Appraisal of the geostatistical methods to estimate Mazandaran coastal ground water quality

Transcription

1 Caspa J. Ev. Sc. 2014, Vol. 12 No.1 pp. 129~146 Copyrght by Uversty of Gula, Prted I.R. Ira Caspa Joural of Evrometal Sceces [Research] Apprasal of the geostatstcal methods to estmate Mazadara coastal groud water qualty F. Karadsh 1 *, A. Shahazar 2 1- Water Egeerg Departmet, Zabol Uversty, Zabol, Ira. 2-Water egeerg Departmet, Sar Agrcultural Sceces ad Natural Resources Uversty, Sar, Ira. *Correspodg author s E-mal: F.Karadsh@uoz.ac.r (Receved: Aug , Accepted: Dec ) ABSTRACT The preset study was carred out to evaluate three terpolato methods cludg weghted movg average (WMA) wth the power of 2 ad 3, Krgg ad Cokrgg methods. Data of 23 wells Mazadara provce were collected fall ad sprg Seve parameters cludg electrcal coductvty (EC), ph, total dssolved solds (TDS), sodum adsorpto rato (SAR), total hardess (TH), chlorde cocetrato (Cl - ) ad sulphate cocetrato (SO 4 2- ) have bee chose as groudwater qualty dces the study area. Varogram aalyss ad extractg the spatal dstrbuto maps of groudwater qualty parameters were doe usg Geostatstcs exteso program GIS evromet. All terpolato methods have bee evaluated based o mea bas error (MBE) ad mea absolute error (MAE) crtera. The sphercal model for sem-varograms had the less value of RSS (resdual sum of square) for Cl -, EC, ph, SAR ad SO 4 2- parameters. TDS ad TH parameters followed a Gaussa model. All sem-varograms ad cross varograms had hgh cofdet level due to lttle values of ugget effects (C o ) relatve to sll. The covarace matrx demostrated that magesum cocetrato (Mg 2+ ), sodum cocetrato (Na + ), Total aos, Cl -, EC ad TDS parameters have bee the best covarate for estmatg TH, SO 4 2-, Cl -, PH, TDS ad EC parameters, respectvely. Co-Krgg was the best method for estmatg all parameters far apart TH for whch Krgg method was the best. Spatal dstrbuto maps of groudwater qualty dces demostrated that the groudwater the study area s slghtly basc ad the values of EC exceeded the permeable lmt more tha 40% of the study area. Also there was sodum hazard ad hgh cocetrato of TDS the orth-east part. Therefore, further studes are eeded to recogze the polluto sources order to reclam the polluted part the study area. Key Words: Groudwater qualty, Geostatstcs, Krgg, Co-Krgg, Mazadara, Spatal dstrbuto. INTRODUCTION Groudwater s a very mportat source of fresh water all over the world. It s used for domestc, dustral water supply ad rrgato. However the absece of approprate waste maagemet strateges, m ay hu ma actvtes ad ther byproducts have the potetal to pollute ths worthy water source. Idustral effluets, wastes from urba frastructures, agrculture, hortculture, trasport ad dscharges from hortculture, trasport ad dscharges from abadoed mes ad delberate or accdetal polluto, mproper dsposal due to rapd urbazato developed coutres stream pollutos, all evetually affect the groudwater qualty. Accordg to World Health Orgazato (WHO, 2003) 80% of dseases huma beg are water bore. Therefore t s mperatves to regularly motor the qualty of groudwater ad to take measures to prevet the polluto. A lot of researches are coducted o aalyzg groudwater qualty ad ts temporal Ole verso s avalable o

