A grid-based distributed hydrological model for coal mined-out area

Abstract

Water-conducting cracks and mined-out area caused by coal mining change the regional hydrological processes. To address this issue, this research proposed a grid-based distributed hydrological model for coal mined-out area (GDHCMA), and validated the model in one representative coal mining watershed (Wujiayao watershed in China). The impact of coal mining on wet front depth was further analyzed based on the GDHCMA model. The results revealed that: (1) ground subsidence or cracks induced by coal mining accelerate the leakage of water flow into the mined-out area or replenish the groundwater reservoir, thereby reducing the flood peak flow; (2) The parameters of GDHCMA model was calibrated by the Shuffled Complex Evolution (SCE) global search algorithm and the model showed high accuracy before and after coal mining. During the pre-coal mining period, the calculated NSE (Nash-Sutcliffe efficiency coefficient) was above 0.9, and the error percentage of peak flow and flood volume was less than 15%; During the coal mining period, the main improvement is that the lower boundary conditions for the calculation of unsaturated soil infiltration are treated with free drainage boundaries. The calculated mean NSE is 0.95, the error percentages of flood peak and flood volume are less than 10%, and the peak time error is 0. (3) The leading factors affecting the downward depth of the wetting front are rainfall, soil type, the coal mined-out area etc. The above are of great practical significance for studying the mechanism of the coal mining on the water cycle.