Background,thought and method of groundwater monitoring in large coal base of northwest China

Among the 14 large-scale coal bases in China,there are five coal bases in the north-western China,including Shendong,Shanbei,Huanglong,Ningdong and Xinjiang coal base. In 2018,the output of raw coal in these coal bases accounted for 46. 28% of total production in China. These coal bases are located in arid and semi-arid area with poor water resources. The coal exploitation has strong turbulence intensity on the aquifer,and even causes structural damage to the aquifer,groundwater seepage,descending of lake level and a series of environmental problems. To mini- mize the damage of aquifer in coal mining areas,some achievements have been made by the scientific planning and in- novation of coal mining technology and methods. However,coal exploitation has a dynamic effect on groundwater dis- turbance. In order to monitor it,the authors have established groundwater monitoring network in the mining areas. This paper discusses the backgrounds and ideas of underground water monitoring network construction in the northwest coal base,China. Meanwhile,it introduces the layer selection,construction and deployment,data collection,transmission re- ceiving and management of underground water monitoring network of Shanbei,Shendong and Huanglong coal bases in Shaanxi. The main water-bearing systems include Carboniferous-Jurassic clasolite and overlying Quaternary unconsoli- dated formation pore aquifer systems,Cretaceous clastic rock pore-fissure confined-phreatic water system and Cambri- an-Ordovician carbonate rock karst water-bearing system in the three large coal bases. The selection principle of groundwater monitoring layer should consider the layer with water supply value,ecological significance,and the aquifer being affected strongly by mining. Furthermore,it mainly monitors the groundwater of Quaternary Salawusu formation loess,Quaternary loess and burnt rock and Jurassic weathering bedrock in Shanbei and Shendong coal bases ( in Shaanxi). In addition,Huanglong-Yonglong mining area mainly monitors Cretaceous groundwater and Weibei mining area primarily monitors the Ordovician karst groundwater in Huanglong coal base. The research has built the monitoring network of large-scale coal bases being composed of 218 monitoring wells by newly-build or reconstructed original hydrological long-time observation hole in Shaanxi. The monitoring system uses automatic data acquisition, wireless transmission and receiving and unified management,which basically achieves the real-time dynamic monitoring data of observation and standardized management.