Study on evolution of groundwater-lake system in typical prairie open-pit coal mine area

Due to the drought climate and a large amount of groundwater drainage, there are widespread environmental geological problems in prairie open-pit coal mining areas, such as hydrological cycle imbalance, soil desertification and prairie degradation. This study takes the Hulunbeir Prairie Yimin Open-pit Coal Mine as the research object. Basing on the investigation of the groundwater-lake system in the mining area, data of hydrological, meteorological and remote sensing image, the mathematical model of groundwater level-lake area response mechanism in the mining area was constructed by using the principle of water balance. And the influence of mining area development on the lake area of Yimin basin had been predicted and analyzed. The results show that in the past 35 years of coal mining, the number of lake groups in Yimin basin has changed from 5 before mining (1982) to 2 (2018), and the total area of lakes has reduced from 6.94 km² before mining to 1.43 km² with an area reduction rate of 79%. The prairie lake-groundwater coupling model was constructed based on the principle of water balance, and the goodness-of-fit reached more than 0.83 after testing. Based on the model, it's predicted that when the Yimin Coal Mine is closed (2045), the area of Chaidaminol lake will shrink to 1.37 km² under the condition of little fluctuation of climatic factors and stable mine development.