STORMFLOW SIMULATION USING A GEOGRAPHICAL INFORMATION SYSTEM WITH A DISTRIBUTED APPROACH1

With the increasing availability of digital and remote- ly sensed data such as land use, soil texture, and digital elevation models (DEMs), geographic information systems (GIS) have become an indispensable tool in preprocessing data sets for watershed hydrologic modeling and post processing simulation results. How- ever, model inputs and outputs must be transferred between the model and the GIS. These transfers can be greatly simplfied by incorporating the model itself into the GIS environment. To this end, a simple hydrologic model, which incorporates the curve num- ber method of rainfall-runoff partitioning, the ground-water base- flow routine, and the Muskingum flow routing procedure, was implemented on the GIS. The model interfaces directly with stream network, flow direction, and watershed boundary data generated using standard GIS terrain analysis tools; and while the model is running, various data layers may be viewed at each time step using the full display capabilities. The terrain analysis tools were first used to delineate the drainage basins and stream networks for the Susquehanna River. Then the model was used to simulate the hydrologic response of the Upper West Branch of the Susquehanna to two different storms. The simulated streamflow hydrographs compare well with the observed hydrographs at the basin outlet. (KEY TERMS: GIS; DEM; stormflow; modeling; distributed.)