基于地形特征的流域水文相似性

流域地形控制着地表径流的路径和累积水量的空间分布。地形指数ln(a/tanβ)反映了径流在流域中任一点的累积趋势以及重力使径流顺坡移动的趋势,流域地形可以用地形指数的空间分布来表示。地形指数可用作水文相似性指数,即具有相同地形指数的点对降雨具有相同的水文响应。TOPMODEL利用地形指数频率分布计算流域径流过程,可以认为:具有相同地形指数频率分布的流域具有水文相似性。分析认为长江流域上游的沿渡河流域与香溪河流域具有水文相似性,利用香溪河流域率定的模型参数计算的沿渡河流域径流过程,与实测过程拟合较好

Hydrological similarity of catchments based on topography

The topographic index ln( a /tan β ) is an important parameter of many physically based hydrological models In terms of a DEM, a is the cumulative upslope area draining through per contour length to a pixel, which reflects the tendency of water to accumulate at any point in the catchment, tanβ is the local slope angle of the cell, which reflects the tendency for gravitational forces to move that water downslide Catchment topography generally have a major control overflow pathways for surface flow processes and an important effect on parttern of likely water accumulation in the catchment The catchment's topography may be summarised by the distribution of the index values The topographic index may be used as an index of hydrological simularity All points with the same value of the index are assumed to respond in a hydrologically similar way Frequency distribution of the index is used in TOPMODEL for simulating hydrographs It may be expected that the catchments with the same frequency distribution of the topographic index have hydrological similarity A simple algorithm for the calculation of topographic index ln( a /tan β ) is used, In the algorithm, a and tan β of each cell is extracted separately ,and the cells, whose slope is zero, are treated specially so that ln( a /tan β ) can be calculated The frequency distribution of the topographic index ln( a /tan β ) is obtained It can be found that Xiangxihe catchment and Yanduhe catchment have hydrological similarity The frequency distribution of the index and estimated TOPMODEL parameters of Xiangxihe catchment are used to simulate the hydrographs of Yanduhe catchment and good results are obtained