RWH

implementation and its impact studies was collected and a critical review was

carried out, as shown in the following sections.

2.1 ESTIMATION OF GROUNDWATER RECHARGE

Chiew et al. (1992) estimated groundwater recharge by adopting an

integrated surface and groundwater modelling approach. The model was

calibrated against stream flow and potentiometric head data, with recharge

estimated as an output from the calibrated model. The model was applied to

the Campaspe River Basin in north-central Victoria and the results showed

that this modelling approach can satisfactorily quantify the spatial and

temporal distribution of regional recharge rates resulting from rainfall and

irrigation water. The simulations forcasted by the integrated model were

better than those forcasted when the surface and groundwater models were

used separately. Osterkamp et al. (1995) analysed the techniques of

groundwater recharge estimates in both arid and semi arid areas with examples

from Abu Dhabi.

18

Lee et al. (2001) estimated the groundwater recharge rate for the

fractured hard rock aquifer, Chojeong area, South Korea. Six different

methods were adopted to estimate groundwater recharge rate including Multi-

linear Regression analysis, SCS-CN method and aquifer modeling techniques.

Those results from various techniques have fallen in the large range from six

percent of annual recharge rate by groundwater modeling analysis to twenty

seven percent by simple flood formula. It was suggested that flood formula

and SCS-CN are more applicable to the top unconfined or alluvial aquifer and

when the aquifer composed of several layers, which had different hydraulic

conductivity including lower fractured hard-rock formation, recharge

estimation by aquifer modeling analysis could be more recommendable in

Korea. The recharge rates estimated from those statistical models turned out

more than twice than the value from aquifer model. It was concluded that

Groundwater Management Plan for Chojeong area was established based on

six percent of recharge rate by the aquifer modeling technique.

Segun et al. (2006) estimated the groundwater recharge in a part of

the Sokoto basin, Nigeria. Empirical, hydro chemical (chloride mass balance)

and climatic-hydrological methods were used. The empirical method showed

exaggerated values of recharge compared to other methods such as the

chloride and water balance methods. The chloride method showed average

recharge was on the order of 19.6 mm/yr based on an annual rainfall mean of

670 mm from 1916-1993 in the Sokoto area. In most of the study area, the

spatial variability of recharge was discovered to be more in wetter years than

in dry years. The results showed recharge around the Wurno and Goronyo

areas was <1 % of annual rainfall while for areas beyond this region recharge

was 3.2 % of annual rainfall. This sharp difference was linked to climate and

lithology. It was concluded that the chloride mass balance method was the

most suitable for estimating of recharge in most of the basin.

19

David Lorenz and Geoffrey Delin (2006) developed a Regional

Regression Recharge (RRR) Model to estimate regional groundwater recharge

in Minnesota. RRR model was based on a regression of basin-wide estimates

of recharge from surface water drainage basins, precipitation, growing degree

days (GDD) and average basin specific yield (SY). The model was applied to

state wide data in Minnesota, where precipitation was the least in the western

and north western parts of the state (50 to 65 cm/year), recharge calculated by

the RRR model also was the lowest (0 to 5 cm/year).

Rasoulzadeh and Moosavi (2007) studied the groundwater recharge

in the vicinity of Tashk lake area located in northeast of Shiraz using the CRD

method. It was focused on using both R-CRD and CRD methods to simulate,

and consequently predict transient water table fluctuations. A user-friendly

program named Groundwater Recharge Estimation Model (GREM), written

in VB language was used to reduce the variation between simulated and

observed water table elevations. The simulated water table revealed good

agreement with the observed water table (modelling efficiency = 0.933). The

percentage of the CRD(r), which resulted in a recharge from precipitation,

was estimated at 33.6. The results indicated that the natural recharge was not

adequate to balance the high volume of groundwater extraction in the study

area.

Bingguo Wang et al. (2008) estimated the groundwater recharge in

Hebei Plain, China under differing land use practices, using bromide and

tritium tracers. Mean recharge rates and recharge coefficient determined by

tritium and bromide tracing for different sites were 0.00-1.05 mm/d and 0.0-

42.5%, respectively. The results also revealed higher recharge for the initial

year of tracer travel than for the second. As total precipitation and irrigation

were greater in the first year than in the second, this might show temporal

variability of recharge.

