Best Management Practices (BMPs) and Water Quality Parameters of Selected Farms Located in the Arroyo Colorado Watershed

BMPs Implemented at Demonstration Sites• Croprotation• Cropresiduemanagement• NutrientManagement• PestManagement• IrrigationLandLeveling• IrrigationManagement• Irrigationwithpoly-pipe• Subsurfacedrainage• Vegetationfilterstrips

Agriculture in the Arroyo Colorado Watershed

ExcesswaterfromvariouslandscapeactivitiesintheLowerRioGrandeValleyaredrainedthroughtheArroyoColoradoeventuallyemptyingintothelowerLagunaMadre.TheLagunaAtascosaNationalWildlifeRefugeandseveralcountyandcityparksarelocatedwithintheArroyoColoradowatershed.Thewatershedisalsothehabitatofseveralsemi-tropicalplantsandanimalspecies.TheArroyoColoradoalsoboastsmanyrecreationalopportunitiesandattractsalargenumberoftouristsannually.Agriculture,municipalandindustrialactivitiesareallcontributorstowaterqualityissuesandimpairmentsintheArroyoColoradowatershed.Themainconcerncomingfromagriculturearechemicalssuchasfertilizersandpesticidesthatcanbecarriedwiththeirrigationwaterthroughrunoffanddeeppercolation.AgriculturalproducerscanimprovethewaterqualityoftheArroyoColoradobyimplementingbestmanagementpractices(BMPs)thatreducenonpointsource(NPS)pollutionfromagriculturallands.Severaldemonstrations,onefurtherdescribedbelow,havebeen

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developedsince2006tocharacterizethewaterqualityofirrigationandrunoffwaterandtoevaluatetheeffectivenessofBMPsonwaterqualityatthefieldandsub-watershedlevel.TheseactivitieshavebeenconductedinanefforttoimplementtheArroyoColoradoWatershedProtectionPlanandachieveitsgoalsofreducingpollutionfromvarioussources,oneofthosebeingagriculture.

ObjectivesOneofthemainsourcesofpollutionarethenutrientloadingsfromagriculturalrunoffandleachates;therefore,astudyfocusedonidentifyingtheeffectofagriculturalmanagementpracticesonNPSpollutionfromsurfaceirrigatedfarmsintheArroyoColoradowatershedwasinitiated.Theobjectiveofthestudywastoobtainwaterqualityinformation(parametersincluding:totaldissolvedsolids,nitratesandnitrites,orthophosphatephosphorus,totalphosphorus,andtotalKjeldahlnitrogen)ofirrigationwaterrunoffandgroundwaterinsixagriculturalfieldsduringthe2009and2010growingseasons.

Figure1:Irrigationpolypipeutilizedduringanirrigationevent

Best Management Practices (BMPs) and Water Quality Parameters of Selected Farms located in the Arroyo Colorado Watershed

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ResultsThepredominantirrigationsystemintheLowerRioGrandeValleyissurfaceirrigation.TheprimaryBMPsadoptedbyirrigatingfarmersintheArroyoColoradowatershedareconservationcroprotation,irrigationlandleveling,theuseofpoly-pipeandnutrientmanagement.Duringthisprojectonlyonesitehadfilterstripsatthelowerendoftherowswhichreceivedirrigationrunoff.Themainresultsofthisstudyarelistedbelow.

1. Theresultsindicatedthattheirrigationwateralreadycontainedhighconcentrationsofnitrates,nitrites,orthophosphates,totalphosphorusandtotalKjeldahlnitrogen.Also,theseconcentrationsvariedfromirrigationtoirrigation.

2. Thegainsofnitrates,nitritesandtotalKjeldahlnitrogenloadingsfromthefieldsweresmall.Theactivitythatresultedinthehighestinfluenceonnutrientloadingswastheamountofrunoff.Thiscouldbereducedthroughimprovedirrigationmanagement.

3. Nutrientloadingsduetoorthophosphatesandtotalphosphoruswereextremelylowforallsitesduringbothyears,andtheseloadingswerealsoinfluencedbytheamountofrunoff.Hightotaldissolvedsolidscouldhaveresultedfromhigherfurrowflow-ratesthatproduceincreasederosionandtransportofsediments.Thesehigherflowratesalsoresultinhighernutrientloadingsoforthophosphatesandtotalphosphorus.Theuseofpoly-pipecanreduceerosion,facilitateirrigationmanagementandmayhaveaninfluenceonorthophosphatesandtotalphosphorus.

4. Thenutrientvalueswithingroundwaterfluctuatedfromyeartoyearandfromirrigationtoirrigation,buttheyweregenerallylow.ThefewsitesthathadnutrientmanagementimplementedasaBMPwerethesitesthathadsomeofthelowestnutrientvaluesingroundwater.

Figure2:Runoffresultingfromanirrigationeventbeingmeasured.

RecommendationsProducerscanimplementmultipleBMPstoprotectthewaterqualityoftheArroyoColorado.ThecombinationofmultiplepracticescancreateagreaterimpactofnutrientreductionstotheArroyoColorado.Somepracticessuchaslandlevelingwithsomegradeandtheuseofpoly-pipefacilitateirrigationmanagementandthus,haveanimpactonimprovingyieldsandprofits.ThetwoBMPsthatreducednutrientrunoffthemostwerenutrientmanagementandirrigationmanagement.Nutrientmanagementtypicallyconsistsofapplyingfertilizerataspecificrateaccordingtoasoilanalysistest.Irrigationmanagementincludescontrollingthetotalamountofwaterappliedtothelandfocusingonusingnon-erosiveflow-rates,therebyreducingrunoff.

ThisprojectwasfundedbyaCleanWaterAct§319(h)grantthroughtheUnitedStatesEnvironmentalProtectionAgencyadministeredbytheTexasStateSoilandWaterConservationBoard.

TexasWaterResourcesInstituteEM-113