This dataset classifies bedrock and superficial geologic units according to their aquifer designation - Principal Aquifers, Secondary Aquifers (Secondary A, Secondary B, and Secondary undifferentiated), and Unproductive Strata. The Environment Agency (EA) and Natural Resources Wales (NRW) help to protect groundwater by identifying different types of aquifers ‐ underground layers of water‐bearing, permeable rock or drift deposits from which groundwater can be extracted. The groundwater protection policies for the EA and Natural Resources Wales use aquifer designations that are consistent with the Water Framework Directive. These designations reflect the importance of aquifers in terms of groundwater as a resource (such as a drinking water supply) but also their role in supporting surface water flows and wetland ecosystems. The aquifer designation dataset is jointly owned by the British Geological Survey (BGS) and Natural Resources Wales (NRW). The dataset covers geologic units mapped in Wales, and is derived from BGS Geology 50k (DiGMapGB-50).