Palaeo-groundwater levels in the sandy-soil landscapes of The Netherlands prior to human influence

The sandy soil regions often experience excess water during winters and scarcity during summers, contributing to a compromised water situation in the Netherlands. The declining groundwater table, influenced by meteorological drought and anthropogenic activities such as intensive drainage and groundwater extraction, is putting land use and biodiversity that rely on phreatic groundwater at risk. Currently, spatial planning hardly considers natural soil and water systems, rendering the sandy regions unsustainable for the future. Thus, there is a need for a paradigm shift: land use should align with natural potential rather than human needs. Understanding how landscapes function with minimal human influence is crucial for applying natural principles to future climate-robust land use planning. Therefore, a study will be conducted in the Wapserveensche Aa catchment, situated in the sandy regions of the Netherlands, with the aim of developing a spatially explicit quantitative understanding of the natural soil-water land use system. The methodology involves reconstructing palaeo-groundwater levels and relevant hydrology from the Middle Holocene (2000-4000 BCE), utilizing a regionally calibrated numerical model (MIPWA) combined with field observations. MIPWA is a groundwater model with the combination of MetaSWAP (unsaturated zone) and MODFLOW (saturated zone) having a resolution of 25 m. Existing data on climate, topography, hydrological network, and vegetation will serve as model inputs, and unavailable data will be reconstructed using existing knowledge and resources. Model output (historical groundwater levels) will be validated with historical maps and data, hydro-pedological data (soil profiles, redox features, podzolic features), and archaeological findings associated with groundwater (e.g., past settlements). The existing hydro-pedological data from soil surveys and/or research will be supplemented by additional fieldwork and data collection as needed. The results obtained can be utilized to determine nature-based land use, making sandy landscapes with a nature-based phreatic water table sustainable and climate-robust in the Netherlands or beyond. Additionally, this research will contribute to expand the method of palaeo-groundwater reconstructions and promote nature-based solutions.