20

2.2 RAINWATER HARVESTING STUDIES ALL OVER THE

WORLD

Rainwater harvesting is a very old practice that has been

increasingly receiving attention in the world, fueled by water shortages from

droughts, pollution and population growth (Nolde, 2007; Meera and Ahameed,

2006).

Runoff may be collected from roofs and ground surfaces as well

as from intermittent or ephemeral watercourses and thus water harvesting

falls into two groups. Water harvesting techniques which harvest runoff

from roofs called RWH and all systems which gathers discharges from

water courses named flood water harvesting (Critchley et al. 1991).

Gitte and Pendke (2002) conducted a study on the water

conservation practices, water table fluctuations and groundwater recharge

in watershed areas. The study revealed that the water conservation

measures were found to be effective for rising of water table in

observation wells, located in the middle and lower reach of the watershed.

The overall groundwater recharge due to corresponding rainfall was to the

tune of 3.76 to 8.85 cm in the influence of area of soil and water

conservation structure.

Mondal and Singh (2004) conducted a study of unconfined

aquifer response in terms of rise in water level due to rainfall; a rapid and

cost-effective procedure was developed in hard rock terrain. Cross

correlation of rise in water level and precipitation was established. The

entire area was divided into various zones depending on the difference in

21

coefficient of correlation. Thus, best zone for artificial recharge was

depicted with the help of correlation coefficients.

It has been said that rainwater harvesting can promote considerable

water saving in residences in different nations. In Germany, a study done by

Herrmann and Schmida (2008) showed that the potential of potable water

saving in a house might differ from 30% to 60%, depending on the need and

area of roof. In Brazil, a study performed by Ghisi et al. (2009) revealed the

potential water saving by using water harvesting in 62 cities ranged from 34%

to 92%, with an average potential for potable saving of 69%.

Sturm et.al (2009) described Rainwater Harvesting as an alternative

water resource in rural sites in Central Northern Namibia and presented the

results of the examinations of rainwater harvesting (RWH) in central northern

Namibia as a part of the trans-disciplinary research project CuveWaters

(Cuvelai-Etosha Basin in central-northern Namibia). On the basis of various

conditions, suitable solutions for RWH were developed, and evaluated. The

main aim was to analyse their technical and economical feasibility as well as

their affordability for future users. In detail, two small-scale RWH systems

were investigated i.e, roof catchments using corrugated iron roofs as rain

collection areas and ground catchments using treated ground surfaces.

2.3 RAINWATER HARVESTING STUDIES IN INDIA

Singh and Thapaliyal (1991) assessed the effect of watershed

programme on rain fed agriculture in Jhansi district at the state of Uttar

Pradesh and found that the underground water table in the area showed

a considerable increase, the average mean increase in the water table

being 3.7 meters. A change in the area from pulses to cereals and vice

versa was noted in Rabi and Kharif seasons, respectively.

22

Hazra (1997) in his study of crop yield performance in Tejpura

watershed reported that, because of water and soil conservation works

and water storage structures, the wells which earlier used to get water for

about 1-2 hours, got water for more than 8-10 hours due to the increased

groundwater table by 10 to 23 feet after the construction of water

storage structures.

Naik (2000) reported that the main reasons for non-adoption

of water harvesting structures in the state of Karnataka were the non-

availability of credit and high interest rates, (69% each) followed by long

gestation period (68%), high hiring charges of improved implements

(65%) and small holdings (61%) etc. in the non-watershed area.

Bisrat (2001) studied the economic analysis of watershed

treatment via groundwater recharge of Basavapura micro-watershed in

Kolar district of Karnataka and showed that the average output of bore well

increased from 1150 gallons per hour (GPH) to 1426 GPH (24 per cent

increase) after the construction of water harvesting structures.

Naidu (2001), in the study on Vanjuvankal watershed of Andhra

Pradesh, found that because of water harvesting structures and

percolation ponds, the groundwater level in watershed area showed a rise

by 2 to 3 meters.

Kadirvelu (2002) described the impact assessment of RWH in

Madras University-Marina campus. RWH structures were designed on the

basis of the in situ soil conditions. The frequent monitoring of three open

wells was carried out. The water levels during the pumping before and after

the implementation of RWH were recorded. The water levels and the water

quality were compared with the observation well which was situated near the

study area and maintained by TWAD. The benefit cost ratio was also

23

analysed on the basis of the construction cost of RWH and the population to

be served by the harvested rain. Finally, it was concluded from the results that

the quantity and quality improved. The benefit cost ratio was also arrived at

2.38. The impact of RWH was positive in the study area due to the

improvement in quantity, quality and benefit cost.

