CHAPTER 4

HYDROGEOCHEMISTRY

4. 1. INTRODUCTION

Groundwater is a very important constituent of our ecosystem

and plays a significant role in augmenting water supply to meet the

ever increasing demand of domestic, agricultural and industrial uses. It

is now generally recognised that the quality of groundwater is as

important as its quantity. The suitability of natural water for a

particular purpose depends upon the standards proposed by the

various international bodies such as World Health Organization (WHO),

Central Public Health and Environmental Engineering Organisation

(CPI-IEEO), Ministry of Urban Development, Government of India and

Bureau of Indian Standard (BIS). The preservation and improvement of

groundwater quality is of vital importance for human well being as well

as for the sustainability of clean environment. Groundwater gets

polluted by several anthropogenic and natural sources such as

industrial and domestic waste, artificial recharging by polluted water,

pesticides, fertilisers, intrusion of saline water, soluble pollutants such

as arsenic, fluoride, etc., present in the rock formations (Raj, 2003).

Taking into consideration of the fact that groundwater occurs in

alliance with geological materials, generally high concentration of

dissolved constituent are found in groundwater than in surface water

because of its greater exposure to soluble minerals of the geological

formations. Groundwater passing through igneous rocks dissolves only

Table 4.1 Various Sources of ions in water (Hem, 1959)

i Major ions SourcesCalcium Car p Carbonates, gypsum[_ __ _ O O

p Magnesium Mg2* Olivine, pyroxene, amphibole g H lSodium Nat W | Clays, feldspars, evaporates, industrial wastePotassium Kt y Feldspar, fertilizers, K-evaporatesBicarbonate HCO3- a Soil and atmospheric CO2, carbonates

I

Chloride Cl­ Windborne rain Water, sea water and natural

Sulphate SO42­

, brines, evaporates deposits;gpol1utiong g _ WGypsum and anhydrite, sea water, windborne,

NltI'Elt€ N03‘

goxidationof pyrite 7 g7 windborne, oxidation of ammonia or organicnitrogen, contanlination g g

Silica,SiO2 g Ig Hydrolysis of silicatesMinor ions (1 to 0.1 mg/1)

Iron, Fe?­

Manganese Mm?­corrosion of iron piges W WOxides and hydroxides

Oxides and sulphides, e.g. heamatite and pyrite;

Boron B X Tourmaline, evaporates, sewage, sea wateri Fluoride F­

, O — _ _ ~ OFluorine-bearing minerals, viz. fluorite, Biotite

Trace elements (< 0.1 mg/1)___­

M As

l

Arsenic minerals, e.g. arsenopyrite, arsenicinsecticides O Ol

J O Marine vegetation, evaporates1, Zn Sphalerite, industrial waste g g3 Heavy metals (Hg, if Industrial waste and igneous rock weathering,4Pb, Cd,”Cr) g gRadioactive elements

t_(U’ Ra? etC_'_L g O . O

, under mild reducinéggeonditgionsg g U pg 7= Uraniferous minerals, nuclear tests and nuclearpower_pla.nts, H W H g p g

l

l

1

l

l

1

7

l

l

a small quantity of mineral matter because of the relative insolubility of

the rock composition (Todd, 1980).

The characteristics of groundwater as to whether hard or soft

(mineralised or non mineralised) depend on the extent of reactions it

made with the country rock (Edmunds, 1994). Compared to surface

water, the groundwater moves very slowly through the pore spaces

found in the surrounding country rocks. Thus it gets more residence

time and hence more ions will be dissolved into the groundwater as a

result of the interaction between the groundwater and the wall rocks. In

contrast to surface water bodies, if groundwater body is polluted once,

it will remain as it is for a considerable time (up-to tens of hundreds of

years) because the natural processing of flushing is very slow.

Hydrochemical data can help to estimate such properties like the

amount of recharge, the extent of mixing, the circulation pathways,

maximum circulation depth, temperature at depth and residence time5

of groundwater (Edmunds, 1994).

The quality of groundwater is controlled by several factors, viz.,

climate, soil characteristics, interaction with the country rocks, saline

water intrusion in coastal areas and the human activities on the

ground. A source of various ions in water as given by Hem (1959) is

furnished in the Table 4.1. The analysis of groundwater for its quality

includes the determination of the cations like Na, K, Ca, Mg and Fe

anions CO3, HCO3, Cl, SO4, N03 and PO4, trace elements, pl-l, Electrical

Conductivity (EC), Total Dissolved Solids (TDS) etc. An attempt has

72

been made in this chapter to understand the quality of groundwater for

the domestic and irrigation purpose.

4.2 GROUNDWATER SAMPLE COLLECTION

Groundwater samples have been collected from 81 dug wells in

the Bharathapuzha river basin during pre monsoon and post monsoon

(Fig. 4.1). Groundwater samples were collected in pre cleaned plastic

polyethylene bottles. Prior to sample collection, the plastic bottles were

rinsed two to three times with the respective groundwater sample. The

parameters like pH, EC and TDS were measured in the field itself. For

fixing total iron, samples were preserved in the field by adding

concentrated I-lCl (2ml/ 100ml] as a preservative agent and transported

to the laboratory for the analysis.Cations and anions were determined

following the standard procedures recommended by American Public

Health Association (APHA, 1985), standard methods for examination of

water and waste water (Table 4.2)

4.3 LABORATORY WORK

4.3.1 Physical parametersThe non ionic substances like pH, TDS 85 EC present in

groundwater affect the general quality of water and are discussed

below.

pH

pH is a measure of hydrogen ion concentration and determines the

acidity or alkalinity of water sample. The desirable range of pH of water

73

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Table 4. 2 Methods followed for the determination of various physicaland chemical parameters of groundwater

‘ S.No. i Constituents Equipmentszgd methodspi pH (Hydrogen ion

i 1 K Concgntration) g M A4 g PH meter, pH Scanl N KT 2 ‘ Electrical Conductivity (EC) Conductivity meter CM 183

3 Calcium EDTA4 Magnesium EDTA

; 5 Sodium 8:, Potassium Flame photometer1 6 Chloride Argentometry

7 A Sulphate 85 Nitrate Spectro photometerC C -‘V C C ’8 Carbonate 81; Bicarbonate 5 Acidimetryi C lC 9 Fluoride SPADNS 5

< 10 A Total Dissolved Solids TDS meta CM 183C tons)I 11 Alkalinity Volumetric method12 all Hardness ETDACl C lgC C! Ci 13 1 Total Iron Spectrophotometerii, __ _ __ _ _ H

prescribed for drinking purpose by BIS and WHO (1984) is 6.5 to 8.5.

The pH of natural waters is slightly acidic (5.0 - 7.5) and is caused by

the dissolved carbon dioxide and organic acids (fulvic and humic acids),

which are derived from the decay and subsequent leaching of plant

materials (Langmuir, 1997). The water with pH value above 10.0 is

exceptional and may reflect contamination by strong bases such as

NaOH and CaOH.

74

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The pH distribution of groundwater of the basin for both season

are given in the Table 4.3a 8; 4.3b and Figure 4.2a 8:. 4.2b. The pl-I

value ranges from 6.11 at Thonurkara to 9.1 at Palakkad for the

premonsoon with a mean value of 8.01 (Table 4.3a). While, for the post

monsoon it varies from 6 at Thiruallathur to 8.9 at Thathamangalam

and Kannapara with an average value of 7.67 (Table 4.3b). During the

pre monsoon, the pH value shows (Fig. 4.2a) that majority of the area

falls within the 8 — 8.5 category reflecting the alkaline nature. The

acidic nature of the basin is seen at the southwestern and

northwestern areas for both the seasons, whereas the alkaline nature

of the basin is noticed in the eastern and southern part (Fig. 4.2a 8:»

4.2b). It is also observed that there is a decreasing trend of pH values

from pre monsoon to post monsoon season. The acidic nature of the

groundwater can be attributed to the dissolution of CO2, which is being

incorporated into the groundwater system by bacterial oxidation of

organic substances (Matthess and Pekdeger, 1981) and the addition of

CO2 through rainwater. Moreover the acidic nature of basin is related to

the wide distribution of lateritic soil (CESS, 1984). Further the study

area encompasses extensive agricultural fields and the observed acidic

nature could be related to the use of acid producing fertilisers like

ammonium sulphate and super phosphate of lime as manure for

agriculture purpose (Rajesh et al. 2001). The higher pH values in the

basin may due to the higher concentration of bicarbonates. Except few

locations all other areas of the basin are fall within the permissible limit

of BIS and WHO standards (6.5 to 8.5).

75

".

••

••

Lec·ad

pH

. <6.S

. 6.5-7

. 7 - 7.5

. 7.5 -8

.8- 8.5

D >8.5

'a ' Pre mODaooD

,.."" n-,SO'"e

CbI Po. t mODaoon

Le,. ad

pH

_ .6.5 . 6.5-7

. 7-7.5

. 7.5-8

• 8 - 8.5

0 '8.5

7S-3OVE

-4· •

15 30 Km , ' . i$,. ":MltiVL7ZUVZA

•

15 30 Km E .tt., . '{.' .. i:.1i"ZZZl2Zll2

Fig. 4.2 Distribution of pH in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

1G'45·O"N

10"JOVN

1l"O"O'l(

10"45·O"N

10030vtI

Electrical conductivity (EC)

Electrical conductivity is a measure of salt content of water in the

form of ions (Karanth, 1987). It is measured in micro siemens/cm

(pS/cm). In the present study, EC during pre monsoon ranges from 86

uS/cm at Karakkod to 1435 pS / cm at Kanjikode and the mean value is

443 pS/cm (Table 4.3a), while in the post monsoon it ranges from 53

pS/cm at Thozhupadam to 1325 pS/cm at Kanjkode and with a mean

value of 403 pS/cm (Table 4.3b). The spatial distribution maps of EC

for the study area (Fig. 4.3a 81, 4.3b) reveals that for both the seasons,

low EC values are recorded at north and northwest region, while higher

values are observed at eastern part. The high EC values on the eastern

part may be due to the addition of some salts from the agricultural

practices. The map also reveals that majority area of the basin in both

seasons, the EC values fall within the range of 250 - 750 and the water

is good for drinking and domestic uses. The lowering of EC values

during the post monsoon than in pre monsoon season is due to the

dilution of soluble salts by rain fall.

