Appendix D. SWAT Model Report SWAT Model Calibration Report for Sandusky River Watershed October 18, 2013 Preparedfor EPA Region 5 Preparedby Tetra Tech, Inc. One Park Drive, Suite 200 Research Triangle Park, NC 27713 i (Thispageisintentionallyleftblank) ii Contents SanduskyRiverWatershed.................................................................................................................1 SWATModelConfiguration.................................................................................................................5 ElevationandSlope.........................................................................................................................................5 WatershedModelSegmentation......................................................................................................................7 LandUseRepresentation.................................................................................................................................9 SoilCharacteristics........................................................................................................................................13 HydrologicResponseUnitDelineation............................................................................................................15 MeteorologicalData.......................................................................................................................................15 PointSources................................................................................................................................................17 CalibrationDataandLocations.......................................................................................................................18 SWATModelingResults....................................................................................................................20 HydrologyCalibrationandValidation..............................................................................................................20 WaterQualityCalibrationandValidation........................................................................................................23 References.........................................................................................................................................25 iii Tables Table1. IdentifiedWaterQualityImpairmentsintheSanduskyRiverWatershed.....................................4 Table2. AggregationofNLCDLandCoverClasses...............................................................................11 Table3. LandUseDistributionforSanduskyRiverWatershed(NLCD2006)........................................12 Table4. AgricultureClassSpecificityforSWATModel........................................................................12 Table5. MeteorologicalStationsfortheSanduskyRiverWatershedModel............................................15 Table6. CalibrationandValidationLocationsintheSanduskyRiverWatershed....................................18 Table7. HydrologyCalibrationCriteria.................................................................................................20 Table8. WaterBalancefortheSanduskyRiverWatershedSWATModel..............................................21 Table9. Hydrologycalibrationandvalidationsummary.........................................................................22 Table10. PerformanceTargetsforWaterQualitySimulationofMonthlyAverages(Moriasietal.,2007) 23 Table11. Waterqualitycalibrationandvalidationsummary.....................................................................24 iv Figures Figure1. SanduskyRiverWatershedLocationMap...................................................................................3 Figure2. ElevationintheSanduskyRiverWatershed................................................................................6 Figure3. ModelSegmentationfortheSanduskyRiverWatershed.............................................................8 Figure4. LanduseintheSanduskyRiverWatershed...............................................................................10 Figure5. HydrologicSoilGroupsintheSanduskyRiverWatershed(thecross-hatchedareasrepresentdual HSGs,thatis,A/D,B/D,andC/D)............................................................................................14 Figure6. MeteorologicalStationLocationsfortheSanduskyRiverWatershed(SummaryoftheDay