Submitted to: Hydrological Processes
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/14/2014
Publication Date: 6/25/2015
Publication URL: http://handle.nal.usda.gov/10113/61394
Citation: Rathjens, H., Oppelt, N., Bosch, D.D., Arnold, J.G., Volk, M. 2015. Development of a grid-based version of the SWAT landscape model. Hydrological Processes. 29(6):900-914. Interpretive Summary: River basin models are now commonly used in conservation and environmental assessments by USDA, USEPA, and others. However, most applications do not account for spatial positioning of land use and management across the landscape. In this study, a grid-based version of the SWAT (Soil and Water Assessment Tool) watershed model was developed to simulate the position of fields on the landscape. For example, a corn field in the flood plain may be managed and respond differently than a corn field on a ridge or hill slope. The model was tested at the ARS Little River Experimental Watershed near Tifton, Georgia, and results indicated it could accurately simulate water balance and transport across the landscape. The enhanced version of SWAT provides agencies and policy makers with a tool that can address landscape positioning for river basin scale assessments.
Technical Abstract: Integrated river basin models should provide a spatially distributed representation of basin hydrology and transport processes to allow for spatially implementing specific management and conservation measures. To accomplish this, the Soil and Water Assessment Tool (SWAT) was modified by integrating a landscape routing model to simulate water flow across discretized routing units. This paper presents a grid-based version of the SWAT landscape model that has been developed to enhance the spatial representation of hydrology and transport processes. The modified model uses a new flow separation index that considers topographic features and soil properties to capture channel and landscape flow processes related to specific landscape positions. The resulting model is spatially fully distributed and includes surface, lateral, and groundwater fluxes in each grid cell of the watershed. Furthermore it more closely represents the spatially heterogeneous distributed flow and transport processes in a watershed. The model was calibrated and validated for the Little River Watershed (LRW) near Tifton, Georgia (USA). Water balance simulations as well as the spatial distribution of surface runoff, subsurface flow, and evapotranspiration are examined. Model results indicate that groundwater flow is the dominant landscape process in the LRW. Results are promising and satisfactory output was obtained with the presented grid-based SWAT landscape model. Nash-Sutcliffe model efficiencies for daily stream flow were 0.59 and 0.63 for calibration and validation periods, and the model reasonably simulates the impact of the landscape position on surface runoff, subsurface flow, and evapotranspiration. Additional revision of the model will likely be necessary to adequately represent temporal variations of transport and flow processes in a watershed.