Groundwater quality assessment from a hard rock terrain, Salem district of Tamilnadu, India

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ORIGINAL PAPER

Groundwater quality assessment from a hard rock terrain,Salem district of Tamilnadu, India

K. Srinivasamoorthy & C. Nanthakumar & M. Vasanthavigar & K. Vijayaraghavan &

R. Rajivgandhi & S. Chidambaram & P. Anandhan & R. Manivannan & S. Vasudevan

Received: 23 October 2008 /Accepted: 2 July 2009 /Published online: 21 August 2009# Saudi Society for Geosciences 2009

Abstract A total of 162 groundwater samples for threerepresentative seasons were collected from Salem districtof Tamilnadu, India to decipher hydrogeochemistry andgroundwater quality for determining its suitability fordrinking and agricultural proposes. The water is neutral toalkaline in nature with pH ranging from 6.6 to 8.6 with anaverage of 8.0. Higher electrical conductivity was ob-served during post-monsoon season. The abundance ofmajor ions in the groundwater was in the order ofNa > Ca > Mg > K ¼ Cl > HCO3 > SO4 > NO3. Pip-er plot reveals the dominance of geochemical facies as mixedCa–Mg–Cl, Na–Cl, Ca–HCO3, Ca–Na–HCO3, and Ca–Cltype. NO3, Cl, SO4, and F exceed the permissible limitduring summer and post-monsoon seasons. Sodiumadsorption ratio was higher during post-monsoon andsouthwest monsoon season indicating high and lowsalinity, satisfactory for plants having moderate salttolerance on soils. Permeability index of water irrespec-tive of season falls in class I and class II indicating wateris moderate to good for irrigation purposes. As per theclassification of water for irrigation purpose, water is fitfor domestic and agricultural purposes with minor exceptionsirrespective of seasons.

Keywords Geochemical facies . Groundwater quality .

Salem district . Sodium adsorption ratio . Spatial distribution

Introduction

Quality of groundwater is the function of its physical andchemical parameters which depend upon the solubleproducts of weathering, decomposition, and the relatedchanges that occur with respect to time and space(Bhargava and Killender 1988; Prasad 1984). Pollution ofgroundwater due to external contaminants such as industrialurban and agricultural practices is influenced by number offactors like geology, soil, weathering, growth of industries,emission of pollutants, sewage disposal, and other environ-mental conditions, with which it alters from point of itsentry to exit (Viessman et al. 1989). Hence, the chemicalcomposition of groundwater plays a significant role indetermining the water quality for various utility purposeslike domestic, agricultural, and industrial purposes. Criteriaused for classification of water for particular purpose is notsuitable for other standards; better results can be obtainedby combining chemistry of all the ions than the individualor paired ionic character (Hem 1985).

A detailed work on quality and utility assessment ofgroundwater in Naini industrial area in Uttar Pradesh of Indiawas attempted by Mohan et al. (2000); they identifiedchanges in geochemical facies and locations unsafe fordrinking purpose. Srinivasamoorthy et al. (2008) studiedabout lithological influence of groundwater chemistry inMettur talk, Salem district of Tamilnadu state in India andidentified lithological domination along with anthropogenicimpact in water chemistry. Groundwater quality from Etah

K. Srinivasamoorthy (*) :M. Vasanthavigar :K. Vijayaraghavan : R. Rajivgandhi : S. Chidambaram :P. Anandhan : R. Manivannan : S. VasudevanDepartment of Earth Sciences, Annamalai University,Annamalai Nagar 608002 Tamilnadu, Indiae-mail: [email protected]

C. NanthakumarDepartment of Statistics, Salem Sowdeswari College,Salem, Tamilnadu, India

Arab J Geosci (2011) 4:91–102DOI 10.1007/s12517-009-0076-7

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district of Uttar Pradesh in India was attempted by Umar andUmar (2002) and suggested that deeper aquifers can be usedfor domestic aquifers than shallow aquifers due to their highintensity of pollution from anthropogenic impacts. Waterquality variation and its suitability for domestic and irrigationpurposes was discussed by Yvonne et al. (2008), Jalali(2007), Kumar et al. (2009), and Wen et al. (2008).

