1ESM 202Modeling Biogeochemistry to Inform Policy DecisionsProblem Statement DO levels are low during certain times of the year Excessive algal growth Hypoxia (e.g. Gulf of Mexico) Toxic levels of NH3 WQ Objectives exceededDefine objectives/criteriaDefine protocol for monitoringOxygen is depleted in the bottom water.Oxygen is Oxygen is depleteddepletedin in the bottom the bottom water.water.Algae die and accumulateon the bottom where they are consumed by bacteria.Algae die and Algae die and accumulateaccumulateon the bottom where they on the bottom where they are are consumedconsumedby bacteria.by bacteria.Under calm wind conditions, density stratificationoccurs.Under calm wind Under calm wind conditions, density conditions, density stratificationstratificationoccurs.occurs.Nitrogen stimulatesthe growth of algae.Nitrogen Nitrogen stimulatesstimulatesthe growth of algae.the growth of algae.Fish and shellfish may dieor become weakened and vulnerable to disease.Fish and Fish and shellfish may shellfish may diedieor become or become weakened weakened and and vulnerable to vulnerable to disease.disease.The Negative Effects of Excessive Nitrogen inan System The Negative Effects of Excessive Nitrogen inan System Cause and EffectRelationshipsCause and EffectRelationshipsFrequency of HypoxiaDuration of StratificationNitrogenInputsHarmfulAlgal BloomsRiverFlowAlgalDensityChlorophyllViolationsNumber ofFishkillsFishHealthShellfishAbundanceBODProductionSedimentOxygenDemandDOViolationDefine Conceptual Model What compartments will be considered? What processes are important? What are some of the interactions between different chemicals? How do biota affect the processes?Conceptual ModelTypes of Models Mass Balance & Steady State ConditionsDetermine water balance for period of interestDetermine N&P fluxes into waterbody Point Sources (average discharge flux = conc x flow) Export from Non-Point Sources (average contribution) Agriculture Atmospheric Deposition Urban runoff (lawns, golf courses, parks) Septic Systems Groundwater LivestockCalculate concentrations (mass chemical/volume water)Estimate rate(s) of transformationTypes of Models Dynamic ModelsWater flow driven by meteorologyDetermine variable N&P fluxes to watershed Non-Point Sources (atmos dep, ag, urban, septics, …) Determine N&P assimilation in watershed Calculate export of N&P in runoff & GWDetermine variable N&P fluxes into waterbody Point Sources (can consider daily variation) Non-Point Sources (runoff, GW) Estimate rate of transformation in stream/lake Calculate concentrations in stream/lakeLocal Hydrologic ModelLocal Hydrologic Model Hydrology in a CatchmentLocal Hydrologic Model Hydrology in StreamSources of NutrientsAtmospheric DepositionGroundwater irrigationFertilizer applicationTreated wastewaterLivestock & manureSeptic systemsWatershed ProcessesDry deposition of nitrateDry deposition of ammoniaWet deposition of nitrateWet deposition of ammoniaThroughfall (chemical not taken up by canopy)NH4+→ NO3-Export of NO3-& DON in runoff,P in sedimentsShallow infiltrationDeep infiltrationMicrobial decompositionMicrobial decompositionCO2→ HCO3-CO2→ HCO3-O2O2Weatheringreleases P,N,Ca,…Export of N,PAlk, Ca in GWNH4+→ NO3-NH4+← NO3-Watershed ProcessesNH4+→ NO3-Increased Export of NO3,DON, PShallow infiltrationDeep infiltrationIncreased Exportof N, P in GWFertilizer applicationNH4NO3/PO4/KSeptic SystemNH4 /NO3/DOM/PO4Watershed ProcessesCase StudySanta Clara RiverImpairment due to high DINBasin Plan:WQ Objectives Nitrate + Nitrite“Not to exceed 10 mg/L nitrogen as nitrate-nitrogen plus nitrite-nitrogen, 45 mg/L as nitrate, 10 mg/L as nitrate-nitrogen, or 1 mg/L as nitrite-nitrogen”10 mg/L as NO3-N = 45 mg/L as NO343.41462MWMWNNO3==NO2-=> NO3-Basin Plan:WQ ObjectivesAmmonia CCC (Critical Continuous Concentration)0481216200 5 10 15 20 25 30Temperature (C)Max Ammonia (mg/L as NH3)pH 5 CCC1pH 7 CCC1pH 9 CCC1pH 5 CCC2pH 7 CCC2pH 9 CCC2Actual Data Statistic Reach 8 Reach 7 above Valencia Reach 7 below Valencia Reach 7 at County Line Reach 3 above Santa Paula Reach 3 at Santa Paula Reach 3 below Santa Paula 50 percentile 7.33 7.89 7.78 8.20 8.00 8.00 8.08 90 percentile 7.53 8.16 8.04 8.30 8.30 8.30 8.35 95 percentile 7.62 8.24 8.17 8.41 8.37 8.37 8.43 Mean 7.31 7.85 7.73 8.15 8.00 8.00 8.03 Std. deviation 0.22 0.29 0.31 0.21 0.26 0.26 0.31 CV* 0.03 0.04 0.04 0.03 0.03 0.03 0.04 Statistics of observed pH dataStatistics of observed temperature data (in oC) Statistic Reach 8 Reach 7 above Valencia Reach 7 below Valencia Reach 7 at County Line Reach 3 above Santa Paula Reach 3 at Santa Paula Reach 3 below Santa Paula 50 percentile 19.89 18.23 20.22 19.03 16.68 16.81 16.81 90 percentile 24.34 23.68 25.32 24.59 19.00 19.73 19.87 95 percentile 25.02 24.58 25.90 25.41 19.48 20.44 20.57 Mean 19.55 18.43 20.21 19.22 16.39 16.52 16.52 Std. deviation 3.92 4.05 3.97 4.15 2.32 2.78 2.85 CV* 0.20 0.22 0.20 0.22 0.14 0.17 0.17 Water Quality Objectives Reach 8 Reach 7 above Valencia Reach 7 below Valencia Reach 7 at County Line Reach 3 above Santa Paula Reach 3 at Santa Paula Reach 3 below Santa Paula CCC w/early life stages 3.50 2.19 2.23 1.29 2.06 2.04 1.80 CCC w/o early life stages 3.50 2.19 2.23 1.29 2.06 2.04 1.80 Numerical Target 3.15 1.97 2.00 1.16 1.85 1.84 1.62 Ammonia Water Quality Objective and Numerical Target (mg/L as N-NH3)Historical Water QualitySCR Reach 7 below Valencia WWTP0246810121416O-89 O-90 O-91 O-92 O-93 O-94 O-95 O-96 O-97 O-98 O-99 O-00Ammonia (mg N/L)Observed dataSimulationNumerical TargetHistorical Water QualitySCR Reach 7 below Valencia WWTP02468101214O-89 O-90 O-91 O-92 O-93 O-94 O-95 O-96 O-97 O-98 O-99 O-00Nitrate (mg N/L)Observed dataRefined calibrationNumerical TargetHistorical Water QualityWatershed Model Define watershed Load watershed characteristics Load meteorology Load PS and NPS data Calibrate Hydrology Calibrate Water Quality Determine sensitivity to key parameters Use it for decision supportWatershed delineationSoil TypesLand Use Map, Data from 2002Daily PrecipitationSanta Clarita, CAPoint SourcesPS Flow: Temporal patternFlow = 4.00E-05x - 0.9970.000.100.200.300.400.500.600.70J-89 J-90 J-91 J-92 J-93 J-94 J-95 J-96 J-97 J-98 J-99 J-00 J-01 J-02Flow (m3/s)PS Concentration: Temporal pattern05101520253035J-93 J-94 J-95 J-96 J-97 J-98