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HYDROLOGICALPROCESSES Hydrol.Process. ,2112–2123(2007) Publishedonline27March2007inWileyInterScience (www.interscience.wiley.com)DOI:10.1002/hyp.6390 GROUNDWATERRECHARGEESTIMATIONINJORDAN EVAPOTRANSPIRATION OVERLAND FLOW LOCALIZED PONDING Figure2.Conceptualmodelorrechargeprocesses(Kuells,2003) panrecharge,transmissionlossesandcolluvialinltra- tion.Preferentialrechargeareasneedtobeidentied regionally.Inthiscontext,isotopeandhydrochemical indicatorsbecomehelpfultoolsandhavebeenusedfor thedelineationoffavourablerechargeareasincom- plexterrain.Withinthisstudytheresearchconcentrates mainlyondirectrechargethroughsoils.Asawork- inghypothesis,itisassumedthatdirectrechargepro- cessesarelargelycontrolledbyclimatologicalconditions andbysoilpropertiesthatcanbequantied,suchas soiltextureandthickness.Themainobjectivesofthe E.ZAGANA 120012501300135014001450 Figure3.SurfacewaterbasinsinJordan pedologicalconditionshavebeenchosen.Thestudyarea inJordanextendsfromDeirAllaneartheRiverJordan atanelevationof235mbelowsealevel(b.s.l.)with anaverageprecipitationof250mmyear ,throughSalt atanelevationof1000mabovesealevel(a.s.l.)with anaverageprecipitationof500mmyear ,throughAl Zarqa/Mafraqatanelevationof600–700ma.s.l.andan averageprecipitationof180–220mmyear ,toSafawi intheeastatanelevationof700ma.s.l.withanaverage precipitationaslowas100mmyear .Thesestationsare GROUNDWATERRECHARGEESTIMATIONINJORDAN Figure4.MapshowingthestudyareaandthesoiltypesinJordan(R oyalJordanianGeographicCentre(1999)),modiedby(Obeidat2001) onwhichsoilsdevelop.SaltandAlZarqaarelocated withinorattheborderoftheareabelongingtothe Mediterranean-typesoilarea.AlMafraqislocatedina transitionzonewithbasaltic bedrock;Safawibelongsto therealmofdesertsoilsthataredominatedbydustand saltaccumulation. Hammadbasin TheHammadbasinisaatplateaucoveringavery largearea,whichincludesthesouthernpartofSyria, thewesternmostpartofIraq,apartofnorthwestSaudi Arabia,thepanhandleofJordanandapartoftheJor- danianSirhan.Inthecourseofthepresentstudy,the Hammadbasinistakentocoverthenortheasternpart ofJordan,eastoftheAzraq–Hammadcatchmentdivide comprisinganareaof18250km (Figure3).Thewest- ernHammadisapartofthebasaltplateau,whereasthe easternHammadisapartofthelimestoneplateau,with E.ZAGANA D ,where ismean annualrainfall, isthemeanchlorideconcentration ofrainfall, isdrydeposition, isthemeanannual rechargerateand isthemeanchlorideconcentration ofsoilwater.Theowbelowtherootzonecanbe rewrittenas ,wherethelastterm isthemeanoftheproductofrespectivedeviationsfrom .Ingeneral,itisassumedthatthistermcancels D Accordingtothemodelassumptions,chlorideshould increaseinthesoilandreachasteady-statevalueat thelowerendoftherootzone.Still,chloridepro- lesdonotalwayshavethatidealshape.Bulge-like prolesmightbefound,whicharemoredifcultto explain.Suchashapecanbetheresultof(a)non- steadyconditions,(b)preferredowpaths,(c)pastcli- maticvariability—changesintherechargerate.Diffu- sionwipesoutverticalvariabilitytoasignicantextent onlywithhighchloridecontents( 8000gm ).Pro- letechniquesusingchlorideintheunsaturatedzone forgroundwaterrechargeestimationshavebeensuccess- fullyappliedinAfrica(Edmunds D Inordertostudychlorideuxesandtoestimate groundwaterrechargewithintheframeofthisstudy, 25.4 cm andwinter. Hydrochemicalandisotopesmeasurements GROUNDWATERRECHARGEESTIMATIONINJORDAN 138014001420144014601480150015201540 1160 1180 1200 1220 1240 1260 SAUDI ARABIA 02040 Figure6.Locationmapofgroundwatersamplingpoints Monthlyrainfallsamplesfro m11rainfallstationsfrom differentpartsofJordanwerecollectedandanalysedfor theirstableisotopecompositionsofhydrogenandoxy- genbythelaboratoriesoftheMinistryofWaterand Irrigation,Jordan(Bajjali,1990).Tritiumdataofprecip- itationfromJordanwereobtainedfromtheInternational AtomicEnergyAuthorityfortheperiod1965–1969and fromBajjali(1990)fortheperiod1987–1989.Jordan E.ZAGANA 05101520253035 012345 Figure7.Soilwatercontentandchlorideconcentra tionatdifferentdepthsatSaltinwinterandsummer 05101520253035 050100150200250300350 Figure8.Soilwatercontentandchlorideconcentra