Correlation of groundwater quality with Indian StandardInstitute (ISI) and World Health Organization (WHO) inGuntur region of Andhra Pradesh was attempted by SubbaRao et al. (2002) by demarcating groundwater pocket zonesas unsafe for domestic purposes. Classification of ground-water was attempted by Ahmed et al. (2002), Bathrellos etal. (2008), and Galip Yuce (2007), suggested groundwatersuitability for drinking and public health. Groundwaterquality suitability for drinking and agricultural purposeswas attempted by Subramani et al. (2005) in Chithar riverbasin, Tamilnadu and identified locations of contaminationby using geographic information system approach.

Srinivasamoorthy et al. (2005) studied groundwaterquality in Mettur Taluk of Salem district and identifiedhigher NO3 and PO4 pollution levels. Similar studies werealso attempted by Stamatis et al. (2006), Pachero et al.(2001), and Antoniou (2002). The study area is a developingurban environment with insufficient surface water resourceswith major population which rely on groundwater fordomestic, agricultural, and industrial purposes. Chain ofindustries like thermal power plant and chemical industries is

confined to the northwestern part of the study area andnortheastern part is dominated by agricultural activities.Meager industries and agricultural practices are distributedthroughout the study area. Few unpublished reports give alimited idea about geochemical behavior of groundwater inthe study area. Hence, an attempt has been made in thisstudy to determine the hydrochemistry of groundwater toclassify its quality in order to evaluate its suitability formunicipal, agricultural, and industrial uses along with thespatial distribution.

Study area

The study area, Salem district, lies in northeastern part ofTamilnadu, state of India, between north latitudes 11°19′ and11°57″ and east longitudes 77°38′ and 78°51″. The totalgeographical extent of the study area is 5,207 km2. It has anextensive area covered by hills in east and undulating plainsexposed in west (Srinivasamoorthy et al. 2005). Generalelevation ranges from 250 to 320 m above mean sea level,and higher elevations of 1,200 to 1,500 m are confined to hillranges due north. Major part of the study area is covered byshallow pediments, bajadas, and denudational landforms.Geologically, the study area is comprised of peninsulargneiss, charnockite, ultramafic complex, and potassic mem-bers confined to Archean (Fig. 1). The study area comprisesa number of folds, faults, lineaments, shears, and joints.

77o 45’ 78o 30’

11o 45’

11o 30’

