基于HWSD的GSAC模型网格化产流参数估计与校正

针对基于网格的萨克拉门托模型(GSAC)产流参数难以估计的问题,提出利用世界和谐土壤数据库(HWSD)土壤属性数据估计和校正该模型产流参数的方法。首先,采用HWSD土粒百分含量和土壤质地分类数据估算流域各网格顶层(T层)与底层(S层)土壤的凋萎系数、田间持水量、饱和含水量等土壤水分常数;再采用一个气候指数和HWSD的T层张力水容量、田间持水量及凋萎系数推求GSAC模型上层厚度,继而利用上层厚度将流域各网格的HWSD土壤水分常数转换为GSAC模型上、下层土壤水分常数;最后利用GSAC模型上层厚度与转换了的土壤水分常数估计流域各网格的产流参数;在估计产流参数的同时,采用12个系数对这些产流参数进行校正,所有的校正系数通过自由搜索(FS)算法率定GSAC模型确定。呼兰河流域的应用结果表明:基于HWSD土壤属性数据估计GSAC模型网格化产流参数的方法简便易行,利用校正产流参数驱动的GSAC模型在率定期与验证期的纳什效率系数(NSEC)分别为0.81和0.83,与不校正产流参数情况相比,校正产流参数的GSAC模型能够取得更高的模拟精度。

Grid Runoff Parameters Estimation and Adjustment of GSAC Model Based on HWSD

The grid-based Sacramento (GSAC) model divides a basin into discrete areas using grids. Conventionally, it is difficult to achieve the grid parameter for runoff module of GSAC model. With an aim to solve this problem, a method for estimating the runoff parameters of GSAC model using the soil property data of harmonized world soil database (HWSD) was proposed, in which the physical and chemical characteristics of each soil layer were given on the basis of the division of topsoil (0~30cm) and subsoil (30~100cm). Firstly, the percentages of sand and clay content and texture classification in topsoil (T-layer) and subsoil (S-layer) of HWSD were extracted. And the data was used to estimate the soil water constants such as wilting point, field capacity and saturated water content in each grid. Secondly, the upper layer thickness of GSAC model was adjusted using wilting point, field capacity and tension water capacity of T-layer, and a climatic index defined as ratio of mean annual precipitation to potential evapotranspiration. In each grid, the soil water constants of T-layer and S-layer were converted into those in the upper layer and lower layer of GSAC model by upper layer thickness. Finally, runoff parameters in each grid were estimated using the upper layer thickness and the converted soil water constants of GSAC model. Meanwhile, totally 12 adjustment coefficients were used to adjust the runoff parameters, and all the adjustment coefficients were determined by the GSAC model via the free search (FS) algorithm. The results of model application in the Hulan River Basin indicated that it was feasible to estimate runoff parameters of GSAC model using HWSD soil property data;the better runoff simulation results were obtained by GSAC model using the adjusted runoff parameters;and Nash efficiency coefficients (NSEC) were 0.81 and 0.83 of the calibration phase and verification phase, respectively.