The Exploration Of Correlation Between Water Quality And Land Use/land Cover In Pengxi River Basin?modao River Basin In Three Gorges Reservoir

Water resources are an important material basis for sustaining human survival and supporting human development.Nowadays,water shortages and pollution have become serious global issues.The causes and solutions for exploring water environmental issues have become a major problem for all humanbings.In recent years,the amount of industrial and residential sewage discharge as well as the solid pollutants in the Three Gorges Reservoir Area has remained a high level.Fertilizers and pesticides are applied at a high rate and the flowing pollution from ships is gradually increasing.The natural ecology and environment itself are inherently fragile in the Three Gorges Reservoir area,because of the hilliness basins,with special geological structures,topography and subtropical humid monsoon climate,and meanwhile soil erosion is very serious.The main source of non-point source pollution comes from land,and its utilization mode has a significant impact on water quality.The Pengxi River and Modao River watersheds in the Three Gorges Reservoir area have similar geographical locations,natural and geographical conditions conditions.This paper takes Pengxi River,Modao River watershed as research objects.Water samples were collected from rivers to determine the the metal ions in the the section of Gaoyang Lake and the nutrients in the Pengxi River and Modao River.The indexs of water were combined with the land use/land cover data of 2010 and 2015 to analyze two watersheds and explore the effects of agricultural non-point source pollution on the water bodies.At the same time,the villages of Pengxi River and Modao River Basin were selected to investigate the household conditions of households and the use of pesticides and fertilizers in agricultural production.The paper took the use levels of pesticides and chemical fertilizers as dependent variables,and household income,educational level,and household income taking the agricultural labor force as independent variables,by constrcting logistic binary regression models to explore the factors that affected farmers' irrational use of pesticides and chemical fertilizers.Concluded as follow:(1)There is a significant correlation between dissolved Cr and dissolved Pb,Cu,Zn,Ca,and Hg in Gaoyang Lake water.Therefore,this article reveals that the source of Cr is relatively wide and Cr ions are associated with other metal ion pollution sources;during the water period(the period of slow flow in the main stream and the tributaries of the reservoir area),there is a significant difference in the mass concentration of metal ions between the sampling points,but in the low water level and the recharge period(periods where the flow speed of the tributaries and trunk water bodies in the reservoir area is fast),There is no significant difference in the concentration of metal ions studied between sampling sites;in spring,summer and autumn,the main source of Hg ions is sediment;the electrical conductivity of Gaoyang Lake has no significant correlation with metal ions,and the water electrolyte is mainly composed of non-metal ions.(2)The eutrophication in Pengxi River and Modao River is serious.At different water level periods,the nitrogen and phosphorus contents of the two tributaries are significantly different.During the periods of low and high water levels,the levle of nitrogen dominates in water eutrophication;during the discharge and impoundment period,phosphorus plays a leading role.According to the investigation of the land use changes from 2010 to 2015,a large areas of cultivated land and forest land had a downward trend,but industrial and mining,residential land had a rising trend.In the catchment area,nitrogen and phosphorus in water bodies were significantly positively correlated with the cultivated area and negatively correlated with the forest land.Comparing the 100 m,200,and 1km buffers,it was found that the relationship between land use and water quality was significant at the 100 m buffer scale.(3)The study of two watersheds in this paper shows that the upper villages have a lower income comparing to the estuary villages,and the means of livelihood are relatively simple;it is common that the local farmers lack the knowledge of non-point source pollution and the phenomenon of over-use of pesticides and fertilizers.The results reflect the current related issues of insufficient publicity and technical training;Through the Logistic binary regression analysis of the questionnaire,it is found that planting and breeding farmers are more inclined to overuse of pesticides and fertilizers.The survey shows that the single-growing farmer's labor force is older and the family's annual income is relatively low.There is not enough funds to purchase enough pesticides and fertilizers.Therefore,compared to the farmers who grow and farm,they tend to use pesticides and fertilizers at low standard rates.Households with large numbers of agricultural labor forces have little willingness to rely on excessive use of pesticides and fertilizers to obtain more agricultural products.