Rainfall analysis for the period of 1901-1990 for Amod,

Jambusar and Vagra was carried out (Khandelwal et al. 2002) to find

out the onset and withdrawal of effective monsoon, rainfall depth-

duration relationship, irrigation and surface drainage requirement, as well

as to develop design parameters for rainwater harvesting structures

on the unit catchment area basin in Gujarat, India. Water requirement and

irrigation schedule for cotton and pigeon pea under rain fed conditions

were also assessed using the CROPWAT model. Results showed that the

earliest and the latest probable date of onset of effective monsoon (OEM)

varied from 12-14 June to 15-16 July in the region. Mean date of

withdrawal of the monsoon was during 19-21 September. Correlation

between the 2-7 day annual maximum rainfall and 1-day annual

maximum rainfall showed that coefficient of determination and

correspondingly F ratio decreased with an increase in rainstorm duration

from 2 to 7 days. Surface drainage coefficient based on the maximum

moving rainfall of 7 consecutive days with a 7-day tolerance period varied

from 25.1 to 35.8 mm/d. Qualities of water requirement under rain fed

and 20% yield decrease condition for two (pigeon pea and cotton)

crops under irrigation were t h e same, which indicated that even under

non-irrigated conditions, 80% of the potential yield of both crops could be

achieved in an average normal rainfall year.

Ravikumar et al. (2003) described the roof top rainwater harvesting

in Chennai Airport using GIS. The estimation of surface runoff using SCS

24

method and design of rainwater harvesting structures in Chennai Airport

Terminal buildings was explained. Thematic maps were digitized in map Info

GIS software and roof drainage delineation was done in GIS environment.

Based on the topography and lithology of the airport, artificial recharge

structures like recharge shaft, recharge well and recharge pit were designed

and located.

Ramesh Chand et al. (2005) assessed the groundwater recharge via

neutron moisture probe in Hayatnagar micro-watershed, India. The soil

moisture values were calculated using neutron moisture probe from a total of

eight sites at Hayatnagar micro-watershed at regular intervals of time for two

hydrogeological cycles. The total volume of water (recharge) as a result of the

rise in water-level was estimated and it was found to vary from 0.22 to 0.37 m,

with an average of 0.30 m. The effective specific storativity component as a

result of increase in water level was estimated and it was found to change

from 6.9 to 10.6%, with an average value of 9.0%.

Sharda et al. (2006) assessed the groundwater recharge from water

storage structures in a semi-arid climate of India. Groundwater recharge was

calculated as 7.3% and 9.7% of the annual rainfall by Water Table Fluctuation

(WTF) method for the years from 2003 to 2004, respectively, while the

average recharge for two years, was estimated as 7.5% using Chloride Mass

Balance method. The study has further revealed that a minimum of 104.3 mm

cumulative rainfall was required to produce 1 mm of recharge from the water

storage structures. An empirical linear relationship was found to reasonably

connect the changes in the chloride concentration with the water table rise or

fall in the study area.

Venkatesh and Jose (2007) conducted a rainfall study on the

coastal and its nearby areas of Karnataka. The statistical analyses

conducted are cluster analysis and analysis of variance. The study

25

revealed that there existed three different zones of rainfall regimes in

the study area, namely, Transition Zone,Coastal zone, and Malanad

zone. It was found that the maximum rainfall occurred on the windward

side ahead of the geographical peak. Further, the average monthly rainfall

distribution over the zones had been shown to help agricultural planning in

the study area.

Sreekanth et al. (2009) used a prediction model to forecast

ground- water level at Maheshwaram watershed, Hyderabad, India. The

model’s efficiency were calculated based on the root mean square error

(RMSE) and coefficient of determination (R2). The model gave the best fit

and the predicted trend and also the observed data closely (RMSE = 4.50 and

R2 = 0.93).

