Elementary polygons of groundwater bodies - 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) 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内的独立地下水体积，是水框架指令（Water Framework Directive, WFD）规定的用于评估的水生环境基本划定单元。 地下水体的划定依托BDLISA数据库的相关工作成果。 地下水体的划定遵循以下核心原则： - 以地质与水文地质条件作为地下水体的划定依据； - 为考量人为活动压力需调整地下水体范围的，应严格控制调整幅度； - 地下水体的边界需具备稳定性与可持续性； - 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了BDLISA修订版中定义的水文地质实体分类方案，以含水层系统的地质属性、水动力特征或“宏观”运行特性（如含水层性质、水流速度）为划分依据，包含两级特征参数（主特征与次特征）； - 地下水体间可进行水权交易； - 所有日取水量超过10立方米，或用于供水服务覆盖超过50人的饮用水取水活动，均需纳入某一地下水体范畴； - 与河流及地表生态系统无关联、无取水活动，且因水质（如盐度、温度等）问题或技术经济原因（取水成本过高）不适宜作为饮用水水源的深层地下水，可不划定为地下水体； - 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的空间异质性； - 在空间任意点位上，可存在多个地下水体重叠的情况。 （资料来源：法国地质矿业研究局（BRGM）《水框架指令实施：南部水体的识别与划定——方法学指南》，2003年1月） 数据集图层需采用符合水体数据库SANDRE数据字典1.4版标准的格式进行发布。