Elementary polygons of groundwater bodies — Mayotte — State of Places version 2019

A groundwater body is a separate volume of groundwater within one or more aquifers, constituting the elemental division of aquatic environments intended to be the WFD assessment unit. Groundwater bodies are derived from work carried out on the BDLISA repository. The splitting used for water bodies meets the following main principles: — Water bodies are delimited on the basis of geological and hydrogeological criteria; — The redivision of water bodies to take account of the effects of anthropogenic pressures must remain limited; — The limits of water bodies must be stable and durable; — Similar to surface water bodies, the delimitation of groundwater bodies is organised from a typology. This typology is largely inspired by that developed for hydrogeological entities defined in the framework of the revision of BDLISA. It is based on the geological nature and hydrodynamic behavior or “big” operation of aquifer systems (nature, flow velocity). It comprises 2 levels of characteristics (main and secondary); — Bodies of water may have exchanges between them; — All water withdrawals for drinking water supplying more than 10 m³/day or used for the supply of water to more than 50 persons must be included in a body of water; — Deep groundwater, unrelated to rivers and surface ecosystems, in which no sampling takes place and which are not likely to be used for drinking water because of their 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 certain spatial heterogeneity in terms of both its hydrogeological characteristics and its qualitative and quantitative state; — At any point several bodies of water may overlap. (source: according to BRGM, DCE IMPLEMENTATION: Identification AND DELIMITATION OF SOUTERRAINE WATER MASSES — Methodological Guide, January 2003) The layers are distributed in a format consistent with the SANDRE data dictionary of the Water Mass Reference, version 1.4.