Effects of Riverbed Deposition and Water Consumption on Ecological Environment in Middle and Lower Sections of Upper Reaches of Mainstream of Tarim River

The riverbed has shown a deposition state in the middle and lower segment of the upper reaches of the Tarim River. The total sediment thickness is up to 120 cm in the recent 40 years,with an average annual of 3.0 cm. In which,the total sediment thickness is 50 cm in the period of 1965 to 1990,with a mean annual of 2.0 cm. However,in 1991 to 2007,the total sediment thickness is up to 70 cm,with an mean annual of 4.7 cm. The silting of the riverbed is accelerating. Due to the silting of the rivers,river flood cross-section shrink,floods spillover is increasing,leading to the water consumption showed an increasing trend in the upper reaches. And the upper reaches of the Tarim River has become the largest water consumption district since 2001. The average annual mountainoussediment load of three source flows is 6 310×104t,influx the Alar Station,which is the leading station of the Tarim River,the average annual mountainoussediment load is 2 050×104t. The mean annual sedimentation volume is 1 462×104t in the upper reaches of the Tarim River,accounting for 71.3% of the sediment load in Aral stations,and is the largest sedimentation area andflood overflow area and the water consumption district of the main streamin the TarimRiver. The annual sediment discharge is decreasing dramatically in the hydrological stations in the mainstreamof the TarimRiver. The channel of sedimentation is mainly the 318 km river which is from Shaya Twp-pasture to Yingbazha. The upper reaches of the TarimRiver is 495 km long,the average water consumption is 14.48×108m3,accounting for 31.5% in annual runoff of Aral Station. The middle reaches of the TarimRiver is 398 km long,the average water consumption is 24.84×108m3,accounting for 54.0% in annual runoff of Aral Station. The lower reaches of the TarimRiver is 428km long,the average water consumption is 6.68×108m3,accounting for 14.5% in annual runoff of Aral Station. The mean annual water consumption is 39.32×108m3in the upper and middle reaches,accounting for 85.5% in annual runoff of Aral Station. The upper reaches has became the largest water consumption district in Tarim River since 2001,that resulting in the water consumption reached 50.0×108m3in the upper and middle reaches in 2002,2005 and 2006,accounting for 88% of annual runoff of Aral station,and becoming the maximum in its history.