Coupling simulation of water and energy budgets and analysis of urban development impact

A distributed watershed model-is developed for coupling simulation of hydrological and energy processes in watersheds with complex land covers. In the model, the state variables include depression storage on land surfaces or canopies, soil moisture content, land surface temperature, groundwater level, and river water stage. The subgrid heterogeneity of land use is also taken into consideration using a mosaic method. Estimation methods are proposed for impervious ratio of land use and parameters of soil, aquifer, and vegetation. The model is applied to the Ebi watershed in Japan and validated through comparing simulated river discharges, groundwater levels, and surface temperatures with observed values. In addition, impact of urban development on water budgets is shown through comparing two simulation results for present and future land uses. Lastly, mitigation alternatives of installing infiltration trenches and/or storm-water detention ponds are examined. Joint implementation of infiltration trenches and storm-water detention ponds is suggested for improving the hydrological cycle in the watershed.