Our recent knowledge about the role of different fluid driving forces in the response of groundwater flow systems to climate change is still limited. This current study aimed to evaluate possible spatial and temporal changes in complex, gravity- and overpressure-driven groundwater flow systems induced by climate change and look for general trends and characteristics of the flow field using 2D transient groundwater flow simulations. Results showed significant large-scale changes in the transient subsurface flow field and flow dynamics due to recharge reduction. Local gravity-driven flow systems are the most vulnerable to atmospheric processes, while overpressured regimes are expected to be independent of direct climatic variability. By the involvement of different degrees of overpressure, it was revealed that, as the degree of overpressure increases, the penetration depth of the topography-driven local flow systems decreases. The higher the overpressure, the lower the climate change-induced groundwater level decrease over time, suggesting the buffering effect of overpressure as a fluid driving force in the flow systems’ response to the changes in hydrologic parameters. The main novelty of the study is the involvement of different fluid driving forces in the evaluation with the combination of a regional scale investigation, which is unique in the context of climate change effects on groundwater systems.

Climate change and increasing human impacts are more emphasised in recharge regions, where the main flow direction is downward, resulting in negative water balance. Two wetlands located in the recharge position of regional groundwater flow systems were investigated in the Nyírség region, Hungary, as pilot areas for representing wetlands in similar hydraulic positions. Hydraulic data processes, chemical data evaluations, and numerical simulations revealed that the wetlands are fed via local flow systems, superimposing regional-scale recharge conditions in the area. The wetlands are discharge and flow-through types in connection with local flow systems. Nevertheless, in the case of significant regional water table decline—due to the high vulnerability of recharge areas to climate change—local flows are degraded, so they are not able to sustain the wetlands. To preserve the groundwater-dependent ecosystems in the areas, water retention at the local recharge areas of the wetlands may help in the mitigation of water level decline under present-day conditions. If the regional water table continues to decline, comprehensive water retention solutions are needed in the whole region. The results highlight that understanding the natural wetland–groundwater interactions at different scales is crucial for the preservation of wetlands and for successful water retention planning.