Application of a Distributed Hydrologic Model in Wei River Basin

摘要

In this paper, a conceptually - based distributed hydrologic model including components of canopy interception, evapotranspiration, snow accumulation and melt, and runoff generation via the infiltration excess and saturation excess mechanisms is proposed. Both vertical and horizontal water budgets are simulated at a daily time step, and the model is applied sequentially to a matrix of grid squares at each time step. The vertical water budget includes precipitation, canopy interception, snowmelt, surface runoff, subsurface flow and groundwater outflow. Each element of the grid square is simulated as five non - linear reservoirs: the interception storage, the storm flow storage, the subsurface storage, the groundwater storage, and the drainage storage. The actual storage contents in each reservoir vary for each time step and the maximum storage contents are different with the changes of land cover or/and soil type. Digital elevation data are used to integrate the topographic effecls on air temperature, precipitation, and wind speed. Evapotranspiration is estimated using a revised Penman equation that incorporates local net radiation, surface meteorology, soil characteristics, and moisture contents. Snow accumulation and melt are simulated using a simplified energy balance approach that includes the effects of local topography and vegetation cover. Overland flow is modeled by using kinematic equation and groundwater flow is simulated using a simplified Darcy routing scheme. The horizontal water budget accumulates surface runoff, subsurface flow and groundwater outflow from each element in a 4 - layer grid square, and the combined outflow is converted to streamflow and routed along the channel network. The model is applied at a 2 - km scale to the 139,000 km~2 Wei River basin, the largest subbasin of the Yellow River basin, and is tested using 4 years of recorded precipitation and meteorological datasets. Results of application shows that the conceptually - based distributed hydrologic model can reproduce major characteristics of the hydrograph with a satisfactory.