SCENARIO TOOL Lake Champlain Basin TMDL

Lake Champlain Phosphorus

■ Monitoring data – In lake

■ Lake segments – Water column – Sediment

– In flows ■ River Basin (VT and NY)

■ How is phosphorus loading distributed in watershed?

■ Soil and Water Assessment: SWAT – USDA ARS and Texas A & M – Used to predict parameter fate and transport:

■ Climate ■ Hydrology ■ Landscape characteristics and processes

– Technical documentation 600+ pages

In-lake Watershed

SWAT Output ■ 30 year time series of estimated P loading

■ Calibrated/Validated on empirical P data

■ Output at approximately HUC 12 scale

EPA Scenario Tool

■ Goal: BMP scenario that achieves TMDL based on SWAT loading estimates

■ Specifies which BMPs go on what land ‘type’

■ Land ‘type’ = SWAT land use, slope class, and hydrologic soil group

■ Estimates P-loading rate, BMP efficiency, P-reduction, etc.

■ Described at BASIN scale

■ Exhaustive; in some cases, 100% of land ‘type’ requires BMP; in other cases, <100% BMP implementation is indicated

Example Scenario Tool Output

1. Select Drainage Area 2. Select Landuse Type 3. Select HSG

4. Select Slope Area (ha) TP Load (kg/yr)

Mississquoi River Corn-hay rotation on non-clayey soils A All 1800.79 853.18

Mississquoi River Continuous hay B All 45.75 16.58

5. Select BMP Type

BMP Efficiency (%)

6. Enter Applied Area (%)

TP Load Reduction (kg/yr)

Cover Crop - Conservation Tillage - Grassed Waterways - Ditch Buffer - Riparian Buffer 0.89 1.00 763.03

Riparian Buffer 0.41 0.80 5.44

EPA Scenario Tool Application

■ Starting point for potential BMP placement

■ Modeled estimate of P-loading, potential reduction; consistent framework

■ Watershed Management Tool (WMT): Will provide map interface that will summarize loadings, potential reductions, and possible BMPs by township, NHD+ catchment, etc. *Still under discussion*

■ Inclusion of Tactical Basin Plan (TBP) implementation tables

EPA Scenario Tool Application: WMT

COMID 234735 Drainage Area Lamoille River Landuse Continuous hay HSG D Slope All Total Catchment Area (ha) 5 Basin Area (ha) 2590.65 Basin TP Load (kg/yr) 2595.44 TP Rate kg/yr *ha 1.00 BMP Type Riparian Buffer BMP Efficiency (%) 0.41 Basin TP Load Reduction (kg/yr) 851.30 Catchment TP Load Reduction (kg/yr) 2.05