AUTOMATED CALIBRATION APPLIED TO WATERSHED-SCALE FLOW SIMULATIONS

Complexity in simulating the hydrologic response in large watersheds over long times has prompted a significant need for procedures for automatic calibration. Such a procedure is implemented in the Basin-Scale Hydrologic Model (BSHM), a physically-based distributed- parameter watershed model. BSHM simulates the most important basin-scale hydrologic processes, such as overland flow, ground-water flow, and stream-aquifer interaction in watersheds. Here, the emphasis is on estimating the ground-water parameters with water levels in wells and ground-water baseflows selected as the calibration targets. The best set of parameters is selected from within plausible ranges of parameters by adjusting the values of hydraulic conductivity, storativity, ground-water recharge, and streambed permeability. The baseflow is determined from streamflow hydrographs by using an empirical scheme validated using a chemical approach to hydrograph separation. Field studies determined that the specific conductance for components of the composite hydrograph were sufficiently unique to make the chemical approach feasible. The method was applied to the Big Darby Creek Watershed, Ohio. The parameter set selected for the ground-water system provides a good fit with the estimated baseflow and observed water well data.

Hydrological Processes, in press, 1998.

8/26/98