| The eutrophication of the tributaries of the Three Gorges Reservoir area has deteriorated year by year,which has greatly affected the production and development of the people in the reservoir area,the safety of drinking water,and the sustainability of the ecological environment.Existing studies have shown that point source pollution such as enterprise sewage points,urban drainage outlets,etc.Under better control,agricultural non-point source pollution has gradually become the main culprit of serious eutrophication of the water environment in the reservoir area.How to scientifically prevent and control agricultural non-point sources in the reservoir area has become a hot topic of academic research.The Three Gorges Dam was completed in 2003.After the impoundment,the water velocity slowed down and the self-purification capacity decreased.If no measures are taken,the water pollution in the reservoir area will be aggravated and the sustainable development of the regional economy and society will be restricted.Therefore,exploring and analyzing the causes and changes of water pollution and how to effectively prevent it is a hot issue that many scholars and experts pay close attention to.In addition,the implementation of the Three Gorges Project resettlement will also have an impact on land use changes in the reservoir area,which may cause new soil erosion and biodiversity degradation.Effectively control the status of soil erosion in the Three Gorges Reservoir area,reduce agricultural non-point source pollution,protect the water quality of rivers,improve the capacity of forests to conserve water resources,reduce the frequency of flood disasters,curb the degradation of biodiversity in the reservoir area,and optimize the Three Gorges reservoir area as a whole The ecological environment,promoting the sustainable development of regional economy,has become the focus and goal of the entire country,government,society and scholars.As a key unit of the source of ecological problems in the Three Gorges Reservoir area,the villages along the banks of the Three Gorges Reservoir have rarely been studied.This paper takes Quxi Village,Zhenxi Town,Fuling District,Chongqing City as an example.Through practical investigation and theoretical analysis,a comprehensive analysis of the land use/cover change and its degree of land use in the study area is carried out,and the law of change is grasped.The scenario development model simulates the future land use pattern,evaluate the non-point source pollution load changes and ecological benefits of the land use pattern under different development scenarios,find out the best vegetation buffer configuration model that is in line with economic and social development and take into account the ecological environment protection of the coastal area,and plan the land use of the coastal villages,Ecosystem protection and restoration,and regional sustainable development provide scientific reference and decision support.Through the analysis of the dynamic change of land use,non-point source pollution load,configuration of different scenarios and the analysis of ecological benefits in Quxi Village,the following conclusions are drawn:(1)From 2001 to 2018 in Quxi Village,2001 was a natural village,and the land use structure from 2015 to 2018 was all expressed as cultivated land> woodland> grassland>construction land>water area.Cultivated land and forest land accounted for more than 70% of the village area in each year.Cultivated land first increased and then decreased.Forest land and water area showed a trend of first decrease and then increase;construction land and grassland were constantly increasing.Both the comprehensive dynamics of land use and the degree of land use showed a trend of first increasing and then decreasing.The main reason may be that the newly established shipyards along the coast of the village have absorbed young and middle-aged labor,making the use of cultivated land weaker.(2)Through the improved output coefficient model,using terrain index and vegetation coverage to correct the river inflow coefficient,the TN and TP load of Quxi Village in 2018 were simulated.The TN load discharge was 5,416.62 kg,and the TP load discharge was 635.66.kg,the unit load intensity is 11.33 kg/hm~2 and 1.33 kg/hm~2 respectively.Rural life and farmland pollution are the main sources of TN and TP pollution.(3)Through scenario analysis,six different scenario modes were set up,and buffer zones with a width of 100m-600 m were set up around the shore,and the improved output coefficient model was used to estimate the non-point source pollution load under different modes.The reduction rates of TN in these scenarios are 11.19%,16.34%,20.33%,23.54%,26.51%,28.88%,among which the first 100 meters setting has the largest reduction rate of TN pollution;the reduction rate of TP is 12.83% respectively,18.89%,23.50%,27.14%,30.63%,33.40%.Similarly,the first 100 meters setting has the largest reduction rate of TP pollution.(4)Through the establishment of an index evaluation system for the value of the ecosystem,seven types of ecosystem service function values for regulating water volume,purifying water quality,soil fixation,fertilizer preservation,carbon fixation,oxygen release,and maintaining biodiversity are selected,using market value method,The alternative market method and the outcome reference method are used to estimate the value of ecosystem services under different scenarios.The total value of ecosystem service functions in Quxi Village is 16.4564 million yuan,and the ecosystem service values under different scenarios are 2152.04,2438.84,2738.13,3,063.55,3,381.016,and 3,681.96 million yuan.The value of regulated water is the largest,accounting for more than half;The second is to maintain fertilizer and regulate the value of water.Through the analysis of the value of village ecosystem services combined with the cost,it is found that scenario6 is the most cost-effective.Scenario 6 can be promoted first when the ecological compensation fee is sufficient.Scenario 1 is more suitable when the cost is limited. |
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