Subash Chandra et al. (2011) developed lithologically Constrained

Rainfall (LCR) method for quantifying spatio-temporal recharge distribution

in crystalline rocks of Bairasagara watershed and Maheshwaram watershed of

India. The LCR method requires three input criteria i.e. vadose zone thickness,

soil resistivity, and precipitation. The average recharge at Bairasagara

watershed was found varying from 7.5% to 13.8% with a mean of 10.5%

during 1990-2002. The study concluded that the LCR was a generalized, least

cost method developed to quantify natural recharge spatially and temporally

from rainfall in hard rock terrain.

2.4 APPLICATION OF RS & GIS TO ARTIFICIAL RECHARGE

Remote Sensing (RS) and Geographic information system (GIS)

technology have shown novel ways in groundwater studies. The concept of

integrated remote sensing and GIS has shown to be an effective tool in

integrating urban planning and groundwater recharge studies. GIS is

beneficial to, analyze and represent spatial information and database of any

26

resource, which can be easily used for the planning of environmental

protection, resource development, and scientific researches and investigations.

Remote sensing is a very convenient tool in assessing, monitoring and

conserving groundwater resources. Satellite data provide instant and useful

baseline information on the criteria controlling the occurrence and movement

of groundwater like lithology/structural, soils, geomorphology, land

cover/land use, lineaments etc. Many literatures are available to know the

importance of RS and GIS in artificial recharge modeling.

Frank et al. (1996) used remote sensing and GIS to quantify

discharge and recharge fluxes for the Death Valley regional groundwater flow

system, USA.

Ramasamy and Anpazhagan (1997) integrated water level

fluctuation data, geological data, geomorphologic data and sub-surface

geological data for identifying suitable sites for artificial recharge in Ayyar

sub-basin in the Cauvery drainage basin of Tamil Nadu. Water level

fluctuation data, geologic data, geomorphologic data and sub-surface

hydrogeologic data were used for identifying the suitable areas of recharge.

Sites with all the four parameters favourable were classified as first priority

sites. Sites with any three parameters including water table fluctuation and

hydrogeology favourable for recharge were categorised as second priority

sites and water table fluctuation are favourable were classified as third

priority classes. Suitable site for various artificial recharge structures were

demarcated.

Saraf (2002) developed an integrated remote sensing and GIS

technique for groundwater recharge investigations in the hard rock terrain in

Silai watershed of West Bengal. The weighted overlay analysis and Boolean

logic method was discovered and it was very useful for delineation of

recharge suitable areas. The data used were IRS 1A LISS II and IRS 1C LISS

27

III false colour composites, SOI topographic sheets, thematic maps of geology,

geomorphology and soil from National Bureau of Soil Survey and Land Use

Planning. Water level data from 34 wells, collected by State Water

Investigation Directorate were also used for the study. Manual digitisation

was done by ILWIS Software. Remote sensing data were interpreted using

supervised classification technique. Arc View 3.1 was used for analysis and

processing.

Kshirish and Santhosh (2002) investigated suitable recharge zones

using remote sensing data and geographic information system for Rangareddy

District, A.P. Parameters such as surface contour, drainage, lineament and

groundwater depth are taken into consideration and converted into thematic

layers. Overlay of these thematic layers gave the final recharge zone map. The

area was categorised from excellent to poor zones. The result of the study has

given a clear picture about the recharge suitability of the areas.

Mbilinyi et al. (2007) used GIS-based decision support system

(DSS) for identifying suitable sites for rainwater harvesting in Tanzania. The

inputs into the DSS were maps of slope, rainfall, soil depth, soil texture,

drainage and land use/cover and the outputs were maps showing potential

sites of stone terraces, water storage systems, borders and bench terraces.

Ghayoumian et al. (2007) used GIS techniques to decide areas best

suited for artificial groundwater recharge in a coastal area in southern Iran.

Thematic layers for slope, depth to groundwater, infiltration rate, quality of

alluvial sediments and land use were prepared, categorized, weighted and

combined in a GIS environment by means of Boolean and Fuzzy logic. To

know the relationships between geomorphological units and the suitable sites

for groundwater artificial recharge, land-use and geomorphological maps

were used from satellite images. The results showed that about 12% of the

28

study area was suitable and 8% was moderately suitable sites for artificial

groundwater recharge.

Yu-Feng Lin et al. (2009) used PRO-GRADE GIS Toolkits for

groundwater recharge and discharge estimation. GRADE-GIS used a mass

balance method that needs only water table, hydraulic conductivity, and

bedrock elevation data for simulating two-dimensional steady-state

unconfined aquifers. PRO-GRADE was developed to assess the water

resources in Illinois and Wisconsin, in the United States. Maggirwar and

Umrikar (2009) identified the feasibility of artificial recharge in developed

miniwatersheds using a RS-GIS approach. The thematic layer of drainage

map, soil map,village map, geomorphology and land use maps were prepared.