Fig. 1 Location, geology, andgroundwater sampling pointsof the study area

92 Arab J Geosci (2011) 4:91–102

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Tab

le1

Statistical

parametersforgrou

ndwater

during

differentseason

s

Param

eters

Maxim

umMinim

umAverage

Median

Mode

Standarddeviation

POM

SUM

SWM

POM

SUM

SWM

POM

SUM

SWM

POM

SUM

SWM

POM

SUM

SWM

POM

SUM

SWM

pH8.6

8.6

8.5

6.6

6.3

7.1

7.9

7.4

7.8

87.5

7.8

7.9

7.3

8.1

0.36

0.41

0.33

EC

2,965

3,09

04,180

221.5

550

520

1,56

51,628

1,761

1,605

1,560

1,63

91,470

1,56

01,330

536

507

808

HCO3

976

887.6

861

4.7

3355

405

346

328

372

354

319

354

33.7

305

180

201

112

CL

974

1,00

81,400

30.5

3588

357

286

351

270

248

266

266

124

8923

320

126

6

SO4

160

210.2

127

0.65

07

9390

6192

9454

9892

6043

4033

PO4

4.80

0.01

20.1

00

01

00

10

00

01

10

NO3

162

87.7

5613

.61.0

331

3926

3035

2718

3532

1721

12

F7

34

0.40

0.07

01

21

12

11

22

12

1

H4SIO

451

.622

.445

3.4

2.6

524

2625

2427

2430

3130

711

8

Ca

130

196

134

37.37

1694

6057

8260

5470

6070

4728

26

Mg

483

166.1

167

20.5

3.9

867

7548

5859

4338

4218

3168

26

Na

834

415.9

1,038

3341

.823

175

213

323

149

139

167

–14

813

410

418

429

1

K38

412

0.1

474

10.4

113

3259

613

184

312

1768

106

TDS

1,980

1,56

72,741

179

148.7

217

856

820

951

726

737

771

––

–37

637

055

9

%Na

7987

9316

1021

4249

6140

4565

––

–24

18

RSC

1112

1015

3615

36

13

31

1–

13

32

SAR

519

331

01

42

83

14

––

–4

01

CR

00

00

00

00

00

00

––

–0

00

TH

890.0

1,12

9.5

1,020.0

187.5

129.0

114.0

509.3

437.2

338.6

474.0

402.8

307.8

332.00

431.0

421.5

203.7

189.7

150.3

PI

8599

.044

3312

7058

5869

5558

––

–1

121

1

Allvalues

inmilligramsperliter

except

ECin

microSiemenspercentim

eter

andpH

POM

post-m

onsoon

,SU

Msummer,SW

Msouthw

estmon

soon

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Magnesite, bauxite, magnetite, and chromite are the impor-tant minerals and ores constrict in the district. The drainageof the district is contributed by two major river systems,Cauvery which flows due north south and Vellar along theNW part of the study area. The mean annual temperaturevaries between 20°C and 35°C. The district receives meagerrainfall (504.6–920.8 mm/annum) due to its location in rainshadow region. The occurrence and movement of ground-water in the study area is restricted to open system offractures like fissures and joints in unweathered portion andalso the porous zones of weathered formations. Theweathered layer in gneissic terrain of the study area variesfrom 2.2 to 50 m. In charnockite, thickness was rangingbetween 5.8 to 55 m. At contacts of gneiss and charnockite,thickness was ranging between 9.0 to 90.8 m indicating goodgroundwater potential. The groundwater fluctuation in thestudy area ranges from 0.2 to 13.5 m below ground level. Itreaches the lowest level during summer (SUM; March–June)and after it starts rising till the end of monsoon season(August–January).

Materials and methods

Groundwater samples were collected in 1 l polyethylenebottles during post-monsoon (POM; January), summer(March), and southwest monsoon (SWM; July) seasonsbroadly to cover the seasonal variations. A total of 162samples were collected at the rate of 54 samples per season.The samples were filtered using 0.45 μ Millipore filters andanalyzed for chemical constituents. pH and electrical conduc-tivity (EC) were measured in situ. Water analyses were carriedout by using standard procedures (APHA 1995). Bicarbonate,calcium, magnesium, and chloride were analyzed by titrationmethod. Fluoride, determined by using Orion fluoride ionelectrode model (94-09, 96-09). Sulfate, nitrate, and silicatewere determined by using Digital Spectrophotometer modelGS5 700A. Phosphate was determined by using ascorbicacid method; sodium and potassium are by flame photometer(Systronics mk-1/mk-III). The charge balance betweencations and anions varies by about 5–10% and in few sitesbetween 20% and 30%. Total dissolved solid (TDS)/EC ratiois 0.9/1.7 indicating additional sources of anions other thanweathering reactions.

Results and discussions

Hydrogeochemistry

Statistical parameters like maximum, minimum, average,median, mode, and standard deviation are represented forthe chemistry data in Table 1. Almost all the parameters

except pH showed wide fluctuations irrespective of sea-sons. Groundwater from the study area is neutral to alkalinewith pH ranging from 9.0 to 7.0. Maximum was notedduring SUM followed by SWM and POM seasons. EC wasranging from 222.0 to 4,282.0μS/cm. Higher concentrationwas noted during SWM indicating effective leaching ofions into the groundwater system during recharge. TDSvalues range from 179.0 to 2,741.0 mg/l; higher concen-tration was noted during SWM. Bicarbonate values rangefrom 5.0 to 979.0 mg/l with higher concentration duringPOM season. Silica was ranging from 3.0 to 52.0 mg/l withhigher concentration noted during SUM. Potassium wasranging from 474.0 to 0.01 mg/l during SWM and POMseasons and Na from 1,038.0 to 23.0 mg/l during SWMseason. Chloride concentrations range from 1,400.0 to31.0 mg/l during SWM and SUM seasons. Nitrate concen-trations range from 162.0 to 1.0 mg/l during SUM andPOM seasons. Calcium concentrations range from 130.0 to3.0 mg/l during SUM seasons. The distribution of SO4 ishighly variable from 1.0 to 184.0 during POM and SUMseasons, respectively. The abundance of major ions in thegroundwater was in the order of Naþ > Ca2þ > Mg2þ >

