1a.Objectives (from AD-416)
The overall objective of this project is to develop a national water quality modeling system that would provide input data for applications of multiple water quality models for EPA's Office of Water. The system will consist of input data organized around the National Hydrography Dataset (NHD) stream reaches and catchments, and input file configuration subroutines to support applications of both USDA's Soil and Water Assessment Tool (SWAT) and USGS's Spatially Referenced Regressions on Watershed Attributes (SPARROW). Phase II will include finer spatial resolution down to 4 square kilometer grid cells which allows local assessment. Phase II will also include simulation of the fate and transport of selected heavy metals and pharmaceuticals.
1b.Approach (from AD-416)
The Hydrologic and Water Quality System will be an extension of the Hydrologic Unit Model of the United States (HUMUS), which has recently been upgraded for USDA's Conservation Effects Assessment Project (CEAP). The system developed in this project will extend CEAP-HUMUS by upgrading modeling capabilities and improving the quality of input data. Specifically, input data will be re-formatted or replaced with data organized around NHD stream segments and catchment delineations.
The SWAT model was parameterized for the entire conterminous U.S. using 2,150 USGS (United States Geological Survey) 8-digit subwatersheds and more than 250,000 hydrologic response units to represent soil and land use heterogeneity. The model was calibrated and validated for flow, sediment yields, nitrogen, and phosphorus at more than 50 stream gauges across the U.S. We are currently downscaling to use 55,000 USGS 12-digit subwatersheds, with the ultimate goal of parameterizing SWAT for all watersheds defined by the National Hydrography Dataset (3,000,000 subwatersheds in the conterminous U.S.). A conceptual model for fate and transport of pharmaceuticals (hormones and antibiotics) across the landscape was refined. Experts in fate and transport of pharmaceuticals from LSU, Texas A&M, and Baylor were consulted to refine the conceptual model. It is currently being tested at the City of Austin biosolids application area and at the Shell Creek watershed in Nebraska. The ADODR works with Texas AgriLife Research, Blackland Research Center, to develop and review the reports before sending to USEPA. The reports document progress, identify issues, and ensure that the project is on schedule.