|BIEGER, KATRIN - Texas Agrilife Research|
|RATHJENS, HENDRIK - Stone Environmental Consulting|
|Bosch, David - Dave|
|ALLEN, PETER - Baylor University|
Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/21/2018
Publication Date: 2/4/2019
Publication URL: https://handle.nal.usda.gov/10113/6699705
Citation: Bieger, K., Arnold, J.G., Rathjens, H., White, M.J., Bosch, D.D., Allen, P.M. 2019. Representing the connectivity of upland areas to floodplains and streams in SWAT+. Journal of the American Water Resources Association. 55(3):578-590. https://doi.org/10.1111/1752-1688.12728.
Interpretive Summary: Watershed models are currently being used to aid decision makers in determining the impact of climate and land management scenarios on water quality. Current watershed modeling studies do not typically consider many landscape processes such as upland and flood plain interactions. In this study, the SWAT+ (Soil and Water Assessment Tool) model was parameterized and calibrated for stream flow at the ARS Little River Experimental Watershed in Tifton, Georgia. The watershed drains 334 km2 and is characterized by broad flood plains and gently sloping uplands, which leads to saturated conditions along the streams. Three scenarios were simulated with SWAT+ with different ratios of channelized surface runoff from upland areas. The most realistic scenario was calculated using the upland/floodplain area ratio. The study demonstrated that SWAT+ was capable of simulating transport from uplands to flood plains in the U.S. Coastal Plains region. Simulating these landscape processes is critical in determining areas that are prone to runoff and in developing strategies to improve water quality.
Technical Abstract: In recent years, watershed modelers have put increasing emphasis on capturing the interaction of landscape hydrologic processes instead of focusing on streamflow at the watershed outlet alone. Understanding the hydrologic connectivity between landscape elements is important to explain the hydrologic response of a watershed to rainfall events. SWAT+ is a new version of the Soil and Water Assessment Tool with improved runoff routing capabilities. Subbasins may be divided into landscape units, e.g. upland areas and floodplains, and flow can be routed between these landscape units. We ran three scenarios representing different extents of connectivity between uplands, floodplains, and streams. In the first and second scenario, the ratio of channelized flow from the upland to the stream and sheet flow from the upland to the floodplain was 70/30 and 30/70, respectively, for all upland/floodplain pairs. In the third scenario, the ratio was calculated for each upland/floodplain pair based on the upland/floodplain area ratio. Results indicate that differences in streamflow were small, but the relative importance of flow components and upland areas and floodplains as sources of surface runoff changed. Also, the soil moisture in the floodplains was impacted. The third scenario was found to provide more realistic results than the other two. A realistic representation of connectivity in watershed models has important implications for the identification of pollution sources and sinks.