Study on temporal and spatial evolution characteristics of water accumulation in coal mining subsidence area with high groundwater level: taking Anhui Province Mining Area as an example

In recent years, with the large-scale and high-intensity mining of coal resources, the problem of water accumulation in mining areas with high groundwater levels has become particularly prominent, which has had a serious impact on the surrounding ecological environment. In order to provide scientific basis for the restoration of the ecological environment, the study on the temporal and spatial evolution characteristics and influencing factors of the coal mining subsidence area with high groundwater level were carried out. Taking the whole mining area of Anhui Province as the research subject, based on Landsat TM/OLI remote sensing data, the NDWI and visual interpretation method were used to conduct surveys on the water accumulation area in the subsidence area from 1995 to 2020 (22 periods ) and 12 months in 2020 (12 periods) and the spatial information of waterlogging in the coal mining subsidence area in Anhui Province in recent 25 years was obtained. Combined with hydrological and rainfall data, the factors affecting the spatio-temporal evolution of waterlogging in the subsidence area were analyzed and discussed. The results show that: ① In the past 25 years, the area of accumulated water in the coal mining subsidence area in Anhui Province has been growing in three stages: slow, fast and stable. During the study period, the average stagnant area increased by about 6 times, from 18.95 km2 to 118.09 km2, with an average annual increase of 3.97 km2. ② From the time scale, the evolution of accumulation area in the subsidence area can be divided into three stages: the first stage (1995—2005), due to the fact that most of the accumulation water has not yet stabilized initially, the growth rate is relatively slow, with an average annual growth rate of 4.65%; In the second stage (2005—2013), based on the rapid growth of coal mining, the area of accumulation water has also entered a period of rapid growth, with an average annual growth rate of 6.64%; In the third stage (2013—2020), the growth rate has begun to decrease, and the accumulation water has gradually stabilized, with an average annual growth rate of 3.42%. From the spatial scale, the accumulation water is mainly concentrated in Huainan and Huaibei cities, accounting for about 70% of the total accumulated water area. ③The long-term factor for the change of the water accumulation is coal mining volume, while the main influencing factor in short time scale is atmospheric rainfall. ④The logistic regression curve was used to establish a prediction model for the water accumulation area of coal mining subsidence in Anhui Province. It is predicted that the coal mining subsidence water area in Anhui Province will still be in a low-speed growth stage in the future. By 2030, the accumulation area in the dry season will reach about 130 km2. The high-precision water accumulation information in the subsidence area was obtained, and its temporal and spatial evolution laws and influencing factors were analyzed, which can provide a scientific basis for the treatment of water accumulation in the coal mining subsidence area with high groundwater level and the ecological restoration of the subsidence area.