The Groundwater Body (GWB) is the management unit under the Water Framework Directive (WFD). Groundwater bodies are subdivisions of large geographical areas of aquifers so that they can be effectively managed in order to protect the groundwater and linked surface waters.
GWB delineation methodology is described in the document, "Approach to Delineation of Groundwater Bodies", Guidance Document GW2, GWWG.