Nutrient and Sediment Modeling of the Yahara Lakes Watershed Yahara CLEAN Project Rob Montgomery John Panuska
Watershed Remediation Flow Chart - Watershed-scale Analysis - Pheasant Branch Field-scale pilot project Watershed Scale analysis - SWAT Field-scale analysis SNAP Plus Relative ranking of sub-areas Implement management practices Evaluate lake water quality Goal met Goal not met
Topic Overview Watershed model input data Results of watershed scale modeling The field scale modeling approach Implementation to meet watershed goals
Watershed Model Input Data Topographic, soils, land use Climate Livestock and manure spreading Stream gage data on runoff and nutrients
Building the Watershed Model Define watersheds Assemble and check data Define modeling process Calibrate model to stream gage data
Existing Land Use Sediment Delivery Variable by location Related to land use, soils, topography All areas contribute sediment
Manure Analysis Where & How Much? Manure application rates based on: Number of animal units Haul distances Agricultural land available for spreading
Existing Land Use Phosphorus Delivery Extremely variable by location Dependent on soils, manure application, tillage practices Highest loadings to Mendota, but also substantial loadings to Waubesa and Kegonsa
Phosphorus Contribution by Watershed 70% 60% 50% 40% 30% 20% 10% Phosphorus Contribution to the Yahara Chain of Lakes 0% Mendota Monona Waubesa Kegonsa
Nutrient Delivery Under Alternative Land Use Scenarios 1. Continuation of existing land-use patterns 2. Increases or decreases in manure application 3. Planting the watershed to continuous perennial crop
Phosphorous Load Reduction Across Watershed Existing Land Use Manure Control Manure Control & Perennial Crops
Nutrient Reduction by Land Management Scenario - Lake Mendota Watershed - Land Management Change Estimated Total Reduction in P 100% Manure Control ~ 40 60 % 80% Manure Reduction ~ 30 50 % 60% Manure Reduction ~ 25 35 % 25% Manure Increase ~ +10 +15 % No Manure & Perennial Crops ~ 50 70 % Urban TSS Reduction ~ < 5 %
Nutrient Reduction by Land Management Scenario - Lake Monona Watershed - Land Management Change Estimated Total Reduction in P 100% Manure Control ~ 10 15 % 80% Manure Reduction ~ 8 10 % 60% Manure Reduction ~ 6 8 % 25% Manure Increase ~ +2 +4 % No Manure & Perennial Crops ~ 20 25 % Urban TSS Reduction ~ 10 15 %
SWAT Modeling Summary Described nutrient and sediment loading variability in both time and space Prioritized sub-watershed areas for nutrient control practices Evaluated whole watershed loading responses to major load reduction measures
Watershed Remediation Flow Chart - Field-scale Analysis - Pheasant Branch Field-scale pilot project Watershed Scale analysis - SWAT Field-scale analysis SNAP Plus Relative ranking of sub-areas Implement management practices Evaluate lake water quality Goal met Goal not met
Wisconsin Phosphorus Index (WPI) - Part of SNAP Plus A tool to rank fields for runoff P loss potential The WPI is used throughout WI for nutrient management planning and is familiar to producers, LCD staff and crop consultants Field 2 Field 1 Stream
Research Base for P Index Simulated rainfall runoff trials with different managements and soils ( > 500 plot events). Replicated small plots with long-term natural runoff collectors, different managements and soils (100 plots) Year-round runoff monitoring in field-scale watersheds with different soils and management (21 sites)
WPI Estimates Average Annual P Loss from Agricultural Fields to Perennial Streams Soil erosivity and soil test P Land slope and slope length Average annual climate Fertilizer and manure application Crop and tillage type
WI Phosphorus Index Map - Pheasant Branch Watershed Pilot -
WI Phosphorus Index Distribution - Pheasant Branch Watershed Pilot - 80 70 60 Frequency 50 40 30 20 10 0 0 3 6 9 12 15 P - Index Value 18 21
What can SNAP Plus & WPI do at the field scale?? WPI 18 16 14 12 10 8 MdC2 (Slope 9%) Tillage is SC-N-N-N-SC-SC-SC As-A-A-A-Cg-Cg-Cs OfAs-A-A-A-Cg-Cg-Cs As-A-A-A-Cs-Cg-Cg OfAs-A-A-A-Cs-Cg-Cg SNAP Plus the WPI can evaluate..... 6 4 2 0 2008 2009 2010 2011 2012 2013 2014 2015 2016 Year Manure Application the impact of crop rotation and tillage on P losses 7.0 WPI 6.0 5.0 4.0 3.0 2.0 1.0 Liquid, Surface Liquid, Incorporated Solid, Surface Solid, Incorporated also the impact of manure and application method on P losses 0.0 0 20 40 60 80 100 120 Manure P Added (Lbs)
SNAP Plus / WPI Modeling Summary Rank fields by sediment and P loss. Evaluate alternative field-scale Mgmt. practices to reduce P loss. - tillage, fertilizer, manure and cropping systems Work toward percent reduction goals identified by the watershed model. Use an adaptive management strategy.