Elementary Groundwater Body Polygons — Mayotte — Version Status of the Places 2013

A body of groundwater is a separate volume of groundwater within one or more aquifers, constituting the elementary separation of aquatic environments to be the WFD assessment unit. It defines environmental objectives, assesses the state of the environment and subsequently verifies the achievement of these objectives. Groundwater bodies, based on work on the BDRHF V1 hydrogeological repository, were first identified and delineated in 2004 and updated in 2010. They were the subject of a report 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. At the beginning of 2013, work was carried out to bring the February 2011 report to Europe into line with the sandstone format. This version is still available on the SANDRE website; however, it contains a number of anomalies, present in the reported data, and highlighted in report BRGM/RP-62141-EN. These anomalies have been corrected in this version of the Water Mass repository: the 2013 “internal water body reference” in its version is the result of the update of the State of the Places, in line with the data models of the Sander and consolidated at the national level, at www.sandre.eaufrance.fr. This reference version comes from the State of the Places 2013 and is not reported to the European Commission. This version is used at national level to prepare the SDAGE 2016-2021. The layers are distributed in a format consistent with the SANDRE Data Dictionary of the Water Body Reference, version 1.2. The separation of water bodies meets the following key principles: Water bodies are demarcated on the basis of geological and hydrogeological criteria, The redistribution of water bodies to take account of the effects of anthropogenic pressures must remain limited. Water body boundaries must be stable and sustainable Like bodies of surface water, 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 as part of the revision of the RHF BD. It is based on the geological nature and hydrodynamic behaviour or “big” functioning of aquifer systems (nature, flow rate). It consists of two levels of characteristics, main and secondary. Water bodies may have exchanges between them. All Potable Water Captures, providing more than 10 m³/day of drinking water or used to supply water for more than 50 people, must be included in a body of water. Deep groundwater, unrelated to rivers and surface ecosystems, from which no sampling takes place and which is not likely to be used for drinking water due to their quality (salinity, temperature, etc.), or for technical and economic reasons (cost of disproportionate abstraction) may not constitute water bodies. Given its size, a body of water may be spatially heterogeneous in terms of both its hydrogeological characteristics and its qualitative and quantitative status. At any point several water bodies can be superimposed. The PolygMasseDEauSouterraine layer results from the agglomeration into a single file, from all groundwater bodies divided into elementary multipolygons corresponding to each of their depth levels. The entire national territory is covered, the polygons overlap. In other words, if we try to identify the bodies of water present at a point in the territory, this layer can render 1 to 10 water bodies differentiated only by the associated order of overlay. Conforming to the SANDRE V1.2 data dictionary, the layer is composed of the same attributes as the MasseDEauSouterraine layer with: — The addition of the field “Level”: Depth level of the elemental multipolygon of the groundwater body; — The addition of the field “CdPolygMasseDEauSouterraine”: Unique code of the elemental multipolygon of the groundwater body.