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

Non-point SourcesNon-point Sources

Iowa DNRIowa DNR

November 14, 2012November 14, 2012

DNR StaffDNR Staff

Jackie Gautsch, Watershed MonitoringJackie Gautsch, Watershed Monitoring

Rick Langel, Watershed MonitoringRick Langel, Watershed Monitoring

Mary Skopec, Watershed MonitoringMary Skopec, Watershed Monitoring

Keith Schilling, Geology and GroundwaterKeith Schilling, Geology and Groundwater

Steve Williams, WastewaterSteve Williams, Wastewater

Adam Schnieders, WastewaterAdam Schnieders, Wastewater

Calvin Wolter, GISCalvin Wolter, GIS

Iowa’s Ambient Monitoring NetworkIowa’s Ambient Monitoring Network

98 Sites throughout State98 Sites throughout State

Includes Sites Upstream and Downstream Includes Sites Upstream and Downstream of Urban Centersof Urban Centers

Monitored monthlyMonitored monthly

Mostly paired with USGS Gage locationsMostly paired with USGS Gage locations

Data from 2000-2010Data from 2000-2010

Stream Load Estimation MethodsStream Load Estimation Methods

AutoBeale, Pete Richards, 1998AutoBeale, Pete Richards, 1998

Load Estimator (LoadEst), Rob Runkel, Load Estimator (LoadEst), Rob Runkel, USGS, 2004USGS, 2004

Mean 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 data

Data for 2003 Nutrient BudgetData for 2003 Nutrient Budget

Data from 2000-2002Data from 2000-2002

71 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 data

Data from 2000-2010Data from 2000-2010

77 sites estimated77 sites estimated

Mean ValueMean Value

Data from 2000-2010Data from 2000-2010

Mean value for NO3-N and Total P from all Mean value for NO3-N and Total P from all samplessamples

Mean flow rate from USGS gagesMean flow rate from USGS gages

77 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 loads

Residual error more than +/- 2.0Residual error more than +/- 2.0

Error ratio > 10Error ratio > 10

NO3-N concentration > 25 ppmNO3-N concentration > 25 ppm

Total P concentration > 10 ppmTotal P concentration > 10 ppm

Check 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 FacilitiesFacilities

Load = Flow * ConcentrationLoad = Flow * Concentration

Use Average Annual Flow = 2/3 Wet Use Average Annual Flow = 2/3 Wet Weather Design FlowWeather Design Flow

Use 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 facilitiesfacilities

Assume concentration reduction for TN Assume concentration reduction for TN from 25 mg/l to 10 mg/lfrom 25 mg/l to 10 mg/l

Assume concentration reduction for TP Assume concentration reduction for TP from 4 mg/l to 1 mg/lfrom 4 mg/l to 1 mg/l

Use 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 N

Non-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 programs

Point 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