GEOGRAPHIC ESTIMATION OF RUNOFF-MODEL PARAMETERS.

The U. S. Geological Survey is developing techniques to estimate and evaluate unit-hydrograph and loss-rate parameter values for rainfall-runoff models using Geographic Information System (GIS) procedures. The data base includes basin, soil, and climatological characteristics that will be stored in a GIS, and unit-hydrograph and loss-rate parameters obtained from calibration of a commonly used flood-hydrograph rainfall-runoff model for 616 storms in 98 gaged drainage basins. Development of unit-hydrograph and loss-rate parameter-estimation techniques includes statistical methods (exploratory data analysis, regression analysis, and categorical data analysis) to relate the model parameters to hydrologic characteristics. The estimation techniques are evaluated by use of error analysis of simulated hydrograph characteristics (peak discharge, flood volume, and time to peak discharge). The hydrographs will be simulated with parameters estimated by the techniques for (1) 102 storms occurring at 36 gaged basins; and (2) a large storm system (one which produced floods with a 50-to 100-year recurrence interval).