Testing the Addition of Topographic Features for Field Scale Infiltration Excess Water Quality Modeling in SWAT

Friday, 19 December 2014
Amy Collick1, Zachary M Easton2, Peter J A Kleinman1, Andrew Sommerlot2, Mike J White3, Daren Harmel3 and Daniel Fuka2, (1)USDA-ARS Pasture Systems and Watershed Management Research Unit, University Park, PA, United States, (2)Virginia Tech, Blacksburg, VA, United States, (3)USDA-ARS Grassland, Soil and Water Research Laboratory, Temple, TX, United States
Watershed planners and managers need reliable tools that can capture the spatial and temporal complexity of agricultural landscapes, and water quality models are increasingly relied upon to represent P loss from agricultural watersheds. While a significant amount of modeling work has attempted to incorporate factors controlling P loss (e.g. representing solubility, manure types, timing and application type), these models still typically require significant calibration and are thus difficult to apply meaningfully in areas without copious data with which to calibrate. This is partially because these models were never really intended as field scale tools, while we are trying to use them to define different hydrologic pathways, area weighted potential energy (slopes and saturated conductivities), and the resulting lag time of P in different transport states. The movement of water within the landscape as surface (or near-surface) storm runoff and interflow is driven by gravity, topography, contributing area and soil and landuse characteristics, which play roles in concentrating water flows. Soil surveys have played a key role in the development of pedology and spatially derived pedon soil maps have become valuable datasets for natural resource management. Unfortunately, the soil surveys, commonly available at ~1:20,000 scale, are not designed to provide the high-resolution models of the soil continuum required in field scale environmental modeling applications and site specific crop and water quality management. The goal of this project is to test a methodology designed initially for representing saturation excess hydrology in the SWAT model to incorporate topographic attributes, and resulting spatially explicit soil morphology, that are missing from standard SWAT model initializations.