Best Management Practices in Stone Fruit Project

Final Project Report by Nicole David San Francisco Estuary Institute

CONTRIBUTION NO. 590 SAN FRANCISCO ESTUARY INSTITUTE 7770 Pardee Lane, Second floor, Oakland, CA 94621 SEPTEMBER p: 510-746-7334 (SFEI), f: 510-746-7300, www.sfei.org 2009 Thisreportshouldbecitedas:

David,N.2009.BestManagementPracticesinStoneFruitProject.FinalProjectReport. SanFranciscoEstuaryInstitute,Oakland,CA.SFEIContributionNumber590.

2 TABLEOFCO
TE
TS

1.Abstract...... 4 2.Introduction...... 4 2.1.RecentPatternsandTrendsinOPandPyrethroidPesticideApplicationsin California ...... 5 2.2BestManagementPracticesUsedinthisProject...... 7 3.Methods...... 7 3.1StudyAreaandSamplingLocations ...... 8 3.2SedimentandBioassessmentSampling ...... 11 3.3WaterSampleCollection ...... 12 3.4AnalyticalMethods ...... 13 3.4.1BioassessmentAnalysis ...... 13 3.4.2PesticidesAnalysis ...... 14 3.4.3
utrientsAnalysis ...... 16 4.ResultsandDiscussion...... 17 4.1Bioassessment ...... 17 4.2Pesticides ...... 19 4.2.1PesticidesinWaterandSediment ...... 19 4.2.2PesticideLoads ...... 24 4.3RiskQuotients(RQ) ...... 26 4.4
utrients ...... 29 4.4.1
utrientsinWater ...... 29 4.4.1
utrientLoads ...... 32 4.5AncillaryMeasurements ...... 34 5.Conclusion...... 36 5.1Recommendations ...... 36 6.Acknowledgments...... 37 7.References...... 37

3 1.Abstract Contaminationfrompesticideapplicationtoorchardcropsisamajorwaterqualityissue inCalifornia.Thisstudywasinitiatedtoevaluatewaterandsedimentqualityinrunoff frompeach,prune,andwalnutorchardsbeforeandaftertheimplementationofBest ManagementPractices(BMPs).Theinformationprovidedbythisstudywillbeusefulin developingpolicyandrelatedmanagementpracticestoreducepesticideandnutrient concentrationsinwaterdischargingintostreamsandriversincludedonthe303(d)Listof impairedwaterbodies.Thisprojectalsoincludedoutreach,education,andtechnical supportforgrowerstotestalternativestosyntheticpesticidesandinorganicfertilizers. BMPsimplementedbyparticipatinggrowersincludedlow-riskpesticides,improvedpest controltiming,covercrops,andmonitoringofinsectsandinsectfertility.Average pesticideconcentrationsinwaterandestimatedloadsforchlorpyrifos,diazinon,and phosmetwerenotstatisticallysignificantlydifferentaftertheimplementationofBMPs duetosamplesizelimitations.However,therewasatrendtowardlowerpesticide concentrationsandloadsinthesecondyearofthisstudy.Nutrientresultsdidnotvary appreciablybeforeandafterBMPimplementation.Interannualvariabilityprobably accountsforpartoftheobservedchanges,andresultsfromthisshort-termstudymaynot reflecttheeffectivenessofBMPsaccurately.Alongerstudywithalargersamplingeffort wouldbenecessarytofullyevaluatetheefficacyoftheseBMPs.Thetrendtowardlower waterqualitycontaminantconcentrationsafterBMPimplementationsuggeststhata longerstudyiswarranted.

2.Introduction Intensiveuseoforganophosphate(OP)pesticides,pyrethroids,herbicides,andfungicides inorchardsandotheragriculturalfieldsappearstobeaconsistentsourceofpesticide contaminationtowaterbodiesintheCentralValley.ThisProjecttargetedseveral pesticides,includingtheOPpesticidechlorpyrifos,whichisparticularlyharmfulto aquaticorganisms.AccordingtoU.S.EPA(2002),asingleapplicationofchlorpyrifos posesriskstosmallmammals,birds,fish,andaquaticinvertebratespeciesfornearlyall registeredoutdooruses.AccordingtotheCaliforniaDepartmentofPesticide Regulation’sAnnualPesticideUseReport(2007),theOPpesticidesphosmet,diazinon, andchlorpyrifoshadthehigheststatewideuseoutofallmonitoredpesticidesinthe presentstudy,withatotalofover97,000poundsofactiveingredientapplied(Table1a). Inaddition,monitoringbytheUSGeologicalSurvey,DepartmentofPesticide Regulation,andothershasconfirmedwidespreadoccurrenceofdiazinon,chlorpyrifos andotherOPpesticidesintheSacramentoandFeatherRiversandtheirtributaries(Lydy andAustin2004).Thus,reducinguseandrunoffofthesepollutantswouldhelpto improvethehealthofwatershedsthroughouttheCentralValley.

TheBestManagementPractices(BMPs)inStoneFruitProjectisamulti-facetedeffort thatpromotesagriculturalpracticestoreducetheriskofwaterpollutionfromorchard cropproduction.InthisProject,theCommunityAllianceofFamilyFarmers(CAFF) trainedgrowerstoapplyBMPsforpollutionpreventionandtointroducethemtovarious techniquesintendedtodecreasecontaminantsindrainagewater.Theoverallgoalwasto reducepesticideandnutrientconcentrationsinSutterandButtecountywaterbodies

4 includedonthe303(d)Listofimpairedwaterbodies.Peachesandprunescomprisethe majorityofthestonefruitgrowninSutterandButtecounties.

TheobjectivesofthisProjectwere: 1)OutreachtoandtrainingofgrowerstointroducevariousBMPsintendedtodecrease contaminantsindrainagewater 2)Evaluatewaterandsedimentqualityinrunofffrompeach,prune,andwalnutorchards beforeandaftertheimplementationofBMPs 3)Evaluatepotentialpesticideandnutrientloadreductionstowaterbodiesreceiving orcharddrainagewater.

AspartofthisProject,demonstrationsitesweresetupon13differentfarmsinorderto reachouttohundredsoflocalgrowers(atotalof550wereonthemailinglist)whohad notadoptedanymeasurestoreducepollutantrunofffromtheirorchards,andto demonstratehowtoimplementBMPsintheirorchardseffectively.Surveyswere conductedwithparticipatinggrowerstoobtaininformationoncrops,acreageplanted, andBMPsimplementedtodocumentthesuccessofthedemonstrationsites.An additionalgoalwithinthisoutreachcomponentwastostrengthenlinkagesbetween growersandtheirpollutionpreventionresources,withaspecialemphasisontheEast Indiancommunity.YubaCityisoneofthecentersofPunjabi-Americancultureinthe UnitedStatesandalargenumberofPunjabi-Americansareresidingandfarminginthis region . Toreachthiscommunity,CAFFconductedoutreachtargetedtoPunjabi- Americanfarmersthroughlocalmedia,includingradio,television,newsletter,andfact sheets.

WaterqualitymonitoringforthisProjectwasconductedbytheSanFranciscoEstuary Institutetoevaluatedifferencesinpesticideandnutrientconcentrationsinwaterand sedimentinditchesthatdrainorchardsinthestudyareaanddischargetotheLower FeatherRiverandtheSacramentoRiver.Chemicalconcentrationsandflowwere measuredtoestimateandevaluatepesticideandnutrientloadchangesoverthecourseof twoyears.

2.1.RecentPatternsandTrendsinOPandPyrethroidPesticideApplicationsin California Whilemanyfactors,includingweatherandcropvariation,determinetheamountof pesticidesused,itappearsthatthetotaluseintheCentralValleyhasdroppedfrom129 millionpoundsin1993to114millionpoundsin2003.However,theamountofactive ingredientappliedisanincompletemeasureofpesticideuseimpacts.Differentpesticides vary,notonlyintheamountneededtotargetpests,butalsointheextenttowhichtheir applicationcausesenvironmentalandhealthimpacts.

Statewide,peachandpruneacrestreatedwithpesticidesmonitoredinthisstudyand poundsofactiveingredientsappliedwerelowin2007(Table1a).Theinsecticideuse decreasedbyabout9%in2007comparedtopreviousyearsduetorelativelylightpest pressure.Themajorsyntheticandnaturalinsecticidesusedinstonefruitwere: esfenvalerate,phosmet,diazinon,chlorpyrifos,horticulturaloils,orientalfruitmoth

5 (OFM)matingdisruptionpheromones(E–8–dodecenylacetate,Z–8–dodecenylacetate, andZ–8–dodecenol),andspinosad.SutterandButtecountyapplicationsconstitutedthe majoritybymassofstatewideapplicationsfordiazinonandphosmet(Tables1aand1b). However,applicationratesofchlorpyrifos,diazinon,phosmet,parathion,methidathion, andesfenvalerateweregenerallylowerforSutterandButtecountiesin2007thanin manyprioryears(Table2).

Table1a.Statewideuseofpesticidesmonitoredinthisstudyinpeachesandprunesin 2007(DPR2007). lbsappliedapplications acrestreated Azinphos-methyl64232 Chlorpyrifos20,86968211,846 Cyfluthrin2447 Diazinon30,15354316,960 Esfenvalerate5,2383,94195,871 Lambda-Cyhalothrin46268416,227 Malathion3339 Methidathion4,730833,521 Permethrin1,3102305,215 Phosmet46,5221,38318,628 Propargite81433216

Table1b.PesticideuseinSutterandButtecountiesinpeachesandprunesin2007(DPR 2007). lbsappliedapplicationsacrestreated Diazinon16,0001988,200 Chlorpyrifos3223190 Phosmet36,647723,067 Esfenvalerate2,0371,09534,144

TheoveralluseofOPpesticidesontreecropsinCaliforniahasbeensteadilydecreasing overthepastdecadebuttheyarebeingreplacedbythemoretoxicpyrethroids,especially esfenvalerateandpermethrin(Epsteinetal.2000)(Table2).Whilepyrethroidpesticides havethepotentialtobeacutelytoxictomanyaquaticorganismsandespeciallyfish,their chemicalpropertiescausethemtobindstronglytosedimentparticles.Therefore,the bioavailabilityofpyrethroidsinwatermaybereduced.However,dataonchroniceffects toaquaticorganismsarelimitedandacuteandchronicimpactsonsediment-dwelling organismsandbottomfeedershavebeenreported(Muiretal.1985,Amwegetal.2005).