Kþ ¼ Cl > HCO3 > SO4 > NO3. Majority of higher con-centrations were noted higher during SWM season indicat-ing the effective leaching of ions into the groundwaterduring rainfall infiltration. It must be noticed the highdispersion of values for most variables (high standarddeviations), which indicates variations in chemical compo-sition along the sampling area.

Presentation of geochemical data in the form ofgraphical charts such as Piper–Hill diagram (Piper 1994)helps us in recognizing various hydrogeochemical types ina groundwater basin. The plot irrespective of seasons fallsin mixed Ca–Mg–Cl, Na–Cl, and Ca–HCO3 type withminor representations from mixed Ca–Na–HCO3 and Ca–Cl type (Fig. 2) indicating alkalinity exceeds alkaline earthand strong acids exceed weak acids. In general, the totalhydrochemistry of the study area is dominated by alkali andstrong acids.

Classification based on water use criteria for drinkingpurpose

The suitability of water for different purposes likedrinking, industrial, and irrigation is assessed due toits extensive developmental activities like over draftingand infiltration of agricultural and industrial effluentsinto the groundwater system. This has insisted on forthe classification of groundwater based upon its utilityfor various purposes. Drinking water standards arebased upon, presence of objectionable taste, odors orcolors along with presence of substances with adversephysiological effects. Potability of drinking water is

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mainly based on recommended permissible limits ofcertain parameters; when water exceeds the permissiblelimit, it is unfit for human consumption. The Table 2shows the range of ionic concentration in groundwater ofthe study area and prescribed specifications of WHO(1996) and ISI (1995). Parameters exceeding permissiblelimits were identified in most of the locations indicatinghigher ionic concentration. Mg and Cl exceed the

maximum limit in all the seasons and may be due toweathering from silicate-rich rocks and leaching from soildue to infiltration of anthropogenic activities. NO3 is alsoexceeding the permissible limit of 45 mg/l indicatinganthropogenic impact from fertilizers. HCO3 is higher andexceeds ISI limit for drinking water indicating precipita-tion of CO3 as scales in pipelines and affects pumpscausing loss to farmers (Rengarajan and Balasubramanian

Table 2 Comparison of groundwater quality with standards

Parameters WHO (1996) Highest desirable ISI (1995) maximum permissible POM SUM SWM

pH 6.5–8.5 7.5–8.5 6.5–9.2 6.6–8.6 7.2–6.30 7.1–8.5

EC 1,400.0 – 221–2,965 550–3,090 520–4,180

TDS 1,000.0 500 1,500.0 179–1,980 148–1,567 216–2,741

Ca 500.0 75 200.0 3–130 7.3–196 16–134

Mg 30 100.0 20–483 4.0–146 8–166

Na 200.0 – – 33–834 41–415 23–1,038

K – – – 1–384 0.46–120 1–474

HCO3 – 300 600.0 4–976 33–887 54–860

CL 250.0 250 1,000.0 30–974 35–1,008 87–1,400

SO4 400.0 200 400.0 0.65–665 0.01–210.2 6–127

NO3 45.0 – 45.0 13–162 1.0–87 2.5–55.5

F 1.0 1.5 1.5 0.40–7.00 0.07–3.00 0.0–4.00

TH 100.0 500 150.0 129–890 187–1,129 114–1,020

Fig. 2 Geochemical classifica-tion of groundwater in the studyarea

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1990). Sixty-five percent of groundwater in study area issuitable for domestic and drinking purpose with fewabnormalities.

