Development of WEP model and its application to an urban watershed

A distributed hydrological model, water and energy transfer processes (WEP) model, is developed to simulate spatially variable water and energy proces ses in watersheds with complex land covers. In the model, state variables i nclude depression storage on land surfaces and canopies, soil moisture cont ent, land surface temperature, groundwater tables and water stages in river s, etc. The subgrid heterogeneity of land use is also taken into considerat ion by using the mosaic method. For hydrological processes, evapotranspirat ion is computed by the Pemnan-Monteith equation, infiltration excess during heavy rains is simulated by a generalized Green-Ampt model, whereas satura tion excess during the remaining periods is obtained by doing balance analy sis in unsaturated soil layers. A two-dimensional simulation of multilayere d aquifers is performed for groundwater flow. Flow routing is conducted by using the kinematic wave method in a one-dimensional scheme. For energy pro cesses, short-wave radiation is based on observation or deduced from sunshi ne duration, long-wave radiation is calculated according to temperatures, l atent and sensible fluxes are computed by the aerodynamic method and surfac e temperature is solved by the force-restore method. In addition, anthropog enic components, e.g. water supply, groundwater lift, sewerage drainage and energy consumption, etc. are also taken into account. The model is applied to the Ebi River watershed (27 km(2)) with a grid size of 50 m and a time step of 1 h. The model is verified through comparisons of simulated river d ischarges, groundwater levels and land surface temperatures with the observ ed values. A comparison between water balance at present (1993) and that in the future (2035) is also conducted. It is found that the hydrological cyc le in the future can be improved through the implementation of infiltration trenches for the storm water from urban canopies. Copyright (C) 2001 John Wiley & Sons, Ltd.