Table2.Reportedapplications(pounds)oforganophosphateandpyrethroidpesticidesin California(DPR2007). AI19971998199920002001 Chlorpyrifos3,212,1652,451,9802,259,2212,094,1791,673,097 Diazinon956,267901,388983,6281,058,311999,578 Phosmet568,933645,380638,704580,522482,481 Esfenvalerate

6 Table2,continued AI200220032004200520062007 Chlorpyrifos1,419,6651,545,6701,778,3422,006,0621,922,5471,430,034 Diazinon690,375523,957492,148398,620385,923350,640 Phosmet405,236341,541658,087547,813628,892421,109 Esfenvalerate26,70932,36734,76324,22214,246

2.2BestManagementPracticesUsedinthisProject. Tominimizetheenvironmentalimpactsofpesticideuse,applicatorshavetoconsider weatherandwindconditions,adjustmentofthespraynozzlesanddropletsizeforspray, andpestmonitoringresults.Carefulmanagementofpesticideapplicationsreducesthe amountofchemicalsappliedperseasonandlowerscostsforthegrower.Implementing thesemanagementpracticeswithparticipatinggrowersandCAFF’seffortstooptimize sprayinghelpedtoreducechemicalconcentrationsinthedrainagewater.Spraying optimizationmethodsincludedadjustmentofsprayersandspraynozzlestotargetedtree heightanddistance.

AnotherBMPthathasbeensuccessfullyemployedtoreducepesticideapplicationand dischargearecovercrops.Thebenefitsfromgrowingcovercropsinclude

• improvingsoilqualitybyaddingorganicmatterandnitrogen • protectingthesoilfromundesirableweeds • attractingbeneficialinsects • reducingoverallrunofffromtheorchards.

CAFFdemonstrationprojectsforlowcost,reseedingcovercropsthatareeasily maintainedincludedwintergreenmanurecropsthataremowedorcultivatedinspring, annualreseedinglegumesorgrasses,andperennialsods.Theparticipatinggrowersin thisstudyaimedtoreducetheuseandrunoffofpesticidesandnutrientsbyapplyingthe techniqueslearnedthroughtheBMPsinStoneFruitProject.

3.Methods SixsamplingsiteswereselectedinanareaofSutterandButtecountieswhereintensive outreachanddemonstrationwasconductedwiththegoaltohaveasignificantimpacton productionpractices.Atthesites,sampleswerecollectedfromdrainageditchesthat receivedrunofffrom5to15orchardseach.Someofthegrowersineachwatershed transitionedtoBMPsoverthecourseofthestudy.Sitesweremonitoredovertwoyears withtwowetseasonandonedryseasonsamplecollectedineachyear.Thetemporal distributionofsamplingwaschosentodeterminepesticideandnutrientconcentrationsin orchardrunoffduringthedormantseasonandtheirrigationseasonbeforeandafterBMP implementation.Mostgrowersinthisareairrigateutilizingsprinklerstoreducethecost forwaterandpreventpotentialrootdamageontreesbutfloodirrigationisstillusedin approximately30to40%oftheorchardsthatdrainedtomonitoredditches.Chemical analysiswasconductedfor19OP,pyrethroid,andorganosulfitepesticidesandfour

7 nutrientformstoassesspotentialpesticideandnutrientloadreductionsresultingfrom outreachandtheintroductionofBMPs.

3.1StudyAreaandSamplingLocations TheSacramentoValleyistheportionoftheCaliforniaCentralValleythatliestothe northoftheSacramento-SanJoaquinRiverDelta.TheSacramentoRiverandits tributariesdominatethegeographyoftheSacramentoValley,andtheSacramentoRiver flowsabout620km(382miles)southwestbetweenthePacificCoastRangeMountains andtheSierraNevadaMountainRange.Theprimaryeconomicactivityinthe SacramentoValleyisagriculture.Peachandprunegrowingisparticularlyimportantin thisregion.Californiapruneorchardsproduce99%ofU.S.productionand70%ofthe world’sprunecrop.SutterandButtecountieshavethegreatestpruneacreage,leadingthe toptencountiesinthestateinpruneproduction(USDA2008).

SutterandButtecountiesarelocatedalongtheSacramentoRiverinthewestandthe FeatherRiverintheeastintheCentralValleyofCalifornianorthofthestatecapital Sacramento.Togethertheyspananareaofapproximately5,920km 2 (2,290mi 2)(US CensusBureau2000).Approximately,88%oftheareaisprimefarmlandandgrazing land.AgricultureinSutterandButtecountiesisdiversifiedwithapproximately70 differentcommodities.However,themajorityoflanduseconsistsoffruitorchards,rice fields,andcattlegrazing.Treecropsarecriticaltotheregionaleconomy,accountingfor about$454millioninfarmrevenuein2007.

TheorcharddrainageditchesmonitoredinSutterandButtecountieswereselectedto covergeographicalareaswithsimilaragriculturaluses,sitecharacteristics,andsimilar pestproblems.Thesimilaritywasessentialtoprovideagoodtemporalcomparison betweenorchardswithpredominantlyconventionalpracticesbeforethebeginningofthis ProjectandthesamegroupoforchardswithincreasedfocusonBMPimplementation. Thesiteswerewithina17-mileradiusofeachother.

Eachselectedsitewasvisitedduringfieldreconnaissanceandrecorded(Figure1,Table 3).Ateachsite,PhysicalHabitatQualityFieldFormsforloticsystems(David,N.andD. Yee.2007.QualityAssuranceandProjectPlanfortheProject(QAPP))werecompleted todocumentsitecharacteristicsandlanduse.Informationrecordedateachsiteincluded stationID,date,time,waterdepth,weatherconditions,watercolor/clarity,latitude, longitude,andestimatedpositionerror.Flowrate,flowdiversions,flowvolumes, anthropogenicimpacts,andwildlifepresencewerealsonoted.

Table3.Latitudesandlongitudesforsamplingsites. SiteIDAddressLatLongAccuracy A405WestEvansReimer39.3385000-121.705680017feet B4332PenningtonRd.39.3385000-121.705680013feet C8361SheldonAve.39.25405-121.64470815feet D8055SinnardRd.39.2524920-121.649250019feet EPaseoRd.39.2503580-121.654322017feet FButteHouseRd.39.161546-121.69604116feet

8 99

20

Figure1.MapofallsamplingsitesinSutterandButtecounties,inCalifornia,USA. Horizontalaccuracyofcoordinateswasbetterthan30feet.

9 SiteDescriptions SiteA ThissiteisonWestEvansReimerRoadinGridley,CA,onthenorthsideofthestreet andtheeastsideofthechannel.Thechannelislinedwithgrasses(Johnsongrassand Ricegrass),blackberrybushes,andthistlesandiscompletelyovergrownwithinvasive aquaticweeds,predominantlyparrot’sfeather( Myriophyllumaqualicum )andcoontail (Cyratophyllumdemersum ).Fewopenpatchesallowthesamplingofsedimentatthis site,whichhasahigherclaycontentandbecomesdarkerandanoxicbelow3cm.Asian clamsareabundant,alsoafewmosquitofisharepresent.

SiteB SiteBislocatedonPenningtonRoad,LiveOak,CA,andisinasteepchannelwithdense blackberrybushes.Thissamplingsiteisonthesouthsideofthestreetandtheeastsideof thechannelwherethewatercrossesunderneathanoverpass.Mosquitofisharepresent. Sedimentcharacteristicsshowmoreconsolidatedfineswithahigherclaycontentthan SitesE,D,andC.Thecolorofthesedimentchangestoadarkergrayandsmellsanoxic below3cm.Bioassessmentsampleswerenotcollectedatthissitebecauseofthesteep channelbankandthedifficultaccesstothemid-channelsediment.

SiteC SiteCislocatedonSheldonAvenueinLiveOak,CA,upstreamofSitesEandD. Sampleswerecollectedonthewestsideoftheroadwherethechannelcomesoutfrom underneaththestreet.Thechannelbottomissandyandsilty.Invasivegrasses(Johnson grassor Sorghumhalipense andRicegrassorG lycera )andblackberrybusheslinethe channelsides(notreesadjacenttosamplinglocation).Asianclamsarepresent.In2009, cattail( Typhaspp .),sedgegrass( Carexspp .),andcorkscrewrush( Juncusspp .)seemed tobemoreabundantalongtheditch,verylikelyduetohigherrainfallduringthewet season.

SiteD ThissiteislocatedonSinnardRoadandispartofthesamechannelasSiteE,upstream ofthePaseoRoadlocation.Thechannelislinedbygrassesandrocks,andnotreesare present.Thebottomofthechannelisalsorockyandsandy.Sampleswerecollected beforethechannelcrossesunderneaththestreetontheeastsideoftheroad.Asianclams areabundant.In2009,cattail( Typhaspp .),sedgegrass( Carexspp .),andcorkscrewrush (Juncusspp .)seemedtobemoreabundantalongtheditch,asobservedforSiteC.

SiteE ThissiteisonPaseoRoadinLiveOak,CA,rightacrossfromalumberyard.The drainagechannelislinedbytrees(oak[3],treeofheaven[2],oleander[1])thatpartly shadethechannel.Mosquitofisharepresent.Dissolvedoxygenlevelswerealwaysabove 5.7mg/L.Apipelikelyfromthelumberyardacrossthestreetdischargesintothechannel althoughduringthetimesofsamplingnoeffluentwasvisible.Sampleswerecollected upstreamofthepipeonthenorthsideoftheroad.Ayardwithasmallcottage,front lawn,andaparkinglotisadjacentonthechannelsideofthestreet.HigherpH(8.26– 9.04)comparedtotheothersamplinglocationswasmeasured.Sedimentfromthissiteis

10 semi-consolidatedwithsandandsilt.Bioassessmentsamplesshowedsnails (Cipangopaludina orChinesemysterysnail),manybivalves(Asianclam),andworms (Capitellid ,apolychaete)presentatthissite.

SiteF SiteFislocatedonButteHouseRoadinYubaCity,CA.Runoffiscollecteddirectly fromanapproximately80acrepruneorchardattheendoftheorchardbeforetherunoff entersthedrainageditch.Thesamplingsiteislocatedonthesouthsideofthestreet betweenthewestendoftheorchardandtheeastsideofanirrigationcanalthatruns perpendiculartothestreet.SiteFistheonlymonitoredsitewhererunoffwasdirectly collectedfromthetailditchofanorchard.Bioassessmentsampleswerenotcollectedat SiteFbecauseextendeddryperiodsbetweenirrigationscausedanadditionalstressorto aquaticorganisms.