2 Apprasal of the geostatstcal chages due to varous factors (Sayaa et al, 2010; Satsh et al, 2007; Sutha et al, 2002). Udayalaxm et al. (2010) examed the qualty of groudwater usg Wlcox plot ad Pper tragular dagram a 40 km squared of Ida. It was foud that the samples the study area fell uder C3S1 class ad are characterzed by alkale therefore the groudwater the etre rego was too hard for drkg. Obefua et al. (2010) evaluated the groudwater qualty for drkg ad rrgato use Yola ortheaster Ngera. Ther results showed that lear regresso equatos could be appled predctg groudwater qualty that area. Temporal motorg of groudwater qualty would let havg some observed data some pots (wells) a area. However well uderstadg of polluted area eeds to covert measured pot data to cotuous surface. As measurg the groudwater qualty parameters s too costly, therefore choosg a proper terpolato method to estmate the favorte object would be ecoomc ad has a great effect o data maagemet (Habash, 2007). Geostatstcal methods are oe of the best terpolato techques (Akhava et al., 2010) whch ther accuracy for spatally predcto of groud water qualty has bee useful dfferet studes. Krgg method has bee recogzed as the best method for estmatg the values of TDS (Ahmed, 2002), heavy metals (Istock ad Cooper, 1998) ad trate cocetrato (Barcae ad Passarella, 2008) groudwater. Gaus et al. (2003) had a geostatstcal aalyss of arsec cocetrato groudwater Bagladesh usg dsjuctve krgg method. Ther results showed that 35 mllo people were exposed hgh cocetrato of arsec (50ppm) ad 50 mllo people were exposed 10ppm. Fetoua et al. (2008) have assessed groudwater qualty the rrgated pla of Trffa orth-east of Morocco usg Krgg method. Amad et al. (2012) assessed the groud water qualty by geostatstcal methods Easter Nger Delta. The usefuless of geostatstcal methods terpretg the hydro geochemcal data as well as detfyg ad categorzg pollutats are beg demostrated ther study. Rzzo ad Mouser (2000) supposed that Cokrgg method was a approprate method to terpolate water qualty dces. Dagosto et al. (1998) studed spatal ad temporal varablty of groudwater trate cocetrato. They demostrated that Cokrgg method could crease the accuracy of estmatg groudwater trate cocetrato. Nazar et al. (2006) used geostatstcal method to study spatal varablty of groudwater qualty Balarood pla. The result showed that the sphercal model was the best model to estmate EC, chlorde cocetrato Cl - ad SO 42 - varables. Although geostatstcal methods are sutable for preparg spatal dstrbuto of groudwater qualty dces, a approprate geostatstcal method for estmatg a varable depeds o the selected varable ad the study area (Safar, 2002). Thus, the preset study was carred out to evaluate three terpolato methods cludg weghted movg average (WMA) wth the power of 2 ad 3 Krgg ad Cokrgg teded to estmate dfferet groudwater qualty varable cludg electrcal coductvty (EC), ph, total dssolved sold (TDS), sodum adsorpto rato (SAR), total hardess (TH), chlorde cocetrato (Cl - ) ad sulphate cocetrato (SO 42 - ) Mazadara, Ira. MATERIAL AND METHODS Study Area ad Research Method The study area falls wth logtudes of m ad m; lattudes of m ad m Mazadara, Ira. De-Mart method used clmate regme assessmet revealed a humd clmate, wth a average aual ra fall of 700 mm. Data of 23 wells obtaed from Mazadara Regoal Water Orgazato were used. Fg. 1 shows the locato of the selected wells the study area. Data were collected twce fall ad sprg 2006.

3 Karadsh ad Shahazar Seve parameters cludg electrcal coductvty (EC), ph, total dssolved sold (TDS), sodum adsorpto rato (SAR), total hardess (TH), chlorde cocetrato (Cl- ) ad sulphate cocetrato (SO 4 2- ) were chose as groudwater qualty dces the study area. Itally to vestgate terpolato methods, the hstogram of all selected parameters was drawg. The the ormalty hypothess of all parameters was checked usg SPSS software. Data whch had hgh skewess, were ormalzed usg logarthmc method. A sutable covarate amog HCO 3-, Na +, Mg 2+, Ca 2+ ad K + was determed for each groudwater qualty dex usg a covarace matrx. The ormalty of covarates was also checked. Fg.1. Posto of wells the study area used aalyzg groud water qualty After data ormalzato ad choosg a sutable covarate, Varograms aalyss were performed usg Geostatstcal exteso program Geographc Iformato System (GIS). The expermetal sem-varogram was calculated, ad the the best model was ftted wth expermetal varograms. The best model was selected based o less Resdual Sum of Square (RSS) value. The, the cofdece level of all varograms was evaluated usg the rato of ugget varace to sll whch s regarded as a crtero for classfyg the spatal depedece of groud water qualty parameters. If ths rato s less tha 25%, the the varable has strog spatal depedece; f the rato s betwee 25 ad 75%, the varable has moderate spatal depedece ad the rato greater tha 75%, represets weak spatal depedece (Taghzadeh et al, 2008). After varograms aalyss, the accuracy of ordary krgg, Cokrgg ad weghtg movg average (WMA) wth power of 2 ad 3 terpolatg