The overlay analysis of drainage and geomorphology was done by

superimposing the geomorphology and drainage thematic layers for the

identification of suitable zones.

Sukumar and Sankar (2010) delineated the potential zones for

artificial recharge using GIS in Theni district, Tamilnadu, India. Various

thematic maps like soil depth, permeability, water holding capacity, drainage

intensity, and soil texture maps were prepared using National Bureau of Soil

Survey and Land use Planning map, Bangalore. GIS has been utilized for the

integration of various thematic maps to depict the suitable zones for artificial

recharge. Each theme was given a weightage depending on its effect on

groundwater recharge. Each unit or class in the map was given a knowledge-

based ranking from one to four depending on its importance in storage and

transmittance of groundwater. The final map was prepared stating high,

moderate and least favourable zone for artificial recharge.

Balachandar et al. (2010) used Remote Sensing and GIS for

Artificial Recharge Zone in Sivaganga District, Tamilnadu, India. Various

thematic maps were prepared which included Drainage density, Drainage,

29

Lineament density, Lineament, Geomorphology, Land use and Land cover

using Landsat data and used Digital Image processing, the supervised and

unsupervised Classification, Band ratioing, Filtering and Normalised

Difference Vegetation Index (NDVI) Techniques for updating the all thematic

maps. Weightages were given to all the thematic maps and were integrated for

identification of suitable site for artificial recharge.

Ismail Chenini et al. (2010) had done the groundwater Recharge

Zone Mapping using GIS-Based Multi-criteria Analysis for the Maknassy

Basin in Central Tunisia.

The advent of RS and GIS has opened new paths for groundwater

recharge studies. This is due to the fact that earth monitoring devices give

most latent, precise, unbiased and detailed spatial, spectral, and temporal

information on conditions of water resources. In order to execute artificial

groundwater recharge, it is important to delineate potential groundwater

recharge zones. Conventionally, remote sensing, photo geological,

hydrogeological and geophysical methods are deployed to select suitable sites

for implementing artificial recharge scheme. Further, the effectiveness of

recharge may be studied by monitoring the structures.

2.5 GROUNDWATER MODELLING

Most groundwater models used today are mathematical models.

Mathematical groundwater models are based on conservation of mass,

momentum, and energy, give cause and effect relations. A mathematical

model can be used as a design tool to determine the need for groundwater

artificial recharge. Many researchers around the world have tried to carry out

groundwater recharge modeling.

30

Gnanasundar and Elango (2000) carried out the groundwater flow

modeling of a coastal aquifer near Chennai, India using MODFLOW. The

model was calibrated under steady and transient conditions. The spatial

distribution of groundwater head and well hydrograph was compared with the

historical data. It was concluded that rapid urbanization would lead to further

reduction of water table at few locations along the northern coast of the

aquifer system and the model was sensitive even for 5% reduction in recharge.

Gogu et al. (2001) created GIS-based hydrogeological databases

and groundwater modelling of Belgium for the Walloon region. Data from a

total of five river basins, chosen for their different hydrogeological

characteristics, were included in the database. A "loose-coupling" tool was

developed between the spatial-database scheme and the groundwater

numerical model interface GMS (Groundwater Modelling System). The

hydrogeological data stored in the database could be easily used following

time and spatial queries within different groundwater numerical models. Ward

Sanford (2002) reviewed recharge and groundwater models.

Shammas and Jacks (2007) used the codes MODFLOW and

MT3DMS for solute transport to decide the flow of the freshwater/saltwater

interface. The study proposed the conservation of the groundwater in Salalah

plain aquifer in Oman from further encroachment by artificial recharge with

reclaimed water along the Salalah coastal agricultural strip.

Palma and Bentley (2007) simulated the groundwater flow in the

Leon-Chinandega aquifer in northwest Nicaragua by using MODFLOW

under transient and steady-state conditions for determining groundwater

availability for irrigation, without considering the effects of groundwater

development.