3.2SedimentandBioassessmentSampling SedimentsamplingwasconductedusingaPetitePonargrabwithasurfaceareaof0.1 m2.Thegrabwasmadeofstainlesssteel,andthejawsanddoorswerecoatedwith Dykon ® tomakethemchemicallyinert.Allscoops,buckets,andstirrersusedtocollect andhomogenizesedimentswerealsoconstructedofTeflon ® orstainlesssteelcoatedwith Dykon ®.Sedimentsamplingequipmentwasthoroughlycleaned(sequentiallywith detergent,acid,methanol,andrinsedwithultrapurewater)ateachsamplinglocation priortoeachsamplingevent.Inordertofurtherminimizesamplecontamination, personnelhandlingsamplesworeclean,powder-freenitrilegloves.Samplingequipment wascleanedateachstationwithafivesteprinsingprocedure:Alconox™rinse,water rinse,1%HClrinse,methanolrinse,andfinalde-ionizedwaterrinse.FurtherQA requirementsaredescribedintheProjectQAPP(DavidandYee2007).

Toensurethequalityofthesedimentsamples,eachgrabhadtosatisfyseveralcriteriain ordertobeaccepted:completeclosureofthePonardoors,noevidenceofsediment washoutthroughthePonardoors,evendistributionofsedimentinthegrab,minimum disturbanceofthesedimentsurface,andminimumoverallsedimentdepthappropriatefor thesedimenttype.

Sampleswererejectedunderthefollowingconditions:

1.Therewasarockorshellfragmentwedgedbetweenthejawsofthegraballowing thesampletowashout. 2.Thesamplesurfacewassignificantlydisturbed. 3.Thesamplewasunevenfromsidetoside,indicatingthatthegrabwastiltedwhen itpenetratedthesediment. 4.Thesurfaceofthesamplewasincontactwiththedoorsofthegrab,indicating over-penetrationofthegrabandpossiblelossofmaterialaroundthedoors.

11 Redoxpotential(Eh)wasmeasuredineachsedimentgrabwithamultifunctionalwater qualitymeter(e.g.,WTWMulti340).Afterthemeasurementswerecompleted,thetop5 cmofsedimentwerescoopedfromtheremainingarea(avoidingportionsprobed)ineach ofthegrabsandplacedinacompositingbuckettoprovideasinglecompositesamplefor eachsite.Betweensamplegrabs,thecompositingbucketwascoveredwithaluminumfoil topreventairbornecontamination.Afterallsedimentgrabswereplacedintothe compositingbucket,thebucketwasthoroughlymixedtoobtainauniform,homogeneous mixture.Aliquotsweresubsequentlysplitforsedimentchemistryandtotalorganic carbonanalyses.

BioassessmentsamplingwasperformedatsitesA,C,D,andE.AtSiteB,bioassessment samplingwasnotconductedduetosafetyconcerns.SiteFwasexcludedduetoextended dryperiods,andbioassessmentsamplesfromthissitewouldhavebeenbiasedbythis hydrology(seeSiteDescription).Forbioassessment,aPetitePonargrabwasusedto collect0.005m 3 sedimentsamples.Twotothreesedimentgrabsweretakenand compositedfromeachsite.Thecompositedsedimentwaswashedina0.5mmmesh sievebucket,withlargedebrisbeingcleanedmanuallytoretainattachedinvertebratesin thesample.

Thematerialremaininginthebucketwastransferredtothesamplejarusingawash bottle,followedbytransferwithforcepsandbyhand.Sampleswerepreservedwith95% v/vethanolinthefield,andthentransferredto70%ethanoltwotothreedaysafter collection.Sampleswereprocessedwithinfivemonthsaftercollection.Processed samplesthatneededlongerstorageforQAandotherreanalysis(e.g.,remnant examination)weresupplementedwith10%glyceroltohelpreducesampledeterioration.

3.3WaterSampleCollection Watersampleswerecollectedatadepthof1m(sites>2mdeep)ormid-watercolumn (sites<=2mdeep).Aportableperistalticpumpwasusedtotransferwater,withall tubingcleanedpriortoeachsamplingevent.Toavoidaerosolcontamination,thesample tubinginletandoutletwaskeptcoveredwithcleanfoilatalltimesthattruckengines wereoperating.Theinletofthesamplingpumptubingwasattachedtoanextendable samplingpoleanddeployedupstream(andupwindwhenpossible)ofthesamplingsite. Beforefillingsamplecontainers,tubingwasflushedwithsitewaterforatleasttwo minutes.Eachsamplecontainerwastriplerinsedwithsitewaterunlessthecontainer containedapreservative.Thecontainerswerefilledcompletelytoeliminateany headspace,andcarewastakentominimizeexposureofsamplestosunlight.Immediately aftercollection,thecontainerswereclosedandplacedoniceinacooler.

Sampleswereshippedtoandreceivedatthelaboratoriesingoodconditionbetween January2008andJune2009.Allofthecoolerscontainingwaterandsedimentsamples forpesticideandnutrientanalysiswerereceivedatthelabattherecommended temperatureofapproximately4ºC.

Dissolvedoxygen,pH,temperature,specificconductance,andsalinityweredetermined withamultifunctionalwaterqualitymeter(e.g.,WTWMulti340).Ataminimum,

12 surfacereadingsweretakenat1mdepthormidwatercolumnforsitesshallowerthan2 m.Wherepossible,data(particularlyDO)fromthebottom,middleandtopportionsof thewatercolumnwerealsotaken.Turbiditywasmeasuredeitherinthefieldorinthe laboratory.Turbiditysamples,ifnotmeasuredinthefield,werestoredat4°Cand processedwithintwoweeksofcollection.Velocityateachsitewasmeasuredwitha GlobalWaterInstrumentation,Inc.(Sacramento,CA)FP211digitalwatervelocitymeter (Figure2).

Figure2.SFEIstafftakingvelocitymeasurementsatSiteD.

3.4AnalyticalMethods 3.4.1BioassessmentAnalysis Duetotheverylownumberofindividualsineachsample,everyindividualwascounted andtaxanomicallyidentifiedtoorderandfamily.Becauseofthelownumbersof organismsfoundateachsite,thebioassessmentresultscannotbeusedasanindicatorof streamecosystemhealthorforidentifyingpotentialimpairmentwhencomparedbetween years.Threebiologicalmetricswerequantifiedinthisstudy.

• Numberoftotaltaxa(designatinganorganismoragroupoforganisms) • Numberoftotalindividuals • Percenthighlytoleranttaxa

Qualityassuranceinbioassessmentsampleswasensuredthroughre-countsoftotal relativeabundance,speciesrichness,andspeciesdiversityinoneoutofevery10

13 bioassessmentsamples.Allre-countswerewithin10%oftheoriginalnumbers.The bioassessmentcountsthereforemetthescoringguidelinesoutlinedintheQAPP(David andYee2007).Allsampleswerecountedandre-countedbythesamepractitionerfor consistency.

3.4.2PesticidesAnalysis Sedimentandwatersampleswereanalyzedforthefollowingchemicalgroupsand pesticidesgenerallyappliedbygrowersduringthestonefruitseason.

1.Organophosphatepesticidesmonitoredinwatersamples:Chlorpyrifos (insecticide,nematicide),diazinon(insecticide),azinphos-methyl(insecticide), dimethoate(insecticide),disulfoton(insecticide,acaricide),malathion (insecticide),methidathion(insecticide,acaricide),parathion(insecticide, miticide),phorate(insecticide,acaricide),phosmet(insecticide),andthe organosulfitepesticidepropargite(acaricide)inwater

2.Pyrethroidpesticidesmonitoredinsedimentsamples:Bifenthrin(insecticide, acaricide),cyfluthrin(insecticide),cypermethrin(insecticide),deltamethrin (insecticide),esfenvalerate(insecticide),fenpropathrin(insecticide,miticide), lambda-cyhalothrin(insecticide,acaricide),permethrin(insecticide)

TheanalyticalmethodsforOPpesticides(inwater:EPA8140)andforpyrethroids(in sediment:EPA8081BM)werechosentoattempttoensurethatmeasuredconcentrations wereabovethedetectionlimitforthemethod(seeProjectQAPP;DavidandYee2007). Sixoutof11monitoredpesticidesinwater(azinphos-methyl,dimethoate,disulfoton, malathion,phorate,andpropargite)werenotdetectedinthisstudy.However,according tothepestcontroladvisor,theapplicationratesforthesepesticideswerenegligibleor theywerenotusedatallin2008and2009.

OPpesticidesinsurfacewaterwereanalyzedbymodifiedEPAMethods8140and 8141AM.Analysisentailedliquid-liquidextractionandhighresolutiongas chromatographywithFlamePhotometricDetector(FPD)inphosphorusmodeand ThermionicBeadSpecificDetector(TSD).Sampleextractionentailedtreatinga measuredsamplevolumewithmethylenechloride(DCM)usingaseparatoryfunnel.The DCMextractwasdriedwithsodiumsulfate,evaporatedusingKuderna-Danish(K-D) andsolventexchangeintopetroleumether.Theextractwasconcentratedwitha microsnyder(microK-D)apparatusandadjustedwithiso-octane,priortoanalysisbygas chromatography.

PyrethroidpesticidesinsedimentwereanalyzedusingamodifiedEPAMethod8081BM (seeprojectQAPP;DavidandYee2007).Sampleswerepreparedusinganautomated extractionsystemforthedeterminationoftraceresiduelevelsofselectedpyrethroid pesticides.Dualcolumnhigh-resolutiongaschromatographywasusedwithelectron capturedetectiontodetermineconcentrationsoftargetcompounds.

14 TheRelativePercentDifferences(RPDs),calculatedasthedifferenceinconcentrationof apairofanalyticalduplicatesdividedbytheaverageoftheduplicates,wereallwithinthe targetrangeof+/-25%(Table4aand4b).ThePercentRecoveries(PRs)forLaboratory ControlSolution(LCS)andLaboratoryControlSolutionDuplicates(LCSDs)were predominantlywithinthetargetrangeof75-125%,withtheexceptionofafewchemicals indifferentbatchesforpyrethroidandOPpesticidesthatweremarginallyoutsidethe targetrange(Table4aand4b).Thequalityassurancesamplesincludedonetotwo methodblanksforeachanalyticalbatchandinallcasesnopesticideconcentrationswere detectedinthemethodblanksamples.Also,allfieldblanksampleswerebelowtheMDL forallpesticides.Noblankcorrectionfactorwasappliedtotheresults.

Table4a.QualityAssuranceresultsforpesticidesmeasuredinwater.Allblankswere belowdetectionlimits. Detection Relative PercentRecovery Limit Reporting Percent ofLabControl (MDL)in Limit(RL) Difference Solution(LCSand Parameter ug/L inug/L (RPD)+/-25% LCSD) Azinphosmethyl 0.030.050*75-119 Chlorpyrifos 0.0050.0211.8-12.590-119 Diazinon 0.0050.021.5-3.681-109 Dimethoate 0.030.050*70-117 Disulfoton 0.010.050*54-108 Malathion 0.030.050*76-110 Methidathion 0.030.051070-118 Parathion,Ethyl 0.010.020*86-106 Parathion,Methyl 0.010.050*70-107 Phorate 0.030.050*81-108 Phosmet 0.030.050*89-105 Propargite 0.200.500*68-118

*Non-detectsinallsampleswithduplicates.

