Study Of Clean Water Delivery Pattern Of Ecological Water Delivery Small Watershed In The Water Source Area Of Beijing And Tianjin

Based on the concept of ecological water delivering small watershed, this study focusedon the clean water delivering pattern. The basic task of water source area includes two aspects,the quantity and the quality of the water. While the quantity is enough for the downstreamarea, the quality of water needs to be ensured at the same time. In agricultural smallwatersheds, most of the pollution is caused by agricultural non-point pollution, but non-pointpollution is extremely hard to simulate and control due to its complexity. With thedevelopment of technology, GIS and erosion models have provided practical methods fornon-point pollution control.Using various methods, this study simulated and evaluated the pollution in the northeastgully watershed and finally gave some pollution control measures. The results are as follows:(1)With the application of GIS technology, a non-point pollution database wasestablished based on the DEM, remote sensing image and investigation of northeast gullywatershed, which laid the foundation for further study.(2)The pollution source was figured out by investigation, and the pollution load ofdifferent source was estimated. The result showed that the annual TN load was10038kg andthe annual TP load was1191.37kg. The pollution load from farmland was the highest amongall the sources, with the TN load of4151.67kg and the TP load of578.71kg. Meanwhile, thewater quality was monitored by monitoring points. The data showed that the water qualitywas obviously defined by the areas.(3) Based on the land use, soil properties, geology and hydrology of the watershed, thecritical source area of non-point pollution was identified and classified by using MUSLEmodel.The result showed that the critical areas were mainly distributed along the river,especially the farmland in the north and east part of the watershed. The proportion offarmland increased significantly while the pollution risk upgraded.(4) AnnAGNPS model was applied to the northeast gully watershed. First, the model wasevaluated by the rainfall data, and the correlation index were above0.8which means themodel is applicable. Then the simulation result showed that the annual runoff was29.98×105m3, the annual sediment was7.17×103t, the annual TN was8.28t and the annual TP was1.24t. The pollution load from farm land was highest with46.39%of total sediment,53.96% of TN，44.84%of TP. And the pollution were mainly distributed in June, July and August.(5) According to the evaluation of the pollution in the watershed, this study gave someadvices for pollution control which included policies for pollution source and measures forpollution approaches.