4 Apprasal of the geostatstcal groudwater qualty dces was evaluated usg cross valdato techque. Evaluato crtera cluded mea bas error (MAE) ad mea absolute error (MBE). Fally, spatal dstrbuto maps of selected water qualty dces have bee prepared Geographc Iformato System (GIS). After all, a physcochemcal aalyss of the groudwater qualty the study area was carred out based o prepared maps. Iterpolato Methods Iterpolato methods ca be broadly classfed to two major categores: exact ad approxmate. The terpolated surface goes through observed pot data exact methods whle t may devate from pot data approxmate methods. For stace, Thesse polygo ad WMA are exact whle krgg ad th plate smoothg sple TPSS are approxmate. Iterpolato methods vary based o how they estmate the weght parameter of the followg geeral equato: * Z ( x) Z( ) (1) 1 * x Where Z ( x) s the estmated value of locato x; Z x ) s the value of ( observato pot x ; s the umber of pots; ad s the weght. For example, the weght WMA method, also kow as Iverse Dstace Method (IDW), s determed based o the dstace betwee the data pots as follows: D 1 D (2) Where D s the dstace betwee the observed ad target pots; s the power; ad s the umber of data pots. Spatal correlato ad smoothg fucto are used for estmatg the weghts krgg ad TPSS methods, respectvely (Issaks ad Srvastava 1989; Hutchso 1994; Tabos ad Salas 1985). I ordary krgg, ca be obtaed by the soluto of the followg matrx of lear equatos (Issaks ad Srvastava, 1989): C. D (3) Where [c] s the matrx of covarace betwee observed data pots; ad [D] s the matrx of covarace betwee pars of observed ad target pots. For solvg Eq.3, a semvarogram model must be used. Cokrgg s a dervatve method from Krgg whch uses a covarate, such as elevato, the estmato process. The cross varogram betwee the ma varable to be estmated ad the covarate used the determato of weghts. Cokrgg has bee extesvely descrbed by Goovaerts 1997, 2000 ad Issaks ad Srvastava Due to the kow fluece of elevato o rafall the rego of study, the elevato was used as the covarate. I the TPSS method, the followg relatoshp must be mmzed (Hutchso1994): 1 Z F( 2 x, y ). J m ( F) 2 (4) Where Z s the observed value; F(x, y) s the sples fucto at the locato (x, y); s the umber of data pots; 2 s the varace of observed d ata; (F ) s the J m tegral of MTh order dervatves of F(x, y); ad s the smoothg parameter. The order (power) of dervatve ad must be optmzed by the cross valdato techque. Overall, ordary krgg, Cokrgg ad WMA wth power of 2 to 4 were compared ths study. Varogram Aalyss Ad Estmato Varace I classc statstcal aalyss, samples are treated as f they were strpped of spatal dmeso. I geostatstcs, however, the locato of a data pot s cosdered

