Impact of running water transport to the mainstream of the Tarim River on ecological efficiency of the river

The mainstream of the Tarim River extends 1 321 km to Taitema Lake.In 2005,stream flow at the Aler Gauging Station where the Tarim River begins was 57.18×10~8 m~3,it belongs to a high flow year.The inter- zone water consumptions are estimated to be 31.63×10~8 m~3 at the upper course,18.93×10~8 m~3 at the middle stream and 7.206×10~8 m~3 at the down stream in the Tarim River mainstream.The riverbed of the Xinquman Station was filled up from 1960 to 2004 and the total thickness of sediment was 120 cm,while the average sediment discharge at Aler was 2 283×10~4 t/a.Due to the riverbed filling up and flood flowage increasing continually,thev made the water consumption of the upper course rising trend ceaselessly.The ecological water transportation to the green corridor for the lower reaches of the Tarim River from 2000 to 2005 accounted 7 times for 6 years with accumulative total of 900 days,by using the favorable opportunity of high flow years of the Kaidou-Kongjie river at first stage and water-saving measures in the integrated rehabilitation for 3 source rivers of the Tarim River at later stage.The water volume of 25.06×10~8 m~3 were transported from Bosten Lake and the mainstream,the water transportation to river courses of lower reaches reached 20.4×10~8 m~3 at the sluice of the Daxihaizi reservoir,and the water was reached Taitema Lake five times.2005 was a milestone year with the fifth water flowing into Taitema Lake continuously.Transporting water in 7 times are not only improving the ecological condition for the green corridor at the lower reaches of the Tarim River,but also recovering the ecological Populus diversifolia and forest-grasses of both banks along the mainstream more quickly,and coming back the river ecological system injured before in the whole course of flowing water at the mainstream of the Tarim River. There were forest land and grassland of 142.1×10~4 hm~2 in area in the mainstream valley,among them 46.9×10~4 hm~2 in the upper reach,which occupied 33.0% of total forest-grass lands and situated at second position,81.1×10~4 hm~2 in the middle reach,which occupied 57.1% and belonged to first position,14.1×10~4 hm~2 in the lower reach,which occupied only 9.9% thirdly.The present ratio of allocation water has lost the harmony, compared with the water consumption of ecological forest-grass lands of the upper reach if the water volumes for upper,middle and lower reaches are allocated according to allocation of the initial water rights in the Tarim River basin.To ensure water transport forever along the Tarim River mainstream and maintain its ecological function in the region,it is urgently recommended that the ratio releasing water to the upper,middle and lower courses of the mainstream based on protecting ecology is further adjusted through the measures of controlling and dredging up the upper course etc.It is possible to realize the ecological river objective of comprehensive rehabilitation in the Tarim River basin.