下垫面非均匀流域的幂指数TOPMODEL的模拟研究

Simulation Study of Power Law TOPMODEL for a Chinese Mountain Catchment with Inhomogeneous Underlying Surface Condition

利用取消流域土壤表层饱和导水率0K、土壤饱和导水率有效衰减系数m和地下水补给速率R为空间均匀假设的幂指数TOPMODEL,对流域水量平衡各分量进行敏感性研究试验,揭示空间非均匀性对幂指数TOPMODEL模拟结果的影响。从特定研究流域所得结果中可得的主要结论有:1)0K、m和R的空间变化对流域的逐日地表径流和基流以及逐日总径流有影响,针对设定的0K、m和R的空间变化,其中m的空间变化较明显地增加了逐日地表径流和洪峰流量。2)就设定的0K、m和R的空间变化而论,对流域多年平均年总径流以及蒸发模拟结果影响不大,但改变了径流在地表径流和基流之间的分配;其中R的空间变化影响最显著,m和0K的空间变化影响则较小。

The Topographic Index Model （TOPMODEL） has been implemented into land surface models （LSMs） to improve modeling of hydrological process components. In recent years, great effort has been made by many researchers for adjusting some of the assumptions contained in the classic TOPMODEL, which will broaden its application scope. For example, the general power law has been used to describe the variation of saturated hydraulic conductivity with depth as an extension of the classic TOPMODEL. Known as power law TOPMODEL, its derivation is based on the assumption of spatially uniform land surface. In this paper, the power law TOPMODEL is extended to a spatially inhomogeneous land surface with spatially non-uniform saturated hydraulic conductivity at the ground surface （K0 ）, effective soil depth （m）, and water recharge rate to the ground water （R）. In addition, numerical experiments with assumed spatial variable patterns of K0 , m, and R are conducted to evaluate the hydrological effects of the spatial heterogeneity. The main conclusions are as follows： 1） The assumed spatial distributions of K0 , R, and m affect daily surface runoff, daily baseflow, and daily total runoff. Among these, the spatial distribution of m significantly increases daily surface runoff and flood discharge. 2） The assumed spatial distributions of K0 , R, and m do not significantly affect the total runoff and evaporation averaged over many years, although they change the partition of total runoff between surface runoff and baseflow. In particular, the spatial distribution of R0 enhances averaged surface runoff of many years and significantly reduces the averaged baseflow during the same period. The other two variables change surface runoff and baseflow less than does the assumed spatial distributions of R0.