AnnAGNPS模型应用于辽河源头小流域的主要参数确定方法

Methods for determining the main parameters of AnnAGNPS model applied to the watershed of the source areas of the Liaohe River

农业非点源污染已成为辽河源头区水体污染的治理重点,农业非点源污染模型AnnAGNPS(Annualized Agricultural Non-point Source Pollution Model)模拟农业非点源污染是可行的,但模拟精度取决于模型参数.本文以辽河源头区典型小流域为例,根据集水区的划分与流域非点源污染的空间分布密切相关,以不同的临界汇水区面积CSA(the critical source area)和最小初始沟道长度MSCL(the minimum source channel length)划分出不同数量的集水区进行多次模型模拟,当多种污染源负荷均趋于稳定时确定集水区单元划分数量;针对我国土壤普查数据的土壤质地体系与建立AnnAGNPS模型的土壤质地体系不同,假设土壤累积粒径成对数正态分布,利用插值进行土壤粒径的转换,采用EPIC(Erosion-Productivity Impact Calculator)模型计算土壤可蚀性因子;经多次模拟实验与野外实测数据分析,上述确定参数方法是可行的.

Non-point source agricuhural pollution has become the focus of water pollution control in the source areas of the Liaohe River. Although AnnAGNPS model is applicable in simulating agricultural non-point source pollution, the accuracy of model results depends on the reliability of the model parameters. In this paper the watershed of the source areas of Liaohe River was taken as a case study. As the sub-division number of a watershed is closelyrelated to the spatial distribution of non-point pollution sources, the CSA （critical source area） and MSCL （the minimum channe! length） were iteratively employed to determine the number of sub-division of watershed and it was captured when a variety of non-point source pollution loads were stabilized. As the soil texture system in the Chinese Soil Survey is different from that used in AnnAGNPS,the soil erodibility factor was calculated by using EPIC model after the soil textures were adapted to AnnAGNPS model by interpolation method, with an assumption that the soil cumulative sizes follow the lognormal cumulative. The methods of determining the parameters were proved feasible by comparing the simulated results with the field survey data.