Comprehensive application mode of flood and waterlogging control as well as water resources regulation in coal mining subsidence area of Nansihu basin, China

The basin of Nansihu lake is dominated by alluvial plain landform in Shandong Province, China. The region is rich in coal resources and coal mining has formed a large number of subsidence areas. In view of the difficulty of surface water regulation and storage in plain area and the fact that coal mining subsidence area can provide effective storage capacity. The mode of combination of flood, waterlogging control and water resources regulation by using coal mining subsidence area in the basin is put forward. The advantages and disadvantages compared constructing plain reservoirs with using coal mining subsidence area as reservoirs is recognized. The effects of flood control and waterlogging control in coal mining subsidence areas from the scale of watershed and specific cases are analysed. From the perspective of flood and waterlogging control effect, in 2025 and 2035, coal mining subsidence area can reduce the flood of 5% frequency by 12.43% and 34.22% respectively. By 2025, urban waterlogging at 20% frequency will be reduced by 56.19%. In 2035, the ability of coal mining subsidence area to resist urban waterlogging at the same frequency can reach 100%. The coal subsidence area in Longguhu can reduce the flooding at 10%, 5% and 2% frequencies by 15.8%, 12.1% and 9.2%, respectively. It can completely resist the one-day waterlogging in the city at 20% frequency and reduce the waterlogging in the city for three-days by 70.8%. The reconstruction of plain reservoir using the coal mining subsidence area is feasible in technology and engineering construction. But it is still faced with the problem to be solved of the guarantee rate of water supply, water quality etc...