The Effect Of Land Use And Landscape Pattern On Water Quality In Sancha River

Sancha river is the important tributary of the Wujiang river. The main characteristics of the Sancha river basin are the intense rocky desertification, the serious soil erosion, the low vegetation coverage and the fragile ecological basis, therefore focusing on the water quality and improving the water environment quality of Sancha river is crucial to protect the water quality of Wujiang river. Based on the sampled data of Sancha river basin in August and February 2014, the remote sensing image of Sancha river basin in 2014 and 90 m digital elevation model(DEM), the article study the effect of land use and landscape pattern on water quality under the sub-basin scale and cushion belt scales with the statistical methods. The main conclusions are as follows:(1) In 2014, the land use of Sancha river basin was dominated by forest-land and farm-land, accounted for over 80% of the total area. All forms of land use in the basin were distributed in the area with the height from 1200 m to 2200 m and the slope from 8 degree to 25 degree. In the riparian buffer area, with the radius of buffer area increasing, the ratio of the farm-land and building-land was gradually reduced in the area, and the ratio of forest-land and grass-land was gradually increased.(2) Contrasting the effect of sub-basin scale land use on the water quality with the effect of buffer area scale land use, the parameters of water quality(TN, TP, NH3-N)are significantly affected by land use under the sub-basin scale in the area. The forest-land and grass-land have positive effect on the water quality. Conversely, the farm-land, building-land and basin have negative effect. The result of redundancy analysis is that the nitrogen and phosphorus of high flow period are mainly from the farm-land and unapplied-land. However, the phosphorus of low flow period are mainly from farm-land.(3)In the high flow period, there is a significantly positive correlation between TP and Number of Patches(NP), and a significantly negative correlation between TP and Fractal dimension(F); In the low flow period, there is a significantly negative correlation between TP, TN and Contagion Index(CONTAG), and a significantly positive correlation between TP, TN and Shannon Diversity(SHDI), Shannon evenness(SHEI). In two periods, Largest Patch Index(LPI), Contagion Index(CONTAG) were negatively correlated with the export of TN, TP, NH3-N, pH, COD and Edge Density(ED), Shannon Diversity(SHDI), Shannon evenness(SHEI) was notably positively correlated with the export of TN, TP, NH3-N, pH, COD. Compared with the structure of land use, only a few landscape pattern index could be used for forecasting the export of NH3-N, TN in the water, and the correlation between most landscape pattern index and water quality is weaker than the correlation between land use and water quality.