Study On Response Of River Water Quality To The Dynamic Of Land Use Pattern In The Quxi River Basin

With the accelerating of urbanization, the social economy develops fast, at the same time, humans are facing a huge eco-environmentalstress, especially the water environment pressure. Water resources arelife sourceof human beings’daily life and production processes safety is crucial to social development and stability.Therefore, it is significant to studying response ofriver water quality to the dynamic change of land use pattern.QuxiRiver is a tributary of Yangtze River. It rising in Zhongxiancounty, flows through Fengdu county and joins Yangtze atFulingcounty. In the sphere of Quxi river Basin,where landform is karsts type, hills and lower mountains are the main geomorphic type. Inthe drainage area of Quxi River, there arelarge areas of forest, dry land, paddy and building land, but there are no large-scale industrial land.It is a typical area where men subsist mainly on agriculture and grass-feeding Livestock. Along with the development of economy and the improvement of people standard of living, rivers water pollution becomes more and more obvious. In the drainage area of Quxi River, water is mainly influenced by economic progress and human life. In addition, after the Three Gorges Reservoir impounded, the basin area increased, some farmland have been drowned, this led to non-volatilized fertilizerused by farmers flowed into rivers. Water pollution threaten the health of human beings, therefore the protection of water quality is an important tasks for prctecting the environment.Taking Quxi river basin as the study area, using the three-period land use data in 2015-2014 years, the 1:50000 scale DEM data of Chongqing, and the water quality monitoring data as the basic data source, this article analyzes the time and space changes of land use and the time and space differences of water quality, and does a research about the relationship between land use and its pattern and water quality with the methods of redundancy analysis, Spearman correlation analysis, and multiple regression.The main conclusions:(1) In 2005-2014, both the type and pattern of land use have significant changes in Quxi river basin. The main changes of land use structure is the tendency of massive reductions of farmland area, a large increase of waters and construction land area, and a fluctuating change of forestland area, the land use pattern has a significant different and regular change of the time and space, the "farmland-forestland" type is the main composite type of the land use in Quxi river basin, the forestland of upstream in Quxi river basin has a geographic meaning, forestland and construction land of midstream has a geographic meaning, in addition, all the farmland, grassland, waters and construction land of downstream have a geographic meaning. Nevertheless, comprehensive index of land use in Quxi river basin has no obvious differences in time and space, and its value is between 257 to 263.(2) The overall condition of the water quality is poor in Quxi river basin, most of it is IV degree, and there is the high nitrogen concentration mostly. Also, The upstream water quality is superior to midstream and downstream water quality, the upstream water pollution is mainly affected by agriculture, and the midstream and downstream water pollution is mainly combined effected by agriculture and urban sewage.(3) The most significant correlation is between land use type and water pollution condition in the whole watershed scale. The most obvious impact on river water quality is cultivated land, forest land and construction land, among them, forestland mainly plays a protective role, while cultivated land and construction land play a deteriorated role. In addition, the land use pattern has obvious scale effect on river water quality, among them, landscape diversity has obvious positive effect on water pollution with a distance close to the river, landscape fragmentation has significant negative effect on water pollution with a distance close to the river, landscape aggregation has significant negative effect on water pollution with a distance close to the river, and interspersion & juxtaposition index has significant positive correlation with water pollution with a distance close to the river.(4) Human activities of agricultural production and social life are the main factors that lead to the deteriorated river water quality, also the land use and its pattern are one of the most significant impacts on water quality.