5 Karadsh ad Shahazar cojucto to ts value. Semvarogram s a varable. The expermetal sem Varogram s calculated as follows (Borgaad Vzzaccaro, 1997; Issaks ad Srvastava, 1989): ( h) 1 ( h ) Z ( x h) Z( x ) 2. ( h) (5) 1 Where (h) s the umber of sample pars separated by d stace h; Z x ) s the ( measured value at locato x ; ad Z ( x h) s the measured value at d stace h from dstace where x.rage (R) s the reaches a costat value. The value of semvarogram at R s defed as sll. I theory, sll value s equal to the sample varace uder the assumpto of secod-order statoary. The value of at h=0 the semvarogram s called the u gget effect C. s used krgg 0 methods for estmatg the weght parameters [Eq.3] ad dervg the spatal dstrbuto of estmato varace. Oe of the characterstcs of geostatstcal methods s ther ablty to determe the estmato varace (Hoh 1999), usually show as 2 E, as a dcator of the error betwee the actual ad estmated values. The estmato varace s calculated as follows: E (6) j 1 Where s the umber of data pots; s the weght at locato ; s the ugget effect; 0 data pots ad j. s the sem- varace betwee Evaluato Crtera All terpolato methods must be evaluated for ther accuracy ad/ or proper parameters electo. I the cross-valdato techque, a gve pot s removed the terpolato process ad estmated by the remag observatos. The dfferece betwee the estmated ad observed values 0 j 2 measure of spatal correlato of a gve represets the error. Ths procedure s repeated for all pots ad the cumulatve error s determed for each terpolato method. Followg Wllmott (1982), mea absolute error MAE ad mea bas error MBE were used for the selecto of the most accurate terpolato method. MAE MBE * Z ( x ) * Z ( x ) Z( x Z( x ) ) (8) (7) * Where Z ( ) s the estmated x value, Z x ) s the observed value. MAE ( dcates the average error of terpolato ad MBE represets the devato betwee the average of estmated data ad the average of observed data. RESULTS AND DISCUSSIONS Varogram Aalyss Table 1, summarzed the evaluated statstcal parameters amely mmum (M), maxmum (Max), mea, stadard devato (S.D), Skewess ad kurtoss values for each of the measured costtuet of the groudwater samples from study area. Table 1 shows that the majorty of studed parameters had hgh skewess, due to suffcet umber of samples ad usutable dstrbuto. However, all data were ormalzed usg logarthmc method apart from ph ad calcum cocetrato (Ca 2+ ). Table 2 shows the resdual sum of square (RSS) of dfferet varograms models for all selected parameters. Results showed that sphercal model had the less value of RSS for Cl -, EC, PH, SAR ad SO 2-4 parameter. However TDS ad TH parameter followed a Gaussa model the study area. The results are agreemet wth Nazar et al. (2006) who used geostatstcal methods to study spatal varablty of Groudwater qualty Balarood pla. Ther results showed that

6 Apprasal of the geostatstcal the sphercal model was the best model for estmatg EC, Cl - ad SO 4 2- cocetrato. Sem-varograms of selected parameter the study area were llustrated Fg. 2. Table 3 also summarzed the parameters of sem-varograms the study area. The rato of ugget varace to sll showed that there was a moderate spatal depedece amog the values of TH, TDS, ph ad SO 4 2- parameters. However three parameters cludg SAR, EC ad Cl - had weak spatal structure separately. Taghzadeh et al. (2008) demostrated that there was a weak spatal structure amog the values of Cl - parameter Yazd-Ardaka pla. Table 3 showed that the rage of fluece raged betwee ad 34 klometer. The maxmum ad mmum value of the rage of fluece beloged to EC ad TDS respectvely. However ths value SO 4 2- (32 Klometer) s ear to the maxmum value of the rage of fluece (34 Klometers). Lttle value of C o relatve sll all parameters (apart from TH) showed that determstc varace s low. I the other words, varograms had hgh cofdece level. Amog all parameters apart from TH (3300) C o value raged betwee Table 1: Statstcs of groudwater qualty aalyss. Parameters clude electrcal coductvty (EC), sodum adsorpto rato (SAR), total dssolved sold (TDS), total hardess (TH), ph, chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), bcarboate cocetrato (HCO 3 -), sodum cocetrato (Na + ), potassum cocetrato (K + ), magesum cocetrato (Mg 2+ ), ad calcum cocetrato (Ca 2+ ). Parameter M Max Mea S.D Skewess kurtoss SAR SAR** TDS (mg/lt) TDS (mg/lt)** TH (mg/lt) TH (mg/lt)** PH Cl - (mg/lt) Cl - (mg/lt)** SO 4 2-** SO 4 2-(mg/lt)** HCO 3 - (mg/lt) HCO 3 -(mg/lt)** Na + (mg/lt) Na + (mg/lt)** K + (mg/lt) K + (mg/lt)** Mg 2+ (mg/lt) Mg 2+ (mg/lt)** Ca 2+ (mg/lt) ** Usg logarthm to ormalze data

7 Karadsh ad Shahazar Table 2. RSS values (resdual sum of square) of dfferet expermetal methods for dfferet groudwater qualty dexes. Parameters clude total hardess (TH), sodum adsorpto rato (SAR), chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), PH, total dssolved sold (TDS) ad electrcal coductvty (EC). Parameter TH SAR SO4 2- Cl - ph TDS EC Sphercal 2.20E E E E E E E-03 Expoetal 2.37E E E E E E E-03 Gaussa 2.37E E E E E E E-03 Fg. 2: Expermetal varograms of a) chlorde cocetrato ( Cl - ), b) electrcal coductvty (EC), c) ph, d) Sodum adsorpto rato (SAR), e) sulphate cocetrato ( SO 4 2-), f) total dssolved sold (TDS) ad g) total hardess (TH)