Table4b.QualityAssuranceresultsforpesticidesmeasuredinsediment.Allblankswere belowdetectionlimits. Detection Relative Percent Limit Reporting Percent RecoveryofLab (MDL)in Limit(RL) Difference ControlSolution Parameter ng/g inng/g (RPD)+/-25% (LCSandLCSD) Bifenthrin 0.51.00.0-8.071.2-104 Cyfluthrin 2.04.00.0-19.262.4-110 Cypermethrin 2.04.00.0-14.959.4-105 Deltamethrin 2.04.00.0-8.538.2-122 Esfenvalerate 1.02.00.0-22.768.4-147 Fenpropathrin 2.04.00.0-3.672.4-93.4 Lambda-Cyhalothrin 1.02.00.0-4.771.6-92.0 Permethrin 4.08.00.0-8.785.9-94.7 Permethrin,Cis 2.05.00.0-19.069.2-99.2 Permethrin,Trans 2.05.00.0-20.074.1-98.8

*Non-detectsinallsampleswithduplicates.

15 3.4.3
utrientsAnalysis AnalyticalmethodsselectedfornutrientswereCaliforniaDepartmentofFishandGame methodsQC10107041Bfornitrateandnitrate,QC10107062EfortotalKjeldahl nitrogen,QC10115011Dfortotalphosphorus,andQC10115011Mfordissolved-ortho phosphate(seeProjectQAPP;DavidandYee2007).Fortheanalysisofinorganic compoundsLachatQuikChemFlowInjectionAnalyzer(FIA)methodswereused. OrthophosphatewasdeterminedusingamodifiedEPAMethod365.1(seeProjectQAPP; DavidandYee2007).DuringFIAanalysis,theorthophosphateionproducedreacted withammoniummolybdateandantimonypotassiumtartrateunderacidicconditionsto formacomplex.Thiscomplexwasreducedwithascorbicacidtoformabluecomplex, whichabsorbedlightat880nm.Theabsorbancewasproportionaltotheconcentrationof orthophosphateinthesample.

NitriteandNitrate(NOx)wereanalyzedusingEPAMethod353.2(seeProjectQAPP; DavidandYee2007).Nitratewasquantitativelyreducedtonitritebypassageofthe samplethroughacopperizedcolumnofcadmiumgranules.Theresultingnitrite(in additiontothenitriteinitiallypresentinthesample)wasdeterminedbydiazotizingwith sulfanilamidefollowedbycouplingwithN-(1-naphthyl)ethylenediamine dihydrochloride.Theresultingwater-solubledyehadamagentacolor,whichwasread colorimetricallyat520nm.Nitritealonecouldbedeterminedbyperformingthesame analysiswithoutthecadmiumreductioncolumnstep.Oncenitritehadbeenquantified, thisamountcouldbesubtractedoutoftheNOxresultstoyieldthenitrateconcentration alone.

TotalKjeldahlnitrogen(TKN)(sumoforganicandammonianitrogen)wasanalyzedby EPAMethod351.2(DavidandYee2007).Thesamplewasheatedfortwoandahalf hoursinthepresenceofsulfuricacidandpotassiumsulfate,toconvertnitrogen compoundstoammonium.DuringFIAanalysisthesamplepHwasraisedwhereinthe ammoniumionwasconvertedtoammonia.Theammoniawasheatedwithsalicylateand hypochloritetoproduceabluecolor,whichisproportionaltotheammoniaconcentration. TotalnitrogenwascalculatedbysummingtotalKjeldahlnitrogen(TKN)andnitrateplus nitritenitrogen(NO 3+NO 2).

TotalPhosphoruswasanalyzedusingEPAMethod365.4(DavidandYee2007).This methodutilizedanoff-linedigestiontoconvertallformsofphosphorusinto orthophosphateusinganacidicpersulfatedigestion.DuringFIAanalysis,the orthophosphateionproducedreactedwithammoniummolybdateandantimony potassiumtartrateunderacidicconditionstoformacomplex.Thiscomplexwasreduced withascorbicacidtoformabluecomplex,whichabsorbedlightat880nm.The absorbancewasproportionaltotheconcentrationoforthophosphateinthesample.

TheRPDsfornutrientsrangedfrom0to35%andwerewithintheQAtargetrangewith theexceptionoftotalphosphorusforwhichtheRPDwas10%abovethetargetrange (Table5).ThePRsforLCSandLCSDswerewithinthetargetrangeandspannedfrom 89-116%.Thequalityassurancesamplesincludedonetotwomethodblanksforeach analyticalbatchandwereinallcasesbelowthedetectionlimit.Also,allfieldblank

16 sampleswerebelowthemethoddetectionlimitandnocorrectionfactorwasappliedto theresults.

Table5.QualityAssuranceresultsfornutrientsmeasuredintheBMPsinStoneFruit Project.Allblankswerebelowdetectionlimits. Detection Relative PercentRecovery Limit Reporting Percent ofLabControl (MDL)in Limit(RL) Difference Solution(LCSand Parameter mg/L inmg/L (RPD)+/-25% LCSD)
itrate+
itrate 0.0050.010.0-5.4989-111 TK
0.250.401.56-19.192-109 TotalPhosphorus 0.02500.03000.0–35.095.0-116 ortho-Phosphate 0.0020.0050.0-5.2992.7-103

TheBMPsinStoneFruitProjectbeganinSeptember2006withthepreparationofthe ProjectAssessmentandEvaluationPlan,theMonitoringPlan,andtheQualityAssurance ProjectPlan.AftertheCentralValleyRegionalWaterQualityControlBoardapproved thesedocuments,water,sediment,andbioassessmentsamplingbeganinthewetseason of2007/2008.TheSamplingandAnalysisPlanwascloselytailoredtoaddressingthe goalsandobjectivesoftheProject.Theresultsprovideinformationontheeffectiveness ofBMPimplementation.AllmonitoringeffortswerecompatiblewithSurfaceWater AmbientMonitoringProgram(SWAMP)datacollectioncriteria,andthemonitoringplan wasdevelopedwithfullconsiderationofcurrentSWAMPrequirements.

4.ResultsandDiscussion 4.1Bioassessment Nocleartrendinbiodiversityandabundanceoforganismsatthemonitoredsiteswas observedinthestudy(Figure3).Biodiversitywasmeasuredbynumberoftaxa(order andfamily)presentatthesitesandrangedfrom0(SiteC)to5(SiteA).Abundancewas measuredbythenumberoforganismspertaxa,andonlyonesite(SiteEduringsampling event3,inAugust2008)hadasubstantiallyhighernumberofaquaticorganisms comparedtotheothersamplinglocations.

17 30

25

20 r e

b NumberofOrganisms 15 m

u NumberofTaxa N

10

5

0 8 8 8 8 9 9 9 9 8 8 0 0 0 0 0 0 0 0 0 0 v v n n n n n n g g o o a a a a u u u u J J J J J J N N A A ------D A A E C A E E A A SamplingSitesandMonths

Figure3.BioassessmentsamplescollectedatSitesA,C,D,andEduringfivedifferent samplingeventsin2008and2009.Twositesweresampledforeachofthefivesampling events.

SiteEhadthehighestnumberofindividualorganismspersample,whileSiteAshowed themostbiodiversitywiththemosttaxa.Benthicorganismsfoundinthebioassessment samplespredominantlybelongedtothetaxapolychaeta,oligochaeta,andbivalvia (mostlytheclam Corbiculafluminea ).Allofthesearetoleranttaxa;however, identificationtospecieswasnotperformed.Inafewsamples,pelagicspecieswerealso identified.Theseincludeddivingbeetles( Coleoptera )andflylarvae( Tipulidae ).

Possibleimprovementsinwaterandsedimentqualityatthemonitoredsitesoveratwo- yearperiodwouldnotbeexpectedtobereflectedinbenthiccommunitycomposition immediately.Changesinhabitatqualitywouldlikelytakeseveralyearstobereflectedin organism-sedimentrelationshipswhichaccompanybenthicdisturbances.Although speciesmayvaryregionallyorseasonally,theirlife-historyattributesandfunctional relationshipstotheassociatedsedimentappeartoberelativelystable(Rhoadsand Germano2004).Overtime,itwouldbeexpectedthatless-tolerantspecieswillbeableto inhabittheditchesthatimprovedinwaterqualityandthatbiodiversityatthemonitored siteswillincreaseslowly.

Becauseofthelownumbersoforganismsfoundateachsite,thebioassessmentresults cannotbeusedasanindicatorofstreamecosystemhealth,identifyingpotential impairment,orinterannualcomparison.Thebioassessmentpartofthisstudywasalso differentfromstandardbioassessmentstudiesinseveralways.Typicallythesestudiesare performedinpermanentwaterbodiesandnotinintermittentsystemsliketheirrigation waterdrainageditches.Whenevaluatingthebioassessmentresultsfromthisstudy, interpretationsandconclusionshavetobedrawncarefully,takingintoconsiderationthe temporaryandalteredhabitatfromwhichthesampleswerecollected.Thedrainage ditchesreceivingorchardrunoffareartificiallycreatedtocarrysurfacewaterfrom irrigationoffthefield.Waterpassesthroughthetailditchesduringirrigationandwinter

18 stormsonly.Theyaredrythroughoutextendedpartsofthegrowingseason,whichadds anotherstressorfortheorganismsthattrytoliveintheseditches.Comparisonofbenthic communitiesfromsitetositeisthereforechallengingandtheresultsshouldnotbe interpretedasasensitiveindicatorofhabitatconditionsandchemicalexposure.

4.2Pesticides Trendsforpesticidesmonitoredinthisstudyshowedadeclinefromthestartofthe ProjecttotheendafterBMPshadbeenimplementedbymanygrowers.Decreasing pesticideconcentrationsandloadsinthisProjectareconsistentwiththeconceptthatthe BMPsappliedcanpotentiallyreducepesticidesinreceivingwaterbodies.However,the complexityofvariablesthatplayaroleinpesticiderunoffandthelimitsofthespot samplingdesigndonotallowforastatisticalcomparisonofthedata.Interannual differencesregardingthehydrologyoftheditches(e.g.,magnitudesofstorms,flow regimes,andlengthsofwetseasons),aswellasdifferencesinpestpressures,pesticide applications,andirrigationtimingandintensityallledtovaryingconditionsunderwhich thesampleswerecollected.Thiscausedalargeamountofvarianceinthedata(Table6). Therefore,thecomparisonbetweenyearswasonlyconductedgraphically.

