Thinking outside of the Lake: Can controls on nutrient inputs into Lake Erie benefit stream conservation in its watershed?

Authors: KEITZER, S. - The Ohio State University; LUDSIN, STUART - The Ohio State University; SOWA, SCOTT - Nature Conservancy; ANNIS, GUST - Nature Conservancy; Arnold, Jeffrey; DAGGUPATI, PRASAD - Texas Agrilife Research; FROEHLICH, AUGUST - Nature Conservancy; HERBERT, MATT - Nature Conservancy; JOHNSON, MARI-VAUGHN - Natural Resources Conservation Service (NRCS, USDA); SASSON, ANTHONY - Nature Conservancy; YEN, HAW - Texas Agrilife Research; White, Michael; REWA, CHARLES - Natural Resources Conservation Service (NRCS, USDA)

Submitted to: Journal of Great Lakes Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2016
Publication Date: 6/22/2016
Citation: Keitzer, S.C., Ludsin, S.A., Sowa, S.P., Annis, G., Arnold, J.G., Daggupati, P., Froehlich, A.M., Herbert, M.E., Johnson, M.V., Sasson, A.M., Yen, H., White, M.J., Rewa, C.A. 2016. Thinking outside of the Lake: Can controls on nutrient inputs into Lake Erie benefit stream conservation in its watershed? Journal of Great Lakes Research. 42:1322-1331.

Interpretive Summary: Excessive amounts of nitrogen and phosphorus entering Western Lake Erie are causing harmful algal blooms, making drinking water unsafe for people in Toledo and surrounding areas. In addition, nutrient loadings to streams within the basin are degrading fish habitat and fish populations throughout the watershed. Significant emphasis has been given to drinking water and fishing in Western Lake Erie, however, less attention has been given to the condition of streams within the watershed. In this study, we linked a hydrologic watershed model to an instream biological model. The hydrologic model (SWAT – Soil and Water Assessment Tool) was used to predict the impact of different agricultural management on sediment, nitrogen and phosphorus loadings into streams within the Western Lake Erie basin. Model results showed that the implementation of conservation practices on farm acres in critical and moderate need of treatment, representing nearly half of the watershed, would be needed to reduce spring/early summer total phosphorus loads into Western Lake Erie to acceptable levels. This widespread conservation practice implementation also would improve potential stream biological conditions in 11,000 km of streams and reduce the percentage of streams where water quality is limiting biological conditions, from 31% to 20%. This is the first study to link SWAT with a fish habitat model. This study provided insight to managing water quality issues in both Western Lake Erie and within the watershed. The linked model will provide decision makers with a tool for direct impact of land management on fish health.

Technical Abstract: Investment in agricultural conservation practices (CPs) to address Lake Erie's re-eutrophication may offer benefits that extend beyond the lake, such as improved habitat conditions for fish communities throughout the watershed. If such conditions are not explicitly considered in Lake Erie nutrient management strategies, however, this opportunity might be missed. Herein, we quantify the potential for common CPs that will be used to meet nutrient management goals for Lake Erie to simultaneously improve stream biological conditions throughout the western Lake Erie basin (WLEB) watershed. To do so, we linked a high-resolution watershed hydrology model to predictive biological models in a conservation scenario framework. Our modeling simulations showed that the implementation of CPs on farm acres in critical and moderate need of treatment, representing nearly half of the watershed, would be needed to reduce spring/early summer total phosphorus loads from the WLEB watershed to acceptable levels. This widespread CP implementation also would improve potential stream biological conditions in 11,000 km of streams and reduce the percentage of streams where water quality is limiting biological conditions, from 31% to 20%. Despite these improvements, we found that even with additional treatment of acres in low need of CPs, degraded water quality conditions would limit biological conditions in 3,200 stream km. Thus, while we expect CPs to play an important role in mitigating eutrophication problems in the Lake Erie ecosystem, additional strategies and emerging technologies appear necessary to fully reduce water quality limitation throughout the watershed.