本文利用SWAT模型结合实测数据,对南四湖流域2001-2010年年均非点源氮磷污染进行模拟,分析了南四湖流域非点源氮磷负荷空间分布特征,计算各河流流域对南四湖湖区污染的贡献率,并对非点源氮磷污染严重的关键区进行识别.研究表明:(1)先模拟湖东和湖西的两个典型小流域的非点源氮磷污染,并将模型推及整个南四湖流域,该方法不仅提高了计算效率,且得到了较好的模拟结果.通过对比发现,湖东的模拟效果要好于湖西,一定程度上说明SWAT模型在起伏较大的地区能取得更高的精度.(2)南四湖流域非点源氮磷污染严重,几乎所有区域的氮负荷超标,40％以上的区域磷负荷超标严重.湖东非点源氮磷污染较湖西严重,其中洗府河流域是南四湖湖区非点源氮磷污染的主要贡献者.(3)通过对径流量、泥沙负荷、氮负荷、磷负荷的相关分析可以得出,南四湖流域非点源氮负荷以溶解态为主,随径流进入水体；非点源磷负荷以吸附态为主,随泥沙进入水体.%SWAT model and measured data were used to simulate the Non-Point Source (NPS) N and P pollution from 2001 to 2010 in Lake Nansi watershed. The spatial distribution of the pollution was analyzed, and the contribution of all the rivers in watersheds to the pollution of Lake Nansi were calculated. The key areas with serious pollution were distinguished. The results indicated that: ( 1) typical watersheds were simulated with SWAT model, and then the derived models were used to simulate the Lake Nansi watershed. This method can not only improve efficiency, but also with higher simulation accuracy. The simulation results in the east of the lake were better than those in the west part of the lake, which indicated that SWAT model was suitable for the hilly areas. (2) The NPS pollution was serious in Lake Nansi watershed. The nitrogen loading exceeded the criteria in almost all regions, and the phosphorus loading exceeded the criteria in more than 40% of the region. The NPS pollution was more serious in east than that in west of the lake. The Guangfu River watershed was the major contributor to the NPS pollution in Lake Nansi watershed. (3) The soluble nitrogen, flowed into the lake through streams, is the main form of loading in Lake Nansi watershed. While, the P loading in Lake Nansi watershed was mainly in the form of adsorption, which ran into river with sediment.
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