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Developing Modeling Tools in Support of Nutrient Reduction Policies
Randy Mentz
Adam Freihoefer, Trip Hook, & Theresa NelsonWater Quality Modeling Technical Team
WDNR Bureau of Water Quality
Administrative Code• NR 217 • NR 151
A Modeled Approach
NR 217 Subchapter III
Water Quality Based Effluent Limitations for Phosphorus
NR 151Subchapter II
Nutrient Management
The Motivation
The Motivation: NR 217
Adaptive management eligibility• Water quality criteria exceeded• Point sources < 50% • Filtration or equivalent technology
required to meet water quality criteria
NR 217 Subchapter III
Water Quality Based Effluent Limitations for Phosphorus
Pollutant Load Ratio Estimation Tool (PRESTO)
PRESTO is a statewide GIS-based tool that calculates basin specific average annual phosphorus loads from point and nonpoint sources.
WatershedDelineation
Pollutant Runoff
Effluent Aggregation
PRESTO – Overview
Village of Almena WWTPUpstream Watershed: 32.9 mi2
Nonpoint Load
Village of Almena WWTP
Upstream Point
Sources
6%
16%
78%
Point to Nonpoint Phosphorus Load Ratio
22% : 78%Point Source
Red Cedar River Watershed (HUC 08, 1,890 mi2)
20 Outfalls
PRESTO – Input Datasets
Point Source : Nonpoint Source Load Ratio
SWAMP Outfall Locations And Effluent Point Loads
Elevation
Land cover
Hydrography
Tabular Model Parameters
Sub-basin Boundaries
PRESTO – Phosphorus EstimationPoint Source Phosphorus Load• Permitted sites with phosphorus monitoring
data• Average annual discharge & concentration
calculated using that year’s monitoring record
Nonpoint Source Phosphorus Loads• Export coefficients• Multiple regression models
MR1 – Grassland within 30m riparian zone, forested land, & stream density
MR2 – Cropland, urban land, & stream density
PRESTO – Outputs
Output Attribute Categories
Watershed Characteristics
Land Cover Composition (%)
Point Loading
Nonpoint Estimation Model – Export Coefficient (EC)
Nonpoint Estimation Model – Multiple Regression Model #1 (MR #1)
Nonpoint Estimation Model – Multiple Regression Model #2 (MR #2)
PS : NPS RatioPer Nonpoint Estimation Model
PRESTO – Statewide Analysis
PRESTO – Documentation & Download
PRESTO Version 1.0 Release includes:
http://dnr.wi.gov/org/water/wm/ww/presto/
PRESTO Model FilesUser ManualDocumentation, Validation, &
Analysis ReportFact Sheet
NR 151Subchapter II
Nutrient Management
The Motivation: NR 151
• Identify fields / farms with Nutrient Management Plan need
• Evaluate the phosphorus index performance standard (PI = 6) per field
• Ensure soil conservation
WI Nutrient Targeting & Tracking Tool – Overview
Develop a state-wide assessment tool to identify critical source areas of potential non-point sediment and phosphorus loss.
Target fields at county or subwatershed scale
Prioritize TMDL implementation efforts
Manage agricultural practice & BMP data
WI Nutrient Targeting & Tracking Tool – Overview
Mead Lake Watershed
SWAT modelSubwatershed Prioritization
How do we determine field prioritization?
WI Nutrient Targeting & Tracking Tool – Concept
Field-scale Prioritization• Relies on rotation average P index
(lb. P / acre / year) using established WI Phosphorus Index
• Requires significant amount of data
• Additional question that follows: If one field is improved, what is
the water quality benefit at the subbasin outlet?
WI Nutrient Targeting & Tracking Tool – Approach
1Develop Statewide Model Grid
2 Select watershed
5 In-Stream Transport
3Calculate Grid-Specific Phosphorus ExportBased on annual export from Snap-Plus model,other lands would rely on separate export calculations
4Determine Delivery from Grid Cell to Stream
WI Nutrient Targeting & Tracking Tool – Approach
Data Collection and Management To Support Cell Specific Export
County Average Soil P
Grid Tool Relies on Spatial Inputs Including:
30-meter grid Precipitation
NLCD Land cover Slope
Land Management(Tillage, Rotation, Fertilizer)
Flow Direction And Volume
Soil Properties Closed Depressions
Phosphorus Soil Test Distance to Waterway
WI Nutrient Targeting & Tracking Tool – Next Steps
Develop framework for managing and tracking landscape data
Beta test on watershed with existing field and stream data
Determine impacts of using county average data
Summary
• The DNR has developed and will continue to develop modeling tools to support existing and future policy.
• Out of the box models such as SWAT and Snap-Plus may only get us so far towards our questions.
• PRESTO and Nutrient Targeting & Tracking Tool are screening tools, bridging the gap between no answer and a detailed analysis.
• Testing and validation of these tools ensures defensibility.
