Assessing performance of best management practices in the Great Lakes Priority Watersheds using SWAT

Session: 35. - Watershed Modeling across all Scales from Small to Large

Katherine Merriman-Hoehne, US Geological Survey, [email protected]
Amy Russell, USGS Central Midwest Water Science Center, [email protected]

Abstract

This work examines effectiveness of best management practices (BMPs) funded by Great Lakes Restoration Initiative to reduce nutrients using field-scale Soil & Water Assessment Tool (SWAT) models of three small watersheds in Ohio (Eagle Creek), Michigan (Alger Creek), and Wisconsin (Upper East River) within the Great Lakes Priority Watersheds. BMP placement and quantity was derived from the USDA-NRCS National Conservation Planning (NCP) database. Differences in nutrient loadings were assessed for NCP scenarios as well as hypothetical scenarios developed in consultation with local NRCS. Results document individual and combinations of BMPs can have a large range of effectiveness at the field scale. Field-scale nutrient reductions for BMPs were similar in watersheds modeled: cover crops reduced TP 16-25% in Ohio and 11-33% in Michigan, no-tillage reduced TP 14-40% in Michigan, grassed waterways reduced TP 46-71% in Ohio, crop rotation reduced TP 0-31% in Ohio, and nutrient management plans reduced TP 0-2% in Ohio and 0-13% in Michigan. Additions of filter strips or grassed waterways increased TP reduction an additional 5-40%. At watershed scale, NCP practices did not result in large reductions (<10% TP). Hypothetical scenarios indicate large increases in BMPs acreage are required for substantial reductions in nutrient loads in small watersheds. 

1. Keyword
Great Lakes Restoration Initiative (GLRI)

2. Keyword
nutrients

3. Keyword
modeling

4. Additional Keyword
SWAT