Table6.Averageconcentrationsandstandarderrors(SE)forpesticidesandnutrients. DateJan-08May-08Aug-08
ov-08Feb-09Jun-09 Eventtype2ndFlushIrrigationIrrigation1stFlush2ndFlushIrrigation Flow(m 3/sec) 0.70±0.460.33±0.010.32±0.130.39±0.210.03±0.120.38±0.28 SSC(mg/L) 93±406.4±2.110±2.840±1650±256.3±1.4 Chlorpyrifos( µg/L) 0.014±0.005 0±00.713±0.568 0.002±0.001 0±00.014±0.008 Diazinon( µg/L) 2.31±1.821.97±1.970±00±00.53±0.180±0 Methidathion( µg/L) 0±00±00±00±00.049±0.003 0±0 Phosmet( µg/L) 2.01*0±00±00±00.20*0±0 Parathion( µg/L) 0±00±00±00.02*0±00±0 Esfenvalerate(ng/g) 69.1*40.9±18.718.2±7.90±051.7±19.84.7* T
(mg/L) 0.71±0.280.06±0.050.02±0.020.46±0.221.70±0.700.10±0.10 TP(mg/L) 0.41±0.150.17±0.130.07±0.020.20±0.050.34±0.110.06±0.03

*NoSEcalculationbecausen=1

4.2.1PesticidesinWaterandSediment Pesticideswereanalyzedin32watersamplesoverthetwo-yearstudyperiod(January 2008toJune2009).Fiveoutof11pesticidesanalyzedwereabovetheMDLinwhole watersamplescollectedduringthestudyperiod(Figure4).Forty-onepercentofthese samples(n=13)haddetectablechlorpyrifosanddiazinonconcentrations,9%(n=3)had detectablemethidathionconcentrations,6%(n=2)haddetectablephosmet concentrations,andonlyonesamplehaddetectableparathionconcentrations.Insediment onlyesfenvaleratewasdetectedoutofthesuiteofpyrethroidsthatwastestedfor.Of32 sedimentsamplescollected,34%(n=11)haddetectableesfenvalerateconcentrations.

19 PesticidesinWater

phosmet parathion

1 methidathion diazinon chlorpyrifos

051015202530354045

Detectionin%ofallsamples

Figure4.Allpesticidesdetectedinwholewatersamplesindicatingthe%ofsamples analyzedabovetheMDL,independentofsitelocation.

EventhoughtheuseofchlorpyrifosanddiazinoninCaliforniawasreducedbetween 1997and2007(Table2),mostlyduetotheincreaseinuseofpyrethroidpesticides,they arestillcommonlyusedinorchardsandwerepresentinenvironmentalsamplesinthis study.OPpesticides,likechlorpyrifos,diazinon,andparathion,havealsobeenfoundin ambientairsamplesinhighconcentrationsintheCentralValley(Harnlyetal.2005). Aerialdepositionandspraydriftmaycontributetotheconsistentchlorpyrifos concentrationsfoundatallsamplingsitesinthisstudy.

Theaveragechlorpyrifosconcentrationrangedfrombelowthe0.005µg/Ldetectionlimit inMay2008andJanuary2009(Figure5,samplingevent2and5)to3.2µg/LinAugust 2008(Figure5,samplingevent3).LC50concentrationsaslowas0.27µg/Lhavebeen reportedfortheamphipod Ampeliscaabdita (ScottandRedmond1986)andLC50 concentrationshavebeenreportedaslowas0.01µg/Lforthewaterflea Daphniamagna (VanderHoevenandGerritsen1997),showingthattheaverageconcentrationsatthe monitoredsitesposedapotentialrisktotheenvironmentduringtheAugust2008 samplingevent.TwoindividualsamplescollectedinAugust2008wereabovetheLC50s for Daphnia (0.01µg/L)and Ampelisca .Theelevatedconcentrationswere3.2µg/Lat SiteCand0.3µg/LatSiteD.ThehighconcentrationsinAugust2008probablyoccurred duetochlorpyrifosapplicationsinoneormultipleorchardsthatdrainintothemonitored ditchespriortothesamplingevent.Additionally,longerirrigationperiodsattheendof thesummercouldhavecausedthepeakinconcentrationsbyflushingthesoilmore thoroughly.Betweenthedormantseasonapplicationandthesummerapplication, chlorpyrifoswaslikelynotbeimgappliedtothemonitoredorchardssinceallresultsfor thesamplingeventsinMay2008werebelowthedetectionlimit.

20 SiteA

10 SiteB SiteC SiteD 1 SiteE ) L / SiteF g u ( s o f

i 0.1 r y p r o l h C 0.01

0.001 0123456 SamplingEvents

Figure5.Chlorpyrifosconcentrationsinwater(µg/L)atallmonitoredsites.Sampledates wereFeb08(1),May08(2),Aug08(3),Nov08(4),Jan09(5),Jun09(6).Note logarithmicscalethatdoesnotplot0values(May2008andJanuary09).

Diazinonconcentrations(Figure6)rangedfrombelowthe0.005µg/Ldetectionlimitto 11.8µg/L.Althoughthehighestconcentrationwasfoundduringthedryseason,diazinon wasdetectedmorefrequentlyduringthewetseason.Twooutof32sampleswereabove theLC50for Daphniamagna (1.0µg/L)duringthefirstyear(SiteEandF,inFebruary andMay2008)andoneduringthesecondyear(SiteE,inNovember2008).Allresults werefarbelowtheLC50forrainbowtrout(2,600µg/L).Diazinonhadanaverage concentrationof1.5µg/Latallsitesduringthefirstyear,whichexceedstheLC50for Daphniamagna ,andanaverageconcentrationof0.2µg/Lduringthesecondyear.

21 SiteA

100 SiteB

SiteC

10 SiteD

SiteE

1 SiteF D i a 0.1 z i n o n ( u

g 0.01 / L

) 0123456 SamplingEvents

Figure6.Diazinonconcentrationsinwater(µg/L)atallmonitoredsites.Sampledates wereFeb08(1),May08(2),Aug08(3),Nov08(4),Jan09(5),Jun09(6).Note logarithmicscalethatdoesnotplot0values(August2008,NovemberandJune2009).

Averageesfenvalerateconcentrationsinsedimentweresimilarinthetwosamplingyears (13.4ng/gin2008and14.1ng/gin2009)(Figure7).Esfenvalerateconcentrationsranged frombelowthe1ng/gdetectionlimitto106ng/g(SiteC).Alldetectedsamples(11out of32)posedapotentialrisktomysidshrimps, Daphniamagna, andrainbowtrout, exceedingtheLC50sof0.04,0.24,and0.26ng/g,respectively.Asthedetectionlimit(1 ng/g)wasgreaterthantheseLC50s,itisalsopossiblethatsamplesbelowdetectionlimits posedpotentialrisk.

SiteA 1000 SiteB SiteC 100 SiteD

) SiteE g /

g SiteF n 10 ( e t a r e l a

v 1 n e f s E

0.1

0.01 0123456 SamplingEvents

Figure7.Esfenvalerateconcentrationsinsediment(ng/g)atallmonitoredsites.Sample dateswereFeb08(1),May08(2),Aug08(3),Nov08(4),Jan09(5),Jun09(6).Note logarithmicscalethatdoesnotplot0values.

22 Forabetterevaluationofecologicalconcerns,pesticidesedimentconcentrationswere carbon-normalized(Figure8).TheLC50for Hyalella foresfenvalerateis0.89ug/gOC (Amwegetal.2005).Sixoutof32sampleshadesfenvalerateconcentrationsabovethis LC50for Hyalella ,indicatingapotentialriskforsensitivespecies.Fourexceedances occurredduringthefirstyearofmonitoringandtwoduringthesecondyear.

SiteA SiteB SiteC 100.00 SiteD SiteE

10.00 SiteF

1.00

0.10 E s f e n

v 0.01 a l e 0123456 r a t

e SamplingEvents ( u g / g

FigO ure8.Organiccarbonnormalizedesfenvalerateconcentrationsinug/gTOCatall C site) s.SampledateswereFeb08(1),May08(2),Aug08(3),Nov08(4),Jan09(5),Jun 09(6).Notelogarithmicscale.

23 Figure9.SamplecollectionatSiteC.

4.2.2PesticideLoads Thecalculationofloads(massofasubstanceflowingthrougheachsamplingchannel crosssection)providesanalternativemethodforevaluationofpotentialimpactson receivingwaters.Loadscanalsobecomparedtotheamountofchemicalappliedto provideanestimateofproportionallosses. Pesticidesloadsing/daywerecalculatedusingthefollowingequation:

Load(g/day)=PesticideConc.(ng/L)xflowrate(cfs)x0.00245(multiplierforunit conversionintog/day)

Flowsindrainagesditcheswerehighlyvariablethroughoutthedaydependingonthesite (sometimesgreaterthan50%variability).Asreal-timeflowdatawereunavailable,the “average”flowratewasestimated,basedonfieldmeasurementsduringsitesampling events.Furthermore,theconstituentconcentrationwasonlyrepresentativeoftherunoff atthesamplingtimeandshouldnotbeextrapolatedtosubsequentirrigationorrainfall events.Theloadcalculationsmadeforagriculturaltailwaterflowsinthisstudyare thereforepreliminaryestimates.

Estimatedaveragepesticideloads(Table7)duringthefirstyearofthisstudywere generallyhigherthanthesecondyear.Theonlyexceptionsweremethidathionand

24 parathion,whichhadslightlyhigherloadsinthesecondyearandwerenotdetected duringthefirstyear.Chlorpyrifos,diazinon,andphosmetloadswerereduceddrastically inthesecondyear.Thesecondyearloadswerebetween1%(chlorpyrifosindryseason) to14%(chlorpyrifosinwetseason)ofthefirstyearloads.Diazinonandphosmetloads fromthesecondyearwerecalculatedatonly2%and4%ofthefirstyearloads, respectively.However,differencesinloadsfromthefirsttothesecondyearwerenot statisticallysignificantlydifferentduetothehighsignaltonoiseratioexperiencedinthis study.

