AN EXAMPLE OF USING LANDSAT AND GOES DATA IN A WATER-BUDGET MODEL

Landsat and GOES satellite data are used in analyzing monthly water budgets on a 538-km2 watershed in central Oklahoma for 1984-1985. The budget components examined are water yield, percolation loss, evapotranspiration and change in soil water content. The hydrologic model employed is SWRRB (Simulator for Water Resources in Rural Basins) developed by the Agricultural Research Service of the U.S. Department of Agriculture. Landsat imagery is used to subdivide the basin into land covers for model application. The land cover subareas are more homogeneous than subbasins with mixed vegetation and their use allows tracking of the unique contribution of each type of cover to the water budget. Daily insolation is determined from GOES imagery. A comparison of budget components based on pyranometer insolation versus unbiased GOES estimates shows a maximum difference less than 4% and 5 mm for any component of the annual and monthly budgets, respectively. Satellite-derived temperatures are simulated by adding systematic and random errors to observed temperatures. A temperature bias of a few degrees greatly changes the growing season and monthly budgets of winter wheat.