Simulation Of Agricultural Non-point Source Pollution In Zhongtianhe Catchment Based On AnnAGNPS Model

The Zhongtianhe catchment is a part of the source conservation areas of Tianmu Lake Reservoir, which is60million people drinking water source of Liyang City Jiangsu Province, and the agricultural non-point source pollution has been very prominent in this catchment. Based on the investigation of the present non-point source pollution, this paper used AnnAGNPS to quantify the catchment non-point source pollution output load and analyze its present station and the variation of spatial and temporal. For the current pollution Situation, proposing the management of reservoir water quality improvement and upstream of the reservoir catchment pollutant reduction, this provide importance reference for further studying the non-point source pollution, the control of water quality deterioration and ensure drinking water in drinking water sources safety, and Provide the basis for the government’s non-point source pollution control planning and macroeconomic policy-making. Therefore, it is significant to research the agricultural non-point source pollution in Zhongtianhe catchment.Zhongtianhe catchment was the study area, the data source based on the1:50000topographic maps and aerial images visual interpretation of2009, through the comprehensive collection the basin-information and the data about water quality, weather, vegetation, soil, geology and geomorphology, establish the AnnAGNPS model database, analyze the sensitivity of the model parameters and calibrate and validate model output for the model, the following conclusions:(1)Through established the non-point source pollution model AnnAGNPS datebase of Zhongtianhe catchment, and then carried through calibration and validation. The model was suitable for the study of non-point source pollution load in the Zhongtianhe catchment. Zhongtianhe catchment was simulated by the AnnAGNPS model, the average annual runoff depth is358.15mm, the total output of sediment were19,805.4t, the average annual output of the total nitrogen and total phosphorus were26.61and5.13t. The average annual sediment, total nitrogen and total phosphorus output intensity are414t/km2·a,556.7 kg/km2·a and10.7kg/km2·a, respectively.(2) The spatial differentiation characteristics, of nitrogen, phosphorus and sediment is distinctive, and the spatial distribution is similar. The more serious areas of Nitrogen and phosphorus pollution output are mainly concentrated in the middle and lower reaches of the terrain is flat agricultural land area. The sediment output is more strongly in the river downstream and the west bank of middle reaches; the sediment output is general in the upper reaches where the soil type is skeleton soil; the sediment output is weak in east bank of the middle reaches and the west bank of the river downstream.(3) The law of time-varying characteristics of non-point source pollution load output was similar. The rainfall was higher and the non-point source pollution load was much more. The disparity of the non-point source pollution is large between different month or season in the same year. The main non-piont source pollution load were in the summer and autumn, the total nitrogen load account for59.64%and18.28%; and the total phosphorus load account for63.84%and18.06%, respectively. The rainfall is the direct dynamical of non-point source pollution. Compared with sediment and nutrients of nitrogen and phosphorus, the runoff simulation value of rainfall is more consistent trend over time. And, the peak value of the rainfall and the different non-point source pollution load appeared in the same month.(4) According to the condition of non-point source pollution in Zhongtianhe catchment, we have put forward correlative countermeasures and measures.