Inspire harmonised – groundwater bodies

In order to manage the groundwater, the Flemish subsoil is divided into several three-dimensional units: groundwater bodies. Within these groundwater bodies, environmental objectives shall be monitored and, where appropriate, measures imposed. The delimitation of groundwater bodies is mandatory in the European Water Framework Directive 2000/60/EC, which defines a groundwater body as “a separate body of water in one or more aquifers”. The classification of the subsoil into different groundwater bodies is mainly based on the physical characteristics of the groundwater reservoirs and on the regional groundwater flow. The main starting points are the succession of aquifer (sand, gravel, chalk, rock, etc.) and regional non-aquifers (clay, etc.) and the prevention of clear barriers to groundwater flow (thick clay layers, fractures, groundwater separations, heavily draining rivers, salinage limits, etc.). The determination of the groundwater bodies was therefore based on the hydrogeological coding of the Subsoil of Flanders (HCOV coding) and on the classification of Flanders’ subsoil into groundwater systems. The groundwater bodies are three-dimensional and can occur side by side and above each other. In total, there are 42 groundwater bodies. They are very different: * surface area of 50 km² to 6 000 km² * thickness from 20 m to 1 000 m * Kh from 0,000005 to 2 300 m/day * from sweet to salt * composed mainly of limestone, sand, gravel, peat, silt, etc. *... The groundwater bodies have both a name and a code. The code is structured as follows: The denomination of a groundwater body is always based on the HCOV code of the main aquifer. Each groundwater body has also received a meaningful code “GWS_HCOV_GWL_NR”. The code consists of an abbreviation of the groundwater system in which the groundwater body is located (e.g. CVS, Central Flemish System), followed by the HCOV code, which corresponds to a main aquifer (e.g. 0600 stands for the Ledo-Paniselian-Brusseli Aquifer system). The abbreviation ‘GWL’ is then added, followed by a sequential number NR indicating the further spatial division of the aquifer in different regions. In some cases, the letters ‘s’ and ‘m’ were added, indicating that a groundwater body was split into a part to be located on the one hand in Scheldedistrict or, on the other hand, in the Maas district. In order to help clarify the three-dimensional aspect of groundwater bodies, horizons were added, i.e. the order in which groundwater bodies occur in depth. This dataset contains a comma separated list of horizons containing the groundwater body. E.g. ‘1’ means that the body of groundwater occurs only as the first (least deep) groundwater body; ‘1,2,3’ means that, depending on the location in Flanders, the body of groundwater is the first, second or third body of groundwater to occur in depth; ‘3,4,5’ means that the body of groundwater has a minimum of two and a maximum of four bodies of groundwater. The ‘groundwater bodies (horizons)’ layer can be used to know exactly the order of groundwater bodies in a given location.