The effect of watershed scale on HEC-HMS calibrated parameters: a case study in the Clear Creek watershed in Iowa, US

摘要

In this paper, we use the Hydrologic Modeling System (HEC-HMS) to simulatetwo flood events to investigate the effect of watershed subdivision in termsof performance, the calibrated parameter values, the description ofhydrologic processes, and the subsequent interpretation of water balancecomponents. We use Stage IV hourly NEXRAD precipitation as themeteorological input for ten model configurations with variable sub-basinsizes. Model parameters are automatically optimized to fit the observeddata. The strategy is implemented in Clear Creek Watershed (CCW), which islocated in the upper Mississippi River basin. Results show that most of thecalibrated parameter values are sensitive to the basin partition scheme andthat the relative relevance of physical processes, described by the model,change depending on watershed subdivision. In particular, our results showthat parameters derived from different model implementations attributelosses in the system to completely different physical phenomena without anotable effect on the model's performance. Our work adds to the body ofevidence demonstrating that automatically calibrated parameters inhydrological models can lead to an incorrect prescription of the internaldynamics of runoff production and transport. Furthermore, it demonstratesthat model implementation adds a new dimension to the problem ofnon-uniqueness in hydrological models.