Iowa Nutrient Load Iowa Nutrient Load Estimations for Point and Estimations for Point and

Non-point SourcesNon-point SourcesIowa DNRIowa DNR

November 14, 2012November 14, 2012

DNR StaffDNR Staff

Jackie Gautsch, Watershed MonitoringJackie Gautsch, Watershed MonitoringRick Langel, Watershed MonitoringRick Langel, Watershed MonitoringMary Skopec, Watershed MonitoringMary Skopec, Watershed MonitoringKeith Schilling, Geology and GroundwaterKeith Schilling, Geology and GroundwaterSteve Williams, WastewaterSteve Williams, WastewaterAdam Schnieders, WastewaterAdam Schnieders, WastewaterCalvin Wolter, GISCalvin Wolter, GIS

Iowa’s Ambient Monitoring NetworkIowa’s Ambient Monitoring Network

98 Sites throughout State98 Sites throughout StateIncludes Sites Upstream and Downstream Includes Sites Upstream and Downstream of Urban Centersof Urban CentersMonitored monthlyMonitored monthlyMostly paired with USGS Gage locationsMostly paired with USGS Gage locationsData from 2000-2010Data from 2000-2010

Stream Load Estimation MethodsStream Load Estimation Methods

AutoBeale, Pete Richards, 1998AutoBeale, Pete Richards, 1998Load Estimator (LoadEst), Rob Runkel, Load Estimator (LoadEst), Rob Runkel, USGS, 2004USGS, 2004Mean ValueMean Value

AutoBeale MethodAutoBeale Method

Method that uses a ratio of load to flow to Method that uses a ratio of load to flow to estimate missing dataestimate missing dataData for 2003 Nutrient BudgetData for 2003 Nutrient BudgetData from 2000-2002Data from 2000-200271 Sites71 Sites

LoadEst MethodLoadEst Method

Method that uses a regression model Method that uses a regression model incorporating flow and time to estimate incorporating flow and time to estimate missing datamissing dataData from 2000-2010Data from 2000-201077 sites estimated77 sites estimated

Mean ValueMean Value

Data from 2000-2010Data from 2000-2010Mean value for NO3-N and Total P from all Mean value for NO3-N and Total P from all samplessamplesMean flow rate from USGS gagesMean flow rate from USGS gages77 sites evaluated77 sites evaluated

Check for Unreasonable LoadEst Check for Unreasonable LoadEst ValuesValues

More than +/- 15% of Mean Value loadsMore than +/- 15% of Mean Value loadsResidual error more than +/- 2.0Residual error more than +/- 2.0Error ratio > 10Error ratio > 10NO3-N concentration > 25 ppmNO3-N concentration > 25 ppmTotal P concentration > 10 ppmTotal P concentration > 10 ppmCheck hydrograph vs. sample date to see Check hydrograph vs. sample date to see if full range of flows sampledif full range of flows sampled

Final Load EstimatesFinal Load Estimates

Use acceptable LoadEst models (59 for Use acceptable LoadEst models (59 for Nitrate, 51 for Total P), Nitrate, 51 for Total P), AutoBeale models (71)AutoBeale models (71)Mean Value models (77)Mean Value models (77)Average of all models available (77 sites)Average of all models available (77 sites)

Total N and P LoadsTotal N and P Loads

Sum up loads for 24 outer basinsSum up loads for 24 outer basinsTotal N = NO3-N/0.82Total N = NO3-N/0.82Sum area of outer basins (83% of state)Sum area of outer basins (83% of state)Scale up to State areaScale up to State area

Stream load Tons/yr

Nutrient Yield Lbs/ac

Total N 280,000 16.0

Total P 13,800 0.77

Point Source Load CalculationPoint Source Load Calculation

For 102 Major Municipal and 28 Industrial For 102 Major Municipal and 28 Industrial FacilitiesFacilitiesLoad = Flow * ConcentrationLoad = Flow * ConcentrationUse Average Annual Flow = 2/3 Wet Use Average Annual Flow = 2/3 Wet Weather Design FlowWeather Design FlowUse 25 ppm N and 4 ppm P in discharge Use 25 ppm N and 4 ppm P in discharge from “Wastewater Engineering” Metcalf & from “Wastewater Engineering” Metcalf & EddyEddy

Non-point Source CalculationNon-point Source Calculation

Total State Load minus Point Source LoadTotal State Load minus Point Source Load

  Total stream load NPDES load Non-point source load

Tons N/yr 280,000 18,300 (6.5%) 261,700 (93.5%)

Tons P/yr 13,800 2,900 (21%) 10,900 (79%)

Point Source Biological Nutrient Point Source Biological Nutrient RemovalRemoval

For 102 Municipal and 28 Industrial Major For 102 Municipal and 28 Industrial Major facilitiesfacilitiesAssume concentration reduction for TN Assume concentration reduction for TN from 25 mg/l to 10 mg/lfrom 25 mg/l to 10 mg/lAssume concentration reduction for TP Assume concentration reduction for TP from 4 mg/l to 1 mg/lfrom 4 mg/l to 1 mg/lUse Average Annual Flow = 2/3 Wet Use Average Annual Flow = 2/3 Wet Weather Design FlowWeather Design Flow

Point Source Biological Nutrient Point Source Biological Nutrient RemovalRemoval

Total N Point source reduction = 11,000 Total N Point source reduction = 11,000 tons/year (4% of Total N stream load)tons/year (4% of Total N stream load)Total P Point source reduction = 2,170 Total P Point source reduction = 2,170 tons/year (16% of Total P stream load)tons/year (16% of Total P stream load)

Non-point Source Reduction Non-point Source Reduction needed to meet 45% goalneeded to meet 45% goal

Non-point Source TN reduction needed = Non-point Source TN reduction needed = 45%-4% = 41% or 115,000 tons Total N45%-4% = 41% or 115,000 tons Total NNon-point Source TP reduction needed = Non-point Source TP reduction needed = 45%-16% = 29% or 4,040 tons Total P45%-16% = 29% or 4,040 tons Total P

SummarySummary

Stream load estimation process could be Stream load estimation process could be improved by tailoring the monitoring improved by tailoring the monitoring schedule to better meet the needs of load schedule to better meet the needs of load estimation programsestimation programsPoint source load estimations could be Point source load estimations could be improved by requiring nutrient sampling improved by requiring nutrient sampling and obtaining flow dataand obtaining flow data