31

Joseph Zume and Aondover Tarhule (2008) simulated the effects of

groundwater pumping on stream-aquifer dynamics in semiarid northwestern

Oklahoma of USA using visual MODFLOW. Water need in semi-arid

northwestern Oklahoma was predicted to increase by 53% during the next

five decades, driven mostly by public water supply, irrigation, and

agricultural demand. Using MODFLOW's stream flow routing package,

pumping-induced changes in base flow and stream leakage were assessed to

find out streamflow depletion in the Beaver-North Canadian River system.

Results showed that groundwater pumping decreased base flow to streams by

29% and also increased stream leakage into the aquifer by 18% for a net

streamflow loss of 47%. The size and intensity of stream flow reduction

varied for different stream segments, ranging from 0 to 20,804 m3/d.

Szucs et al. (2009) investigated the recharge from open-surface-

water resources as a method for remediation of overproduced and polluted

aquifers. MODFLOW-2000 and MT3DMS simulation softwares were used

for the simulation of the best remediation approach to aquifer recharging from

surface waters.

Bhuiyan et al. (2009) modeled the groundwater recharge-potential

in the hard-rock Aravalli terrain of India. A GIS-based water table fluctuation

method was tried for quantitative modelling of groundwater recharge of the

hard-rock Aravalli terrain. This GIS-based model was used to estimate

recharge-potential of the area by integrated assessment of infiltration level,

normal rainfall and its frequency.

Taheri and Zare (2011) carried out the groundwater artificial

recharge modeling of Kangavar Basin, a semi-arid region in the western part

of Iran. MODFLOW was selected to simulate the aquifer. Calibration was

done for the water levels in the existing piezometers during the year 2003.

Groundwater fluctuations from the year 2004 to 2008 were predicted to

32

validate the model. The study revealed that the observed water level data were

good, adjusted to achieve a reasonable fit with the calculated data. Artificial

recharge impacts were evaluated in different positions. Groundwater level

mound of 3 m with recharged water volume of 3.42 MCM in two sites, and

upconing of 6 m in 3 sites with recharged water volume of 7 MCM were

obtained. The maximum radial effect of these artificial recharge sites was

found to be 1.5 km.

Groundwater modeling is a tool to understand the behaviour of

aquifer systems under different hydrological stresses, whether activated

naturally or by humans. From the various literatures, it is clearly known that

with the help of models and with various prediction scenarios, management

policy can be framed for the future protection of aquifers.

2.6 RWH IMPLEMENTATION

RWH is the technique of collection and storage of rainwater at

surface or in sub-surface aquifers before it is lost as surface run-off. The

harvested resource can be utilized at the time of need. Artificial recharge to

groundwater is a method by which the groundwater reservoir is augmented at

a rate exceeding that under natural conditions of replenishment. Methods of

groundwater recharge mainly in urban areas are roof top rainwater, storm

runoff harvesting through Recharge Trench, Recharge Pit, Recharge shaft and

Recharge well, whereas in rural areas, techniques of Contour Bund, Gully

Plug, Percolation tank, Nala Bund, Check Dam, Recharge shaft, Dug well

Recharge and Subsurface Dyke are used.

In Philippines, RWH was started in 1989 in Capiz Province with

the help of Canadian International Development Research Centre (CIDRC).

About 500 rainwater storage tanks were built using wire-framed ferro-cement,

with capacities varying from 2 to 10m3.

33

RWH has become an important choice for Gansu Province, China

to supply drinking water, promote rain-fed agriculture and improve the

ecosystem in dry areas. In 1995/96, the "121" Rainwater Catchment Project

implemented by the Gansu Provincial Government assisted farmers by

constructing one rainwater collection field, two water storage tanks and

giving one piece of land to grow cash crops. This had proved successful in

supplying drinking water for 1.3 million people and developed irrigated land

for a courtyard economy. As of 2000, a total of 2,183,000 rainwater tanks

were built with a total capacity of 73.1 Mm3 in Gansu Province, supplying

drinking water for 1.97 million people and supplementary irrigation for

2,36,400 ha of land.

A marginally larger RWH system exists in the Changi Airport,

Singapore. Rainfall from the runways and the surrounding green areas are

deflected to two impounding reservoirs. One of the reservoirs is devised to

balance the flows during the high runoffs and incoming tides and the other

reservoir is used to collect the runoff. The water is used mainly for non-

potable functions such fire-fighting drills and toilet flushing. Such collected

and treated water accounts for 28 to 33% of the total water used leading to

savings of approximately S$ 390,000 per annum.

