Study On Distributed Non-point Source Pollution Modelling And Its Control Strategies Of The Chengxi Reservoir In Chuzhou City

ChengXi reservoir is the unique surface drinking water source of Chuzhou city.The point source pollution around the reservoir has been controlled well, in recentyears while non-point source pollution has become the main reason for thepollution of Chengxi reservoir,therefore,it must be studied and controlledeffectively.Based on the pattern of land use/cover(LULC), a procedural model wasestablished to simulate the quantity of non-point source pollution exported toaquatic environment and retained by the different LULC on each cell.This studychose phosphorus as an example and did a simulation in the watershed of Chengxireservoir in order to discuss how to protect the water source, the non-point sourcepollution loads was estimated as well as the rule of spatiotemporal distribution ofnon-point source pollution in the watershed scale was analyzed, the temporal andspatial characteristics of the Land use/cover change(LUCC) between two keyperiods and its influence to the pollution loads were analyzed,while the CriticalSource Areas (CSA) were identified by this study. Furthermore, the quantity ofphosphorus exported to the reservoir and phosphorus retained were simulated under5different future land use/cover scenarios. Finally, the protection strategies for thewater source of Chengxi reservoir were suggested.The results showed that:(1)The total of phosphorus that was exported to the reservoir by LULC inwatershed was2085.65kg.a-1in2011.The quantity from farmland occupied85.48%of the total phosphorus loads., so farmland is the main source of non-point sourcepollution to Chengxi reservoir in the watershed.(2)The region beside the riverway in the middle of watershed and the placeXiaosha river entered the reservoir were the high hydraulic connectivity area. In2000and2010,the total of phosphorus that were exported to the reservoir by LULCin watershed was2580.38kg.a-1and2461.20kg.a-1. The Institute of AgriculturalScience, Chengjiao residents’ committee, the Institute of Aquaculture as well asTaiping village in the northwest of watershed were phosphorus critical source areas(CSA) for the exported phosphorus, these regions were the largest harm towater quality.(3)Most of the exported phosphorus was effectively retained by the differentLULC in the process of flow accumulation. In2000and2010, the total ofphosphorus that were prevented from entering the reservoir by LULC in watershedwas5774.49kg.a-1and5422.36kg.a-1. It occupied69.1%and68.8%of the totalphosphorus loads.The retained abilities of forestland and grassland were not bringinto full play due to the irrational distribution of existing LULC.(4)The national policies for returning farmland to forests guided the land coverchanges were based on the gradient. It was unsuitable to avoiding phosphorusnon-point source pollution of aquatic environment in this watershed.The trees andshrubs should be planted along the shore and on the intersection of the runoff, thegrassland should have a banding distribution nearby the gentle slope of farmland,therefore, it can largely improve the ecosystem services efficiency of forestland andgrassland setting vegetation buffer zones. The cells which exported phosphorusrelatively more were mainly distributed in the entrance from Xiaosha river toChengxi reservoir and besides the hydrographic net under different scenarios.