Total dissolved solids (TDS)

Total dissolved solids generally indicate the nature of water

quality/ salinity. The concentration of TDS in water is determined by

weighing the dry residue. The values are expressed in mg/1. The TDS

can be estimated from the formula

S=KxA

76

"

"

••

76' 1SVE

(al Pre monaoon

Lelend Eletrical Conductivity

I,.. S/cm) < 250

250- 500

500- 750

_ 750.2000

7II' 1SVE

(hI Poat monaoGn

Lelend

Eletrical Conductivity (,..S/cm)

_ < 250 _ 250 - 500

0 500 . 750

_ 750 - 2000

78' 0'0"£ 78'1 5'O"E

16' 30"0"'£

,..,....

15 JOKm E, , ~ , _ S""t;VOVzlzl)l

~ • • 15 30 Km

. ., j ' .. C,Vl7LLZl27)I

11'O'O"N

""OV'N

10'3O"0'"N

Fig. 4.3 Distribution of Electrical conductivity in the Bharathapuzha river basin. (a) Pre monsoon (bl Post monsoon

Where,

K = conductance in micro mhos/ cm at 25°C

A = is a conversion factor ranges from O .55 to 0 .75

The build of TDS include carbonates, sulphates and chlorides of

calcium, magnesium as well as sodium. Higher the TDS values, the

greater will be the EC. Drinking water quality is affected by the

presence of soluble salts.

Table 4.4 The potability of water in terms of TDS (mg / l) as perWHO (1984).

, ( monsoon ( monsoon ( monsoon , monsoon T, U _ . _ F~ TDS , No of samples 9 Percentage. Watfif Cl8.SS ltimpra post — 2 '» pre 2 ‘ post T it

gExcellent l<300 g 446 “j 58 ‘@049 71.60 9- _l_ ll ..l(Good 300-600 28 21 35.56 25.93 (

Fair g (600-900 ,4 g 1 ,2, (4.94 2.46 jPoor 900 1200 ‘. y A- "o W‘ ._' _-' . g|_.A unacceptable >12O0 — _-g _( - ,- T g

Usually unconfined aquifer system has relatively low TDS

(Langmuir, 1997). The hydrogeological properties of rocks will have a

strong influence on the extent of water/ rock reaction. Areas with high

groundwater flow velocities usually have relatively low dissolved solids

because of shorter groundwater rock contact time and high water/rock

ratios and vice-versa (Langmuir, 1997). Typical high groundwater

velocities are found in highly fractured or weathered near surface

igneous and metamorphic rocks. Such conditions are usually found in

shallow water table (unconfined) aquifers but not in deep confined

aquifers. On this basis low TDS values can be attributed to high

rainfall, which causes dilution.

In the present study TDS values of pre monsoon ranges from 59

mg/1 Thirunavaya to 803 mg/l Meenakshipuram and the mean value is

2'7 2 mg/l (Table 4.3a) whereas in post monsoon it ranges from 35 mg/1

at Thozhupadam to 758 mg/l at Kanjikode and the mean value is 245

mg/l (Table 4.3b). The spatial distribution maps of the study area in

both seasons reveal that low TDS values are seen at the western region

while the higher values are seen at eastern part of the basin (Fig. 4.4a

81, 4.4b]. The potability of water in terms of TDS as per WHO (1984) is

given in the Table 4.4. and it reveals that the groundwater of the basin

is excellent for above 60% of the samples and good for 35 % of the

samples for both the seasons. Except two locations, the entire area of

the basin falls within the desirable limit of water quality standards of

BIS (500mg/1). When the TDS values are more than 500 mg/ l,

palatability decreases and may cause gastrointestinal irritation (Park

and Park, 1980) and is not ideal for drinking purposes.

The distribution map of TDS (Fig. 4.4) is compared with the

distribution map of water level fluctuation (Fig. 2.5) and it reveals that

higher TDS values shows higher water level fluctuation in the eastern

side of the basin where as lower TDS values reflecting low water level

fluctuation. Similarly, the same figure is compared at the western side

with the geomorphology map (Fig. 5.1) and reveals that the high TDS

values are noticed in the Plateaus whereas the lower TDS values are

seen in the valley fills and pediment zones.

78

...

•

"

••

"."'" 7$' 15'O'"E

la) PR mODaooD

Wlend

Total di .. olved aoUds (m.I / I,

D <: I 00

_ 100 - 300

_ 300 - 600 _ > 600

Le&end

,.., ....

Total dlnolved solids (ml/ l)

0 < 100

_ 100 - 300

_ 300 - 600

• > 600

76'O"O'"E

".~ 76'45'0"£

15 JO Km .r;. . ," ,$-h· /fO VLlllLZZZd

15 30 Km [' ,1\;" , i(,·.l,,~

Fig. 4.4 Distribution of TDS in the Bharathapuzha river basin la) Pre monsoon Ib) Post monsoon

10'"45'O"N

10"3O'O"N

10'45'ln1

10'WD"N

HardnessGroundwater hardness is defined as the sum of divalent cation in

solution but depends largely upon the concentrations of aqueous

calcium and magnesium (Taylor and Howard, 1994). Hardness of water

is caused by the presence of carbonates and bicarbonates of calcium,

magnesium, sulphate, chlorides and nitrates. Hardness is temporary, if

it is caused by carbonates and bicarbonates salts of the ions, it can be

removed easily by boiling. Permanent hardness is caused mainly by

sulphate and chloride of the metals. Water of high hardness is not

suitable for household cleaning purpose and it increases the boiling

point of water. A low pH of groundwater favours the dissolution of

carbonate mineral, which in turn enhances the hardness by dissolving

carbonate minerals in the country rock (Todd, 1980). Based on the

hardness (Sawyer and McCarty, 1967), water is classified into soft,

moderately hard, hard and very hard (Table 4.5).

In the present study, the hardness for the premonsoon ranges

from 10 mg/l at Karakkod to 570 mg/1 at Ozhalapathy and the mean

value is 143.11 mg/1 (Table 4.3a). In the post monsoon, it ranges from

11 mg/l at Desamangalam to 452 mg/l at Meenakshipuram and the

mean value is 125.6 mg/l (Table 4.3b). From the spatial distribution of

hardness of Bharathapuzha river basin (Fig. 4.5a 8:. 4.5 b), it is noticed

that for both the seasons, the low values are seen at the northern

region whereas higher values are seen at eastern part of the basin,

Meenakshipuram, Kanjikkode and Walayar, reflecting the host rock

composition calc-silicate/ calc-granulite with limestone. Generally there

79

".

••

76'O'O'"E 78'\S'!l'"E

ta , Pre mon.oon

Lelend

Hardae .. (m, / I)

D<75

. 75- 150

_ ISO. 300

• • 300

Moderately Hard

H~d

Very Hard

111'15'0'"£

7lI'15V£

(hI Post mODaoGn

Le&end

Hu dne .. (011 / 1)

0< 75

. 75- I SO

• ISO · 300

• • 300

s.f< Mod"rald y Hard

Honl

Vf!.TY Hard

l e'IS'erE

76'3O'O"E

10"45'ln1

10'30"0"1<1

1S JOKm ! ·tt· . ,?{,-·,; ,VLUZlZUil

11'~

10"4S'O"N

10'WO'"N

15 30 Km f ,m . ,G-.. i vZLl2'l.ZZZ2i

Fig. 4.5 Distribution of Hardness in the Bharathapuzha river basin (a) Pre monsoon (h) Post monsoon

is a decreasing trend of hardness values from east to west. Most of the

areas in the basin, the hardness values ranges from 75-150 mg/1 and

moderately hard water class.

Table 4.5 Classification of degree of hardness in water(Sawyer and McCarty 1967)

a3 3 33 33 3 1 3 33 _'3 3 1

‘ Hardness, PercentageGroundwater ( /1 No. of samples 1m ‘ I r ~ .*~ .. ' ;‘—~ *7? — - " —l­class 1 g ) Pre A Post Pre it Post

A as CaCO3 ,. ’ ITIOIISOOII I'I1OI1SOOT1 I'I1OI'1SOOI'l . IT1OI'1SOOI1 1

1Soft 0-'75 31 . 30 4 33.27 ‘ 37.04 ’3 3 _ — _ . ‘r—- ._ ‘IModerately ~ 175-150 20 27 . 24.69 33.34hard ~V33 3 3 3 33 i_ 3 343 3- 13- 3»- ­Hard 150-300 ' 21 1 17 1 25.93 » 20.98 ’1 ‘ ;Very hard ‘ >300 T 9 1 7 11.11 8.64K - V 4' 3_3l - i -3 .

3 _3 3 3 3_-3_L 3 3 3a- 33 33 _ 33 _Alkalinity

It is a measure of quantity of compounds that shift the pH to the

alkaline side or the capacity of water to neutralise the acids. There is no

standard established neither for surface or groundwater. A range of 100

to 250 mg/l for river water is considered normal. The study area shows

a range of 20 mg/1 at Kalladikode to 956 mg/l at Iswaramangalam and

with an average value of 142 mg/l in pre monsoon [Table 4.3a) and in

post monsoon it ranges from ll mg/ l at Kulakkalur to 988 mg/1 at

Iswaramangalam and the mean value is 144.91 mg/l (Table 4.3b). The

spatial distribution map of alkalinity (Fig. 4.6a and 4.6b} shows that

majority of the area falls within the desirable limit (300mg/1 —-BIS)

except lswaramangalam and Karakkod for both the seasons.

80

"

...

