Kartering grondwaterspiegeldiepte in laag Friesland : Actualisatie van een deel van het grondwaterspiegeldieptemodel van de Basisregistratie Ondergrond (BRO)

Samenvatting

The aim of this project is to make up-to-date maps of three water table depth properties – average highest groundwater level (GHG), average lowest groundwater level (GLG) and water table class (Gt) – in the low-lying Holocene part of the province of Friesland, and to quantify the accuracy of these maps. This project is therefore a step in the development of a Water Table Depth Model (WDM) for the whole country, which will become available from 2022 via the National Key Registry of the Subsurface (BRO). The WDM has many uses, including for spatial and land use planning, calculation of crop damage, habitat restoration/creation, designation of special areas of conservation (EU Habitats Directive), supporting applications for derogation under the EU Nitrates Directive and the assessment of effectiveness and risks of plant protection products. The mapping in Friesland was carried out using a stratified simple random sampling design based on soil conditions, field drainage and distance to ditches. In 2019 and 2020, at a total of 296 locations water table depths were measured and soil profile descriptions were drawn up. Based on these data, maps of the average highest groundwater level (GHG), average lowest groundwater level (GLG) and water table class (Gt) were made.