Satellite-derived rainfall estimates for use in BASINS/NPSM for TMDL development

The University of Tennessee, in collaboration with the Tennessee Department of Agriculture (TDA) and the Tennessee Department of Environment and Conservation (TDEC), is evaluating the validity of the hydrological model Better Assessment Science Integrating Point and Nonpoint Sources (BASINS) for use in TMDL development. BASINS/GIS integrates a geographic information system (GIS), national watershed data, and state-of-the art environmental assessment and modeling tools into one package. Precipitation is a crucial link in the hydrologic cycle, and its spatial and temporal variations are enormous in East Tennessee. The objective of this part of our study is to evaluate the usefulness of satellite-derived rainfall estimates to improve the daily rainfall data for the BASINS model in our watersheds. If successful, the generated values will be used to create improved weather files for BASINS/HPSF (Hydrological Simulation Program-Fortran) and BASINS/SWAT (Soil and Water Assessment Tool). Model results of rainfall data will be compared with actual rainfall recorded Knoxville. So far, the satellite estimates do not compare well with the gauge data. In the future, we plan to look at the use of pixel averages, rather than individual pixels, as we did in this first approach. We plan to investigate the use of radar-derived rainfall estimates. Also, incorporation of remotely-sensed estimates in a GIS spatial analysis may hold some promise of improving rainfall estimates for given locations.