"

•

la) PR monaoon

Le,.nd

AlkaliDlty 1m.1/ 1)

_ <75

_7$ . 1~

D 150 · 225 _ 225 - 300

_ "300

7II-' !VE

(b) Post mon.OOD

Lelend

Alkalln!ty Im,ll)

_ <75

_ 15 _ 150

D 150 - 225 _ 22S-300 •. ,.,

, .4t.

•

15 300 Km t."!. . <. ,If WVlZZZZI

,

.4t. •

.o-e l)"'"

10-JCrO"N

IS 30 Km 1.If . <"<" IN tzU;UUZlJ

Fig. 4.6 Distribution of Alkalinity in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

4.3.2 Chemical analysis

The concentration of various anions and cations for the two

seasons were determined following the API—IA,1985 and is given in the

table 4.2. The values of T DS and EC were validated using the following

relationship lpS/cm= O.65mg/1. Cation-anion balance is important in

the case of groundwater analysis. The accuracy in the chemical

analysis of water samples can be checked by calculating the cation­

anion balance, in that the sum of major cations should be equal to the

sum of major anions which is expressed in meq/l. To account for

source dependency an allowable error limit of 10% is acceptable. The

percentage error is termed as ion balance error (e), which can be

determined following the equation given by Matthess (1982).

E = evc - sva / eye + eva

yc == cation sum in meq/l

ya = anion sum in meq/l

The ionic concentration of groundwater can be expressed in two

different ways:

i} The mg / l (parts per million, mg /1) concentration and

ii) The epm (equivalent per million, meq/1) concentration

The evaluation of data was carried out by using several standard

techniques of groundwater hydrochemistry. These techniques include

graphical methods like hydrochernical diagrams, such as Hill-Piper, the

U.S Salinity Laboratory (U.S.S.L, 1954] diagram and Wilcox diagram

H955)

81

Ca*, Mg2*, Nat and K* and Cl‘, C032", HCO33 SO49‘ and N03‘ are

the major cations and anions estimated in the groundwater of

Bharathapuzha river basin. The concentration of these ions in ppm and

epm for the samples during pre and post monsoon are given in the

Table 4.3a 8:, 4.3b and 4.30 8:. 4.3d respectively.

Calcium

Calcium is a major constituent of rocks and soils. The principal

sources of calcium in groundwater are silicate minerals like feldspars,

pyroxenes and amphiboles among igneous and metamorphic rocks and

lime stone, dolomite and gypsum among sedimentary rocks. In addition

to this, disposal of sewage and industrial waste are the main sources of

calcium. Hardness of water is due to the presence of calcium with

magnesium and concentration upto 1800 mg / l and does not impair any

physiological reaction in man (Lehr et al. 1980). The low content of

calcium in drinking water causes rickets and defective teeth. It is

essential for nervous system, cardiac function and in coagulation of

blood (Khurshid et al. 1998). It also has some disadvantages

0 High concentration of Calcium not desirable in washing,laundering and bathing.

0 Initiates scale formation in boilers.

0 Calcium with sulphate inhibits malt fermentation and withchlorides inhibits growth of yeast.

Calcium concentration in the groundwater of Bharathapuzha

river basin during pre monsoon varies from 5 mg/l at Thirunavaya to

135.2 mg/1 at Meenakshipuram and the average value is 35.87 mg/l

82

(Table 4.3a). Calcium concentration in the groundwater of

Bharathapuzha river basin during post monsoon varies from 6 mg/l at

Kootanad to 130 mg/1 at Meenakshipuram and the average value

(mean) is 32.75 mg/l (Table 4.3b). The thematic maps (Fig. 4.7a and

4.7b) show that calcium concentration in both seasons is high at

eastern side and there is a decreasing trend towards western region

irrespective of the fact that the extent has been reduced in post

monsoon.

In the basin calcium concentration in both seasons fall within the

highest desirable limit of WI-IO and BIS standards (75 ppm) except for

Chittor, Palathully, Walayar and Meenakshipuram where the limit is

confined to permissible limit (200 ppm] during pre monsoon and in

post monsoon to that Ambalapara, while Meenakshipuram remains

well within permissible limit irrespective of the seasons. These

variations can be attributed to the soil type present in the area. The

most livelyhood source is of weathering of plagioclase feldspar and

other feldspars of the host rock.

Magnesium

It is an important component of igneous, metamorphic and

sedimentary rocks. Minerals like chlorite, serpentine, biotite,

hornblende, olivine and augite are the main source of magnesium and

the main rock type in the study area are hornblende biotite gneiss and

83

"

"

"

7e'o"O"E 7e"S'O"E

(a) Pre monaoon

w,ead

Calcium (mil l)

_ < 25

0 25-50

_ 50-75 _~75

,..""

(bl Post mon&oon

Lelend

Calcium (mil l)

_ < 25

0 25-50

_ 50.15

_ ~75 •

lS'lOVE

o b _lf.

o

•

15 30 Km 9' P. tf·euzanz?I

78'(5'O"E

lII'(we

• .4p-. •

" 30 Km E .m . > (, ... Z\'.V7Z07l27)J

"'ilVt\I

l1'O~

l O' .S'O"N

10'J.O'O"N

Fig. 4.7 Distribution of Calcium in the Bharathapuzha river basin la) Pre monsoon Ib) Post monsoon

charnockite. Magnesium adds to the hardness of water and with

calcium.

In the study area, magnesium content of groundwater during pre

monsoon ranges from 2 mg/1 ( Kongad) to of 98 mg/1 (Kanjikode) and

with an average value of 19.03 mg/1 (Table 4.3a) whereas in post

monsoon ranges from 1.2 mg/l at Kalladikode to a maximum of 89

mg/l at Kanjikode with an average value of 17.12 mg/1 (Table 4.3b).

The spatial distribution maps (Fig. 4.8a and 4.8b) of magnesium in

both seasons reveals that the northeastern region exceeds the highest

desirable limit (35 ppm) but within the maximum permissible limit and

the remaining area fall within the highest desirable limit of WHO and

BIS standard. In general the Mg content in study for the seasons

remains within the desirable limit. Magnesium and calcium form

bicarbonates in the presence of CO2. The solubility of magnesium

carbonate is nearly ten times more than CaCO3 under atmospheric

conditions. Magnesium is also more soluble in water containing sodium

salts. The concentration of magnesium values in the study area are

decreasing from pre monsoon to post monsoon. The variation at the

northeastern part may be due to the presence of Palghat Gap.

Sodium

Sodium salts are highly soluble in water and once leached from

rocks and soil they remain in solution. The main source of sodium in

groundwater is plagioclase feldspars, feldspathoids and clay minerals.

84

10'45

" .

••

•

'a) Pr. mODaooD

LeleDci

Mapeslum (mil l)

_ < 15

_ 15 - 30

_ 30-45

_ 45-60

0 >60 ~ .....

~ .....

~' 15VE

(hI Po.t mODaooD

Leleoci

Mapeslum (ml/ ll

_ < 15

_ 15-30

_ 30- 45 _ .. 5 - 60

0 >60 16-0'0"E

76'JO'O""E

~.-

~.,...

• .4ft-. •

II'OVN

10'3O'Q"H

15 JO Km 6,n:;. , ,<,-,;/02VZZlzm

• .4ft-. •

II 'OVN

15 JO Km Ii ,n .. ; ... it. .. G.VlZllZllZA

Fig. 4,8 Distribution of Magnesium in the Bharathapuzha river basin (a) Pre monsoon (h) Post monsoon

It has a tendency to get absorbed / adsorbed on the clay particles but

may effectively be exchanged by calcium and magnesium.

National Academy of Sciences report (1977), the higher

concentration of sodium can be related to cardiovascular diseases and

in women, toxemia associated with pregnancy. Sodium content around

200 mg/l may be harmful to persons suffering from cardiac and renal

disease pertaining to circulatory system (Khurshid et a1. 1998). More

than 65 mg/l of sodium can cause problems in ice manufacture (Todd

1980). High concentration of sodium affects soil permeability and

texture which leads to puddling and reduced rate of water intake.

Sodium concentration values in the Bharathapuzha river basin

during pre monsoon varies from 6 mg/1 at Kalladikode to 145 mg/l at

Kanjikode and with an average value of 33.08 mg/l (Table 4.3a). While

in the post monsoon, it vary from 6.1 mg/l at Kottiyodi to 136 mg/l at

Kanjikode and with an average value of 34.78 mg/l (Table 4.3b). In the

study area, during pre monsoon low values are seen in the north

eastern region of the basin (Fig. 4.9a) whereas higher values are seen in

eastern region especially around Meenakshipuram. In the post

monsoon period lower values are seen in the north and north western

part of the basin (Fig. 4.9b). The thematic maps (Fig. 4.9a and 4.9b) of

sodium concentration in the Bharathapuzha river basin during the

both seasons reveal that the eastern side of the basin exceeds the

highest desirable limit (50 mg /1), but within the maximum permissible

limit of WHO standard (200mg.l). Sodium concentration more than 50

85

1I"UlrN

"

"

••

(a) Pre mODSOOD

Lee·Dd

SocUQm (mil l)

. "'25

.25,50

_ 50 - 75

0> 75

n''''''

n ''''''

1lI",5VE

(bl Post mODSOOD

LeCeDd

SodiQm Ima:ii)

. "'25 _ 25-50

_ 50 - 75

0> 75

16'UO"E 16',5'O"E

16'3O'1l'i:

n '''''''

16"3O'O"E

• .4t. •

11'0'O"N

15 30 Km l itf,} . , :S: -.t; ,enzw:otzA

• .4t. •

1O"30"O'll

1S JOKm . >S'h(i.1UL7l7ZlM

Fig, 4.9 Distribution of Sodium in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

mg/1 makes the water unsuitable for domestic use (Jain et al. 1996). At

the eastern side of the basin the sodium concentration exceeds this

limit and make the water unsuitable for domestic use. From the

distribution map, it is clear that there is a general decreasing trend of

sodium concentration from east to West.