tionatdifferentdepthsatZarqainwinterandsummer amountsto3 7mmyear .TableIpresentstheestimated rechargeratesindifferentlocalitiesinnorthJordan. Theeffectofdifferentsoilthicknessfordifferentcli- maticconditionsinJordanissummarizedinFigure11. Therangeofmeasuredelectricalconductivity(asa roughindicatorofevaporativeenrichmentorreciprocal recharge)isshownasaparallelbarforsoilsofdif- ferentdepths( -axis)andfordifferentclimaticgroups (350–450,200–350and100–200mmyear annualprecipitation).Thesere sultsindicatethatrecharge throughthesoilmatrixseemstobemainlycontrolledby climatologyandsoilthicknessandthattheserelationships arevalidoverlargedistancesinJordan. Hydrochemistry Thetotaldissolvedsolids(TDS)ofgroundwaterin theHammadbasinvaryfrom390to 4000mgl GroundwatersamplesinthesouthwestpartofHammad Copyright 2007JohnWiley&Sons,Ltd. Hydrol.Process. ,2112–2123(2007) DOI:10.1002/hyp GROUNDWATERRECHARGEESTIMATIONINJORDAN 05101520253035 020406080100120140 Figure9.Soilwatercontentandchlorideconcentratio nindifferentdepthsatDeirAllainwinterandsummer SaltZarqaSafawiDeirAlla Averagerainfall(mmyear )500180100250 MeanCl concentrationofrainfall(mgl )152531 916 MeanCl concentrationofsoilwater(mgl )5392170085613550 Groundwaterrecharge(mmyear )140 213 05101520253035 2.1 3.1 2.8 1.9 1.8 2.1 1.8 3.6 4.9 5.9 4.9 4.1 3.6 2.8 40_50 60_70 Figure10.Soilwatercontentandchlorideconcentratio natdifferentdepthsatSafawiinwinterandsummer Copyright 2007JohnWiley&Sons,Ltd. Hydrol.Process. ,2112–2123(2007) DOI:10.1002/hyp E.ZAGANA 20-40 60-100 20-40 60-100 025005000750010000 20-40 40-60 60-100 350-450 mm/y mean annual Figure11.Theeffectofsoilthicknesstothesalinityofsoilwaterin differentlocalitiesinJordan Stableisotopes Oand Hinprecipitation. TableII presentstheaveragestableisotopecompositionofpre- cipitationinJordan.Byplottingthevaluesinan 0 Š 3 Š 2 Š 4 3 100% 100% 100% 100% 100% 100% Figure12.PiperdiagramofgroundwatersamplesinHammadbasin Copyright 2007JohnWiley&Sons,Ltd. Hydrol.Process. ,2112–2123(2007) DOI:10.1002/hyp GROUNDWATERRECHARGEESTIMATIONINJORDAN diagram(Figure13)itwasobservedthatmostofpre- cipitationfollowstheMedite -6-5-4-3 Figure13. HdiagramofprecipitationinJordan TableII.StableisotopecompositionofprecipitationinJordan (Bajjali,1990) Station HDeuteriumexcess d No.of 7224 0440 5216 644 0217 1020 2425 5612 DeirAlla 0518 2711 5122 9725 Q.A.Airport 5723 3113 921 1428 RasMunif 1924 8115 9223 5621 Walla 0720 7313 fallsbelowtheGMWL,suggestingthatthewatersare ancientandwererechargedinadifferentclimatethan Mediterranean.Adistinguishingfeaturealsoisthatthey 1400145015001550 0204060km Figure14.Locationofgroundwatersamplesforisotopeanalysisand contoursofequalisotopiccompositionofgroundwaterinHammadbasin Copyright 2007JohnWiley&Sons,Ltd. Hydrol.Process. ,2112–2123(2007) DOI:10.1002/hyp E.ZAGANA -10-9-8-7-6-5-4-3 Figure15. Hdiagramofgroundwaterinthestudyarea TableIII.IsotopecompositionofgroundwaterinHammadbasin Sampleno. 9712 518 010 153 381 410 0513 748 472 H1053(DeepH1) IAEA(1996). thetritiumconcentrationinprecipitationreacheditsmax- imuminApril1963withavalueof1940TU(IAEA, 1996).Thereafter,thetritiumc oncentrationatthatstation hasdecreased,reachingavalueof7TU. Tritiumingroundwater. MostofgroundwaterinHam- GROUNDWATERRECHARGEESTIMATIONINJORDAN ofoxygenandhydrogen.In ApplicationofTracersinAridZone Hydrology ,AdarEM,LeibundgutC(eds).IAHSPublicationNo.232. IAHSPress:Wallingford;417–427. EdmundsWM,GayeCB.1994.Estimatingthespatialvariabilityof groundwaterrechargeinSahelusingchloride. JournalofHydrology :47–59. EdmundsWM,WaltonNRG.1980.Ageochemicalandisotopic approachtorechargeevaluationinsemi-aridzones-pastandpresent.In AridZoneHydrology:InvestigationswithIsotopeTechniques .IAEA: Vienna;47–68. EdmundsWM,DarlingWG,KinniburghDG.1988.Soluteprole techniquesforrechargeestimationinsemi-aridandaridterrain.In EstimationofNaturalGroundwaterRecharge ,SimmersI(ed.). NATO AdvancedSciencesInstitutesSeriesC .Reidel:Dordrecht;125–139. GatJR,DansgaardW.1972.Stableisotopesurveyofthefreshwater occurrencesinIsraelandnorthernJordanRiftValley. Journalof Hydrology :177–212. GatJR,IssarAS.1974.Desertisotopehydrology:watersourceofSinai