红枫湖流域非点源污染控制区划

非点源污染发生的广域性、分散性、随机性等特征使得对其进行效管控难度较大。以非点源污染关键源区识别为基础，对流域进行分区管控是实现非点源污染控制的有效途径。基于源头削减和过程管控协同管理的思路，将GIS技术、ArcSWAT模型、非参数检验和因子分析技术相结合，以农耕养殖程度较高的贵州红枫湖上游羊昌河流域为研究区，通过对流域近5 a非点源污染负荷特征进行模拟，识别影响非点源污染流失的关键因素，在此基础进行污染控制区划。结果表明：1）总氮和总磷负荷高风险区主要集中于地势较高且农业耕作活动频繁区域，刘官乡、黄腊乡、旧州镇及白云镇是非点源污染控制的重点乡镇；2）采用多因素方差分析7种不同因素对流域非点源污染负荷的影响程度表明，施肥量是影响总氮、总磷输出的最主要的因子，坡长、坡度及土地利用方式是次重要因子。针对羊昌河流域长期传统耕作以及化肥过量施用的现实特征来看，土壤有机磷的含量也会对总磷的输出产生一定的影响；3）羊昌河流域可划分为3个污染控制区，第1类：生态农业综合整治区（以近河道耕种区为主，面积254.4 km2）；第2类：污染治理区（农村生活及畜禽养殖区为主，面积405.74 km2）；第3类：生态修复区（高坡度强降雨区为主，面积464.47 km2）。研究结果可有效提升羊昌河流域非点源污染治理的效率，为水源地环境保护提供参考。

Zonation for nonpoint source pollution control in Hongfenghu reservoir watershed

Abstract: Eutrophication caused by the enrichment of nitrogen and phosphorus is degrading surface water quality throughout the world. Sources of nutrients include over-fertilized agriculture lands, urban areas with excessive usage of herbicides and insecticides, and eroded soils. Due to the variation of nutrient export over the area and time, it is difficult to identify, assess and control nonpoint source (NPS) pollution. The prevention and mitigation of NPS pollution have become priority tasks in water monitoring and restoration programs in many countries. The interaction of human activities with the inherent variations in soil type, climate, topography and hydrology gives rise to large spatial and temporal variation in nutrient concentrations in surface runoff. Many research efforts are made to explore the processes and spatial characteristics of NPS pollution for prevention and mitigation measures. Major pollutants, particularly from agricultural activities, which include nitrogen, phosphorus nutrients and sediment that have been released into aquatic environments, have caused problems in the Hongfenghu Reservoir watershed, Guiyang. It is necessary to identify the spatial and temporal distributions of NPS pollutants and the highly polluted areas for the purpose of watershed management. In this paper, GIS technology, ArcSWAT model, ANOVA (Analysis of Variance) and CA (Cluster analysis) were used to identify the zonation of NPS sources and control in Yangchanghe river watershed which is one of the main tributaries in northwest of Hongfenghu Reservoir watershed, with relative strong intensive agricultural activities. The results showed that the spatial distribution of NPS pollution load in Yangchanghe river watershed was of great heterogeneity, the agricultural land at higher elevation had the highest NPS pollution loads, and the Liu Guang, Huang La, Jiu Zhou and Bai Yun towns were identified as the critical towns for NPS pollution control. In addition, the most important factor for total N (TN) and total P (TP) loss was related to fertilizer application amount. Slope length, land use, and slope degree were also important factors. The content of organic P in soil may contribute to TP loss due to long term cultivation and overuse of fertilizer in Yangchanghe river watershed. Moreover, three zones for NPS control in Yangchanghe river watershed were divided as division zone for eco-agricultural area where the agricultural activities was intensive, pollution treatment zone where was a livestock production area and villages, and ecological restoration zone where there were serious soil erosions at higher elevation. Therefore, optimal strategies and practices were needed to simultaneously control P and N export at the farm and watershed scales. One water quality problem may be aggravated while solving another. In a humid-temperate climate, on-farm practices to reduce surface runoff and P export by increasing infiltration would typically increase ground water P concentration and NO3 leaching. Further, different nutrient control goals require adequate methods for different scales within the Yangchanghe river watershed. For the upstream fresh waters and the fresh water arms of the Yangchanghe river watershed, controlling P export should be the primary concern. For the upstream aquifer systems, and within the Hong Fenghu reservoir, controlling N export should be the primary concern.