The importance of transboundary aquifer management between Poland and Ukraine for the protection of common water

Transboundary hydrogeological units between Poland and Ukraine within the Bug and San River basins are identified, based on harmonized geological and hydrogeological data used for development of a numerical simulation of groundwater flows across the state border. This numerical model shows that the cross-border exchange of groundwater in aquifers takes place in a limited area and the flow pattern can be disturbed by the groundwater exploitation. Abstraction at current levels slightly increases the transboundary groundwater flow from Poland to Ukraine and minimally reduces the flow in the opposite direction, though not reversing the direction of water flow at the border. The simulated drawdowns do not have a transboundary range, but negative effects on surface water resources are noticeable. Estimates show that groundwater runoff to rivers decreased and infiltration losses through the riverbed increased. The quantitative status of the transboundary aquifers has not deteriorated significantly under the current exploitation but in the light of ambitious maximum allowable values for water abstraction, and in the absence of joint resource management, this problem will arise in the near future. Joint management should focus on a broader legal consensus, improvement of institutional relations, and integration of monitoring and groundwater status assessment systems.