Groundwater vulnerability map
Description
The map of the vulnerability of the groundwater of the Flemish Region can be defined as a map of the level of risk of contamination of the groundwater in the upper water layer by substances penetrating the ground from the soil, taking into account only static parameters. This map can later serve as a basis for a more detailed map, which can also include dynamic and hydrochemical factors. However, where the top recoverable aquifer is naturally salinized (< 1500 ppm), this is indicated. An aquifer is considered to be the saturated zone of a formation that has a thickness and an extension of sufficient size to extract water from it in an economically sound manner. For the map, a flow rate of at least 4 m3 per hour is assumed. In practice, this sometimes leads to misunderstandings: the map gives an idea of the first economically interesting water layer that in many cases does not correspond to the layer that is first cut, for example, during excavation works. The second important point is that the maps are drawn up for contaminants that penetrate the soil from the bottom, taking only static factors into account. In other words, they are mainly a reflection of the danger of contaminants flowing through the soil and the unsaturated zone, especially in the vertical direction, or of contaminating liquids from the surface to the saturated zone. Factors such as the nature and extent of the pollution, its spread by the flow of the polluted water under the prevailing hydrogeological conditions, as well as the interaction between the pollutant and the formation have therefore not been taken into account. In practical terms, the size and nature of the aquifers and of the coatings, together with their hydraulic parameters, have been taken into account, in particular the nature and value of the permeability. The map is based on three factors. the aquifer, the coating and the unsaturated zone. These are divided into a number of classes, each with a certain index, after which the final vulnerability scale is drawn up on the basis of combinations of the different indices.
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Tags
- grondwater
- vlaanderen
- grondwaterkwetsbaarheid
- hydrogeologie
- grondwaterbescherming
- dov