Study On The Impact Of Land Use Change On Non-Point Source Pollution In Pengxi River Basin

As an important reserve of freshwater resources in China,the water quality conditions of the Three Gorges reservoir area not only affects the production activities and living water safety of residents in the Three Gorges reservoir area,but also the production and life activities,social and economic development of the residents in the middle and lower reaches of the Yangtze River region and the South-to-North Water Diversion Project.With the rapidly social economic developing and the strengthening of human production activities,the land use in the Three Gorges reservoir area has largely changed,which brought a large number of non-point source pollutants into the river,and has a huge negative impact on the reservoir water quality.This paper based on distributed hydrological SWAT model to simulate the non-point source pollution on Pengxi river basin and analysis their temporal and spatial distribution under land use change.Based on the hydrological response unit(HRU)to explore the impact of land use,soil and slope on non-point source pollution,and to analyzed the distribution of non-point source pollution in the basin,so as to provide important technical support for the rational planning of land use and management the river basin water environment on it and expand to other watersheds in the Three Gorges reservoir area The main research results are as follows:1.Based on Digital Elevation Model(DEM),land use and soil data,the Soil and Water Assessment Tool(SWAT)model for the Pengxi River Basin was established.The monitoring data of hydrology and water quality series from 2010 to 2014 was used to calibrate the parameters and validate the model.Results shows that the correlation coefficient R2 and the Nash-Suttcliffe coefficient(ENS)of the calibration period and verification period are greater than 0.71 for runoff,TN and TP simulation,which have a better accuracy of simulation.The Model simulation can meet the requirements of the study area.2.The temporal and spatial regularities of distribution of non-point source pollution in the Pengxi River Basin was simulated by the validated SWAT model.The pollution loads simulation showed that,total nitrogen and total phosphorus loads decreased with the rainfall varies from 2010 to 2014,the correlation coefficient between total nitrogen and total phosphorus loads with rainfall were 0.783 and 0.768,indicating that rainfall has important impact on the temporal variability of pollution loads,and its impact on total nitrogen loads was greater than total phosphorus loads.The spatial distribution of total nitrogen and total phosphorus loads were significantly affected by the comprehensive influence of rainfall and land use.The high pollution area were mainly located in the low-lying area on both sides of the river and tributary river,especially the middle and lower reaches of the Donghe River and the Yangtze River estuary.3.From 2000 to 2013,the land use change situation of the Pengxi River Basin was that,the biggest change in land use area was forest land,which increased from 47.79%to 61.58%,increasing by 13.79%.Farmland grassland area changed a lot.Farmland,which decreased from 31.89%to 24.75%,decreasing by 7.14%,and grassland decreased from 19.63%to 11.96%,decreasing by 7.69%.Other land area changed little.4.Based on the two periods of land use in 2000 and 2013,simulated non-point source pollution,and studied the effects of land use change on non-point source pollution.Under the current situation of land use in 2013,the total nitrogen and total phosphorus load were less than that in 2000 year.Based on the HRU output of the model,the annual average nitrogen and phosphorus load of different land use types under different slope and soil conditions were discussed.The results showed that under the same gradient and soil type,the largest load was farmland,the average annual nitrogen and total phosphorus load were 1631.47t and 146.34t respectively.