Stations),USGSFlowStations,OhioEPAWaterQualityStations,HeidelbergUniversityWater QualityStations,andprobablekarst..........................................................................................16 v (Thispageisintentionallyleftblank) vi Sandusky River Watershed ThisdocumentpresentstheresultsofamodelingapproachadoptedfortheSanduskyRiverwatershedusingthe SoilandWaterAssessmentTool(SWAT).AwatershedmodelforSanduskyRiverwatershedwasconstructed usingSWAT2012rev591.Thewatershedmodelwascalibratedandvalidatedtoobservedflowusingseveral USGSStations,andwaterqualitydatafromtheUSGS,OhioEPA,andHeidelbergUniversity. QiandGrunwald(2005)havebuiltaSWATmodelfortheSanduskyRiverwatershed.Themodelwascalibrated andvalidatedforhydrologyonlyforashorttimeframe.ThecurrentmodelbyTthasa30+yearsimulationtime- frameanditiscalibratedandvalidatedforhydrology,sedimentandnutrients.Thepurposeofthismodelistohelp intheestablishmentoftotalmaximumdailyloads(TMDL)forimpairedstreamsinthewatershed. TheSanduskyRiverislocatedinnorthernOhio,westofClevelandandsoutheastofToledo,anddrainsintothe SanduskyBayofLakeErie(Figure1).Theriverisabout125mileslong,oneofOhio’slongestwaterways,and approximately70milesofthemainstemaredesignatedasScenicRiver.The1,827squaremileSandusky watershedfallswithintwelvedifferentcounties,withthemajorityofthewatershedlocatedinCrawford, Wyandot,Seneca,andSanduskyCounties.Theentirewatershedisidentifiedbythe8-digithydrologicunitcode (HUC)04100011,andconsistsof72different12-digitHUCs.Themajortownsandcitieswithinthewatershed includeSandusky,Bellevue,Tiffin,UpperSandusky,Bucyrus,Fremont,Clyde,Fostoria,andCarey. ThisareaofnorthernOhioisheavilyagricultural(75%ofthelandareainthiswatershed),withonlylimitedurban land(8%)andforestedland(8%),withsomewetlandareanearthebay.TheselacustrineareaswhereLakeErie watermixeswithfreshriverwateryielduniquehydrologythroughlargewetlandcomplexes.Duetothelarge amountofcropcultivation,thewaterwaysaresensitivetonutrientloading,andtiledrainsplayalargerolein croplandhydrology.TheSanduskywatershedalsohostskarstgeologywhichresultsinsinkholesandcomplex surface-to-groundwaterinteractions. LakeErieisthesmallestandshallowestoftheGreatLakes.“Theshallownessofthebasinandthewarmer temperaturesmakeitthemostbiologicallyproductiveoftheGreatLakes”(LakeErieLakeManagementPlan [LaMP],2011).Inthe1960sand1970s,excessivephosphorusloadsfromitstributariescausedharmfulalgal bloomsinLakeErie.Whilephosphorusloadswerereducedinthe1970sand1980sbyaddressingpointsource discharges,excessivephosphorusconcentration,begantoreturninthe1990sandtheLakeErieecosystemis againthreatenedbyharmfulalgalblooms(LakeErieLaMP,2009;2011).Therecentalgalbloomsarecausedby manynew,morecomplexfactorsinadditiontonon-pointsourcetotalphosphorusloading,including:changesin nutrientcyclingthroughthefoodwebduetotheinvasionofnonnativespecies,increasesinwatertemperatures, andshorterandsmallericecoverageduringthewinter,andachangeintheformofphosphorusenteringthelake (LakeErieLaMP,2011). TheSanduskyRiveristhesecondlargestLakeErietributaryinOhio,andalongwiththeDetroitandMaumee rivers,isoneofthethreemajortributariestoLakeEriecontributinglargephosphorusloads.TheSanduskyRiver andothertributariestoLakeErie“containamixofnon-pointsourcepollution,includingagriculturalandurban runoff,andpointsourcepollution,suchastreatedmunicipalsewage”(LakeErieLaMP,2011).Themore bioavailableformofphosphorus(i.e.,orthophosphateorsolublereactivephosphorus)isfoundinsewageand fertilizers,anditsexportmaybepromotedbythedrains(LakeErieLaMP,2011).Recentevaluationsshowthat solublereactivephosphorusloadsareincreasingintheMaumeeandSanduskyrivers(LakeErieLaMP,2009; 2011). TributariesintheSanduskyBasin(HUC04100011)arenotattainingtheirdesignatedaquaticlifeuses(ALUs) duetoexcessivenutrientsandsedimentandareonOhio’s2012CleanWaterActsection303(d)list(OhioEPA 2012).TheSanduskyRiver(lower)isnotattainingitsdesignatedALUduetosedimentandisnotattainingits designatedpublicdrinkingwatersupply(PDWS)useatthecityofFreemont’swatertreatmentplantrawwater 1 intakeduetoelevatednitratelevelsfoundintheraw(i.e.,in-stream)andfinishedwater1.Thescopeofthisproject islimitedtoimpairmentstodesignatedALUsandpublicdrinkingwateruses.Table1summarizesthewaterways andtheirimpairments. 1ElevatednitratelevelsinthefinishedwatertriggeredthelistinginOhio’s303(d)list(OhioEPA2011,p.27). 2 Figure1. SanduskyRiverWatershedLocationMap 3