基于SWAT模型的小流域非点源污染负荷分布模拟研究

Simulation of Non-point Source Pollution Load Distribution in Small Watershed Based on SWAT Model

为了解小流域的非点源污染现状,拟采用水系分维值确定最佳集水面积阈值,在清溪河流域建立SWAT模型,研究该流域非点源污染负荷的时空分布规律。结果表明,清溪河流域最佳集水面积阈值为400 ha,划分为37个子流域;模型径流和氮磷模拟的决定系数R^(2)大于0.83,Nash效率系数大于0.58,表明SWAT模型在清溪河流域具有适用性;总氮、总磷年污染负荷与清溪河年径流量的相关系数高达0.87、0.91,正相关关系明显;年内丰水期总氮、总磷的污染负荷占比分别高达69.90%、73.33%,说明丰水期是产生非点源污染的关键时期;来自耕地的总氮、总磷污染负荷分别为3712.62×10^(3)、102.97×10^(3)kg,单位面积负荷分别为25.72×10^(3)、0.71×10^(3)kg/(a·km^(2)),远高于其他土地利用类型,表明农业生产和农村生活是清溪河流域产生总氮、总磷污染的重要污染源。

In order to understand the current status of non-point source pollution in a small watershed, this paper intends to use the fractal dimension of the water system to determine the optimal catchment area threshold, and establishes a SWAT model in the Qingxi River Basin to study the temporal and spatial distribution of non-point source pollution load in this watershed. The results show that the optimal catchment area threshold of the Qingxi River Basin is 400 ha, which is divided into 37 sub-basins;The determination coefficient R^(2) of the model runoff simulation and nitrogen and phosphorus simulation is greater than 0.83, and the Nash efficiency coefficient is greater than 0.58, indicating that the SWAT model is applicable to the Qingxi River Basin;The correlation coefficients between the annual pollution load of total nitrogen and total phosphorus and the annual runoff are as high as 0.87 and 0.91, and the correlation is obvious;The pollution loads of total nitrogen and total phosphorus during the wet water period of the year accounted for 69.90% and 73.33%,respectively, indicating that the wet water period is the key period for non-point source pollution;The total nitrogen and total phosphorus pollution loads from the cultivated land are 3 712.62×10^(3)kg and 102.97×10^(3)kg, and the unit area load is 25.72×10^(3)kg/(a·km^(2)) and 0.71×10^(3)kg/(a·km^(2)),respectively, which is much higher than other land use types, indicating that agricultural production and rural life are important pollution sources of total nitrogen and phosphorus pollution in the Qingxi River Basin.