Methods for determining the main parameters of AnnAGNPS model applied to the watershed of the source areas of the Liaohe River
AnnAGNPS 模型应用于辽河源头小流域的主要参数确定方法

Non-point source agricultural 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 closely related to the spatial distribution of non-point pollution sources, the CSA (critical source area) and MSCL (the minimum channel 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.