Potassium

Potassium is abundant in igneous and metamorphic rocks. The

source of potassium content in groundwater is a function of weathering

rate of silicate minerals such as orthoclase, microcline, nepheline,

leucite and biotic in igneous and metamorphic rocks. The concentration

of potassium in most natural water is very low due to the resistance of

potassium minerals to decomposition by weathering (Golditch, 1938)

and fixation of potassium ions in clay minerals.

In the study area, the potassium concentration in pre monsoon

ranges from 0.6 mg/l at Cheruthuruthi to 56 mg/1 at Palathully and

the mean value is 8.3 mg/1 (Table 4.3a) while in post monsoon it ranges

from 0.8 mg/l at Cheruthuruthi to 59 mg/1 at Chittur and the mean is

9.21 mg/1 [Table 4.3b). The concentration of potassium ranges from 1

mg/1 or less to about 10 to 15 mg/l in potable water (Karanth, 1987).

The Spatial distribution maps of potassium in both seasons shows (Fig.

4.10a and 4.1Ob) that majority area of the basin falls within the

category of below 10 mg/1 reflecting the suitability of water for domesic

use. During both seasons lower values are seen in the western part of

86

"

10'4

".

".

"

76' 011'1: 16' lS"O"E

la' Pre mODsoon

Le,end

Potaulum (mil l)

_ " 10 _ 10 .20

_ 20 - 30 D >JO

1$"5VE

,..,'"

(hI Poat monSOOD

Lelend

Potanlum (mil l)

_ < 10

. 10 . 20

. 20 -30 0 >30

76'Il'O"e 7tI'ISVE

•

76'45'O"E

11 '()'O'l,I

15 30 Km E .re· , ,j{.;. iuUZl211Ll)l

,...'"

7lI' 45VE

• w*,. •

11'OVN

10' 45VN

15 30 Km E .n ·,{ht;,\lllZZlZZlA

Fig. 4.10 Distribution of Potassium in the Bharathapuzha river basin la) Pre monsoon Ib) Post monsoon

the area where as the higher values are seen at the southeast and

southwest part of the basin (Fig. 4.10a and 4.1Ob).

Chloride

The main sources of chloride are sodalite, apatite, micas and

hornblende and in groundwater are present as sodium chlorides. The

chloride content in rainwater is usually less than 10 mg/litre. Man and

other animals excrete very high chloride quantities together with

nitrogenous compounds. Chloride in water is a stronger oxidising agent

than oxygen, chloride with oxygen slowly decompose water.

Concentration in excess of 100 mg / 1 may cause physiological damage.

S0 also higher concentration of chloride can also corrode concrete by

extracting calcium in the form of calcides. Abnormal chloride

concentration may result due to pollution of sewage waste and leaching

of saline residues in the soil.

Chloride concentration values of Bharathapuzha river basin in

the pre monsoon varies from 5.9 mg/1 at Sreekrishnapuram to 262

mg/1 at Kanjikkode and the average value is 63.13 mg/l (Table 4.3a)

while during post monsoon it ranges from 6 mg /1 at Karakurussi to 271

mg/l at Kannadi and the average value is 61.08 mg/1 (Table 4.3b). The

chloride content of the Bharathapuzha river basin has been classified

based on the procedure given by Stuyfzand (1988 81.1989) and is given

in the Table 4.6 and it is plotted in the Figure 4.1 la and 4.11b. Based

on the chloride content in the study, the water type can be classified

into three types namely, oligo haline, fresh and fresh brackish. Fresh

87

'".

"

••

•

76'0'(1"£ 76 ' 15'0"£

(a) Pre monaoon

Legend

Chloride (m,/ I)

_ .. 30 Oligohalme

_ 30 - 150 Fruh

•

_ 150 - 300 Fruh Brackish

Lecend

Chloride (m,/ I)

_ .. 30 O\igohaJine

_ 30 · ISO Fresh

70',5VE

•

_ ISO - 300 F~5h 8rackish

76 '0'(1"£ l S' ,S'DC

• • •

711'3O'Q"E

• w4t, ,

l" O'O"N

• • • 10"JO"ITN

15 30 Km Pf· - 8- .t#V2LZZZl7Zd

• w4t, ,

11"0'O"N

• • 10'4SVN

• 10'JIl'O'"N

15 30 Km PS . ,S\-,;I'NlLiZiV01\

Fig. 4.11 Distribution of Chloride in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

‘ ‘ Colleen- i No. of samples Percentage~ Sl. Groundwater 0 . ‘t tration L 0 = 0 0 K 0

water type are the dominant category seen in the basin during both the

seasons while only a small portion falls in the fresh brackish category

which is seen in the eastern part of the basin.

Table 4.6 Classification of groundwater quality based on chlorinecontent using the procedure given by Stuyfzand (1988,1989)-_ 0 _ or 0 0 , _l 0 0l “ Chloride l 0 0 0 0

N0- ‘ TYP05 Ranges Pre Post Pre ll Post lL = (mg/1) y monsoon monsoon ‘ monsoon ! monsoon

Y 1 glilgohaline 0 <5 ll _ ' _ - 2{ 2 Oligohaline ‘ 5-30 19 23 \ 23.50 l 28.401 0 lj A3 j Fresh * 30-150 56 A‘ 53 i 69.10 65.43ta at it 0 0r0 0 0 ~ s r0 0 as ~llFresh— l l M01 yBI_ackiSh pg 150-3000 6 A 5 L 7.4op £6.17. 1 300- r y _5 Ehagkwh »y1000 ' t ' i ' _E~_' ”r

6 Brackish — l 1000- fill _ _ _ 1 _ Tor Sah o"s 1000 _ _o _*l' y _o _l0000- ~07 _Salt . 020000 t _ _ _ _T Hyp€T l 0 ‘ 0 0 0 A E8 . >20000 l — l — - ­so I$<'1111“1@ _ _ _o _ or in o_ or 0 0

Figure 4.1la and 4.11b reveals that except two places at the

eastern side of the river basin [Kanjikode and Kannadi), all other areas

are fall within the highest desirable limit of WHO (200 mg/1) and BIS

(250 mg/1) standards. In general, high concentration of chloride in

groundwater is attributed to rain water, sea water, natural brines,

evaporates deposits and pollution (Junge and Wrby, 1958; Johnson,

1987). High concentration of chloride values in the study area may be

due to Industrial pollution (Kanjikode) and use of fertilisers.

88

Distribution maps of chloride concentration during both seasons (Fig.

4.1 la and 4. 1 lb) shows that majority area are fresh groundwater types.

Nitrate

In groundwater, very small quantities of nitrates are present

through nitrogen cycle in the earth’s hydrosphere and biosphere. The

presence of nitrate in groundwater is from decomposition of organic

matters like plant debris, animal waste, sewage wastes, nitrate

fertilisers and industrial waste chemicals. Natural nitrate concentration

in groundwater ranges from 0.1 to 10 mg/1 (Davis and Dewiest, 1960).

Nitrate concentration in water more than 45 mg/I may cause

methemoglobinemia in infants. High concentration of nitrates is

reported to cause more mortality in pigs and calves and abortion in

brood animals. Even though high concentration of nitrate is useful in

irrigation, their entries into the water resources increase the growth of

certain algae and trigger eutrophication.

In the present study area, the nitrate concentration of

groundwater in the monsoon ranges from 0.03 mg/1 (Chulanur) and

110 mg/l at (Palapuram) and the average value is 10.28 mg/1 (Table

4.3a) while in post monsoon it ranges from 0.01 mg/1 at Chullanur to

120 mg/l at Palapuram and the average value is 10.16 mg/1 (Table

4.3b). Three locations (Meenkara, Kanjikkode and Palapuram) of the

study area exceed the highest desirable limits of drinking water

standards of WHO and BIS (45 mg/1) in both the seasons (above 45

mg/l). From the distribution map (Fig. 4.l2a and 4.I2b) it is observed

89

".

".

"

"

••

•

n;',5'D"E

fa ' Pre mon aoon

Legend

Nitrate (ma l l)

• • 5

_ 5-20

0 20 - 45

_ ,. 45

M"""

M"""

No poUulion

M«l.ium poUution

High pollution

"'"""~,

Lecend

Nitrat e (lIlt / I)

• • 5

_ 5-20

0 20-45

_ > 45

76'O"O"E

No pollution

Ml'diUIIl pollution

High pollulion

Dangerous

•

1,'O'Q"N

15 30 Km F .e; . . S '· 7#·!?VLLlZl22

,...~

,

w4t . •

" ' (I'O"N

10' 4S'O'"N

15 30 Km , ",:<,. .. / .. VZUZ7Zl/A

Fig. 4 .12 Distribution of Nitrate in the Bharathapuzha river basin la) Pre monsoon Ib) Post monsoon

that majority of the area in the basin for both the seasons are comes

under the medium polluted category and the dangerous category is

seen in the eastern part of the basin.

Sulphate

The sulphate concentration of atmospheric precipitation is only

about 2 mg/1, but the sulphate content in the groundwater varies

widely due to oxidation and precipitation processes as the water

traverse through rocks. The source of sulphates are sulphur minerals,

sulphides of heavy metals which are commonly found in the igneous

and metamorphic rocks, gypsum and anhydrite found in some

sedimentary rocks. The oxidation and hydrolysis of pyrite also produce

sulphuric acid and soluble sulphate. Sulphate concentration around

1000 mg/1 is laxative and cathartic (U.S.E.P.A, 1971). Sulphate with

sodium interferes with normal functioning of the intestine.

In the Bharathapuzha river basin in the groundwater during pre

monsoon season the sulphate content ranges from 1.03 mg/l at

Nochipulli to 87 mg/1 at Meenakshipuram and average value is 19.03

mg/1. (Table 4.3a) whereas in the post monsoon season ranges from

0.49 mg/l at Kulakkalur to 82 mgj/l at Meenakshipuram and average

value is 17.23 mg/l (Table 4.3b). The spatial distribution maps of

sulphate concentration in both seasons (Fig. 4.13a and 4.l3b) reveals

that the entire river basin is within the desirable limit of WHO and BIS

standards (200mg/l).

