Recent Changes in the River Hydrological Characteristics of the Tarim River Basin

The Tarim Basin is in northwestern China,in the southern part of the Xinjiang Uygur Autonomous Region,and the total area is 5.5×105km2.High mountains around the basin prevent ocean air from flowing into the basin.High temperatures,strong winds,and high evaporation rates in the basin result in a very dry climate;annual precipitation averages about 30-60 mm.Surface water and groundwater,recharged mainly by the melting ice and snow from the mountains around the basin,nourish various oases in the basin.Total water resource is 429×108m3 in Tarim River basin,with relatively scarce water and very weak ecological environment.Glaciers cover about 23628.98 km2 of the mountains around the Tarim River Basin,with 2669.435 km3 ice volume;the melt water resources released from the glaciers is about 15×109 m3 per year, roughly 40% of wholly surface water in the Tarim Basin.A number of rivers fed by snowmelt and glacier melt begin in the mountains and drain into the basin with average annual virgin flow of about 35 billion m3.Peak flow months in the rivers are July,August and September.Lowest flow occurs in the period from January through April.Around the rivers may be found oases of small villages and agriculture.The Aksu,Hotan,Yarkant and Kaidu-Konque Rivers are four source rivers of Tarim River drainage.The three tributary river systems that contribute flows to the Tarim River(Aksu,Hotan and Yarkand) join just above the Aler gauging station where the Tarim River begins.In addition the Kaidu-Konque River Basin,which is hydrologically separate from the Tarim River,contributes water to the Tarim River by means of a man-made transfer channel.A number of other subbasins exist within the Tarim Basin that do not contribute flows to the Tarim River because all of their flows either naturally evaporate in the desert or are used in irrigated agriculture areas.The two main subbasins in this category are the Kashgar River and the Weigan River.The Tarim River had historically nine river water systems with 144 tributaries combined as a Tarim River System.As climate changing and human activities are increasing to affect on the ecological environment,the Tarim River now become a pattern of four sources river systems and a mainstream system.Based on hydro-meteorological monitoring data including precipitation,evaporation,runoff,floods,bedload,and water quality in Tarim river basin in past 50 years,this paper details with the deterioration of the ecological environment causes and recent changes of the river hydrological characteristics in the Tarim River Basin.