As groundwater moves or stays for a long period alongits flow path, there is normally an increase in TDS whichdetermines the suitability of groundwater for any purpose(Freez and Cherry 1979). TDS in majority of the samplesare within the permissible limits of WHO and ISI with fewexceptions irrespective of seasons. In Table 3, majority ofthe samples fall in freshwater irrespective of seasons withfew representations from brackish water. Spatial distribu-tion of TDS values was demarcated on the basis ofminimum and maximum permissible limit (<500, 500–1,500, and >1,500 mg/l) and indicated that majority of thestudy area is having higher TDS which cannot be used forsafe drinking purpose (Fig. 3).

Hardness of water refers to soap neutralizing power ofwater. Hardness refers to reaction with soap and scaleformation. It increases the boiling point of water and do nothave any adverse effect on health of human. Hardness ofthe water varies from moderately hard to very hard(Table 4); increasing of hardness was noted in POM season.In general, hardness is increased during POM and SUMseasons and may be due to leaching of Ca and Mg ions intogroundwater.

Chloride was ranging from 31 to 1,400 mg/l. Averagevalues for all the seasons were within the prescribed limits.Spatial distribution of chloride was classified on the basisof maximum allowable limit of 600 mg/l (Fig. 4). Higherconcentration >600 mg/l was confined to northeastern andnorthwestern part of the study area during post-monsoonand summer seasons but during southwest monsoon,dilution effect is well noted.

Nitrogen in groundwater derived from organic industrialeffluents, fertilizer or nitrogen-fixing bacteria, leaching ofanimal dung, sewage, and septic tanks through soil andwater matrix to groundwater. In general, increase of nitratein groundwater may be an indicator of bacterial pollution(Srinivasamoorthy et al. 2005). Nitrate was ranging from 1to 162 mg/l. Higher concentration (>45 mg/l) that wasobserved during summer season might be due to intensiveagricultural activity, and lower concentration (<45 mg/l)that was observed during southwest monsoon seasonindicating surface runoff might have decreased the nitrateconcentration (Fig. 5).

1 23

4

5

6

7

8

91011

12 1314

15

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20

21222324

2526 27

2829

3031

32 3334

3536

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4950

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54

0 10 20

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0 10 20

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TDS - < 500 mg/l

TDS - 500 - 1500 mg/l

TDS - > 1500 mg/l

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8

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46

47

48

49

50

51

52

53

54

0 10 20

POM

Fig. 3 Spatial distribution of TDS in the study area (POM post-monsoon, SUM summer, SWM southwest monsoon)

TDS (mg/l) Nature of water POM (total wells) SUM (total wells) SWM (total wells)

<1,000 Freshwater 39 38 34

1,000–10,000 Brackish water 15 16 20

10,000–100,000 Saline water Nil Nil Nil

>100,000 Brine water Nil Nil Nil

Table 3 Classificationof groundwater based on totaldissolved solids

96 Arab J Geosci (2011) 4:91–102

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0 10 20

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Cl < 600 mg/l

Cl > 600 mg/l

SWM

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0 10 20

POM

Fig. 4 Spatial distribution of chloride in the study area

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54

NO3 - > 45 mg/l

NO3 - < 45 mg/l

0 10 20

SWM

Fig. 5 Spatial distribution of nitrate in the study area

Total hardnessas CaCO3 (mg/l)

Water class POM(total wells)

SUM(total wells)

SWM(total wells)

<75 Soft Nil Nil Nil

75–150 Moderately hard Nil Nil 2

150–300 Hard 7 15 25

>300 Very hard 47 39 27

Table 4 Classificationof groundwater basedon hardness

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Sulfate is found in smaller concentration due to its lesserbreaking down of organic substances from weatheredsoil/water (Miller 1979). The highest desirable limit is200 mg/l and the maximum permissible limit in ground-water is 400 mg/l. SO4 concentration ranges from 1 to184 mg/l. Sulfate was within the permissible limit through-out the seasons.