90

10'45

"

"

••

•

ni'O'O'"E 16'1S'O'E

(a) PR mOl1aGol1

Le,el1d

Sulphate (mllll _< 10

0 10 ,20

_ 20-30

. '30

M·""

78'I5VE

ni' l!5VE

!hI Post m01111OO11

"',end

Sulphate (mil l) _< 10

D 10-20

. 20·30

. ' 30

1!5' O'O'"E

' .

•

11 'C!'I:7'N

10'3O'O"N

15 30 Km Lt;, , ,* '"lii~

1\'O'O"foI

'. •

1B'lOVE 1!5' 4S'O"'E

Fig. 4.13 Distribution of Sulphate in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

Carbonates and bicarbonates

The primary sources of CO3 and HCO3 in groundwater is the

dissolved CO2 in rain water as it falls through the atmosphere and

water flowing through the soil dissolves large amount. The solubility of

CO2 in water decreases with increase in temperature or decreases in

pressure. Water charged with CO2 dissolves carbonate minerals as it

passes through soil and rocks giving rise to bicarbonates.

Carbonates and bicarbonates along with hydroxides are

responsible for the alkalinity of water. Alkalinity is defined as the acid

neutralising capacity of water. In unpolluted water, the major anions

that can neutralise the positive H* ions are I-ICO3, CO3 and OH. But in

polluted waters, other negative ions like P04, N03 may contribute

alkalinity (Raymahashay, 1996).

Large amount of bicarbonate and alkalinity in water is

undesirable in many industries. High amount of CO3 in drinking Water

result in heart ailments and artery blockage.

In the study area carbonate concentration values during the pre

monsoon ranges from 2 mg/l at Trithala to 60 mg/l at Chittur and

Kanjikkode and the average value is 12.64 mg/l [Table 4.3a), but for

post monsoon the values ranges from 2 mg/l at Kinnasseri to 85 mg/1

at Chittur and the mean value is 13.92mg/ l (Table 4.3b). Bicarbonate

values during pre monsoon ranges from 28 mg/1 at Kuttipuram to 351

mg/l at Meenakhipuram and the mean value is 126.36 mg/1 (Table

4.3a) while in post monsoon values varies from 23.5 mg/l at9l

Kuttipurarn to 373 mg/1 at Ambalapara and the mean value is

1l9.75mg/1 (Table 4.3b). The spatial distribution map for both the

seasons’ show (Fig. 4.14a and 4.14b) low values in the north and

western part of the basin. Higher values are seen in and around

Meenakshipuram and Ambalapara. In general, the groundwater of the

study area falls within the desirable category.

Fluoride

Of the many natural geochemical substances contaminating

groundwater, fluoride is most hazardous. Fluorine is the most electro­

negative element. It occurs in water as fluoride ion. The source of

fluoride in groundwater is fluorite and other hydroxyl minerals like

micas and amphiboles. It is capable of forming complexes with silicon

and aluminium and is believed to be exist at a pl-I below 7.

Impact of fluoride in drinking water on health has been well

studied by Dissanayake, (1991) and is given in Table 4.7. According to

him, fluoride is beneficial when present in small concentration (0.8 to

1 mg/1) in drinking water for calcification of dental enamel but it

causes dental and skeletal fluorosis if present in higher amount.

In the Bharathapuzha river basin the fluoride content of

groundwater during pre monsoon ranges from 0.0lmg/1 at

Thirualathur to 1.2 mg /l at Walayar the mean value is 0.48 mg/1 (Table

4.3a) whereas in post monsoon it varies from 0.01mg/l at T honnurkara

92

...

76"0'D"E

la l Pre monsoon

Lea:end

Bicubonat e (m&/l)

;oe"wo"E

76"1SO"E

(hI Post monsoon

Le&end

Bicarbonat e (m&ll)

76"0'D"E

n',....

711"3O"O"'E

• .*. •

l1 'O'iTI'I

10' 3O"1I"N

15 JO Km r;t\ .. ,g .IU llZllll7l)J

• .*. •

11'O'trN

10'4S'ITN

10"lO'iTI'I

15 JO Km f .m.'. , 1l.,tNllZ7LVV)J

Fig. 4.14 Distribution of Bicarbonate in the Bharathapuzha river basin la) Pre monsoon Ib) Post monsoon

to 1.45 mg/l at Nattukal and the average value is 0.42 mg/l (Table

4.3b).

Table 4.7 Impact of fluoride in drinking water on health(Dissanayake, 1991)

. Concentration of 1_ fluoride (ma/1) f D; - ““P*‘°‘ °“ "°“‘"‘ , _ _ _

Nil Limited growth and fertility i( i_T,O - 0.5 Dental caries

J— — — — —— — , V _ _ 7 _ _ __ _ I _ I » ,_ — , — _ __ , —l _l0.5 - 1.5 * Promotes dental health I1.5 - 4 Dental fluorosis(mottling of teeth)— a .l.{_ _ _ _ _ a _ _ _ ,_ a — _— ._ .m‘.4 — 1O T Dental and skeletal fluorosis ‘

\ > 10 Crippling fluorosis N_ _ _ _ _ I , , _ , _ I _ JThe spatial distribution maps of fluoride concentration in both the

seasons (Fig. 4.l5a and 4.15b) reveals that in Vandazhi,

Kuzhalmannan, Kannadi and Walayar are in the permissible limit of

BIS 1.5mg/l and the rest of the study area falls with in the desirable

limits (1.0 mg/l). Also it reveals that lower values are seenat northern

and western part of the study area, higher values are seen at eastern

part of the basin. The major rock type (hornblende biotite gneiss) and

the semi arid climatic condition of the Palghat gap (eastern region)

favours the leaching of the fluoride bearing minerals may be one of the

reason for the higher concentration of the fluoride. The leaching of

fluoride from the fluoride bearing minerals are Apatite, Hornblende and

Biotite and very low fresh water exchange due to the semiarid climate of

the region and long residence time of groundwater in the aquifer

¢ ttributes for it content (Wodeyar and Sreenivasan, 1996). An abnormal

93

93

1\'U

~O'.5

".

".

•

76'O'O"E 16"S'O"E

(a) Pre monaooD

Fluoride (me/I)

_ < 0.5

. 0.5. ,

. '- 1.5

n· ....

n· .... re' l SO'E

fb) Po.t mOn-.ooD

LeCeDd

Fluoride (m,/l)

< 0.5

. 0.5 -1

. ,.,.5 " ..... re' ,5VE

n'''''

•

• ..

1e'lOVE

-4· •

10'(S'!TN

10'3II'O"N

15 30 Km f ,tj ••. ,zh<i4lZlllZZM

n'4SVE

• _4ft-_ •

11'O'O"N

10'4S"I)"N

10'30'O"'N

15 "' Km E ,~ ,:;::l:!",.~

7S'4S'!rE

Fig. 4.15 Distribution of Fluoride in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

concentration of fluoride (>l.5 mg/1) is recorded in the Rift valley of

Ethiopia calcium fluoride and is derived from bed rocks (Ashley 8s

Burley, 1995). In the region, high degree of weathering and easy

accessibility of circulating waters to the weathered rocks due to

intensive and long time irrigation are responsible for the leaching of

fluoride from their parent minerals (Wodeyar and Sreenivasan, 1996).

The pl-I of the circulating water is a factor which controls the leaching

of fluoride from the Fluoride bearing minerals. Hence it can be inferred

that the fluoride in the study area comes from the fluoride minerals in

bed rock.

Total Iron

The concentration of iron in groundwater will be higher under

more reducing conditions due to bacteriological attack on organic

matter which lead to the formation of various humic and fluvic

compounds (Applin and Zhao,l989; White et al. 1991). Under reducing

condition, the iron from biotite and laterites are leached into solution in

the ferrous state. According to Singhal and Gupta, (1999) iron content

in groundwater is mainly due to the dissolution of iron oxides. A

common method of removal of iron from water is by aeration followed

by sedimentation. In high rainfall state like Assam, Kerala and Orissa

total iron ranges from 6.83 to 55 mg/l (Singhal and Gupta, 1999).

Higher content of iron at certain regions of the study area may be due

to the leaching of Iron from the lateritic top soils as iron can be easily

leached out in anoxic conditions.

94

In the study area, for the pre monsoon the total iron values

ranges from 0.0lmg/1 at Chittur to 2.7mg/l at Kozhinjanpara with an

average of 0.46 mg/1 (Table 4.3a) where as during the post monsoon it

ranges from 0.02 mg/1 at Vandazhi to 2.9mg/l at Mannarkad with an

average of O.6lmg/l (Table 4.3 b). The spatial distribution maps (Fig.

4.16a and 4.16b) of total iron concentration during both the seasons

reveals that majority of the area falls within the O.3mg/1 to 1 mg/l

category which is of desirable category (BIS).

4.4 Groundwater quality standards

The suitability of groundwater for a particular purpose depends up on

the criteria for the purposes such as drinking, agricultural and

industrial.

4.4.1 Drinking water standards

The standard values of the groundwater quality for drinking

water represent the level of constituents present in the water which

does not result in any significant risk to health. Groundwater is mainly

used for drinking and other domestic purposes, for which a detailed

chemical analysis of water is very much important, as certain chemical

constituents became toxic beyond particular concentrations, although

they may be beneficial at lower amount (Singhal and Gupta, 1999). In

the present study drinking Water standards prescribed by WHO, (1984)

and BIS (BIS 10500:1994} is followed and is given in the Table 4.8. The

physico-chemical parameters of the basin is compared with the

drinking water standards and found that drinking water standards in

95

l1'OVN

10"45

"

l1'I)VH

".

