iowa nutrient load estimations for point and non-point sources iowa dnr november 14, 2012
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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