Fluoride ion predominantly present in groundwater isconsidered as toxicological geoenvironmental issue whenpresent in excess or deficit amount. Consumption of higherfluoride groundwater (>1.5 mg/l) can affect bones and softtissues like skeletal muscles, erythrocytes, gastrointestinaltissues, and ligaments. Effect of fluoride on teeth is calleddental fluorosis and on bone is called skeletal fluorosis.Fluoride in groundwater was ranging from 0.2 to 7 mg/l.Higher concentration was noted during summer season dueto weathering and leaching of the greater availability offluoride-bearing minerals like apatite, biotite, muscovite,lepidolite, and hornblende which has been reported fromlitho units of the study area (Ramanathan 1956). Spatialdistribution of fluoride was classified on the basis of itsconcentration as (<0.5, 1.0–1.5, and >1.5 mg/l). Higherconcentration was noted in the areas dominated bypeninsular gneiss and charnockite (Fig. 6).

Classification of water use for irrigation purpose

The suitability of groundwater for irrigation purpose ismainly based upon factors as soil texture and composition,crops grown, and irrigation practices in addition tochemical characteristics of the water. Quality of irrigationwater is judged by estimation of parameters like sodiumadsorption ratio (SAR), Na%, and residual sodium carbon-ate (RSC).

Total Na+ concentration and EC is important inclassifying the irrigation water (Raghunath 1987). Sodiumpercentage is calculated by using the formula:

Percent Na ¼ Naþ Kð Þ � 100f g=CaþMgþ Naþ Kð Þð Þ expressed in meq=1:

Majority of samples (Table 5) irrespective of seasons fall ingood to doubtful zone with minor representations from

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53

54

0 10 20

SWM

F - < 0.5 mg/l

F - 0.5 - 1.0 mg/l

F - > 1.0 mg/l

Fig. 6 Spatial distribution of fluoride in the study area

%Na Water class POM (total wells) SUM (total wells) SWM (total wells)

<20 Excellent 1 2 1

<21 Good 29 18 8

<22 Permissible 17 15 17

<23 Doubtful 6 19 19

<24 Unsuitable 1 Nil 9

Table 5 Classificationof groundwater based on percentsodium

98 Arab J Geosci (2011) 4:91–102

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excellent and unsuitable zones for irrigation purpose. Wilcox(1955) classified groundwater on percent sodium and EC.Majority of samples irrespective of seasons fall (Table 6) inpermissible limit with minor representations in good, doubt-ful, and unsuitable range (Fig. 7). Na+ is an important cationwhich in excess may harm plant growth physically bylimiting the uptake of water through modification of osmoticprocess or chemically by metabolic reactions. Effects of Na%on solid structure reduces permeability and results in soil withpoor internal drainage (Subramani et al. 2005).

Salinity of groundwater and SAR determines its utilityfor agricultural purposes. Salinity originates in groundwaterdue to weathering of rocks and leaching from top soil,anthropogenic sources along with minor influence onclimate. The level of Na+ and HCO3 in irrigationgroundwater affects permeability of soil and drainage of

the area. A better measure of the sodium hazard has beenexpressed as the percent sodium of total cations. A bettermeasure of the sodium hazard is the SAR which is used toexpress reactions in the soil. SAR is based primarily on theeffect of exchangeable sodium on the physical condition ofthe soil. Sodium sensitive plants may suffer injury as aresult of sodium accumulation in the plant tissue whenexchangeable sodium values are lower than those effectivein causing deterioration of the physical condition of thesoil. SAR is computed as

SAR ¼ Nað Þ. ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

CaþMgð Þ=2p� �n o

expressed in eq=m:

When SAR (alkali hazard) and specific conductance(salinity hazard) are plotted in USSL (1954) diagram,classification of water for irrigation purpose can be

EC (μS/cm) Water class POM (total wells) SUM (total wells) SWM (total wells)

