Evolution analysis on springs in contiguous area of Maowusu Desert and Loess Plateau

With Chinese coal mining strategic west shift in the past 20 years,the contiguous area of Maowusu Desert and Loess Plateau becomes an important coal producing area in China. In this area,the water resource is short and the ecological environment is fragile. Springs,as the precious groundwater resources and the main water source for ecolo- gy,production and living,is of great significance. Based on the hydrology and ecology observation of 2 580 springs in 1996 and 2016,springs had been classified by recharge source in dry season. The springs natural characteristics had been analyzed,as well as springs evolution and ecological effect combined with the influence of coal mining. And the trend of springs evolution had been predicted. The results show that springs are divided into 3 types by recharge source in dry season,including sand infiltration recharge spring,loess infiltration recharge spring and combined infiltration re- charge spring. When the spring single flow is greater than 10 L / s,the numbers of sand infiltration recharge spring is the most. And the total numbers of combined infiltration recharge spring is the most. The ecological effect of loess infil- tration recharge spring is most significant. Before 1994,there were 2 580 springs ( groups) in the survey area,with a total flow of 4 997. 059 7 L / s. In 2015,there were 376 springs (groups),with a total flow of 996. 392 L / s. The main reason for the large attenuation of springs in the past 20 years is that combined infiltration recharge springs disappear by structural damage to aquifers-aquicludes and lateral supply truncation. The sand infiltration recharge springs are distributed in future coal mining areas,and aquifers-aquicludes structure is stable in this area. The sand infiltration re- charge springs wave tends to be stable by mining subsidence and overflow of aquifer. With high intensive coal mining, the springs,water body and wetland area reduce in the study area,and the watershed ecological degradation is remark- able.