8 Apprasal of the geostatstcal Table 3: Parameters of expermetal varogram for dfferet groudwater qualty dex. C 0 s ugget effect ad C 0 +C s the varogram sll. Parameters clude total hardess (TH), sodum adsorpto rato (SAR), chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), PH, total dssolved sold (TDS) ad electrcal coductvty (EC). Parameter Model C o C o +C Rage (m) C/(C 0 +C) TH Gaussa SAR Sphercal SO 4 2- Sphercal Cl - Sphercal ph Sphercal TDS Gaussa EC Sphercal I order to determe the covarate parameter Co-krgg method, the covarace matrx was extracted usg SPSS software ad the parameter whch had the hghest correlato coeffcet was selected as the auxlary parameter Co-Krgg method (Table 4). Mg 2+ (Magesum cocetrato), Na + (Sodum cocetrato), Total aos, Cl -, EC ad TDS parameter had the best covarate for estmatg TH, SO 4 2-, Cl -, ph, TDS ad EC parameter usg Co-Krgg method, respectvely, ad the correlato coeffcet was 84%, 99%, 66%, 66% 37%, 99% ad 99% respectvely. Aalyzg dfferet models for cross varograms showed that Sphercal model had the lowest RSS value (Table 5). Cross Varogram of Cl -, EC, TDS, ph, SAR, SO 4 2- ad TH parameters ad the characterstcs of m etoed crossvarograms are llustrated Fg. 3 ad Table 6, respectvely. Table 6 shows that the rato of ugget varace to sll s more tha 75% for all parameters ad therefore all parameters had weak spatal structure the study area. The rage of fluece s raged betwee 10 ad 35 klometers amog dfferet cross varogram. The maxmum values of the rage of fluece belog to ph ad TDS ad EC ad the mmum value belogs to TH parameter. The lowest value of C 0 belogs to TH ad SO 2-4. However the C 0 value of all parameters s close to each other. It s wth the rage of 0 to Therefore all cross varograms have hgh cofdece level.

9 Karadsh ad Shahazar Table 4: Correlato coeffcet amog dfferet groudwater qualty dces. Parameters clude electrcal coductvty (EC), sodum adsorpto rato (SAR), total dssolved sold (TDS), total hardess (TH), ph, chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), bcarboate cocetrato (HCO 3 -), sodum cocetrato (Na + ), potassum cocetrato (K + ), magesum cocetrato (Mg 2+ ), ad calcum cocetrato (Ca 2+ ). TH SAR K + Na + Mg 2+ Ca 2+ Total SO 4 2- Cl - HCO 3 - ph TDS EC TH 1 SAR K Na Mg Ca Total SO Cl HCO ph TDS EC Table 5. RSS values of dfferet expermetal methods for dfferet groudwater qualty dces cludg total hardess (TH), sodum adsorpto rato (SAR), chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), ph, total dssolved sold (TDS) ad electrcal coductvty (EC). Parameter TH SAR SO 4 2- Cl - ph TDS EC Sphercal Expoetal Gaussa

10 Apprasal of the geostatstcal Fg. 3. Expermetal cross varograms of a)chlorde cocetrato ( Cl - ), b) electrcal coductvty (EC), c) ph, d) Sodum adsorpto rato (SAR), e) sulphate cocetrato ( SO4 2- ), f) total dssolved sold (TDS) ad g) total hardess (TH).

