An investigation of the water resources of the fissured limestone/sandstone Corallian Series aquifer was carried out between 1970 and 1974. The techniques employed and the interpretation of flow mechanisms and development potential may be relevant to other similar areas of the United Kingdom as well as further afield. Groundwater movement and chemistry are shown to be strongly related to geological structure. The aquifer is characterized by a relatively high recharge rate and, in some zones, high transmissivity; storage is very limited. This latter characteristic leads to difficulties in the formulation of development proposals, particularly if the aquifer is to be employed in river regulation.