Profile Characteristics Of Hydrogeological Conditions In The Western Alxa

The Western Alxa is composed of Alxa Right Banner and Ejin Banner.More than half of the Alxa Right Banner is covered by the Badain Jaran Desert, the world third largest desert and China’s second largest desert,which covers an area of almost 50,000km2. Ejin Banner, located in the lower reaches of Heihe, the second largest inland river in China, is a key area of ecological environment construction and defense-related science and technology strategy in northwest China. However, because of the large coverage of desert and the low-level field investigation, no unanimous agreement on the regional hydrogeological conditions in the Western Alxa has yet been reached, especially on the viewpoint of regional groundwater flow and source. Therefore, a deep understanding of the regional hydrogeological conditions in the Western Alxa has much significance.This study, based on the previous research on hydrogeological conditions in the Western Alxa, made a field investigation of regional hydrogeological conditions in the Badain Jaran Desert, and thus identified its aquifer type and macro distribution characteristics. Besides, the hydrogeological parameter is preliminarily determined by pumping test and water level monitoring.Based on previous studies of drilled boreholes in desert surrounding areas, WEDP02 drilled borehole data of Lanzhou University and the K1-K4 drilled boreholes in this study, the hydrogeological profile from the Gurinai Lake to Yabulai Mountain and that from Gurinai Lake to Zongnai Mountain are made. Hydrogeological characteristics, including strata age, strata thickness and spatial distribution are analyzed.The profile showed structural characteristics of the aquifer in the Badain Jaran Desert.This study, based on the generalization of the profile from Gurinai Lake to Yabulai Mountain and the construction of hydrogeological conceptual model, constructed two-dimensional numerical models of groundwater with Processing Modflow, and obtained model parameters. Based on the simulation results, it analyzed the groundwater flow and water balance of Gurinai Lake-Yabulai Mountain profile. Through the analysis, it is found that most of the precipitation recharge of groundwater is evaporated, while only less than 30% is discharged into Gurinai Lake through lateral runoff. Besides, the evaporation of the southeast lakes in the BadainJaran Desert accounts for more than 80% of the total evaporation.