Table7.Averagepesticideload(g/d)forthewetanddryseasonofthefirstandsecond yearsofthisstudy.Onlyoneflowmeasurementandonepesticideanalysiswereobtained foreachsamplingevent.Thedailyloadcalculationsthereforerepresentalimited snapshotintime(asmallpartoftheentiretreecropirrigationandfarmingseason). Pesticideloadsing/d 1stwetseason2ndwetseason1stdryseason2nddryseason Chlorpyrifos0.070.012.400.02 Diazinon14.160.310.020 Methidathion00.00300 Phosmet0.00460.000200 Parathion00.0200

OPinsecticides,likechlorpyrifos,diazinon,andphosmet,arepredominantlyappliedto treecropsduringthedormantseasonbetweenlateDecemberandFebruary.This coincideswithseasonalrainfallintheCentralValley,whichgreatlyincreasesthe likelihoodofpesticidesleavingtheorchardswithrunoffwaterdrastically(Domagalskiet al.1997).Inthisstudy,diazinonandphosmetresiduesinsurfacewaterswere approximatelythreetimeshigherduringthewetseasoncomparedtothedryseason,and consequentlyloadestimatesfordiazinonandphosmetwerealsomuchhigher(Table7).

Suspendedsedimentloadsduringthesecondyearwereapproximately55%oftheloads calculatedforthefirstyear.Thebiggestdifferenceinsedimentconcentrationwas observedforthetwoJanuarysamplingevents(Figure10).However,ithastobetaken intoconsiderationthattheJanuary2008stormhadagreaterintensitywith1.7inof rainfallonJanuary4,comparedto0.8inofrainfallonJanuary23,2009.Decreased sedimentconcentrationsduringthesecondyearwerelikelyduetostormmagnitudeas wellasimplementedBMPs.Plantedcovercropsincreasedthesoilinfiltrationrateand reducedtheamountofsedimentthatwaswashedoffoftheorchards.Pesticidesthatbind tosedimentparticles,likethepyrethroidesfenvalerate,werethereforealsolikelyreduced intherunoff(Kelley2003).

25 2008/09JanuarySSCLoads

10000

1000 ) d

/ 100

g Jan-08 k (

C Jan-09 10 S S

1

0.1 ABCDEF SamplingSites

Figure10.Suspendedsedimentloads(kg/d)calculatedforthefirstflusheventforall monitoredsitesinJanuary2008andNovember2008.Notethelogarithmicscale.

4.3RiskQuotients(RQ) Anotherwayofevaluatingtheresultsistoperformanassessmentofecologicalrisk.An ecologicalriskassessmentisconductedbycalculatingtheRiskQuotient(RQ).Thisrisk characterizationintegratesexposureandeffectsdata(Table8)andstatesapotentialfor risk,expressedbytheLevelofConcern(LOC).TheRQiscalculatedasfollows.

RQ=Exposure/Toxicity

•Exposure=Fielddataconcentrations •Toxicity=Publishedtoxicityendpoint(LOEC,NOEC,EC50,LC50,MATC)

Where:

LOECisthe"lowestobservedeffectlevel,"orthelowestlevel(concentration)at whichadverseeffectsareobserved.

NOECisthe"noobservedeffectlevel(concentration),"orthelevelbelowwhich,no adverseeffectsareobserved.

EC50istheeffectiveconcentrationofthepesticideinmg/Lorµg/Lthatproducesa specificmeasurableeffectin50%ofthetestorganismswithinthestatedstudytime. Themeasurableeffectisreproductionorlethalityforzooplanktonandareductionin photosyntheticactivityby50%forphytoplankton.

LC50isdefinedastheamountofpesticidepresentperliterofaqueoussolutionthatis lethalto50%ofthetestorganismswithinthestatedstudytime.

26 MATCisthe"maximumacceptabletoxicantconcentration"andisahypothetical thresholdconcentrationthatisthegeometricmeanbetweentheNOECandLOEC concentration.

Table8.Toxicitydatafordetectedpesticides.Source:PesticideActionNetwork PesticideDatabase http://www.pesticideinfo.org/ PesticideRainbow Bluegill Fathead WaterFlea Selenastrum Trout Sunfish Minnow Chlorpyrifos LC50 LC50 LC50 LC50 (insecticide) 9.0µg/L 10µg/L 330µg/L 0.01µg/L Diazinon LC50 LC50 EC50 EC50 (insecticide) 2.6mg/L 15mg/L 0.22µg/L 3.7mg/L BCF 12µg/L Phosmet LC50 LC50 LC50 LC50 0.23mg/L 0.07mg/L 7.3mg/L 5.6µg/L Methidathion LC50 LC50 LC50 10µg/L 2µg/L 7.2µg/L Parathion LC50 LC50 LC50 LC50 1.9mg/L 4.4mg/L 8.9mg/L 4.8µg/L Esfenvalerate LC50 LC50 LC50 LC50 (insecticide) 0.3ng/g 0.3ng/g 0.2ng/g 0.24ng/g (killfish) 0.04ng/g (Mysid shrimp)

Usingthefielddatafromthisstudy,theRQswerecalculatedfordetectedchemicals, accordingtotheEPAapproach(http://www.epa.gov/oppefed1/ecorisk/#Deterministic), asfollows:

RQ(chlorpyrifos)=3.19/9=0.35(rainbowtrout)forfirstyearofstudy RQ(chlorpyrifos)=3.19/0.01= 319(waterflea)forfirstyearofstudy

RQ(chlorpyrifos)=0.04/9=0.004(rainbowtrout)forsecondyearofstudy RQ(chlorpyrifos)=0.04/0.01= 4(waterflea)forsecondyearofstudy

RQ(diazinon)=11.8/2,600=0.005(rainbowtrout)forfirstyearofstudy RQ(diazinon)=11.8/0.22= 53.6(waterflea)forfirstyearofstudy

RQ(diazinon)=1.3/2,600=0.001(rainbowtrout)forsecondyearofstudy RQ(diazinon)=1.3/0.22= 5.9(waterflea)forsecondyearofstudy

RQ(phosmet)=2.0/70=0.03(bluegillsunfish)forfirstyearofstudy RQ(phosmet)=2.0/5.6=0.4(waterflea)forfirstyearofstudy

RQ(phosmet)=0.2/70=0.003(bluegillsunfish)forsecondyearofstudy

27 RQ(phosmet)=0.2/5.6=0.04(waterflea)forsecondyearofstudy

RQ(methidathion)=0.06/2=0.03(bluegillsunfish)forsecondyearofstudy RQ(methidathion)=0.06/7.2=0.008(waterflea)forsecondyearofstudy

RQ(parathion)=0.02/1,900=0.000(rainbowtrout)forsecondyearofstudy RQ(parathion)=0.02/4.8=0.004(waterflea)forsecondyearofstudy

RQ(esfenvalerate)=93/0.3= 310(rainbowtrout)forfirstyearofstudy RQ(esfenvalerate)=93/0.24= 388(waterflea)forfirstyearofstudy

RQ(esfenvalerate)=106/0.3= 353(rainbowtrout)forsecondyearofstudy RQ(esfenvalerate)=106/0.24= 442(waterflea)forsecondyearofstudy

TheRQforeachchemicalwasthencomparedtoaunitlessvalue,calledtheLevelof Concern(LOC)(Table9).ComparisontotheLOCsshowedexceedancesoftheacuterisk thresholdforthreepesticides(boldabove).TheLOCwasexceededforchlorpyrifosfor acuteriskforwaterfleasduringthefirstyear(approximately319timeshigher)and duringthesecondyear(approximately4timeshigher),indicatingthatthereisahigh threattoaquaticinvertebratesatthechlorpyrifosconcentrationsobservedinthisProject. ConcentrationsfordiazinonalsoexceededtheLOCduringthefirst(approximately54 timeshigher)andsecondyear(approximately6timeshigher).Eventhoughthesampled waterwasstilltoxictowaterfleas,adecreaseinthelevelofexceedancewasobservedin year2.ThethirdchemicalexceedingtheLOCswasesfenvalerateinsedimentduringthe firstyear(approximatelyby310timesforrainbowtrout)andduringthesecondyear (approximatelyby353timesforrainbowtrout).Itshouldbenoted,however,thatthe bioavailabilityofpyrethroidsinsedimentisstronglydependentonthecarboncontentof thesoil,andnotallofthemeasuredesfenvalerateconcentrationwasavailableforuptake byaquaticlife.

Table9.RiskQuotient(RQ)comparedtoLevelofConcern(LOC)forfourdifferentrisk presumptions. RiskPresumptionRQLOC AcuteRiskLC50orEC500.5 AcuteRestrictedUseLC50orEC500.1 AcuteEndangeredSpeciesLC50orEC500.05 ChronicRiskMATCorNOEC1

Thesecomparisonsrepresentaworst-casescenariosincethemaximumconcentration detectedintheentireperiodofthestudywasusedtoevaluatethepotentialecological risk.Thisveryconservativeapproachisagoodbalancetocomparingdetectedpesticide concentrationstoLC50salone.Butitmustalsobekeptinmindthatitispossiblethatthe spotsamplingdesignusedinthisstudymissedthehighestconcentrationsinrunofffrom theorchards.

28 Forpesticidesforwhichboth,theLOCandthetoxicitythreshold(LC50),wereexceeded (e.g.,chlorpyrifos,diazinon,andesfenvalerate),ahighdegreeofecologicalriskfor sensitiveaquaticspeciesisevident.EventhoughtheRQsforchlorpyrifosanddiazinon showedadecreaseinthesecondyear,thepeakconcentrationsstillexceededtheLOC thresholdbyseveral-fold.

4.4
utrients 4.4.1
utrientsinWater Nutrientconcentrationsinthisstudywererelativelyhighanddidnotvarygreatlyfor mostnutrientformsbetween2007/08and2008/09withtheexceptionofNOx.NOx concentrationsrangedfrombelowthelimitofdetectionto5.0mg/L(Figure11).The averageNOxconcentrationinyear1was0.3mg/L(n=17)andthesecondyear’s averagewashigherat1.1mg/L(n=15).TheEPA’sreferenceconditionsforecoregion1, subregion7(CaliforniaCentralValley)recommend0.1mg/LforNOxintheambient waterqualitycriteriaforriversandstream(CRWQCB2007).IncontrasttoNOx,other nutrientformsdidnotexhibitadramaticdifferencebetweenyears.TKNconcentrations, forexample,rangedfrombelowthelimitofdetectionto2.24mg/Lwithanaverageof 0.63mg/L(n=17)forthefirstyearandanaverageof0.87mg/L(n=15)forthesecond year(Figure12).EPAreferenceconditionsrecommendTKNat0.2mg/L(USEPA 2001).EPAreferenceconditionsareusedasguidelinesonlyandarenotenforceable regulations.However,concentrationswithintherangeobservedinthisstudyindicatethat nitrogenrepresentsapotentialwaterqualityconcern.

SiteA 6.0 SiteB

5.0 SiteC SiteD ) L / 4.0 SiteE g m

( SiteF e t a

r 3.0 t i N + e t i

r 2.0 t i N

1.0

0.0 0123456 SamplingEvents

Figure11.NitriteandNitrateconcentrationsinwater(mg/L)atallsites.

