Influence of Long-Term Mine Activity on Hydraulic Relations between Separate Hydrogeological Units—New Aspects of Regional Water Circulation Assessment

In the course of the documentation works aimed at updating exploitable resources of the groundwater intake, an unexpected change in hydrodynamic field arrangement was observed in a fragment of the area. In relation to the observations made so far, lasting several decades, the groundwater table switched its slope, indicating the flow in the opposite direction than originally. Initially, in the range of the surveyed hydrogeological structure, no object was identified whose draining character could cause such an effect. No significant groundwater extraction or drainage points were documented within a radius of several kilometers. It was only the extended scope of spatial analysis that made it possible to identify the probable cause of a local change in the water table position as a mining pit located in the neighboring hydrogeological structure. The two adjacent hydrogeological structures treated separately so far revealed an experimentally confirmed hydraulic connection. An in-depth analysis of the problem showed the necessity of modifying the existing model of the structure in order to map the observed interactions. An additional simulation module of General-Head Boundary type was applied. The quantity of lateral groundwater exchange between two hydrogeological structures was estimated using mathematical modeling at 3.4 thousand m 3 /d (reconstructed current state, after model calibration). Further work should aim at treating reservoirs as hydraulically connected after exceeding limiting parameters.