Modelling the cumulative effects of Late-Holocene anthropogenic activities on phreatic groundwater levels

The sandy soil region of northwestern Europe often experiences excess water during winter and water scarcity during summer, causing a compromised hydrological balance. Lowering of groundwater levels by anthropogenic interventions such as intensive drainage and groundwater abstraction threatens land use and biodiversity that are dependent on phreatic groundwater. Current spatial planning hardly considers natural soil-water systems, rendering these landscapes unsustainable for the future. This calls for a paradigm shift in which land use is guided by the potential of natural systems to sustainably support human needs.

Understanding how landscapes function under minimal human influence is crucial for understanding the natural processes, reversing declining trends and developing climate-robust land-use strategies. Therefore, we studied the Chaamse beek catchment (southern Netherlands) to develop a spatially explicit, quantitative understanding of the natural soil-water land use system and to assess the impact of human interventions over the late Holocene (2000 BCE till now) For this, we reconstructed palaeogroundwater levels using a regionally calibrated numerical model, which consists of MODFLOW (saturated zone) and MetaSWAP (unsaturated zone) for the time slices 2000 BCE, 0, 500, 1500 and 1850 CE. Topography, land use, hydrological features, and soils were reconstructed for each time slice and human interventions (e.g., ditches, artificial structures, abstraction wells) were chronologically removed (from present to past) to simulate increasingly natural conditions and evaluate their effects on groundwater dynamics. Model results were evaluated against historical maps.

Results show that removing drainage ditches (simulating conditions prior to 1500 CE) substantially increases areas with shallow groundwater (0-50 cm). These areas become even larger when removing abstraction wells. Notably, the model successfully simulated the presence of swamps at locations where they historically existed, as verified by historical maps from 1850 CE. These findings provide quantitative insights into human-modified hydrological systems and support the development of nature-based solutions, water buffer zones, and adaptive land-use planning for climate-resilient management of sandy catchments. By constraining hydrological models with palaeogroundwater reconstructions, future forecasting and scenario-based water management strategies can be made more robust.