Abstract
The Eagle Creek watershed, a small subbasin (125 km2) within the Maumee River Basin, Ohio, was selected as a part of the Great Lakes Restoration Initiative (GLRI) “Priority Watersheds” program to evaluate the effectiveness of agricultural Best Management Practices (BMPs) funded through GLRI at the field and watershed scales. The location and quantity of BMPs were obtained from the U.S. Department of Agriculture-Natural Resources Conservation Service National Conservation Planning (NCP) database. A Soil and Water Assessment Tool (SWAT) model was built and calibrated for this predominantly agricultural Eagle Creek watershed, incorporating NCP BMPs and monitoring data at the watershed outlet, an edge-of-field (EOF), and tile monitoring sites. Input air temperature modifications were required to induce simulated tile flow to match monitoring data. Calibration heavily incorporated tile monitoring data to correctly proportion surface and subsurface flow, but calibration statistics were unsatisfactory at the EOF and tile monitoring sites. At the watershed outlet, satisfactory to very good calibration statistics were achieved over a 2-year calibration period, and satisfactory statistics were found in the 2-year validation period. SWAT fixes parameters controlling nutrients primarily at the watershed level; a refinement of these parameters at a smaller-scale could improve field-level calibration. Field-scale modeling results indicate that filter strips (FS) are the most effective single BMPs at reducing dissolved reactive phosphorus, and FS typically decreased sediment and nutrient yields when added to any other BMP or BMP combination. Cover crops were the most effective single, in-field practice by reducing nutrient loads over winter months. Watershed-scale results indicate BMPs can reduce sediment and nutrients, but reductions due to NCP BMPs in the Eagle Creek watershed for all water-quality constituents were less than 10%. Hypothetical scenarios simulated with increased BMP acreages indicate larger investments of the appropriate BMP or BMP combination can decrease watershed level loads.
Highlights
Harmful algal blooms (HABs) threaten the vitality of Lake Erie—drinking water impairments, multiple beach closures, and impacts to fishing and wildlife are just a few of the problems the lake is currently experiencing
Watershed-scale results indicate best management practices (BMPs) can reduce sediment and nutrients, but reductions due to National Conservation Planning (NCP) BMPs in the Eagle Creek watershed for all water-quality constituents were less than 10%
This paper presents a unique effort led by the U.S Geological Survey (USGS), as part of the PWWG, at the EOF and small watershed scale in the Eagle Creek watershed, nested within the larger Western Lake Erie Basin (WLEB)
Summary
Harmful algal blooms (HABs) threaten the vitality of Lake Erie—drinking water impairments, multiple beach closures, and impacts to fishing and wildlife are just a few of the problems the lake is currently experiencing. Current research has pointed to the agricultural activities in the Western Lake Erie Basin (WLEB) as the main source of nutrient delivery to the lakes, one of the primary causes of increasing HABs in Lake Erie [2,3,4,5]. Agricultural nutrient inputs to the lake, especially phosphorus (P), have been a focus of the research community to reduce and prevent HABs. Problems have plagued Lake Erie for decades. The U.S and Canada entered into the 1978 Great Lakes Water Quality Agreement to reduce phosphorus loads by 40% from 1976 levels from entering into the WLEB, where much of HABs are centered [7]. The TP loads had decreased by the 1990s [3,8], but by the early 2000s HABs had re-emerged in the WLEB [2,3]
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