The map shows the potential for the rocks to supply groundwater and the type of groundwater flow within the rocks. The dataset reattributes polygons in the Digital Geological Map Data of Great Britain - 625k (DiGMapGB-625) Bedrock version 5 dataset to indicate whether the bedrock is an aquifer, the type of flow through the aquifer (fracture and fissure flow or intergranular flow) and how productive the aquifer is likely to be. The dataset is based on the known hydrogeological properties of rock types. The dataset covers just the bedrock formations for the UK and the Isle of Man. The data can be used for planning, environmental analysis, water supply and hazards.
The hydrogeological map indicates aquifer potential in generalised terms using a threefold division of geological formations: those in which intergranular flow in the saturated zone is dominant, those in which flow is controlled by fissures or discontinuities and less permeable formations including aquifers concealed at depth beneath covering layers. Highly productive aquifers are distinguished from those that are only of local importance or have no significant groundwater. Within each of these classes the strata are grouped together according to age or lithology. The 1:625 000 scale data may be used as a guide to the aquifers at a regional or national level, but should not be relied on for local information.
This layer of the map based index (GeoIndex) shows the location of available Hydrogeological Maps which have been published at various scales, covering areas ranging in size from the whole of England and Wales, Northern Ireland and to Jersey. They display information on surface water features, the three dimensional geometry of aquifers, groundwater levels, abstractions and quality including saline intrusion in varying amounts of detail.