"

76' 1SV E

la) Pre mODSOOD

Le,end

Iron (ml/ l)

. ",, 0 ,1

.0. 1 - 0.3

. 0.3 - I

0> \

Le,end

IzoQ (ml/ l)

. .. 0 .1

. 0. 1 +0.3

. 0.3 + 1

0 >\ 76'(),()'E

7$' l !>'O"E

• .4t. •

l1 'OVN

10'4 5'O"N

15 JOKm 1.1\'i . 8 · ti-1lOZlZlLZA

a ' 45VE

• .4t. •

11'()'In'!

10'4S'O"H

10'30'C"N

15 JOKm f .m, .> '5 .. ;l\' .V2LLLZLZ4l

Fig, 4,16 Distribution of Total Iron in the Bharathapuzha river ba sin la) Pre monsoon Ib) Post monsoon

_$Q HUG“ _EO\w 3 Om agva qwa E U®Ww®'ax® gm w®g_w_> HEmgW H i I E go l m¢_:O_[_ mic N_GO_ HW UE_S:EHHIQO Q08HQO@_N|mO_O$00\l_2O_OUhA OO©LO8 K2::wwq:N:OWOHONgggmvi fO2mi‘ A ‘l]_mw£2ONT:qO K820:66MOZ_i ‘ tr ‘Ij OOVOON _T O?7OONmN__:Nwlgvd82__Bfiuoévow fOmfimmOmfiO2NEHmm:82wolw Amg_ I O8O8 E% OOWO2QmgNm¢;|H % % 6:Oglewmwcpam\ gmE IOONmN_pgi 02,0 N Ewommmm;mo_OONOw__ad@N__¢mUQgéb A 8%| A I % LO20 Qw030$70“Z£6:mNm'mN I @902 i_HmqwmA M82“OOOHOWNOO©OON80$N©qO_m6OOONCom WOOEHOO@mg¢ Calm A 3_m©mmwmm Q SNmomlom2;OO¢HMWOWi mqmfilmmA _ mgmmwgw:Om_MHZ$8@_w_© Howgiqwmm]:6:0§Q%wW@Eh®nHU_QMWwMEH®Q ®Bw(_B®UBDEEOQ j _§2 HWOQMHIu m_w_m_® N.@'m_© m_w‘\L! T1 JG602owgmm E82owqmmiwgoma_ ‘ ‘ ‘ _ I ‘I N‘ _‘ |_ I_j Ooomofi Goowgoe “mom coowgoa PE“O2 §@:mE Z k AA I {WBHUEEMOH_w_P8Uggw houfig wfixghm w:Og®> sag w®2G> owcwm U26 582 mi“ ®_D_®r__0_

the various physico-chemical constituents of the groundwater fall

within the prescribed levels of BIS and WHO standards. Generally, the

groundwater quality of the Bharathapuzha river basin is good and

potable.

4.4.2 Classification of Groundwater for Agriculture I Irrigationutility

The suitability of groundwater for irrigation /agriculture have

been evaluated by the methods suggested by Piper (1944), Kelly (1974),

Wilcox (1948, 1955) and U S salinity Laboratory (1954). The quality

criteria for irrigation suitability proposed by Wilcox, is generally used in

which EC and sodium content are taken into consideration. The Wilcox

(1948, 1955) classification was later modified by the workers of the US

Salinity Laboratory (USSL, 1954). USSL classification is used in

determination of salinity hazard, sodium hazard and specific effects of

certain toxic constituents like chloride, bicarbonate, boron, lithium etc

(Devis and Dewiest 1960).

The criteria for the irrigation water depend on the types of plants,

amount of water used for irrigation, soil texture and composition, type

of crops, irrigation practices and climate. Important chemical criteria

for the agricultural use are the salinity and sodium hazard. Soluble

salts reduce water availability to the crop, Relatively high proportion of

sodium and or high concentration of bicarbonates reduces the rate of at

which irrigation water enters soil where by sufficient water cannot be

infiltrated to supply the crop adequately (Gupta, 1999).

96

The important parameters used to assess the general suitability

of groundwater for irrigation are total dissolved solids, sodium

absorption ratio, sodium percentage and residual sodium carbonate

and other classification schemes based on these parameters.

Evaluation of groundwater quality for irrigation

Classification of irrigation water by Wilcox (1955) is based on EC,

T DS, Sodium percentage and boron concentration.

Table 4.10 Classification of groundwater quality for irrigation(after Wilcox, 1955)

Ti J J J J if 7* 221)’? *2 *2 if *2 *7 vi *2 J‘ j *2 *2’ *2) 57* 7* 2* 2272* 1);) jijfljj 7 2721* 7%‘).) A EC at 1 1 Sodium )1 Boron (mg/1) ,2 Water Class 250C ‘l TDS(mg/1) 1 0 I (Tolerant J1 / 1 11 _ _ _ r_ 0 1 L113/¢m) F l _ _ 0 _ 1); °1'°12l_2

J2,

Ekneflent <2s0 » <17s » <20 *1 <1 .l Good it 2 250-750 02 9175-525 7 20-40 2 ‘K 1-2 0‘ 2 22-: _ _ j: J; _ to its - _ _ lg _ _ J 2 J I _ __ ­) 7'1. Permissible 1750-2000 525-1400 40-60 M‘ 2-3 i

l

T

1

1

1

1

l

lIf

1 ‘ 2000- , 1400- , 1Doubtful A" 1 l 60-80 1 3—8.75, ~ 3000 1 2100 gl Unsuitable 7 >30002 1; >2100 Y >80 C ‘ >375 0 Z________:____,_ll_,__r _ _ _ _ __ __‘ 22,22 227 2 on 1 _ at _ _ g

4L

4.4.2.a TDS

During rainy season, salts get leached and reach the

groundwater table which lead to pollution of the groundwater regime.

Water with TDS content less the 500 mg/l and 500 to 1000 mg/l are

considered as good and fair for irrigation purpose (Suresh et al. 1991).

Based on the Wilcox,1955 classification (Table 4.10) about 33 % of the

samples of the pre monsoon comes under excellent, 55 % as good for

irrigation and the remaining samples of permissible, water class for the

97

irrigation In general, the groundwater in the river basin is ideal for

irrigation.

4.4.2 b Sodium PercentagePercentage of sodium in water is a parameter computed to

evaluate the suitability for irrigation (Wilcox, 1948). The main effects ofsodium are

a) Reduction in soil permeability and

b) Hardening of soil.

The sodium in irrigation waters is usually denoted as percentsodium and can be determined using the following formula,

% Na = (Nat) X 100/ (Ca2+ + Mg” + Na* + K")

where the quantities of Ca 2*, Mg 2*, Nat and Kt are expressed inmilliequivalents per litre (epm}.

Excess sodium combining with carbonate will lead to the

formation of alkaline soils while with the chloride, saline soils are

formed. Either of the soils will not support the growth of crops.

The sodium percentage in the study area ranges from 8.76% to

62.92% during the pre monsoon where as during the post monsoon it

varies from 8.84% to 61.03% (Table 4.9a and 4.9b). The spatial

distribution maps (Fig. 4.1"/a and 4.17b) of the sodium percentage

shows that majority of the area fall in the excellent (Pre monsoon (av) ­

28%, post monsoon (av)- 19% ) to good (Pre monsoon (av)-63%, post

monsoon (av) 60%) water class and the remaining small areas are seen

as patches which are the permissible water class. As per the Indian

98

10'4$

'O'J(I

"

••

76'O'O"E 76"5"0"£

,a) Pre mODaGOD

Lecend

Sod-hun Percent_c.

_ < 20

_ 20 , ..0

_ 40 - 60 _ . 60

,. . ..,..

n''''''

76' I$1TE

(h) Poat monaoon

Lecend

Socllum Percent.,ce

76'0'O"E

• • • .. •

76'JO'Q"E

• ••• •

l1' ()'(I'l,I

• • . .. •

15 30 Km r ,M · ,,,. ,/f:1lZl7.ZLZZ.l..a

• ••• •

• l1'O'O"N

• •

1(),,30'O"N

15 JOKm E"ij.. t ;¥ " /' wnz:tm2

16'3O'O"E 76'4S'O"E

Fig. 4 .17 Distribution of Sodium percentage in the Bharathapuzha river basin, (a) Pre monsoon (b) Post monsoon

F‘ _.. --ibbI dip

\\f2 \

0"]__.. |Q'[._ .

/ .»._ - /

Standard a maximum of 60% sodium 1s permissible for 1rr1gat1 _r,1;i;bva;§~;¢...,_. . \_, ... I. I .‘_ I(Jain et al. 1996).)­_| ~\_-1//_\-___ /'\.. 7!?! '- - "

'-~.L,-.,_­

4.4.2c EC

The map also reveals that majority area of the basin in both

seasons, the EC values fall within the range of 250 - 750 and the water

is good for irrigation (Fig. 4.3a 85 4.3b). The spatial distribution maps of

EC for the study area reveals that for both the seasons, low EC values

are recorded at north and northwest region, while higher values are

observed at eastern part. The high EC values on the eastern part may

be due to the addition of some salts from the agricultural practices

4.4.2d Wilcox diagram

Wilcox {l955) proposed a diagram based on the percent sodium

and electrical conductivity in order to know the suitability of water for

irrigation. This diagram which is known as Wilcox diagram classifies

the irrigation water into different classes based on their quality as

Excellent to Good, Good to Permissible, Permissible to Doubtful,

Doubtful to Unsuitable and Unsuitable. The plotting of percent sodium

and EC values in the Wilcox diagram shows that (Fig. 4.18a and 4.18b)

in both seasons majority of the area falls in the excellent to good

category where as few locations are in the good to permissible category.

It is concluded that the groundwater quality based on Wilcox

classification, the values of EC, sodium percentage and TDS of the

Bharathapuzha river basin is good for irrigation purpose.

