Effects of Ecological Stream Water Transfusion on Groundwater Level and Quality in the Lower Reaches of the Tarim River

The Tarim River is the largest continental river in China.It is(1 321) km in length,and its catchment area is 102×10~4km~2.The Tarim River Basin is rich in such resources as land,sunshine,oil and natural gas,and it is also an important base for cotton production and petrochemical industry and a strategic energy supply region in China in 21st century.Historically,the inflow of the lower reaches of mainstream of the Tarim River was plenitudinous,the natural vegetation mainly composed of Populus euphratica and Tamarix spp.grew luxuriantly,and a natural green corridor of 3km～10km in width formed in the eastern part of the Tarim Basin.The natural ecological process in the river basin has been significantly changed due to the change of natural conditions and the excessive exploitation and utilization of water resources since recent 50 years.The inflow of the lower reaches was sharply reduced since the 1990s,and the stream of the river section downstream from Yengisu was completely cut off.Because of the stream cut-off of the river section of 321 km in length at the lower reaches of the Tarim River,a sharp drawdown of groundwater level occurs,the natural vegetation relying on groundwater is degenerated,the forests of Populus euphratica are degenerated in large areas,wind erosion and land desertification become more serious,the ecosystems are seriously damaged.In order to save the green corridor,Ministry of Water Resources and People's Government of Xinjiang Uygur Autonomous Region determined to implement the project of transfusing stream water into the lower reaches of the Tarim River so as to restore the ecology in 2000.In this paper,the effects of ecological stream water transfusion on groundwater level and groundwater quality and the relationship between the change of groundwater level and groundwater quality in the lower reaches of the Tarim River are analyzed based on the monitoring data of the 6 times of ecological stream water transfusion and of 9 sections with 40 groundwater-monitoring wells in the lower reaches of Tarim River during the period from 2000 to 2004.The results showed that the groundwater level and groundwater quality in the lower reaches of the Tarim River have been significantly changed since implementing the project.The groundwater level along both riversides of the watercourse has been risen from 8m～11m in depth before implementing the project to 5m～6m;the contents of the main ions and mineralization of groundwater have been decreased.The extents of groundwater level rise and groundwater mineralization decrease are different in the regions with different distances away from the watercourse.