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Impact of Climate Change on Critical Source Areas in a Chesapeake Bay Watershed

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1801831.(doi:10.13031/aim.201801831)
Authors:   Zhongrun Xiang, Hubert J Montas, Adel Shirmohammadi, Paul T Leisnham, Kaye Brubaker
Keywords:   Climate Change, Watershed Response, NPS Pollution, Critical Source Areas, Chesapeake Bay.

Abstract. The hydrologic response of a small suburban watershed located within the Chesapeake Bay watershed, is evaluated using SWAT under 6 CMIP5 climate change models and 4 RCP scenarios: 2.6, 4.5, 6.0 and 8.5. The focus of the analysis is to identify how Critical Source Areas (CSAs, hotspots), where BMPs should be implemented to optimize water quality gains, may vary as climate evolves. Calibrated model predictions of in-stream and land-surface yields of water (discharge or runoff), sediments, nitrogen and phosphorus are considered over a 100 year time frame. End-of-century results indicate significant increases of in-stream and surface yields (amounts) of the 4 target constituents, under all climate models and scenarios, relative to the historical baseline. The areas occupied by CSAs identified using a fixed threshold amount of exported constituents are also found to increase significantly, for all climate models, with relatively small variance between RCPs. On the other hand, CSAs identified using a relative threshold (eg. top 20% of HRUs) are found to match those from current climate with more than 80% agreement. It is concluded that the specific approach used for targeting CSAs can have substantial impacts on BMP implementation planning for mitigating the impacts of future climate change. For some constituents it is the total mass released that needs to be controlled, while for others it is the maximum concentration, and this leads to markedly different sets of future CSAs. Possible relationships between these considerations and TMDL development (that guide threshold selection) and social intervention strategies (that foster BMP adoption) are outlined.

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