The 1:625,000 scale hydrogeological map indicates the aquifer potential of the rocks of the UK. The data provides generalized information on geological formations, categorised into the following three divisions:
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 hydrogeology 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.