Groundwater Masses - Mayotte - State of the Places Version 2019

A body of groundwater is a separate volume of groundwater within one or more aquifers, constituting the basic delineation of aquatic environments intended to be the unit of assessment for the WFD. Groundwater bodies are derived from work done on the BDLISA repository. The water bodies are divided according to the following main principles: - Water bodies are defined on the basis of geological and hydrogeological criteria; - Redistribution of water bodies to take account of the effects of anthropogenic pressures must remain limited; - The boundaries of water bodies must be stable and sustainable; - Like bodies of surface water, the delimitation of bodies of groundwater is organised on the basis of a typology. This typology is largely inspired by the one developed for hydrogeological entities defined in the context of the BDLISA revision. It is based on the geological nature and hydrodynamic behavior or "large" operation of aquifer systems (nature, flow velocity). It comprises two levels of characteristics (main and secondary); - Water bodies may trade with each other; - All water withdrawals for drinking water supplying more than 10 m3/day or used to supply water to more than 50 persons must be included in a body of water; - Deep groundwater, unrelated to rivers and surface ecosystems, from which no abstraction takes place and which is unlikely 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 water bodies; - Given its size, a body of water may have a certain spatial heterogeneity both in terms of its hydrogeological characteristics and its qualitative and quantitative status; - At any point several water bodies may overlap. (source: according to BRGM, IMPLEMENTATION OF THE WFD: IDENTIFICATION AND DELIMITATION OF SOUTHWATER MASSES - methodological guide, January 2003) WFD reporting correspondence: This entity corresponds to WISE's Ground Water Body (GWB) concept. Layers shall be disseminated in a format compliant with the SANDRE Data Dictionary of the Water Body Repository, version 1.4.地下水体是指单个或多个含水层（aquifer）内的独立地下水体积，是为水框架指令（Water Framework Directive, WFD）开展评估所划定的水生环境基本边界单元。 地下水体的划定基于BDLISA数据库的相关工作成果。 水体划定遵循以下核心原则： - 水体以地质与水文地质标准为依据进行定义； - 为体现人为压力影响而对水体进行的重新划定，需严格控制范围； - 水体边界必须保持稳定且可持续； - 与地表水水体类似，地下水体的划定需基于分类体系开展。该分类体系主要借鉴BDLISA修订版中针对水文地质实体制定的分类规则，以含水层系统的地质属性、水动力特征或“宏观”运行规律（如介质性质、水流速度）为基础，包含两级特征层级（主特征与次特征）； - 各地下水体之间可进行水量交换； - 所有日取水量超过10立方米，或用于为50人以上提供饮用水的取水活动，均需纳入对应地下水体的管理范围； - 与河流及地表生态系统无关联的深层地下水，若未进行取水活动，且因水质（盐度、温度等）或技术经济原因（取水成本过高）不适宜作为饮用水源，则可不纳入地下水体划定范围； - 鉴于自身规模特性，地下水体在水文地质特征、水质与水量状态等方面可能存在一定空间异质性； - 同一空间点位可同时隶属于多个地下水体。 （资料来源：BRGM《水框架指令实施：地下水体的识别与划定——方法学指南》，2003年1月） 水框架指令报送对应关系：该实体与WISE的地下水体（Ground Water Body, GWB）概念一致。 相关图层需采用符合SANDRE水体数据库数据字典1.4版标准的格式进行发布。