The impacts of coal mining subsidence on groundwater resources management of the East Midlands Permo-Triassic Sandstone aquifer, England

There are extensive concealed coal mines beneath the East Midlands Permo-Triassic Sandstone aquifer, most of which have used longwall mining techniques. Knowledge of the pumping regimes of the concealed mines shows that there is currently little vertical leakage from the Permo-Triassic Sandstone into these mines. Long-term plans to control the groundwater rebound should prevent any large-scale pollution of the Permo-Triassic Sandstone aquifer system from ingress of mine waters. Currently, the largest impacts on the Permo-Triassic Sandstone aquifer system stem from subsidence associated with the mine workings. This paper examines the impacts on groundwater-surface water interaction, in the context of improving the surface water environment to mitigate effects of long-term over-abstraction. Integral to the assessment of the groundwater-surface water interactions are (i) the change to the hydraulic characteristics of the aquifer system related to the fracturing in the Permo-Triassic Sandstone that the subsidence induces and (ii) the reliability of the installations used to monitor groundwater levels and flows across the aquifer system. These two temporal impacts can be difficult to assess from the available data. The former tends to increase aquifer transmissivity, whereas the latter leads to the underestimation of the impacts of groundwater abstraction caused by datum subsidence of several metres. Two example case histories of impacts on groundwater-surface water interactions are considered: streambed fissuring in the catchments of the River Maun and River Meden, and flow improvements caused by subsidence in the Dover Beck catchment. These two case histories show that there are both beneficial and detrimental outcomes for groundwater resources management caused by coal mining induced subsidence.