<250 Excellent Nil Nil Nil

<250–750 Good 2 1 3

750–2,000 Permissible 37 45 35

2,000–3,000 Doubtful 21 8 12

>3,000 Unsuitable 4 Nil 4

Table 6 Classificationof groundwater basedon conductivity

0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

0 250 500 750 1000 1250 1500 1750 2000 2250 2500 2750

POM

SUM

SWM

EC-->

So

diu

m A

dso

rpti

on

Rat

io

C1S4 C2S4 C3S4 C4S4

C1S3 C2S3

C3S3

C4S3

C1S2 C2S2

C3S2

C4S2C1S1 C2S1 C3S1

C4S1

Fig. 7 Wilcox classificationof groundwater in the study area

Arab J Geosci (2011) 4:91–102 99

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determined (Fig. 8). Majority of samples fall in C3S1 zoneduring summer and post-monsoon indicating high and lowsalinity, satisfactory for plants having moderate salttolerance on soils. Southwest monsoon samples are alsonoted in C2S1, C3S2, C3S3, and C4S3 zones. Thisindicates medium to very high salinity waters whichrenders application of gypsum, makes water feasible, andalso increases soil permeability (Goyal and Jain 1982). Soilin this terrain is preferable for salt tolerance plants.

Permeability index (PI) is an important factor whichinfluences quality of irrigation water in relation to soil fordevelopment in agriculture. PI is obtained by consideringthe ions in milliequivalents per liter. It is obtained by theformula.

PI ¼ Naþ HCO3ð Þf g=ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiCaþMgþ Nað Þ

ph i

� 100 expressedin eq=m:

Based on permeability index, Doneen (1948) classifiedthe groundwater as class I, class II, and class III to find out

suitability of groundwater for irrigation purpose. In all theseasons, most of the plot irrespective of season fall in classI and class II indicating water is moderate to good forirrigation purposes.

In waters having high concentration of bicarbonate, thereis tendency for calcium and magnesium to precipitate as thewater in the soil becomes more concentrated. Hence, itresulted in increased concentration of sodium in water inthe form of sodium carbonate. RSC is calculated by thefollowing equation (Eaton 1954)

RSC ¼ HCO3� CaþMgðð Þ expressed ineq=m:

Majority of samples irrespective of seasons fall in“good” zone of RSC (Richards 1954) classification(Table 7) indicating water is fit for irrigation purposes.Few representations of “medium” and “bad” water werealso noted.

Groundwater extracted from the study area for variouspurposes is transported by metallic pipes that may or maynot be suitable for the transport. This fact is highlighted

0

25

50

75

100

0 5 10 15 20 25 30 35

POMSUMSWM

Exc

elle

nt

to g

oo

d

Go

od

to

per

mis

sib

le

Do

ub

tfu

l to

un

suit

able

Un

suit

able

Permissible to Doubtful

Total Concentration (meq/l) --->

Per

cen

t S

od

ium

--->

Fig. 8 USSL classificationof groundwater in the study area

RSC Water class POM (total wells) SUM (total wells) SWM (total wells)

<1.25 Good 47 48 44

1.25–2.5 Doubtful 3 2 4

>2.5 Unsuitable 4 4 6

Table 7 Classificationof groundwater based on residualsodium carbonate

100 Arab J Geosci (2011) 4:91–102

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using corrosivity ration proposed by Ryznes (1944). Theformula for calculating CR is

CR ¼ CI=35:5ð Þ þ SO4=96ð Þf g=2 HCO3ð Þ=100 expressed in eq=m:

The CR for the study area is less than one for all thesamples irrespective of seasons indicating groundwater ofthe study area is noncorrosive.

Conclusion

1. Groundwater from the study area is neutral to alkalinein nature. The abundance of major ions in thegroundwater was in the order of Na > Ca > Mg >K = Cl > HCO3 > SO4 > NO3.

2. Hydrochemistry of the study area is dominated byalkali and strong acids. As per comparison with WHOand ISI standard, 65% of groundwater in study area issuitable for domestic and drinking purpose with fewabnormalities.

3. Higher TDS and EC values were observed in north-eastern and northwestern part of the study areadominated by agricultural practices and industrialdominance. Higher concentration was noted in post-monsoon season following summer.

4. Cl, NO3, SO4, and F were found higher than permis-sible limit indicating anthropogenic impact along withleaching of fluoride from major litho units.

5. Total hardness shows an increasing trend during post-monsoon and summer seasons. As per the classificationof water for domestic and irrigation purposes, water isfit for irrigation purposes with minor exceptionsirrespective of seasons.

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