Hydrologic simulation of watersheds with artificial drainage

Abstract

A deterministic hydrologic watershed model that simulates the watershed discharge and soil moisture status continuously throughout the crop season was developed for drainage watersheds with depressional storage. The model simulates the processes of interception, surface storage, infiltration, surface runoff, soil profile storage, percolation to the water table, subsurface tile drainage, soil moisture redistribution, evapotranspiration, and routing through depressions, tile mains, and the drainage ditch. The resulting outputs are daily evapotranspiration, soil moisture status in the crop root zone, and watershed discharge. The model simulated the watershed discharge and soil moisture status of the 24‐mi² East Fork Hardin Creek watershed near Jefferson, Iowa, for the 1964 crop season as well as could be expected with the input data that were available. Discrepancies between the measured discharge and the predicted discharge were in part due to spatial variations in precipitation over the watershed, which were not accounted for in the model input data.