A new watershed-scale model for depressional landscapes

Authors: EVENSON, G.R. - Virginia Polytechnic Institution & State University; JONES, C.N. - Virginia Polytechnic Institution & State University; MCLAUGHLIN, D. - Virginia Polytechnic Institution & State University; GOLDEN, H.E. - Environmental Protection Agency (EPA); LANCE, C.R. - Environmental Protection Agency (EPA); DEVRIES, B. - University Of Maryland; ALEXANDER, L. - Environmental Protection Agency (EPA); McCarty, Gregory; LANG, M.W. - Us Fish And Wildlife Service; SHARIFI, A. - University Of Maryland

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2018
Publication Date: 11/1/2018
Citation: Evenson, G., Jones, C., Mclaughlin, D., Golden, H., Lance, C., Devries, B., Alexander, L., McCarty, G.W., Lang, M., Sharifi, A. 2018. A new watershed-scale model for depressional landscapes. Hydrological Processes. 1:100002. https://doi.org/10.1016/j.hydroa.2018.10.002.
DOI: https://doi.org/10.1016/j.hydroa.2018.10.002

Interpretive Summary: Low-relief landscapes are often dominated by wetlands, which provide a wide array of ecosystem services – ranging from critical habitat provisioning to improvements in downstream water quality and streamflow regulation. Despite their relative importance in providing many ecosystem services and their abundance in many landscapes, contemporary models do not adequately represent wetland hydrological processes and the consequent loss of these dynamics at the watershed scale. New modeling tools are needed to better represent wetland processes to effectively manage watershed-scale hydrological, biogeochemical, and biological functions and predict potential restoration outcomes. In this paper we use a modified version of the USDA Soil and Water Assessment Tool (SWAT) model to incorporate: (1) an improved structural representation of depressional wetlands, and (2) an improved representation of depressional wetland hydrological processes. The findings demonstrate that our modified model can successfully replicate streamflow and surface water observations in the studied watershed. This modified model is an effective tool to quantify wetland functions at broad spatial scales and will enable better wetland restoration strategies for low relief watersheds.

Technical Abstract: Wetlands are often dominant features in low relief depressional landscapes and provide an array of ecosystem services. However, contemporary models do not adequately quantify wetland hydrological processes across watersheds. Such tools are critical to better understand watershed-scale hydrological, biogeochemical, and biological functions and predict management and policy outcomes at varying spatial scales. Here, we present a new approach for simulating depressional landscapes, by modifying the Soil and Water Assessment Tool (SWAT) model to incorporate: (1) an improved structural representation of depressional wetlands, and (2) an improved representation of depressional wetland hydrological processes. We applied this improved model, termed SWAT-DSF (DSF for Depressional Storage and Flows) for the ~289 km2 Greensboro watershed within the Delmarva Peninsula of the US central Coastal Plain. Model calibration and verification used both daily streamflow observations and remotely sensed surface water extent data provided at about a 2-week temporal resolution. Our findings demonstrate that SWAT-DSF can successfully replicate streamflow and surface water extent observations for the studied watershed. SWAT-DSF provides an improved temporal and spatial characterization of watershed-scale water storage and flows in depressional landscapes, providing a new tool to quantify wetland functions at broad spatial scales.