The Study Of The Ecology Response And Ecology Water Guarantee After The Water Transfers In The Lower Reaches Of The Tarim River

From the first emergency water transfer in 2000, the lower reaches of the Tarim River, has carried on seven times during the seven years and the total water transfer quantity achieved 2.048 billion m3. It has brought the obvious change for the downstream ecological environment, particularly in the groundwater level and the vegetation coverage in 1920km2 study area.Firstly, based on the seven times water transfers data, this paper analyses the relation among the runoff losing rate, the flood peak impellent speed and the runoff volume, and simulates the current impellent character. Then it educes the linear equations of groundwater rising and dropping at different distance away riverway on the basis of the groundwater changes in all previous water transfers.Secondly, this paper analyses the vegetation response of the study area by using the MODIS NDVI data products. Through the data analysis and sampling, the conclusions can be drawn as follows: (1) The vegetation which different NDVI values represent has obvious response to water transfers, especially the desert decrease and the lower coverage vegetation increase remarkably. (2) There is a nicer relativity between the area of each kind of vegetation and the water transferring volumes. (3) By analyzing the vegetation index difference and the vegetation coverage, the variation of vegetation coverage has already achieved a better level after the first five-water transfers. And the following two water transfers keep and advance this benign change. (4) Under the linear water transfers, the response of vegetation has gradually tended to stabilization, and the each kind of vegetation pixels achieved a good configured proportion in 2005. (5) The vegetation change is quite limited as a whole, and cannot form corresponding microclimate. These show that only through the multithreading or planar water transfers can further improve the ecological environment of the lower reaches of the Tarim River.Finally, this paper discusses the problem of guaranteeing the ecological water utilization and attempts to study it by using the virtual water theory. Basing on the former studies, and through the virtual water theory, the Tarim River basin must reduce 50,000 hectares cultivated land at least in order to guarantee the downstream ecology water utilization. This can avoid increasing ecology water depending upon the heaviest rainfall years, and can increase the ecological water transferring contribution of the main current to the downstream, which has certain instructional significance to reality.