Groundwater bodies — Mayotte — Release 2016

A body of groundwater is a distinct volume of groundwater within one or more aquifers, constituting the elementary separation of aquatic environments to be the WFD assessment unit. It makes it possible to define environmental objectives, to assess the state of the media and subsequently to verify the achievement of those objectives. The groundwater bodies, building on the work carried out on the BDRHF V1 hydrogeological benchmark, were identified and delimited for the first time in 2004 and were updated in 2010. They were reported to the European Commission on the implementation of the WFD on 22 March 2010, followed by a corrective report in February 2011, taking into account the latest updates. A draft version for the 2013 state of play was published in 2015. The version now distributed on the pike-perch site is in line with the 2016 report. The next version of the Water Mass (temporary bodies of water, defined for the Premises State) is planned for 2019. The layers are distributed in a format consistent with the picker data dictionary of the Water Benchmark Ref. version 1.3. The breakdown chosen for water bodies follows the following main principles: Water bodies are delimited on the basis of geological and hydrogeological criteria; Recutting of water bodies to take account of the effects of anthropogenic pressures should remain limited. Water body boundaries must be stable and sustainable Like surface water bodies, the delimitation of groundwater bodies is organised on the basis of a typology. This typology is largely based on that developed for hydrogeological entities defined in the context of the revision of the HF DB. It is based on the geological nature and hydrodynamic behaviour or large operation of aquifer systems (nature, flow rate). It comprises two levels of main and secondary characteristics. Water bodies may have exchanges between them. All water supply catchments, supplying more than 10 m³/day of drinking water or used for water supply for more than 50 people, must be included in a water body. Deep groundwater, unrelated to water courses and surface ecosystems, in which no abstraction takes place and which is not likely to be used for drinking water because of its quality (salinity, temperature, etc.), or for technical and economic reasons (disproportionate cost of abstraction) may not constitute bodies of water. Given its size, a body of water may have a degree of spatial heterogeneity in terms of both its hydrogeological characteristics and its qualitative and quantitative state. At any point more than one water body may overlap.