Department of Water Resources, China Institute of Water Resources & Hydropower Research (IWHR)1, Department of Hydraulic Engineering, Tsinghua University; Beijing IWHR Technology Co., Ltd.2
Introduction. With continuous growth of coal production in China, coal mining is aggravating local water stress situation by disturbing hydrogeological structure and water cycle, as well as water utilization and drainage pollution throughout the whole process of coal production[1-2]. Due to reverse distributions of coal resources and water resources, 14 large coal bases, planned as essential parts of energy layout in the 11th Five Year Plan (2011-2015) of China, may bring severe issues of water resources and eco-environment in these water-deficient areas. The most strict water resources management has been implemented to deal with increasingly serious water issues, in which 3 red lines are identified including total water use control red line, water use efficiency control red line and pollutant control red line of water function zones. In this context, scientific research is urgently needed to reveal the response and feedback between coal mining and water resources system and to suggest mitigation measures for sustainable development of coal industry and water resources.
Methods/Materials. First, the mechanism of coal mining impacts on water resources is studied which takes into account regional surface runoff, groundwater storage and aquifer structure, and water quality, including aquifer structure destruction in underground mining, change of groundwater flow field and surface water infiltration, water loss and pollution caused by mine drainage, as well as living and production water uses and drainages during coal mining and washing. Then, the assessment system of coal mining impacts on water resources system involving geological indicators and hydrological indicators is established on basis of 5 sub-regions in China. There are 2 parameters for geological impacts which are ground settlement area and soil erosion area, and 4 parameters for hydrological impacts including quantity and utilization rate of mine drainage, water quota for coal mining and washing, and waste water discharge of coal washing. After that, the coal production limits of primary coal provinces based on the three red lines of water resources management are calculated and compared with current coal production. The regional indicators of total water use control and water use efficient control in primary coal bases are collected, and the constraints on water use ratio of coal production are properly confirmed. Finally, national and regional impacts of coal mining on water resources system under different coal production schemes and corresponding monetization results on socio-economic losses are evaluated, and mitigation measures are proposed to support for national coal related policy-making.
Results and Discussion. (1) The whole processes of coal production make great influence on both surface water and groundwater. The caving zones, fault zones and bending zones around coal pits due to underground work of coal mining would increase infiltration of surface water and change hydrological replenishment and discharge of groundwater, as well as hydraulic gradient filed and flow field of groundwater. The mine drainage is inevitable which causes groundwater losses and surface water pollution. Living and production water uses during coal mining may aggravate regional water shortage and correspondent drainage may bring pollution to local water body. (2) The whole nation of China is divided into 5 sub-regions based on geographical location and coal mining situation including Jin-Shan-Meng-Ning-Gan, Eastern China, Northeastern China, Southern China and Xin-Qing-Zang. The assessment system of coal mining impacts on water resources system includes 6 parameters (see Table 1), and parameter values for different sub-regions are investigated from observational data and related literatures. It's worth noting that national utilization ratio of mine drainage is just 59% with highest of 76% in Jin-Shan-Meng-Ning-Gan and lowest of 38% in Southern China. (3) The current scale of coal mining in some coal bases have broken through the coal production limits under local water resources constraints based on the three red lines, such as Shuozhou and Lvliang of Shanxi Province, Yulin of Shaanxi Province, and Erdos of Inner Mongolia Autonomous Region, which should be properly controlled because excessive water use of coal production may intensify the conflicts of regional water supply and demand. (4) The monetized losses of water resources due to coal mining are evaluated based on the assessment indicator system of coal mining impacts on water resources, of which the Eastern China is the highest, while the Jin-Shan-Meng-Ning region and the Xin-Qing-Zang region are the lowest. The coal mining impacts on surface water, groundwater, geological condition and water quality in coal control schemes with reduced coal production are much lower than those in the basic scheme, indicating that the coal control would make a positive impact on rational allocation and effective conservation of regional water resources.
Conclusion. The mechanism of coal mining impacts on water resources is studied, and qualitative and quantitative analysis as well as monetized results of water resources losses due to coal mining are presented. It's concluded that the planning of coal mining should be properly demonstrated following the principle of coordination between coal production and carrying capacity of water resources and environment.
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