Author(s): Fred L. Ogden; Sharika U. S. Senarath

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Abstract: Distributed-parameter hydrologic models are increasingly being used to assess the impact of land-use and/or climatic change on watershed hydrography. These studies require the modeling of the soil moisture storage as well as the water-fluxes to and from the soil layer over an extended period of time. This requires re-casting the traditional role of a rainfall-runoff model from event-based to continuous form. The two-dimensional, physically-based, distributed-parameter hydrologic model CASC2 D (Julien et al. 1995) used in this study has adequate parameterization to simulate infiltration into a deep soil layer (Ogden and Saghafian, 1997). Hence, in this study, evapotranspiration is added to CASC2D using two different approaches. The first method considers bare-ground evaporation from the land-surface using a formulation suggested in Deardorff (1978). The second method estimates the evapotranspiration from a vegetated land-surface using the Penman-Monteith equation (Monteith, 1965,1981). Continuous simulations are found to improve calibration uniqueness for distributed parameter, physically-based hydrologic models.

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Year: 1997