29 2.5 SiteA SiteB

2.0 SiteC SiteD )

L 1.5 / SiteE g m ( SiteF N

K 1.0 T

0.5

0.0 0123456 SamplingEvents

Figure12.TotalKjeldahlnitrogenconcentrationsinwater(mg/L)atallsites.

NOxconcentrationsreportedinpeer-reviewedliteraturehavebeenmeasuredinsoybean tailwaterashighas20mg/L(Strocketal.2004).Allmeasuredresultsinthisstudywere farbelowthesemaximumreportedconcentrations.InterestinglythehighestTKN concentrationswereobservedatSiteFwhererunoffwaterwascollecteddirectlyfrom thetailditchofonlyonepruneorchardanddilutionwasminimalcomparedtotheother sites.AtthesametimeNOxconcentrationsatSiteFwererelativelylow,consistentwith ahigherorganicfractionoftheappliednitrogenfertilizerorureaapplications.Ureacan

bereadilynitrified(convertedtonitrate[NO 3]).Whenaureaparticledissolves,thearea arounditbecomesazoneofhighpHandammoniaconcentrations(Wangetal.1992)and oneofthehighestpHvalue(9.5)inthisstudywasalsoobservedatSiteF.Othersitesthat weresampledfartherdownstreamwithhigherdilutionandrunofffrommultipleorchards intheareadidnotshowsuchclearresults.

Ortho-phosphate(PO 4)concentrationsrangedfrombelowthelimitofdetectionto0.6 mg/Latallsitesduringthetwo-yearstudy(Figure13).Thefirstyearaveragewas0.12 mg/L(n=17)andthesecondyearaveragewasverysimilarat0.13mg/L(n=15).Total phosphorus(TP)concentrationsrangedfrombelowthelimitofdetectionto1.0mg/L withanaverageof0.3mg/Lforbothyearsofmonitoring(Figure14).EPA recommendationsforTParereportedat0.08mg/L(USEPA2001),alsoindicatingthat phosphorusrepresentsapotentialwaterqualityconcernduringmost(22outof32)ofthe samplingevents.

30 0.8 SiteA SiteB ) L / 0.6 SiteC g m ( SiteD e t a SiteE h

p 0.4 s

o SiteF h P o h t

r 0.2 o

0.0 0123456 SamplingEvents

Figure13.Ortho-phosphateconcentrationsinwater(mg/L)atallsites.

1.2 SiteA SiteB 1.0

) SiteC L / g SiteD

m 0.8 ( s

u SiteE r o

h 0.6 SiteF p s o h P

l 0.4 a t o T

0.2

0.0 0123456 SamplingEvents

Figure14.Totalphosphorusconcentrationsinwater(mg/L)atallsites.

Sincenutrientconcentrationsoccasionallyhadhighpeaks,probablycausedbysample collectionshortlyafterfertilizerapplicationinadjacentorchards,medianandmaximum concentrationsarealsopresentedinTable10a.Thistablewasgeneratedtominimizethe biasofoneextremelyhighconcentrationintheentirebatchofsamplescollected. Averagenutrientconcentrations(Table10b)alsoindicatedahighertotalphosphorus concentrationatSiteF(runoffcollecteddirectlyfromorchard),probablyduetotheuse

31 ofchickenmanurethathasahighcontentoftotalphosphorus.Thesamesitehadbyfar thelowestaveragesuspendedsedimentconcentration(SSC)measuredinthisstudy, whichcouldbetheresultofcovercropsimprovingoverallsoilhealthandinfiltration rates.

Table10a.Medianandmaximumnutrientconcentrationsinmg/Lforallsites.
utrientABCDEF Nitra te+Nitrite0.07(0.39)0.32(0.76)1.37(4.95)0.44(3.40)0.18(0.58)0.14(1.72) TKN0.42(1.29)0.38(0.60)1.03(1.43)0.70(1.24)0.33(2.09)1.65(2.24) ortho-Phosphate0.08(0.09)0.09(0.14)0.09(0.17)0.02(0.07)0.03(0.08)0.57(0.68 TotalPhosphorus0.11(0.68)0.14(0.25)0.26(0.57)0.16(0.71)0.06(0.18)0.87(1.01) SSC 5.40(30.2)7.40(19.7)10.3(105)28.7(232)9.40(95.1)159(187)

Table10b.Averagenutrientconcentrationsinmg/Lforallsites.
utrientABCDEF Nitrate+ Nitrite0.110.381.700.930.240.67 TKN0.520.400.780.730.671.81 ortho-Phosphate0.110.090.080.040.040.60 TotalPhosphorus0.190.140.250.250.080.91 SSC 314462130689

4.4.1
utrientLoads Nutrientloadswerereducedforallparametersfromthefirsttothesecondwetseasonof thisstudy(Table11).Nutrientloadsduringthesecondwinterwerebetween17%(NOx) and50%(TKN)ofthenutrientloadsofthefirstwinter.Forthedryseason,nutrientloads werehigherduringthesecondyear.NOxloadsduringthefirstdryseasonwere20%of thesecondyearloadswhileortho-phosphateloadsestimatedforthefirstyearwere approximately60%ofthesecondyearloads.Overall,changesinloadsfromthefirstto thesecondyearwerenotstatisticallysignificantlydifferent.

Table11.Nutrientloads(kg/d)forthefirstandsecondyearofthisstudy.
utrientloadsinkg/d 1stwetseaon2ndwetseason1stdryseason2nddryseason NOx23.554.022.0710.17 TKN13.937.027.8221.42 orthophosphate6.191.161.392.31 totalphosphorus 10.012.202.176.36

Nutrientinputsfromrainfall,nitrogenfixation(Nonly),soilandbedrockweathering(P only),andpotentiallyfromanimalandhumanwaste(NandP)toallorchardsfromwhich runoffwasmonitoredwereprobablyverysimilargiventherelativelysmallsizeofthe studyareaandthesimilarsitecharacteristicsrepresentedbythesamplinglocations.The onlymajordifferenceinnutrientinputwouldbeexpectedtocomefromdifferencesin fertilizerapplications.Sustainablesoilmanagementintreecroporchardsincludesthe applicationofpoultrymanureandcompost,whilesyntheticfertilizerispredominantly usedontheconventionalorchardsthatdidnotparticipateinthisstudy.

32 TheNOxtoTN(totalnitrogen)ratioswouldbeexpectedtobelowerinthesecondyear ofthestudycomparedtothefirstyearduetoahigherorganicportionoftheapplied fertilizer(poultrymanure)buttheaverageNOxtoTNratioswereslightlyhigher. However,thisstudydidnotfocusontheapplicationoforganicfertilizers,andcovercrop plantingwastheonlyBMPthatcouldhavereducedtheuseofsyntheticfertilizers.The secondyeardidshowslightlyloweraveragePO 4 toTPratios,indicatingahigherorganic contentinthefertilizeratsomeoftheorchardsthatdrainedtothemonitoredditches.

Averagenutrientconcentrationsmeasuredinthisstudywereslightlyhigherthanthose foundinotherstudiesinvestigatingnutrientsinorchardrunoff.Forexample,runofffrom orchardsoilinSouthChinashowedTNconcentrationshigherthan0.35mg/Linover 90%ofthesamplescollected.TPconcentrationswerehigherthan0.1mg/Linover50% ofthesamples(Zengetal.2008).MedianNOxconcentrationsinstreamsofmixedland- useandagriculturalregionsoftheSacramentoRiverBasin(USGS2005)weresimilarto theconcentrationsobservedinthisstudy(Figure15).AccordingtoUSGS(2005), concentrationsintheSacramentoRiverwatershedtendtobelowrelativetothose measuredinotherareasoftheUnitedStateswithsimilarfertilizerapplicationswithin theirwatershedsduetodilutionwithcleanwaterfromtheSierraNevadaMountain Range.

Figure15.ConcentrationsofnitriteandnitrateatsitesthroughouttheSacramentoRiver watershed.Thehighestconcentrationsweremeasuredatminingandurbansites(USGS 2005).

33 Elevatedconcentrationsofnitrogenorphosphoruscanstimulatenuisancegrowthof algae.Thelowerconcentrationsinstreamsofmixedland-use,liketheSacramentoRiver watershed,probablycanbeattributedtodilutionbystreamflow.TheSacramentoRiver anditsmajortributariesarederivedfrommeltingsnow,whichhaslownutrient concentrationsrelativetoconcentrationsmeasuredduringthisstudy.Theseriverstendto dilutetheagriculturaldrainage,andthereforenutrientconcentrationsremainlowinthe majorrivers.Inaddition,somein-streamprocessesremovenutrients,suchasalgal growththatcanincorporatenutrientsinalgaebiomass.

Ingeneral,themajorityofsamples(89%)collectedinthisstudyhadlowtotalnitrogento totalphosphorusratios(1–15:1).Highnitrogentophosphorusratios(20–50:1)favor thedevelopmentof Chlorococcales whilelowerratiosfrequentlyleadtocommunities dominatedby Cyanophyta (Smith1983).Sincebloomsofcyanobacteria,especiallyofthe mosttoxicandstableform Microcystis, havebecomeanincreasingthreattofreshand brackishwaters,itisimportanttobeawareofthisincreasedrisk.Thisisparticularlya concernwhenthedrainageditchemptiesintoawaterbodyunderlow-flowconditions. Manyuncertaintiesstillremainaboutthepathwaysleadingtocyanobacterialbloomsand howimportantN:Pratiosareundersitespecificconditions.

4.5AncillaryMeasurements Dissolvedoxygen(DO) isaveryimportantindicatorofawaterbody’sabilitytosupport aquaticlife.Oxygenconcentrationsgreaterthan5mg/Laregenerallyconsideredsafefor aquaticbiota.Dissolvedoxygenconcentrationsvariedfrom1.9mg/LatSiteCinJanuary 2008to11.7mg/LatSiteAinFebruary2009.ThedrainageditchatSiteAwas completelyovergrownwiththeaquaticweeds Myriophyllumaquaticum (parrot’sfeather) and Ceratophyllumdemersum (coontailorhornwort)anddisintegratingplantmaterial wascoveringthebottomoftheditch;anaerobicbreakdownprocessesmayexplainthe lowoxygenconcentrationsatthissite.WithintheobservedDOrange,concentrations fluctuatedwithoutexhibitinganysignificantpatternsatthesixsites.Adifferencein dissolvedoxygenconcentrationsduetoBMPimplementationwasthereforenotapparent. Atotaloffourmeasurementsoutof32werebelow5mg/L,threeinAugustofthefirst yearandoneinFebruaryofthesecondyear.

