Water And Soil Resources Sustainable Untilization In Yanqi Basin Of Xinjiang

The project area, the Yanqi basin, is located in the Northwestern Chinese province of Xinjiang. The climate is continental and dry with low precipitation and high evapotranspiration. The Basin has plentiful water and soil resources, but irrational exploitation pattern results in soil salinization of farmland and polluted ecological environment of Bostan Lake. So it is significant to optimize rational water and soil resources exploitation for local economy and environment sustaining development.Based on explanation of the remote sensing image and the analysis of the chemical composition of salt-affected soil it is concluded that soil salinization in project area is very serious and almost 24% farmland are salinizated and soil salinity increases from the fringe of the torrential fan to the shore of salted lake. The salt type is mainly chlorinate-sulfate and sulfate and salinity in wasteland tends to accumulate at the soil surface while the salinity in farmland tends to be washed to lower soil. Natural factors cause the soil salinization such as high-salinity soil composition, viscous soil texture and dry climate conditions, but the chief reason is the high groundwater table caused by human irrational irrigation.Based on the analysis of the water-salinity dynamics and according to the different salinization characteristics in up-stream field, corps'field, farmers'field and down-stream field Yanqi basin's salinized soil is divided into stabilization desalting soil, desalting and salting soils that are mixed, desalting or salting soil that alternatively occurs and last salting soil. According to the different types different measures are proposed.SEBAL models with satellite image ETM+ and MODIS are established to calculate basin's evapotraspiration and the results are validated with actual data and Penman formula. According to the results of ETM+ image, it is concluded that the lower the mineral concentration of water the higher the evapotraspiration, the larger the area of water the smaller the evapotraspiration and the evapotraspiration of marsh is higher than the lake. According to the results of MODIS image, it is concluded that in arid basin of northwest area the higher the temperature the higher the evapotraspiration and the faster the wind speed the higher the evapotraspiration. Based on the contrast of the two images their respective characteristics and application in evapotraspiration researches are evaluated. Then on the basis of different areas with different evapotraspiration the impact of evapotraspiration on soil salinization is explained and it is concluded that high evapotraspiration is an important factor for salinization but thick salt on the surface to some extent can limit underground water's evaporation to prevent more serious salinization.The paper indicates that oasis's development and Bostan's environment improvement are incompatible contradiction under present water and soil resources exploitation pattern based on the discussion of the mechanism of the interaction between the environmental change of Bostan Lake and the environmental change of oasis in Yanqi Basin. And it points out that only through lowering groundwater table, optimizing the water and soil resource exploitation and reducing ineffective evaporation by the greatest degree can oasis's economy and Bostan Lake's environment develop sustainingly and harmoniously.