Since May 2001, the Government of Tamil Nadu had promoted

awareness about RWH throughout the State. In view of deficit in demand-

supply, Tamil Nadu Government introduced a law in October 2002, followed

with an ordinance in June 2003, enforcing the implementation of RWH

systems compulsory in all existing buildings. Roof top rainwater harvesting

through existing and abandoned wells were executed in premises of all the

residences, government and private establishments. Awareness programmes

and regulatory options were conducted by State and Central agencies to

control the large scale unscientific extraction of the groundwater resources.

34

Central Groundwater Board (CGWB, 2007) had implemented a

number of pilot schemes for the popularization of cost-effective technologies

for artificial recharge of groundwater. Various structures like check dams,

recharge shafts, percolation ponds and subsurface dykes were built in

different hydrogeological settings. In Tamilnadu State, 7 percolation tanks

and a subsurface dyke were constructed.

2.7 IMPACT STUDIES ON RWH

Many researchers around the world have tried to study the impact

of RWH Systems. Gore et al. (1998) estimated the effects of RWH in 16

observation wells in Maharashtra State, by modelling groundwater coupled

with a water balance model, concluding that there was an overall increase in

groundwater from RWH recharge of 8 ha.m/year. Badiger et al. (2002)

monitored 42 wells in four micro catchments and the effect of recharge with

distance from the wells. It was inferred that recharge from RWH was about 3

-8% of rainfall.

Kun Zhua et al. (2004) focused mainly on the quality of rainwater

harvested from different catchment systems and stored at different periods of

time. By analysing the water samples, it was clear that rainwater quality could

be improved much by self-purification during the storage. The results showed

that roof-top catchments that included the "first flush'' usually gave safe

drinking water with low organic contents, even for rainwater collected

immediately after rainfall.

Deepak Khare et al. (2004) analysed the impact assessment of

RWH on groundwater quality at Indore and Dewas, India. The impact

assessment of roof top rainwater harvesting on groundwater was done with

the help of working tube wells to improve the quality and quantity of

groundwater. The roof top rainwater was sent to the ground using sand filter

35

for pre-treatment. Gontia and Sikarwar (2005) reported that groundwater

levels rose by 8 m in wells in the Saurashtra region of Gujarat and this rise

was believed to come from RWH, though no measurements were taken from

the structures themselves.

Sharda et al. (2006) quantified recharge from a number of RWH

structures in Gujarat, using the water balance method and the water table

fluctuation method. It was found that the structures had a limited capacity to

induce maximum recharge and that a cumulative rainfall of 104.3 mm was

required to induce 1mm of recharge.

Impact assessment of rainwater harvesting on the groundwater regime

was done by CGWB, India in Chennai City. The study showed that the water

level, which ranged from 1.75 to 6.96 m (below ground level: bgl) during May

1997, rose to 0.33 to 6.7 m (bgl) during May 2007. The percentage of wells

having water level less than 5m (bgl) had been increasing after RWH. The

wells, which were dry during the summer months (located in Aminjikarai,

Velachery, Gandhi Nagar, Thiyagarya Nagar and Besant Nagar areas within

Chennai City) prior to the year 2004, recorded rise in water levels.

Pachpute et al. (2009) evaluated the sustainability of RWH systems

in rural catchment of sub-Saharan Africa. A study was undertaken in

Makanya catchment of rural Tanzania to assess the sustainability of storage

type of RWH systems including micro dam, dug out pond, sub-surface runoff

harvesting tank and rooftop RWH system. It was found that higher crop

production was observed in 12 to 20 ha area near RWH type micro dams.

Sturm et al. (2009) described the results of investigations of RWH

in Namibia, on the basis of technical, hydrological, social and cultural

conditions. Suitable solutions for RWH were developed, discussed and

evaluated. The calculations indicated that it was economically reasonable to

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use decentral techniques of RWH in terms of the roof catchment systems.

Katrin Vohland and Boubacar Barry (2009) showed that in-situ RWH was a

promising practice to help sustainable development in sub-Saharan Africa

facing climate change impacts. It improved hydrological indicators, enriched

soil nutrients and increased biomass production.

