Environmental Modeling of a Claypan Watershed using HSPF
The Hydrological Simulation Program FORTRAN (HSPF) is a comprehensive, continuous model designed to simulate watershed hydrology and water quality. Its performance in simulating surface runoff, sediment, and pesticide loss from Goodwater Creek, a 72.8 km2 (28 mi2) USDA agricultural research watershed, was evaluated. The watershed is located in Central Missouri in the Central Claypan Major Land Resource Area (MLRA 113) and has a nearly level to gently sloping surface. The low permeability of the claypan layer coupled with the nearly level slope causes unique hydrologic problems. In this evaluation, most of the model parameters related to hydrology, sediment, and pesticide transport were carefully selected from previous studies. Some of the model parameters were directly calculated and others were calibrated, based on the detailed field data on hydrology, water quality, and field operations such as cultivation and chemical application - from a 36 ha (89 ac) research field within the Goodwater Creek watershed.
For accurately simulating watershed responses, field activities were considered by using the SPEC-ACTION block in HSPF. The calibration revealed that some model parameters, most notably infiltration index, take numerical values outside recommended ranges in order to define the claypan watershed behavior accurately. With a proper calibration, however, the HSPF model simulated runoff, sediment yield, and chemical loss from the Goodwater Creek watershed well.
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