11 Karadsh ad Shahazar Table 6. Parameter of cross varogram for dfferet groudwater qualty dex. C 0 s ugget effect ad C 0 +C s the varogram sll. Parameters clude electrcal coductvty (EC), sodum adsorpto rato (SAR), total dssolved sold (TDS), total hardess (TH), ph, chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), sodum cocetrato (Na + ), magesum cocetrato (Mg 2+ ), calcum cocetrato (Ca 2+ ) ad total aos cocetrato. Parameter Covarate Model C o Sll Rage C/(C 0 +C) TH mg 2+ Sphercal SAR Na + Sphercal SO 4 2- Na + Sphercal Cl - total aos Sphercal ph Ca 2+ Sphercal TDS EC Sphercal EC TDS Sphercal Evaluatg Iterpolato Method Evaluatg the dfferet terpolato methods was doe frst based o MBE ad later by MAE (f the decsso was uder doubt). The WMA method was executed usg dfferet umber of eghbourhood pots. Results showed that 9 eghbourhood pots performed the best precso. The metoed method was accomplshed wth power of 2 to 3 ad t was proved that WMA wth the power of 3 performed better ad gave hgher accuracy tha the other power (Table 7). Comparso of the values of MBE amog dfferet methods showed that dfferece betwee observed data ad estmated data of all parameters were low amog dfferet terpolato method (Table 7). Table 7: Results of comparso dfferet terpolato methods estmatg water qualty dexes based o evaluato crtera (mea bas error (MBE) ad mea absolute error (MAE)). WMA-2 ad WMA-3 s weghtg movg average wth power of 2 ad 3 respectvely. Parameters clude total hardess (TH), sodum adsorpto rato (SAR), chlorde cocetrato (Cl - ), sulphate cocetrato (SO 4 2-), ph, total dssolved sold (TDS) ad electrcal coductvty (EC). Method Krgg CO-Krgg WMA-2 WMA-3 Parameter MBE MAE MBE MAE MBE MAE MBE MAE TH SAR SO PH TDS EC Cl Therefore, all methods have eough accuracy to terpolate the selected data of groudwater. Ths result demostrated that Geostatstcal methods were strog eough to estmate the values of groudwater parameters the study area. Ths s agreemet wth the fdg of Safar (2002), Nazarzade et al. (2006), Ahmed (2002) ad Taghzadeh et al. (2008), who stated that Geostatstcs s superor to IDW terpolatg the parameter of groudwater qualty parameters. However Co-Krgg s the best method to estmate SAR, SO 4 2-, PH, TDS, EC ad Cl - whch have the lowest MBE crtera. For TH, Krgg has the lowest value of MBE ad

12 Apprasal of the geostatstcal therefore s the best method for terpolatg the metoed parameter the study area. Ths result s agreemet wth the fdgs of Rzzo ad Mouser (2000). They cosdered Cokrgg as a sutable method for mappg the qualty dcators such as: Na +, Cl -, SO 4 2-, Ca 2+ ad EC. Taghzadeh et al. (2008) have also cluded that the Co-Krgg methods as the most accurate geostatstcal methods estmatg SAR, TDS, EC, TH, Cl - ad SO Also, the ablty of Co-Krgg method for terpolatg the values of trate cocetrato groudwater has bee prove by Dagosto et al. (1998). Table 7 shows that Krgg s the best method for estmatg the values of TH. The ablty of Krgg method estmatg the values of groudwater qualty parameters such as TDS (Ahmed, 2002),heavy metals (Istock ad Cooper, 1998),trate cocetrato (Barace ad Passarella, 2008), arsec cocetrato (Gaus et al, 2003) ad all other groudwater qualty parameters (Fetoua et al, 2008) have bee prove. Physochemcal Aalyss of Groudwater Qualty Based o Prepared Maps GIS Spatal dstrbuto of selected groudwater qualty parameters based o Cokrgg method for Cl-, EC, PH, SAR, SO42- ad TDS ad based o Krgg method for TH are llustrated Fgs. 4-10, respectvely. A physcochemcal aalyss of groudwater qualty has bee doe based o these maps. Chlorde cocetrato of the groudwater samples raged from 0.9 to mg/ lt (Fg. 4). The WHO lmt of chlorde the groudwater s less tha 250 mg/ lt (WHO, 1984). Fg. 4 shows that the values of Cl - the study area s less tha permssble lmt. Sulphates groudwater excess of the WHO lmt of 150 mg/ lt have ot bee see ay part of the study area (WHO, 1984). EC values rage from 1017 to 3981 s/ cm (Fg. 5). The maxmum permssble value of EC groudwater s 1500 s/ cm (BIS, 1983). Fg 5 shows that the value of EC more tha 40% of the study area exceed the permssble value of EC. The ph the study area (Fg. 6) vares from 7.5 to 8 agast permssble lmts of 6.5 to 8.5 (BIS, 1983). The measure of ph s o a scale of 0-14 where ph less tha 7 s acdc ad greater tha 7 s alkale (basc) ad exact 7 s eutral. Thus the groudwater samples are slghtly basc ad are the permssble lmt. The value of SAR groudwater shows the sodum hazard groudwater ad values upper tha 5 could be a alarm of sodum hazard. The SAR values were foud to vary from 2 to 11.9 (Fg. 7). Apart from the ortheast of the study area, all other parts have the values of SAR whch s less tha 3. TDS (Fg. 9) gves the geeral ature of groudwater qualty ad extet of cotamato (Ao, 1946; Robove, 1958; Davs ad de West, 1966; AWWA, 1971). The permssble lmt (BIS, 1983) for TDS s about 500 mg/ l. I geeral, TDS values of <1000 mg/ l are cosdered as fresh water ad values >1000 mg/ l are cosdered bracksh. Based o Fg. 9, The TDS values vary betwee 675 to 3981 mg/ l wth mea value of 1044 mg/ l. the spatal dstrbuto of TDS shows that mostly the ortheast part of the study area has hgh cocetrato of TDS. Total hardess, as a mportat property dcatg the qualty of groudwater, s maly caused by magesum ad calcum catos ad s defed as the sum of ther cocetratos expressed mg/ lt. Bascally t s the soap cosumg property of water. The desrable lmt of TH s mg/ lt ad the etre study are has the value of TH acceptable lmt (Fg. 10).

