Hydrogeological entities - Réunion

The hydrogeological entity is a part of the geological space, aquifer or non-aquifer, corresponding to a physical system characterised in terms of its state and hydrogeological characteristics. The hydrogeological entity must be understood in a systemic sense and corresponds to a division of the geological space carried out at a given stage of knowledge, in particular for deep systems. The constitution of hydrogeological entities comes from the knowledge at a given date of the underground environment (geological map, geological section, geological log, structural scheme and piezometric map). Hydrogeological entities can be multipart. Hydrogeological entities cover the entire territory ensuring a horizontal and vertical relationship of entities in accordance with the principle of completeness. A hydrogeological entity is a part of the geological space: - delimited to a certain scale (level of use) - related to a type of geological formation (theme) - defined by its aquifer potentials (nature) - characterized by a type of porosity (middle) - characterized by the presence or not of a tablecloth, which can be free, captive or free and captive (state) They have been defined according to rules developed within the framework of a common national methodology and validated by a national steering committee under the responsibility of the ministry in charge of the environment. A hydrogeological entity will be represented by its orthogonal projection to the ground. The reference scale is 1/50 000th, i.e. the scale of the national geological repository. Each entity has a code that is assigned by the BRGM (Order of 26 July 2010, SNDE). According to Sandre, dictionary of the SAQ hydrogeological repository version 2.2