ElectricalConductivity(EC) isameasureofhowwellwatercanconductanelectrical current.Conductivityincreaseswithincreasingabundanceofions.Theseionsconduct electricitybecausetheyarenegativelyandpositivelychargedwhendissolvedinwater. Therefore,ECisanindirectmeasureofthepresenceofdissolvedsolidssuchaschloride, nitrate,sulfate,phosphate,sodium,magnesium,calcium,andiron,andcanbeusedasan indicatorofwaterpollution.TheECvariedfrom0.03mS/cmatSiteEinFebruary2009 to0.25mS/cmatSiteBduringthesamesamplingevent.Measurementsthroughoutthe samplingperiodwerefairlyconsistentanddidnotexhibitanypatternsassociatedwith BMPimplementation.Salinity,arelatedparameter,rangedfrom0.01pptatSiteDin January2008andSiteEinFebruary2009to0.3pptatSiteFinMay2008withno particularpatternexhibitedbetweenthebeginningandtheendofBMPimplementation.

34 pH isageneralindicatorfortheacidityofawaterbodyasmeasuredbytheproton(H+) concentration:pH=-log[H+].AmeasurementofpH<7isacidic,pH=7isneutral,and pH>7isbasic.pHrepresentstheeffectiveactivityofhydrogenions(H+)inwater. ChangesinpHcanalsoaffectaquaticbiotaindirectlybyalteringotheraspectsofwater chemistry.LowpHlevelsacceleratethereleaseofmetalsfromrocksorsedimentsinthe streamthatcouldpotentiallycausetoxicity.InthisstudypHvaluesrangedfrom7.1at SiteDinJune2009to9.6atSiteEinFebruary2009.

Temperature ofwaterisanimportantfactorforaquaticlife.Itcontrolstherateof metabolicandreproductiveactivities,anddetermineswhichspeciescansurvive. Temperaturealsoaffectstheconcentrationofdissolvedoxygenandcaninfluencethe activityofbacteriaandtoxicchemicalsinwater.Watertemperaturesrangedfrom4.8°C atSiteFinJanuary2008to24.7°CatSiteBinAugust2008.Theseditchesare sometimesveryshallow,oftenminimallymoving,temporarywatersystemsthateasily heatupduringthesummermonths.

Turbidity isameasureofthecloudinessofwater.Itiscausedbysuspendedmatter,such asclay,silt,organicmatter,plankton,andothermicroscopicorganismsthatinterferewith thepassageoflightthroughwater.Turbidityiscloselyrelatedtototalsuspended sedimentconcentration,themostdominantsourceofturbidityinmostnaturalsystems, butalsoincludesplankton,organicdebris,andpigments.Turbidityinthisstudyvaried widelyfrom5.3NTUatSiteEinMay2008to598NTUatSiteDduringarainstormin January2008,whiletheaverageturbiditymeasurementsduringthesecondyearof samplingwereapproximatelyhalfashighcomparedtothefirstyear.Therecommended turbidityaccordingtoEPA’sreferenceconditionsforriversandstreamsis5.2NTU(US EPA2001),whichisstillfarbelowtheobservedaverageturbidityseeninthesecond yearofthestudyof50NTU.

Hardness isameasurementoftheconcentrationofdivalentmetalions.Inthisstudy, hardnesswasmeasuredasaconcentrationofcalciumsaltCaCO 3.Waterhardness concentrationsvariedfrom12.6mgCaCO 3/LatSiteEinFebruary2009to231mg CaCO 3/LatSiteFduringtheMay2008samplingevent.Waterhardnessdescribesthe presenceofcertainmineralsinthewatercolumn,andstudieshaveshownthathigh calciumandmagnesiumconcentrationsinwatercanreducetheeffectivenessof pesticideswhenhardnessisabove150-300mg/Linsourcewaterforpesticidemixtures (Boerboom2001).Thissuggeststhatforoneoutof32samples(fromthefirstandthe secondyeartogether)bioavailablityofpesticideswaslikelyreducedintheambient water.Insecticides,especiallyshownforchlorpyrifosanddiazinon,arealsoknowntobe verysusceptibletoinactivationdependingonthesiltandsandfractionofthesoil(Harris 1966).Siltandsandwerenotmeasuredinthisstudybutmeasuredorganiccarbon concentrationssuggestedthatthebioactivityofpesticidesmayhavebeenslightlyreduced duetothecarboncontentofthesoil.

DissolvedOrganicCarbon(DOC) isabroadclassificationfororganicmoleculesof variedoriginandcompositionwithinaquaticsystems.DOCconcentrationsrangedfrom 1.9mg/LatSiteEinMay2008to14.0mg/LatSiteFinFebruary2009withan

35 approximatelytwotimeshigheraverageDOCconcentrationduringthefirstyear comparedtothesecondyear.

5.Conclusion Thedatacollectionperiodforthisshort-termstudywasonlytwoyearsandalongerstudy wouldhavebeenneededtointerpretthewaterqualitydatainrelationtoimplemented BMPswithmorecertainty.Interannualvariabilityprobablyaccountsforsomeofthe observeddecreasesinpesticideconcentrationsandloadsatthemonitoredsites,butthe biggerportionofthedescribedtrendsarelikelyattributabletotheeffectsofthe mitigationmeasuresthatgrowersappliedintheregionasaresultoftheoutreachand training.

Eventhoughparticipatinggrowersusedlessofthesyntheticpesticidesthatwere monitoredduringthepresentstudy,thetoxicitythresholdsforchlorpyrifos,diazinon,and esfenvaleratewerestillexceededinthesecondyearofmonitoring.Thechemical concentrationsfoundforchlorpyrifosanddiazinoninwaterandforesfenvaleratein sedimentsampleswerealsoabovetheLOCforaquaticlife.

Nutrientconcentrationswereslightlyhigherinthesecondyearofthisstudy.However, nutrientloadestimatesshowedaclearbutnotstatisticallysignificantreductionfromthe firsttothesecondwetseasonforallnutrientforms.

5.1Recommendations Theconcentrationsandtotalamountsofpesticidesinrunoffwateraredependentupon thecharacteristicsofthepesticides,methodsandrateofchemicalapplication,andtiming ofpost-applicationirrigation.Previousstudiesreportedthepercentageofapplied pesticidesbeingcarriedoffthefieldororchardinrunoffasverylow(0.1–1%)(Spencer andCliath1991).Thepercentageforsoil-appliedherbicidesisusually1–2%.MostOP pesticidesandpyrethroidswerepreviouslyreportedatconcentrationslessthan0.1%of theapplicationrate.Reductionsinpesticideloadscanbeachievedwithgoodtimingof thepesticideapplicationandthefollowingirrigationevent.Eventhoughitmaybe difficultforthefarmersattimestoextendthetimeperiodbeforeirrigation,agreat benefitforwaterqualitywouldbeachievedafterapproximately23-31dayspost pesticideapplication.SpencerandCliath(1991)reportedthetimebetweenthepesticide applicationandtheirrigationeventasinverselyrelatedtothelogconcentrationofthe pesticidefoundinrunoffwater.

Spenceretal.(1985)showedthatduringthefirstirrigation,mostpesticideconcentrations werehighestwithinthefirsttwotothreehoursofthestartofirrigationrunoff. Concentrationsweremuchlowerafterthateventhoughthehydrographpeakedlateron duringtheirrigation.Pesticiderunoffandwaterflowdidnotseemtobecorrelatedinany ofthemonitoredfieldsthatSpenceretal.studied.

Inthisstudytherewasalsonoapparentrelationshipdetectedbetweenthepesticide concentrationsandflowsothatthemainfocusforadditionalimprovementsofwater qualityshouldbeonelapsedtimebetweenapplicationandirrigation.Longerperiods

36 betweenchemicalapplicationandorchardirrigationwillreducepesticideconcentrations inrunoff.Evenifscheduleshavetobeadjustedduringthegrowingseasondueto unforeseenpestoutbreaks,anattemptforpesticidereductionthroughelapsedtimeasa BMPwilllikelyshowanimprovementforwaterquality.

Additionally,filterstripsorvegetatedponds(Huntetal.2008)attheendofthetailditch couldreducepesticideandnutrientloadstoreceivingwaterbodiessubstantiallyby storingrunoffwaterfromapproximatelythefirstfourhoursofrunoff,thetimeperiodfor whichtheconcentrationsseemedtobehighest.Afterthatcriticaltimeperiod,runoff watercouldbypassoroverflowthepondorfilterstrip,leavingthemorecontaminated particlestosettleintheretainingstructure.BothrecommendedBMPswouldbelow-cost, lowmaintenancepracticeswithahighprobabilityforpesticidemitigationeffectiveness.

ThisProjectwasavaluablepilotstudytoevaluatetheeffectivenessofBMPsinstone fruitandhasprovidedaclearerunderstandingofhowtodesignamonitoringprogramto detectimprovementsinwaterqualityfromthesepractices.Foramoredefinitive conclusion,alongerstudywouldhavetobeconducted.Severalyearsofmonitoringwith clear,quantifiableactionstakenbytheparticipatinggrowers,andgoodcommunication withthegrowersregardingtheBMPsimplementedandallpesticideandsynthetic fertilizerappliedwouldhelpindefinitivelydeterminingtheeffectivenessofmitigation measures.Additionally,morefrequentsamplecollection(5insteadof3timesayear) wouldimproveconfidenceinobservedreductionsinchemicalconcentrationsinorchard runoffbyallowingbettercharacterizationofconditionsduringthedryseason.

6.Acknowledgments Theworkforthisstudywasanextraordinaryeffort,andthanksareduetomanypeople fortheirdirectorindirectcontributionstothisdocument.SFEIstaffthatcontributedto thesamplecollectionofthisstudywasAliciaGilbreath,MargaritaQuinones,Michelle Lent,andDanHermstad.Adraftofthisdocumentwasreviewedandimprovedby commentsreceivedfromBenGreenfield(SFEI),JayDavis(SFEI),andLesterMcKee (SFEI).DaveCrane,AbdouMekebri,andPattyBrucknellofCaliforniaDepartmentof FishandGame,MarinePollutionControlLaboratorymanagedthemainsubcontractwith SFEItoperformthiswork.MarkCadyguidedthisProjectasCAFFProjectManagerand theauthorwouldalsoliketothankMinghuaZhang(UCDavis),CarolynPickel(UC IntegratedPestManagement),andJaniceKendall(SutterCountyDepartmentof Agriculture)fortheirknowledgeandsupportwithallaspectsofthesamplecollection. TheProjectwasfundedbyanEnvironmentalProtectionAgencyCleanWaterAct Section319grant,whileoversightforthisprojectwasprovidedbyDianeBeaulaurier, thegrantmanagerattheCentralValleyRegionalWaterQualityControlBoard.

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