13 Karadsh ad Shahazar Fg. 4. Iterpolated groudwater qualty maps of electrcal coductvty (Cl - ) based o Co-Krgg Method Fg. 5: Iterpolated groudwater qualty maps of electrcal coductvty (EC) based o Co-Krgg Method

14 Apprasal of the geostatstcal Fg. 6. Iterpolated groudwater qualty maps of ph based o Co-Krgg Method Fg. 7. Iterpolated groudwater qualty maps of sodum adsorpto rato (SAR) based o Co- Krgg Method

15 Karadsh ad Shahazar Fg. 8. Iterpolated groudwater qualty maps of sulphate cocetrato (SO 4 2-) based o Co-Krgg Method Fg. 9. Iterpolated groudwater qualty maps of total dssolved sold (TDS) based o Co-Krgg Method

16 Apprasal of the geostatstcal Fg. 10: Iterpolated groudwater qualty maps of total hardess (TH) based o Krgg Method CONCLUSION The preset study was carred out to evaluate three terpolato methods cludg weghted movg average WMA wth the power of 2 ad 3, Krgg ad Cokrgg.for estmatg seve groudwater qualty parameters cludg EC, ph, TDS, SAR, TH, Cl - ad SO 2-4 Mazadara, Ira. Aalyzg dfferet geostatstcal terpolato methods showed that Co-Krgg s the best method for estmatg SAR, SO 2-4, ph, TDS, EC ad Cl - whch had the lowest MBE crtera. For TH, Krgg had the lowest value of MBE ad therefore s the best method for terpolatg thsparameter the study area. Spatal dstrbuto of PH showed that the groudwater the study area was slghtly basc ad the values of PH were the permssble lmt, also the value of EC more tha 40% of the study area exceeded the permssble lmt. Spatal dstrbuto of TDS showed that mostly the orth-easter part of the study area had hgh cocetrato of TDS. There was o hazard wth the excessve value of chlorde, sulphate ad total hardess (TH) etre study area. Results demostrated that there was sodum hazard the orth-east of the study area based o SAR values. Therefore, further studes are eeded to recogze the polluto sources order to reclam the polluted part the study area. REFERENCES Ahmed, S., (2002). Groudwater motorg etwork desg: Applcato of geostatstcs wth a few case studes from a gratc aqufer a sem-ard rego. I: Groudwater Hydrology, M.M. Sherf, V.P. Sgh ad M. Al-Rashed (Eds.), Balkema, Tokyo, Japa, 2: Akhava, R., Zahed Amr, Gh. Ad Zober, M., (2010). Spatal varablty of forest growg stock usg geostatstcs the Caspa rego of Ira. Caspa Joural of Evrometal Sceces, 8(1): Amad, A. N., Olasehde, P. I., Ysa, J., Okosu, E. A., Nwakwoala, H. O ad Y. B., Alkal, (2012). Geostatstcal Assessmet of Groudwater Qualty from Coastal Aqufers of Easter Nger Delta, Ngera, Geosceces, 2(3): Ao, (1946). Drkg water stadards, Amerca Joural of Water Works Assocato, 938: AWWA, (1971). Water qualty ad treatmet, McGraw-Hll, NY. p:654. Barcae, E., Passarella, G., (2008). Spatal evaluato of the rsk of groudwater qualty degradato: A comparso betwee dsjuctve krgg ad geostatstcal smulato, Joural of Evrometal Motorg ad Assessmet, 133: BIS IS 10500, (1983). Bureau of Ida stadards, Ida stadards specfcato for drkg Water. p:24.

