Abstract
Subwatersheds within the Great Lakes “Priority Watersheds” were targeted by the Great Lakes Restoration Initiative (GLRI) to determine the effectiveness of the various best management practices (BMPs) from the U.S. Department of Agriculture-Natural Resources Conservation Service National Conservation Planning (NCP) Database. A Soil and Water Assessment Tool (SWAT) model is created for Alger Creek, a 50 km2 tributary watershed to the Saginaw River in Michigan. Monthly calibration yielded very good Nash–Sutcliffe efficiency (NSE) ratings for flow, sediment, total phosphorus (TP), dissolved reactive phosphorus (DRP), and total nitrogen (TN) (0.90, 0.79, 0.87, 0.88, and 0.77, respectively), and satisfactory NSE rating for nitrate (0.51). Two-year validation results in at least satisfactory NSE ratings for flow, sediment, TP, DRP, and TN (0.83, 0.54, 0.73, 0.53, and 0.60, respectively), and unsatisfactory NSE rating for nitrate (0.28). The model estimates the effect of BMPs at the field and watershed scales. At the field-scale, the most effective single practice at reducing sediment, TP, and DRP is no-tillage followed by cover crops (CC); CC are the most effective single practice at reducing nitrate. The most effective BMP combinations include filter strips, which can have a sizable effect on reducing sediment and phosphorus loads. At the watershed scale, model results indicate current NCP BMPs result in minimal sediment and nutrient reductions (<10%).
Highlights
The Saginaw River enters Lake Huron through Saginaw Bay, an inlet that has been plagued by algae-related issues ranging from beach closures, to the formation of toxic muck, and to degradation of a freshwater drinking and recreation resource for close to 500,000 people
This paper presents a unique effort led by the U.S Geological Survey (USGS), as part of the Priority Watersheds Working Group (PWWG), at the EOF and small watershed scale
The objectives of this paper are to: (1) describe the calibration and validation for the Alger Creek, Michigan Soil and Water Assessment Tool (SWAT) model; (2) identify critical source areas with the highest runoff, erosion, and nutrient loss potential; (3) estimate the impact Environmental Protection Agency (EPA) Great Lakes Restoration Initiative (GLRI) best management practices (BMPs) have on nutrient yields in the Alger Creek watershed; and (4) simulate the influence additional levels of BMP implementation would have on nutrient yields through modeling scenarios
Summary
The Saginaw River enters Lake Huron through Saginaw Bay, an inlet that has been plagued by algae-related issues ranging from beach closures, to the formation of toxic muck (which threatens human and animal health and degrades beach quality), and to degradation of a freshwater drinking and recreation resource for close to 500,000 people. Nutrient inputs to Saginaw Bay must be managed to control algal blooms that have occurred in recent years [1]. Lakes Water Quality Agreement between the United States and Canada established a 440 t year−1 total phosphorus (TP) load as a goal to reduce the algal blooms in Saginaw Bay [5]. The Priority Watersheds Working Group (PWWG) (co-chaired by the U.S Environmental Protection Agency (EPA) and the U.S Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS)) focused their efforts on four Priority Watersheds (PWs)—(1) Lower Fox River, Wisconsin; (2) Saginaw River, Michigan; (3) Maumee River, Ohio; and (4) Genesee River, New York—with a goal of reducing the amount of P reaching the Great Lakes from agricultural sources. USDA-NRCS is using additional GLRI funding to saturate the PWs with best management practices (BMPs) to help meet the 40% TP reduction goal
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