Study On The Sustainable Yield Of Groundwater In Yanqi Basin, Xinjiang

Yanqi Basin is located in Xinjiang Uygur Autonomous Region. Recently, Plain of the middle and lower reaches of the basin water table generally increased, about 62% of the irrigation area groundwater level is less than 2m, most of the soil in the plains have seriously salinizated; the quantity of the water which flow into the Bosten lake have decreased, the surface of the lake have shrinked; a large number of agricultural drainage flow into the Bosten lake which lies in the southeastern of the base which resulting in the increasing of the water salinity and environmental degradation Lakes and the degradation of the ecological environment in the lake area, due to a large number of surface water was diversed irrationally to irrigation. As a result, the study of the sustainable exploitation of the groundwater which do not give rise to the surface deterioration of the ecological environment of great significance to alleviate or solve the current problem of the ecological environment in Yanqi Basin.The studies and results of this article have three aspect as follows:(1)According to previous studies, a discussion of the theoretical was carried on about the ecological water level of groundwater in Yanqi Basin, which contained the upper limit of the ecological level is 3.2m which is the water depth of the prevention of the salinization, the minimum ecological water level is about 4m, which is the depth of phreatic evaporation. If the groundwater level remained at about 3.2-4m, the surface vegetation will not be degraded, also, the ecological environment will be protected.(2)Based on the analysis of hydrogeological conditions of Yanqi Basin, a three-dimensional model of groundwater system was established. Through the identification and testing of the model, the reliability of model was demonstrated from the dynamic simulation of the water level of groundwater observation wells, groundwater flow field, water balance simulation, etc, and the feasibility which can be used to the study of the development and utilization of the groundwater, all which will lay a good foundation of the study of the groundwater exploitation program.(3)A study which is the sustainable exploitation of groundwater in Yanqi Basin was carried on, which combined the ecological water level of groundwater and based on the established numerical model. Six groundwater extraction program was designed, the total amount of the groundwater exploitation is 37729×10~4m~3, 42587×10~4m~3, 47392×10~4m~3, 52245×10~4m~3, 57045×10~4m~3, 61902×10~4m~3. The plan four (total extraction volume of 52245×10~4m~3) was the contained the best exploitation program in the study area, which is based on to load the different exploitation programs into the model, and run the model up until the supply and emissions of the groundwater system achieve stability, and then to analysis the run out from the aspects of the water balance, the transform of the water amount, buried depth of phreatic water level, buried depth of added drawdown, which combined with the ecological water level of groundwater. There are 42102×10~4m~3 groundwater resource which can be exploited left in the study area (actual exploitation of groundwater resource is 10143×10~4m~3), therefore, the surface water resources diversion could be decreased through the use of this part of the groundwater resource, which is of great significance to the decrease of the buried depth of phreatic water level, the control of the salinity, increase quantity of water which flow into Bosten Lake and ensure the carrying water capacity to the downstream basin of Kongqueh River.