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Assessing the Effectiveness of Agricultural Conservation Practices in the Western Lake Erie Basin Using SWAT: What We Have Learned Conservation Practices in the Western Lake Erie Basin: What We Have Learned
Citation:
Koropeckyj-Cox, L. AND Y. Yuan. Assessing the Effectiveness of Agricultural Conservation Practices in the Western Lake Erie Basin Using SWAT: What We Have Learned Conservation Practices in the Western Lake Erie Basin: What We Have Learned. 2021 America Society of Agricultural and Biological Engineering Annual International Meeting, Virtual, July 12 - 16, 2021.
Impact/Purpose:
Water bodies and coastal areas around the world are threatened by excessive amounts of nitrogen (N) and phosphorous (P) from upstream watersheds, which can cause rapid proliferation of algae. These algal blooms negatively impact drinking water sources, aquatic species, and recreational services of water bodies by producing toxins, also called harmful algal blooms (HABs). Finding ways reducing N and P losses from agricultural runoff is paramount important for EPA program offices and regional partners to make informed decisions to better control nutrient losses from agricultural-dominated watershed.
Description:
Lake Erie is threatened by eutrophication and harmful algal blooms (HABs) due to excess nutrient loading from agricultural sources. Agricultural conservation practices (ACPs) have been developed and implemented to reduce nutrient losses but estimating ACP effectiveness is challenging. The Soil and Water Assessment Tool (SWAT) has been used to investigate ACP effectiveness for water quality improvement. Many SWAT applications have been developed by different investigators to evaluate ACP effectiveness for reducing nutrient, particularly phosphorus (P), loading in the agriculturally-dominated Western Lake Erie Basin (WLEB). Our objective is to establish what has been achieved by past modeling research and make suggestions for future applications and improvements. We synthesized the findings of 28 SWAT modeling studies within the WLEB. Models generally performed satisfactorily against accepted criteria for streamflow and sediment, but performance for nutrient loads, like soluble reactive P, was mostly “unsatisfactory.” Thus, simulations of P transport and transformation processes need improvement. Also, specific calibration parameters and their values varied widely across different studies, even within the same watershed. This indicates equifinality, where several combinations of model inputs produce similar outputs. Equifinality in the baseline model may impact results when ACPs are incorporated. Future model applications should try to reduce equifinality by constraining the model with characterization of watershed conditions, better understanding of hydrologic processes, and parameter values based on real-world observations. Furthermore, future model improvements should focus on extreme flow events, as SWAT overestimates loads during low flows and underestimates high flows, as demonstrated in other applications. This is especially important as extreme events become more common with projected climate changes. In summary, future model applications should focus on improving P transport and transformation processes, using measured watershed characteristics for parameterization, and improving reflections of climate change, which could result in more accurate assessments of ACP effectiveness to meet targeted goals.