17 Karadsh ad Shahazar Dagosto, V., E.A. Greee, G. Passarella ad M. Vurro, (1998). Spatal ad temporal study of trate cocetrato groudwater by meas of regoalzato. Evrometal Geology, 36: Davs, S.N. ad R.J. De West, (1966). Hydrogeology, Joh Wley ad Sos Ic., NY. p:463. Fetoua, S., Sbaa, M., Vaclooster, M., Bedra, B., (2008). Assessg groudwater qualty the rrgated pla of Trffa (North-east Morocco). Agrcultural Water Maagemet, 95: Gaus, I., Kburgh, D.G., Talbot, J.C. ad R. Webster, (2003). Geostatstcal aalyss of arsec cocetrato groudwater Bagladesh usg dsjuctve krgg. Evrometal Geology, 44: Habash, H., (2007). Evaluatg the accuracy ad valdty of terpolato methods estmatg total sol cotamats of NO3 usg geographc formato system (GIS). The thrd coferece of spatal formato systems, p: 5. Istock, J.D. ad R.M. Cooper, (1998). Geostatstcs Appled to Groudwater Polluto. III: Global Estmates. Joural of Evrometal Egeerg, 114 (4): NazarZade, F., Arshadya, B. ad K. ZadVakly, (2006). Study of spatal varablty of Groudwater qualty of Balarood Pla Khuzesta provce. The frst cogress of optmzed explotato from water source of Karoo ad Zayaderood Pla. Shahrekord Uversty, Persa Verso, pp: Obefua, G.I. ad D.M. Razulke, (2010). Physcochemcal Characterstcs of groudwater qualty from Yola Area, Northeaster Ngera. Joural of Appled Scece ad evrometal maagemet, 14(1): Rzzo, D.M. ad J. M. Mouser, (2000). Evaluato of Geostatstcs for Combed Hydrochemstry ad Mcrobal Commuty Fgerprtg at a Waste Dsposal Ste, 1-11pp. Hydrology 287, 95e123. Robove, C.J., Hagbrd, R.H. ad J.W. Brook Hat. (1958). Sale water resources of North Dakota, USGS Water Supply Paper, p:77. Safar, M., (2002). Determato fltrato etwork of Groudwater usg geostatstc method. M.Sc Thess. Tarbyat Modares Uversty Agrcultural Faculty, Persa Verso. p: 150. Sayaa,V.B.M., Arubabu, E., Mahesh Kumar, L., Ravchadra, S., ad Karuakara, K., (2010). Groudwater resposes to artfcal recharge of rawater Chea, Ida: a case study a educatoal sttuto campus. Ida Joural of Scece ad Techology. 3(2): Satsh Kumar, T., Sudarsha, V. ad G. Kalpaa. (2007). Geochemcal characterzato of groudwater, baks of Musrver, Hyderabad cty, A. P., Ida Poll Research, 26(4): Sutha, V., Rajeshwar, R. B., ad Sudarsha, V., (2002). Hydrogeochemstry of groudwater the Kateda ad Rajedraagar dustral area, Raga Reddy dstrct, A.P. Evrometal Geochemstry. 5 (1&2): Taghzadeh Mehrjerd, R., Zarea, M., Mahmod, S.h. ad A. Hedar, (2008). Spatal dstrbuto of groudwater qualty wth geostatstcs ( Case study: Yazd-Ardaka pla). World Appled Scece Joural, 4(1): Udayalaxm, G., Hmabdu, D. ad G. Ramadass, (2010). Geochemcal evaluato of groudwater qualty selected areas of Hyderabad, A.P., Ida. Ida Joural of Scece ad Techology, 3(5): World Health Orgazato (WHO), (1984). Gudeles for drkg water qualty, Geeva. 1& 2 p: 335. World Health Orgazato, WHO, (2003). Iteratoal Stadards for Drkg Water. 3rd Edto, Geeva,

18 Apprasal of the geostatstcal WMA SAR TDS ph EC SO 4 2- Cl - TH MBE GIS Geostatstcs RSS MAE TH TDS SO 4 2- SAR ph EC Cl - Sll C o TDS EC Cl - NA + Mg 2+ EC TDS ph Cl - SO 4 2- TH TH TH EC TDS

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