99

l

ox

100 00- ‘" Unsuitablea) Pre monsoon

Doubtful\. Unsuitableso 1 -_ 0-0Permissable

toDoubtfulI . \sol

Exceflent 1“to

Good iO

N370 ——I­

Goodto

40 | ., “ ‘_ 0 Permissable, _ t , .~ I.. Q..:.:' ‘Q.9 a ' '3- :: '- '., O

20 l .'

° :'3

000

-:‘­

0 | _ _0 1000

100 0*

80 0

*5 Permissableto

= Doubtful.\~

so -' ' §‘“»; ‘Egcellent 'to "~

GobdE O Q Q Q

Na% ——1­

40

\..90. ‘

30

O

I5.O

20 -1.1, " I

0L.0 1000 2000 3000 4000 5000

Fig. 4.18 Wilcox classification diagram for suitability of 1rr1gat1on

2000 3000Ec*1o"

b) Post monsoon

Unsuitable

Doubtfulto

Unsuitable

g’ to_ I 0 _ Permissable |. I‘ an \ . . I. ::.] . II. O

., i__Ec-10"

4000 5000

water in the Bharathapuzha river basin

4.4.2e Sodium Adsorption Ratio

Sodium Adsorption Ratio (SAR) is the value of adsorption of

sodium by soil, when water percolates. A high value of SAR implies soil

structure damage. The SAR is given by the formula as

SAR = -Na{(081 + Ms)/ 2}/Y

Where the ionic concentration is expressed in meq/l

Excess sodium in water produces undesirable effects of changing

soil properties and reducing soil permeability (Kelley, 1951). Hence, the

assessment of sodium concentration is important while considering the

suitability for irrigation.

The classification of irrigation waters with respect to SAR is

based primarily on the effect of exchangeable sodium on the physical

condition of the soil. Sodium-sensitive plants may, however, suffer

injury as a result of sodium accumulation in the plant tissue when

exchangeable sodium values are lower than those effective in causing

deterioration of the physical condition of the soil. Water has been

classed into four groups as excellent, good, fair and poor based on SAR

values (Richards, 1954) and is given in the Table 4.11

Table 4.1 1 Suitability of groundwater for irrigation purpose basedon SAR (Richards, 1954) in the Bharathapuzha river basin... .7 . ._ 7 ~~ . ___i —~——~ " - — ' .

J Range . No of samples § PercentageWater y ~~ as *9 9 5 1Of C1 a S S ‘ Pre ( Post Pre . Postvalues ; monsoon monsoon monsoong;p_rno_n_soong) i‘ 9 H iii 9' 9 ”” ii H1 <10 Excellent 81 ’ 81 ( 100 F 10010-18.3 Good 4 3» ­18-26 Fair - - - - 1

i, 3 _ 2 _ _ I _>26 Poor - ( _g- — ­During the pre monsoon the SAR values of the study area ranges

from 0.32 to 3.44 (Table 4.9a) and in post monsoon it ranges from0.33 to 3.24 (Tab1e4.9b). The distribution map shows that lower

values of SAR seen in central part of the area. Majority of the area

shows the SAR values between 1 and 2 (Fig. 4.19a and 4.19b).Table 4.11 reveals that the water samples of the Bharathapuzhariver basin belongs to excellent category for irrigation in bothseasons.

4.4.21‘ Suitability of water through USSL diagram

The classification of water for irrigation proposed by the US

Salinity Laboratory (USSL, 1954), Department of Agriculture is based

on the salinity and sodium hazards. Salinity hazard is of specific

conductance and sodium hazard is expressed in terms of Sodium

Adsorption Ratio (SAR)

The classification of water for irrigation purpose is determined

graphically by plotting the values of specific conductance on the

horizontal axis and SAR values on the vertical axis of the USSL diagram

(Fig. 4.20). Sodium and salinity hazards are the two parameters which

can indicate the suitability of water for irrigation.

101

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la. Pr. mon.oon

LeCeDd

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• -4ft-. •

l" O'In<!

• •. , 10"30'O'"N

15 30 Km

E '" ·'-'>5,-,·lf!?:ll2ll27Vl

Fig. 4.19 Distribution of SAR in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

USSL Diag111111( a ) Pre monsoon

3

26

S odium Hazard (SARIE

( b ) Post monsoon

Sod um Hazard (SAR)

4.20 Classification of groundwater based on USSL Diagram in the study area

I9

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SaIinity Hazard (Cond)

( a ) Pre monsoon ( b ) Post monsoon

Legend

Sodium (Alkali) hazardS1; LowS2: MediumS3: HighS4: Very high

Salinity hazardC1. LowC2: MediurnC31 HighC4: very high

On the basis of salinity hazard water have been divided into C1,

C2, C3, C4 and C5 types and that of sodium hazard as 81, 82, S3 and

S4 water types (Table 4.12). Based on U88L diagram for irrigation

quality, the area can be divided into sixteen water classes as C181,

C281, C381, C481, C581, C281, C282, C283, C284, C285 etc.

Table 4.12 Classification of Groundwater quality of irrigation based onU8_8L diarm W 0- 8 d'u 0

SAR Range of finial?“classes values

H . , . . &a ppConductivity R‘§*°=§5§C Salinity

filasses (iisj cm) 1 ghazard p J H p __ hazardy Low 1 s1 <10 i Low. - 5 1 T

C1 2 <250

82 10-18 Medium1

C2 ’ 250-750 Moderatev ' ‘ '750-2250 * ss 18-26 HighC3 Medium2250- §

l Highi 4000 1

C4 l 84 >26 ‘ Very high l

>4000 r Very high 5I IC5 - — ­J

Salinity hazard

Salinity hazard is of specific conductance of water (EC). The

significance and interpretations of quality ratings based on the U88L

diagram can be summarized as follows:

(il Low salinity Water (C1) can be used for irrigation with most crops

on most soils. Some leaching is required, but this occurs undernormal irrigation practices, except in soils of extremely lowpermeability.

102

(ii) Medium salinity water (C2) can be used if a moderate amount ofleaching occurs. Plants with moderate salt tolerance can begrown in most instances without special practices of salinitycontrol.

(iii) Medium to high salinity water (C3) is satisfactory for plantshaving moderate salt tolerance, on soils of moderate permeability

with leaching.

(iv) High salinity water (C4) cannot be used on soils with restricteddrainage. Even with adequate drainage, special management for

salinity control may be required and plants with good salttolerance have to be selected.

[v] Very high salinity water (C5) is not suitable for irrigation underordinary conditions, but may be used occasionally under veryspecial circumstances. The soil must be permeable, drainagemust be adequate, irrigation water must be in excess to provideconsiderable leaching and salt tolerant crops should be selected.

Sodium hazard

Sodium hazard is expressed in terms of SAR and classified as

follows;

Low sodium water (S1) can be used for irrigation on almost all

soils with little danger of the development of harmful levels of

exchangeable sodium. However, sodium sensitive crops, such as stone­

fruit trees and avocados may accumulate injurious concentration of

sodium.

Medium sodium water (S2) can be used for irrigation in fine­

textured soils of high cation exchange capacity, especially under low

leaching conditions, unless gypsum is present in the soil, presents

103

appreciable sodium hazard, but may be used on coarse textured or

organic soils which have good permeability.

High sodium water (S3), may produce harmful levels of

exchangeable sodium in most soils and will require special soil

management like good drainage, high leaching and addition of organic

matter. Gypsiferous soils may not develop harmful level of

exchangeable sodium from such water.

Very high sodium water (S4) is generally unsatisfactory for

irrigation purposes, except at low and perhaps medium salinity.

Application of gypsum or other amendments may render this water

feasible. Application of gypsum also increases the crust conductivity

property of the soil as elaborated by Goyal and Jain (1982).

Classification of groundwater based on USSL diagram ( Fig. 4.20)

of the study area for the pre monsoon shows that 32% of the samples

belongs to ClS1 (low salinity hazard and low sodium alkali hazard)

class, 57% of the samples fall in the C2 S1 class [moderate salinity

hazard and low sodium alkali hazard) and the remaining 11% are in the

C3Sl class (medium salinity hazard and low sodium alkali hazard)

where as during the post monsoon 28% of the samples falls in the

C1S1 class, 61% of the samples are in the C2S1 class and the

remaining 11% of the samples belongs to C3Sl class. From the

distribution maps of groundwater drawn using USSL diagram for the

study area (Fig. 4.21a and 4.2lb) it is seen that for both seasons

104

, ..

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,

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•

1-) Pre mOa.MJOD

_ C l 5 1 Low saliniry '" low sodium hazard

D ClS I Modtral .. saliniry &. low sodium hazard

_ C3S ! M.,dium salinity &. low sodium hazard

le'alTE 7e"S1TE

1l1' UiT£ 76' I~'O"E

tb) Post moa.800a.

_ Cl S l Low salinity &. low !SOdium hllVlrd

D C2S I Mod .. ra l .. salinity &. low sodium hazard

_ OS I M .. dium salinily &. low sodium hazard

7lI'O'lTE 7lI'15VE

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• .4t, •

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\0"30'O"N

15 30 Km Eo' m,· , '·,·"?"-, lWTL/LZ/.L22

Fig. 4.21 Distribution of groundwater based on USSL diagram in the Bharathapuzha river basin. la) Pre monsoon Ib) Post monsoon

eastern side have medium salinity and a low sodium hazard (C3 S1)

whereas north west and southern part of the area it is low salinity and

low sodium hazard (C1S1) and that of central part and river mouth is

characterised by moderate salinity and low sodium hazard (C2 S1). In

general, based on the U.S.S.L diagram (1954) the groundwater of the

Bharathapuzha river basin is considered as good for irrigation.

4.4.2g Residual Sodium Carbonate

Eaton (1950) suggested the Residual Sodium Carbonate (RSC)

index can be used to evaluate bicarbonate hazard. The hazard caused

on soils by excess of carbonate and bicarbonate ions in irrigation water

is called bicarbonate hazard. It is due to the increase of sodium in the

soil which leads to the formation of soda alkali soils.

