|Hjelmfelt Jr, Allen|
Submitted to: International Conference on Water Resources Engineering Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/11/2000
Publication Date: N/A
Technical Abstract: The performance of the Hydrological Simulation Program-FORTRAN (HSPF) version 11.0 in simulating the hydrology of a claypan watershed was evaluated, and model parameters needed to define the hydrologic behavior of claypan soils are discussed. Claypan soils are characteristically poorly drained, partially because of an argillic claypan horizon that limits groundwater recharge and promotes surface runoff and interflow. The claypan watershed studied was Goodwater Creek in Central MO. The topography consists of nearly level to gentle slopes and broad alluvial valleys dissected by small streams. Low permeability of the claypan layer coupled with the nearly level slope caused wetness problems during the rainy season. The model was calibrated using 3 yrs (1993-1995) of observed records from a 36-ha research field within the Goodwater Creek water- shed. The calibration revealed that some model parameters, most notably infiltration index, took numerical values outside recommended ranges to define the hydrology of the claypan watershed accurately. HSPF simulated mean annual streamflow that is strikingly close to the observed, 118.3 cm versus 114.3 cm for the 3 yrs, and consisted of reasonable portions of surface runoff, interflow, and groundwater flow. The simulated surface flow averaged 82% of total stream flow which matched the observation of 85%. However, the model tended to slightly but consistently under predict high peaks and over predict low peaks. After the model was calibrated based on the field data, it was applied to the 73 sq km Goodwater Creek watershed for 11 yrs (1985-1995) of hydrology simulation. Both field and watershed simulations indicate that with good calibration HSPF can simulate the hydrology of a claypan watershed with excellent accuracy.