CaseStudy:ConsolidatedIrrigationDistrictRechargeProgramConsolidatedIrrigationDistrict(CID)islocatedintheSanJoaquinValley,ontheeastern
sideofFresnoCounty,andincludessmallportionsofTulareandKingscounties.Figure1showstheboundariesofCID.IncorporatedcitieswithintheboundariesofCIDincludeFowler,Kingsburg,Parlier,Sanger,andSelma.OthersmallerurbanenclavesarefoundintheunincorporatedareasandincludeCaruthersandDelRey.CIDoverliestheKingsBasin,whichispartofthelargerTulareLakeBasin,asdefinedintheCaliforniaDepartmentofWaterResources(DWR)Bulletin118(DWR,2003).
Figure 1 – Consolidated I.D. Boundary
CIDiscomprisedof145,000acres,themajorityofwhichisinagriculturalproduction.Cropwaterrequirementsaremetthroughirrigationapplicationofbothsurfaceandgroundwater.Surfacewaterdeliveredtoagriculturereducestherelianceongroundwater.Totalurbanwaterdemandsaremuchsmallerthanthetotalagriculturalwaterdemands,butthegrowingurbanizedareasarereliantexclusivelyongroundwater.
Consolidated I.D.
CIDwasorganizedonSeptember8,1921andhasbeenactivelymanaginglocalwatersuppliesthroughconjunctiveusesincetheagencywasformed.Conjunctiveuseisthecombinedmanagementofsurfacewaterandgroundwatersuppliesandstorage.TheDistrict’shistoricconjunctiveuseprogramincludesthediversion,inwetteryears,ofallocatedKingsRiverwaterandKingsRiverfloodreleasesintotheDistrict’sserviceareaforirrigationandgroundwaterrecharge.Partofthesurfacewaterappliedtoagriculture,thatisnotconsumedbythecrops,percolatesdownwardandrechargesthegroundwaterbasin.TheintentionaluseofsurfacewaterinlieuofgroundwaterpumpingispartoftheCIDconjunctiveuseoperations.Indrieryears,growersirrigatewithavailablesurfacewatersuppliessupplementedbypumpingofrechargedgroundwater.
CIDhaswaterrightstotheflowoftheKingsRiverandstoragerightsinPineFlatReservoir.SurfacewaterisstoredinPineFlatanddivertedbyCIDfromtheKingsRiverfordistributionthrough350milesofcanals.Figure2showsthecanalsystemwithinCID.
Figure 2 ‐ Consolidated I.D. Canal System
ASanJoaquinValleypioneeringroundwatermanagement,CIDbeganitsrechargeprogram
byacquiringitsfirstpercolationbasinin1932.Aninitialplanofsixteenpondseventuallygrewtoincludeover50dedicatedrechargebasinswithasurfaceareaofapproximately1,300acres,locatedinthesandysoilsoftheKingsRiver’salluvialplain.Averagepondrechargeisapproximately30,000acre‐feet,rangingfromzerointhedirestofyears,toamaximumof187,000acre‐feet.ThesandysoilsintheCIDareamaketheirpondscapableofrechargingover1,200acre‐feetperday.Inaddition,seepagefromthebottomofthecanalsandditchesrechargesanother300acre‐feetperdaywhenfull.Figure3showsCIDrechargebasins.
Figure 3 – Consolidated I.D. Recharge Ponds
Duringthe2010‐2011wateryear,therewere168dayswhenfloodwaterwasavailable.StartingonDecember30,2010,CIDstarteddivertingfloodwaterfromtheKingsRiveruntilmostoftheirpondswerefull.CIDkeptthepondsfullwithaflowof750cubicfeetpersecond(CFS)tomaintainthewaterlevelsintheponds.Thisresultedin250,000acre‐feetofwaterbeingrechargedintothegroundwaterbasinduringthat168‐dayperiod.ThisvolumeofrechargeinoneyearresultedinraisingtheaveragewatertableelevationthroughoutCIDby7.06feet.
TheaverageannualsurfacewatersupplyforCIDisapproximately238,000acre‐feetbutcanvaryfromthelowof13,500acre‐feetin1976toahighof616,000acre‐feetin1967.WhileCIDiscomprisedof145,000acres,divertedwaterisusedforsurfaceirrigationonapproximately95,000acres.TheremainingareasofCID,includingthecitiesandunincorporatedcommunities,relyexclusivelyongroundwater.Figure4showshistoricsurfacewaterdiversionsandtheaverageddeclineinthewatertableunderlyingCID.
DespitetheactivemanagementofKingsRiverwaterbyCIDandtheotheroverlyingwaterdistricts,groundwateroverdraftisoccurringintheKingsBasinonanaverageannualbasis.Thismeansthat,whileinsomeyearsmorewaterisrechargedthanremovedandgroundwaterlevelsrise,onaverage,moregroundwaterisremovedthanisrecharged.Thisisevidencedby
Figure 4 ‐ Surface Water Diversions vs. Average Depth to Groundwater
thelong‐termdeclineingroundwaterlevelsdepictedinFigure4.TheKingsBasinIntegratedGroundwaterandSurfaceWaterModel(KingsIGSM)wasusedtoevaluatetheregionalwaterbudgetandtoquantifyoverdraftforthemorerecentperiodof1964to2004.BasedontheKingsIGSM,theaverageannualoverdraftwithinCIDforthe40‐yearperiodwasapproximately24,000acre‐feet.TheentireKingsRiverBasinwasoverdraftedbyapproximately160,000acre‐feetperyearduringthesametimeperiod.
TheareatothewestofCIDisreliantexclusivelyongroundwater.Pumpinginthisarea
createsasteepgroundwatergradientfromeasttowest,resultinginthemovementofwaterfromCIDtowardsthetroughinthelowerpartoftheKingsBasin.Figure5showsthegeneraldirectionofgroundwaterflow.ThroughoutthecentralandwesternportionsofCID,thewestwardgradienthassteepenedandgroundwaterlevelshavedroppedasmuchas80to100feet.ThesteepenedgradientandthetrendfordecliningwaterlevelsarelikelytocontinueintothefutureifadditionalgroundwatermanagementstrategiesarenotimplementedwithintheKingsBasin.
Figure 5 – General Direction of Groundwater Flow
