Study On The Non-point Source Pollution’s Mechanism Process And Simulation In Anjiagou Watershed

In this study, taking Anjiagou watershed of Gansu semi-arid hilly loess region as study area.The use of combining water quality tests with SWAT model method, the degree of surface source pollution and pollutant source were researched, the quantitative analysis of slope and channel non-point source pollution load of Anjiagou Watershed. The building suitable Anjiagou watershed runoff and sediment and non-point source pollution models, and the use of C henggou watershed source pollution model validate achieved, which obtained following main conclusions:(1) non-point source pollution sources and pollution levelsThe two small watershed observing non-point source pollution is serious, and water quality worrying 22 possible non-point source pollution indicators were detected in Anjiagou watershed. In different land use measures runoff, runoff pollutants CODMn, BOD5, NO2-N, NH3-N, TP, F-, Cr6+, TN 8 items were exceeded. The total load of the main pollutant runoff 2.018 kg?hm-2 is 2.68 times the total channel runoff pollutant loads, indicating that the slope is small watershed pollutant water pollution in the dominant factor. Pollutants appeared attenuation during runoff process, and the attenuation ratio reached 62.68%.(2) water quality analysis of different land use typesBy land- use practices, soil erosion and runoff characteristics of the combined effects of different land-use practices are quite different pollutant emissions, surface runoff water quality are exceeded, exceeding the average multiple of 3.45 times. Inferior Ⅴclass exceeded Multiples: shrubbery average exceeding 4.38 times, the average agricultural land exceeding 3.96 times, the average forest trees exceeding 3.63 times, the average slopes exceeding 3.53 times, and the average lawn exceeding 3.40 times and 1.19 times of the channel. For affected channel water quality was fromⅤto inferior Ⅴclass.(3) Anjiagou watershed SWAT runoff and sediment modelBased on SWAT model is to build SWAT model of Anjiagou basin, data series from 1982 to 2010 year were used to simulated of runoff and sediment process in Anjiagou watershed. The Nash-Suttcliffe coefficient and fitting coefficient were used to calculate for simulated values and measured values.The values of Nash-Sutcliffe coefficient, and that of the measured and simulation correlation in runoff and sediment calibration period were respectively 0.71, 0.62 and 0.73, 0.70, and the validation period were respectively 0.68,0.61 and 0.69,0.68. All reached the requirements of model simulation, the results have a certain cred ibility. O n this basis, the use of simulation parameters was to establish sediment runoff SWAT model Anjiagou Basin.(4) non-point source pollution of small watershed modelAdoption of the average density estimation method and use of SWAT runoff model for building non-point source pollution model of Anjiagou small watershed were conducted, while the C henggou watershed small river basin to validate the model were with relative error of-14.8% and the error acceptable range(±20%). It shows that the non-point source pollution model has practicability in this watershed.