Groundwater resources in the Quaternary deposits and Lower Palaeozoic bedrock of the Rheidol catchment, west Wales

Abstract

Abstract An assessment of the groundwater potential of the River Rheidol catchment in west Wales is presented, a region where groundwater is an important source of water to Aberystwyth. An alternative approach to a conventional well inventory was undertaken based on the manipulation of data within a geographic information system (GIS). The GIS application revealed that, in the lower reaches of the catchment, 25% of the total recorded abstractions fall on the boundaries between different geological units and, of these, two-thirds relate to the contact between Quaternary deposits and bedrock. These abstractions are typically correlated with spring sources and represent small domestic supplies from shallow, brick-lined pits dug into the valley sides. Simple catchment water balance calculations showed that groundwater abstractions are minor in comparison to total combined surface and groundwater runoff. Compared with the weathered and fractured bedrock, the floodplain gravel aquifer is of greater significance and is further enhanced by an unquantified amount of induced recharge from the River Rheidol. However, the resource contained in the Quaternary gravels is vulnerable to mainly agricultural contaminants derived either from direct leaching through the thin unsaturated zone, especially on the floodplain, or from induced recharge from the River Rheidol.