Research On The Response Of Groundwater Flow System In Yanqi Basin To Changing Environment

Located in Bayingolin Mongolian Autonomous Prefecture,Xinjiang,Yanqi basin has a plain area of6501.5 km~2.The major rivers and lakes in the basin are Kaidu River and Bositeng Lake.In recent ten years,the contradiction between the supply and demand of groundwater resources in Yanqi basin has become increasingly prominent.The exploitation quantity of groundwater continues to increase,and the groundwater level continues to decline,groundwater overexploitation is serious in some areas.On the basis of above reasons,this paper systematically analyzes the relationship between the changes of groundwater depth,degree of mineralization,exploitation quantity and groundwater flow system.The model of groundwater exploitation in Yanqi basin is analyzed through the calculation of water balance and the verification of numerical simulation,so as to promote the sustainable development of groundwater resources.The major conclusions are as follows:(1)Yanqi basin is classified into three water flow systems according to the hydrogeological conditions:Kaidu River-huangshuigou groundwater flow system,north mountain groundwater flow system and south mountain groundwater flow system.The area with the largest groundwater depth in Kaidu River huangshuigou groundwater flow system changed from 1?5m to 5?10m.The area with the largest groundwater depth in north mountain groundwater flow system changed from 1?3m to 5?10m.The area with the largest groundwater depth in south mountain groundwater flow system changed from 3?5m to 5?10m.(2)From 2010 to 2020,the quantity of groundwater exploitation has shown an overall upward trend,but it began to decrease slightly from 2015.From 2005 to 2014,the area of the Yanqi Basin with a buried depth of 1?3m decreased from 5371.71km~2to 266.69 km~2,and the area with a buried depth of 3?10m increased from 628.68 km~2to 3050.08 km~2.From 2014 to 2020,the buried depth of groundwater will be The area of 10?20m increased from 36.49%to 59.99%,and the area of buried depth greater than 30m decreased from 299.74 km~2to 190.12 km~2.(3)From 2010 to 2020,the amount of groundwater extraction has increased from 4.6×10~8m~3to5.5×10~8m~3,but the amount of groundwater extraction has declined slightly since 2015.From 2005 to 2014,the water level in the Kaidu River-Huangshuigou groundwater flow system basically showed a downward trend.The groundwater level in most areas fell by 3?5m,the water level in most areas in the north mountain water system groundwater flow system dropped by 15?20m,and the groundwater in the south mountain water system The groundwater level in the flow system decreased by 20m;from 2014 to 2020,the water level in the south bank of the Kaidu River in the Kaidu River-Huangshuigou groundwater flow system decreased by 15m,the water level in the western region of the Beishan water system groundwater flow system increased by 3?5m,and the water level in the eastern region decreased 1?3m,the groundwater level in the oasis area in the Nanshan water system groundwater flow system drops by 1?3m.(4)By calculating the groundwater balance,the groundwater recharge is 51927×10~4m~3,the discharge is 68213×10~4m~3.Two schemes are used to do the numerical simulation,one is groundwater numerical simulation on the basis of current conditions,and the other is numerical simulation on the basis of groundwater exploitable index.According to the simulation under the current conditions,there is still over-exploitation in some areas,and the groundwater level has a continued downward trend;the groundwater level simulation shows that the groundwater level has a rising trend as a whole.The area with a depth of 0?5m The drop from 573.78 km~2to 565.04 km~2can alleviate the occurrence of secondary soil salinization.