| Agricultural non-point source pollution has become an important source of water pollution. Study on the distribution of non-point source pollution and affect of landscape pattern on non-point source pollution process has a great significance for non-point source pollution control and management. Though the Shuifumiao reservoir watershed is at medium eutrophication level, the eutrophication degree will be aggravating due to many contributing factors such as urbanization process, industrial development, livestock industry pollution and agricultural activities. Research achievements in fields of geography, landscape ecology and environmental science were used to identify the non-point source pollution source, analyst the distribution characteristic of non-point source pollution and discuss management control measures. The main research contents and conclusions are as follows:1. Through calibration and verification of runoff and ammonia nitrogen pollution load, SWAT model suitable for the study of non-point source pollution in Shuifumiao reservoir watershed.was established.Water quality monitoring data and runoff monitoring data from 2006 to 2009 were used for calibration and verification. Deterministic coefficient R2 and Nash-Sutcliffe efficiency coefficient ENS were selected as the indicators to evaluate the merits of the fitting results. R2 and ENS for runoff-fitting were 0.75 and 0.79, and for NH4+-fitting were 0.75 and 0.79. The results above indicated that the input data and parameters for SWAT model were the best ones.2. The sources of non-point source pollution and its distribution characteristic were identified.Agricultural land, orchard land, construction land and unclassified land were identified as the source landscape, and forest, grassland, and water area were identified as the sink landscape. Different land use types sorted by total nitrogen pollution load per unit area size is: construction land>agricultural land>orchard land>forest>grassland. The sources of non-point source pollution can be divided into three parts:sub-watersheds, area around the reservoir, and the reservoir itself. Proportion of three kinds of pollution source were 73.09%, 25.45%, and 1.46%. Non-point source pollution types can be divided into urban non-point source and agricultural non-point sources. Proportion of two kinds of types were 6.94%, 93.06%.The higher values of intotal nitrogen pollution load were in the agricultural and constructive concentration district. The land use within 100 meters around main channel have biggest impact on total nitrogen load. Total nitrogen pollution load per unit area showed significant correlation with Flowlength index, and increased along with increased connectivity between "Source" landscape and "sink" landscape. Total nitrogen load in 2006-2010 were 5.93 × 104t,5.08×104t,5.98×104t,5.89×104t and 6.37×104t, and increased year by year. The proportions of ammonia nitrogen, organic nitrogen and nitrate nitrogen were 64.90%,32.62% and 2.45% respectively. Over 85% of the pollution load is concentrated in the rainy season.3. Non-point source pollution control management practices were made by the optimization of land use pattern optimization and landscape management mode.Four measures were put forward. The first one was changing sloping land type. Total nitrogen was cutted down between 26.01% and 35.01%. The second one was establishing riparian buffers measured 5,10,15 and 20 metres across using herbaceous vegetation, shrub vegetation and grass-shrub compound vegetation. Total nitrogen was cutted down between 13.89% and 14.61%. The third one was changing crop production methods and management measures around the main channel within 100m. Total nitrogen was cutted down between 5.89% and 6.21%. The forth one was dividing the whole river watershed into ban area, restricted area, and suitable area for livestock, and would cut down 6.21% of the total nitrogen. |
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