Olanike and Omotayo (2010) evaluated the potential for RWH in

Abeokuta which had a average annual rainfall of 1,156 mm. 26-year rainfall

data were analyzed to obtain intra annual variability which lied between 0.7

and 1.0 while the inter annual variability was 0.2. Annually, 74 m3 of

rainwater could be harvested per household. Estimated annual need for

flushing, laundry and flushing were 21.6 and 29.4 m3 respectively. Harvested

rainwater in Abeokuta could meet the household monthly water demand for

WC flushing and laundry except for November, December, January and

February. The excess rainwater stored in the month of September and October

was enough to augment the shortfall in the dry months provided there was

adequate storage. Water savings potential is highest in June and September

which is the rainfall peak period in Southwest Nigeria.

Yong-chao Zhou et al. (2010) analyzed the RWH system for

domestic water supply in Zhoushan, China. A computer model was generated

to examine the performance of the DRHS (Domestic RWH system) with

different ratios of water demand/average annual collected runoff and storage

capacity/average annual collected runoff. The performance of DRHS was

analyzed by means of the model simulation.

Glendenning and Vervoort (2011) studied the hydrological effects

of RWH in a catchment of Arvari River, Rajasthan, India. This study analysed

a catchment-scale RWH impacts using a conceptual water balance model. The

simulation results revealed that RWH had a favorable effect on groundwater

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recharge and sustainability of irrigated agriculture, but decreased the stream

flow downstream.

2.8 STUDIES ON RAINFALL RUNOFF MODEL

USDA (1986) developed a simple empirical method called the U.S.

soil conservation Curve Number Method for estimating the amount of

rainwater available for runoff in a catchment. The method was developed by

the analysis of runoff volumes from small catchments in the US. The initial

abstraction values determined by the curve numbers were developed for

different soil types and Land-use practices.

Dunne and Leopold (1978) examined a number of environmental

factors that govern the rate at which water infiltrates into soil. These include;

the rate of rainfall, soil properties (including texture, soil porosity, organic

matter content, structure of soil aggregates, soil depth and moisture carrying

capacity of the soil), topography (slope), vegetation cover and type of land

use.

Schwab et al. (1981) stated that the term runoff can be applied to

stream or river discharge. It can be employed in reference to the gravitational

movement of a fraction of rainfall over the surface of land or as subsurface

flow from an area peripherally bound by a water divide, towards a water

body. Runoff is expressed in terms of volume per unit of time and its

generation largely depends on the amount of rain water that reaches the

earth’s surface.

Schwab et al. (1981) studied the infiltration rate which refers to the

rate at which water enters the soil during or after rainstorm. It plays a key role

in controlling the amount of water that will be available for surface runoff

after a rainfall event. It involves several processes acting together including

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gravitational forces pulling the water down, attractive forces between soil and

water molecules and the physical nature of soil particles and their aggregates.

Ward and Robinson (1990) studied that runoff in a catchment is

generated by the portion of rainfall that remains after satisfying both surface

and subsurface losses. Once these demands have been met, the remaining

rainwater follows a number of flow paths to enter a stream channel. The

course it follows depends on several factors including soil characteristics,

climatic, topographic and geological conditions of a catchment. Overland

flow or surface runoff is the main flow path of runoff that can largely be

influenced by human activities through catchment management practices. It is

also the flow path of rainwater that triggers the process of soil erosion

Beven (2000) stated that both the input and output variables of

stochastic runoff models were expressed in terms of a probability density

distribution. In a stochastic modeling approach, uncertainty or randomness in

the possible outcome of the model was permitted because of the uncertainty

that was introduced by the input variables of the model.

Rientjes (2004) explained that black box models involved the

simulation of empirical relations through the use of regression equations that

were developed after long-term field observations. The use of regression

coefficients was derived from observation rather than from the theoretical or

physical background of natural process.

2.9 SUMMARY

Rainwater harvesting is very important as pressure on

population and natural resources is increasing in India. Large numbers of

RWH models viz., water balance model, regression analysis, water table

fluctuation model, ground water recharge estimation model are available in

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the literature. They are specific to demand and site because RWH system

depends on the topography, land use, land cover, rainfall and demand pattern.

So an evaluation of each model is required for the analysis of hydrology,

topography and other elements like economics and site availability. However,

a common methodology could be evolved. The present study aims at

evaluating the effect of rainwater harvesting in Agastheeswaram taluk of

Kanyakumari District.