RSC is defined as the excess of carbonate and bicarbonate

amount over the alkaline earths mainly of calcium and magnesium.

When it is present in excess of permissible limits, affects the irrigation

adversely (Eaton, 1950 and Richards, 1954). Residual Sodium

Carbonate is given by the equation.

RSC = (CO3 ‘ " + HCO3 ') — (Ca+* + Mg * ")

These units are expressed in meq/1 of water. Excessive RSC

causes the soil structure to deteriorate, due to the restricted movement

of air and water through the soil. Eaton has classified the water for

Irrigation into three classes based on RSC values which are given in the

Table 4.13.

105

Table 4.13 Classification of Groundwater based on Residual SodiumCarbonate, Eaton (1950)

RSC (meq/1) Range A Water class

I < 1.25 Excellent\ . ___" r1.25-2.5 Good ‘W

>2.5 A UnsuitableThe RSC values for the Bharathapuzha river basin ranges from

3.95 meq/1 to 0.55 meq/1 during pre monsoon (Table 4.9a) where as in

the post monsoon it ranges from 3.74 meq/1 to 0.99 meq/1 (Table 4.9b).

The spatial distribution map shows that the RSC values of the basin in

both seasons (Fig. 4.22a and 4.22b) falls with in the excellent water

class.

4.4.3 Corrosivity Ratio

Ryzner (1944) proposed a ratio to evaluate corrosive tendency of

groundwater towards metallic pipes. Badarinath et al. (1984) and

Balasubramaniam and Sastry (1987) used this ratio for the analysis of

groundwater chemistry to evaluate its effects on metallic pipes during

the transport of water from the source to consumer.

Corrosivity ratio (CR) can be calculated by using the formula,

Corrosivity Ratio = 0'02-8 Cl + Q30210.02 (HCO3 + cos)

Where, all values are expressed in mg/ l.

The corrosivity ratio could be positive or negative, and the

groundwater having corrosivity ratio less than one is safe and non~

I06

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Fig. 4.22 Distribution of RSC in the Bharathapuzha river basin (a) Pre monsoon (b) Post monsoon

corrosive. Water with a corrosivity ratio greater than one cannot be

transported to consumer points through metallic pipes.

The corrosivity ratio determined for the groundwater in the study

area is given in the Table 4.9a and 4.9b and the spatial distribution of

corrosivity ratio drawn for both the seasons shows that (Fig. 4.23a and

4.23b) major portions of the study area are fall in the safe zone where

as part in the eastern and western part of the basin is unsafe zone. Poly

Vinyl Chloride (PVC) pipes are recommended in the unsafe zone for

carrying water instead of metallic pipes.

4.5 Hill — Piper Trilinear diagram

Presentation of chemical analysis in graphical form makes

understanding of complex groundwater system simpler and quicker.

The Piper—Hill diagram (Piper, 1953) is used to infer hydrogeochemical

facies. These plots include two triangles, left triangle one for plotting

cations (milli equivalent per litre) as a single point on the left triangle

and the right triangle for plotting anions (milli equivalent per litre). The

cation and anion fields are combined to show a single point in a

diamond-shaped field, from which inference is drawn on the basis of

hydrogeochemical facies concept (Back and Hanshaw, 1965). The

trilinear diagram conveniently reveals similarities and differences

among groundwater samples because those with similar qualities will

tend to plot together as groups (Todd, 1980). These tri-linear diagrams

are useful in bringing out chemical relationships among groundwater

samples in more definite terms rather than with other possible plotting

107

••

•

lal Pre monaooD.

Lea_ad

COrTOsivity Ratio _<1 Sare

U> I Notsafe

~ . .,..

10-\/11"11:.

(hI Post mODSOOD

Le,eDd

COrTOslvity Ratio _< 1 Safe

0> I Not safe

~ . .,.. 18"~V'E

~'>OVE

• .4ft-. •

15 30 Km E ,r: . S.- ,IW7LiLlZlM

• .4ft-. •

WOVN

10030VN

30Km '

Fig. 4.23 Distribution of Corrosivity Ratio in the Bharathapuzha river basin la) Pre monsoon Ib) Post monsoon

methods (Walton, 1970). Chemical data of the area are subjected to

graphical treatment by plotting them in a Piper (1944) trilinear

diagram. Distribution of groundwater samples in different sub divisions

of the diamond- shaped field of the Piper diagram reveals that the water

samples fall in the sub divisions 1 to 9 (Fig. 4.24).

The trilinear diagram described above is useful for visually

describing differences in major ion chemistry in groundwater flow

systems. For this purpose Back (1961 and1966), Morgan and Winner

(1962) and Seaber (1962) have developed the concept of hydrochemical

facies. Facies are identifiable parts of different nature belonging to any

genetically related body or system. Thus hydrochemical facies are

distinct zones that have cation and anion concentration describable

within defined composition categories (Freeze and Cherry, 1979). The

facies mapping approach is one way of smoothing chemical data. The

limited number of possibilities (facies) for classifying the chemical data

effectively eliminates local variability yet preserves broad trends

(Domenico and Schwartz, 1990).

Chemical data of the study area is presented by plotting them on

a Piper tri-linear diagram for Pre and Post monsoons. These diagrams

reveal the analogies, dissimilarities and different types of waters in the

study area, which are identified and listed in Table 4.14. The concept of

hydrochemical facies was developed in order to understand and identify

the water composition indifferent classes (Seaber, 1962 and Back,

1961). Facies are recognizable parts of different characters belonging to

108

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Figure 4.24 C aof major-ion percentages.according to the domain in which they occur on the

( Source : Kumaresan , 2006 )S8 gII1€I'ltS .

any genetically related system. Hydrochemical facies are distinct zones

that possess cation and anion concentration categories. To define a

composition class, Back and Hanshaw (1965) have suggested 29 sub

divisions in the tri-linear diagram (Figure 4.24). The interpretation of

distinct facies from the O to 10% and 90 to100% domains on the

diamond-shaped cation to anion graph is more helpful than using

equal 25% increments.

Piper’s trilinear diagram (Fig. 4.25) has been extensively used to

understand problems relating to groundwater chemistry (Karanth,

1987). Based on the Piper’s trilinear classification the groundwater of

the area under investigation is classified and described in the Table

4.14.

In the study area, the water samples fall in the upper half of the

diamond field suggesting that these water samples are primarily

alkaline in nature. The Table 4.14 shows that for the pre monsoon

(5O.63%) and that of Post monsoon (38.27%), carbonate hardness

exceeds 50% (sub division number 5 of the diamond shaped field) .So

also 45.67% in the pre monsoon and 49.38% in post monsoon

represents no cation - anion pair (sub division number 9 of the

diamond shaped field). Fourty one water samples (5O.65%) in the Pre

monsoon and 31 water samples (38.27%) in the post monsoon falls in

the

109

Table 4.14 Suitability of groundwater based on Hill Piper’s TrilinearDiagram of the Bharathapuzha river basin. (After Piper,1944)

l

SubdivisionNumber

ofdiamondshaped

field

Characterization ofSub division of

diamond shaped field

No. of samples Percentage__~ l _ -t_._t t__t_W____z~,_ g_,_P t lPre g Post Pre OSi 1 monsoo

II101'1SOOI'l lT1OI'lSOOI'1 IT1OI1SOOI'1 p n

1

Alkaline earths (Ca +Mg) exceed alkalies(Na + K)

2Alkalies exceeds S7alkaline earths

3

Weak acids (CO3 +HCO3) exceed strongacids)L304 t 91+ FL

4 Strong Acidsexceedweak acids

5

Carbonate hardness(secondary alkalinity]exceeds5O%(chemical propertiesare dominated byalkaline earths andyyeak acids) _g

l31 50.63 = 38.27 i41I

6

Non-carbonatehardness (secondarysalinity) exceeds 50%(chemical propertiesare dominated byalkaline earths andstrong_acids)g_

i

1

\

7

Carbonate alkali(primary salinity)exceeds 50%(chemical propertiesare dominated byalkalies and weakacids) g_ _

3 10 3.70 12.34

8

Carbonate alkali(primary alkalinity)exceeds 50%(chemical propertiesaredominated byalkalies and weakacids)

9 No cation—anion pairexceedsg50% W 37 40 45.67 i 49.38

llO

Hill - Piper Trilinear Diag:m1n

(a) Pre monsoon 8 0 806 60400:0 20W¢@@¢¢

80 oeooifiW‘Q?» ‘£5 *5: ‘E: $ *5’ Q? =5’

Ca Na+K HCO3 CI

( b ) Post monsoon

no 804 £3“

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63¢ Cb *2» Q» as» ,9 § 05>Ca Na+K HCO3 CI

Fig. 4.25 Hill —- Piper Trilinear Diagram of groundwater of the study area(a ] Pre monsoon ( b ) Post monsoon

4.6 STATISTICAL ANALYSIS OF GROUNDWATER CHEMISTRY

Correlation matrix

The correlation matrix of the chemical parameters in the

groundwater samples of the Bharathapuzha river basin for Pre and Post

monsoons shown in the Table 4.15a and 4.15b. It is inferred from the

table that EC has a high significant correlation with Ca, Na, Mg, TDS,

Total hardness, Cl in both the seasons. Further EC shows a highly

significant correlation with HCO3 for post monsoon. The above

relationship indicates that EC has a major role in controlling the

groundwater quality irrespective of the season. Ca also shows a highly

significant correlation with TDS, EC and TH in both the seasons. Total

iron shows highly significant correlation with HCO3+CO3 in pre

monsoon due to the leaching of iron from laterites. Sodium has

significant correlation with EC, TH, TDS, Ca, and Mg in both seasons.

Chlorine shows correlation with EC, TH, TDS, Ca, Mg, and Na in all

seasons. Sulphate has significant correlation with EC, TDS, Ca, and Na

in both seasons.

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