Quaternary aquifers: resource evaluation and development
Detailed geological surveying in the Afon Teifi valley of west Wales has identified the distribution and geometry of a complex array of drift deposits over shales and greywackes of Silurian and Ordovician age. A well and borehole field inventory and groundwater sampling programme provides the basis for evaluating the groundwater flow patterns within these strata. Sustainable yields are mostly small with exceptional yields up to 345 m3 d−1. Potential infiltration derived from an estimate of baseflow is 535 mm a−1; much of this discharges locally and only 9 Mla−1 is estimated to flow longitudinally down the valley as groundwater throughflow. Total groundwater abstraction amounts to 760 Mla−1. Groundwater generally satisfies the EC maximum admissible concentration guideline levels and is Ca–HCO3 to Ca–Cl type. Differences in bedrock groundwater chemistry between the western and the eastern parts of the study area are largely controlled by the drift type. By analogy, the groundwater potential demonstrated in the Afon Teifi valley is likely to be indicative of the potential in geologically similar valleys elsewhere in west and mid Wales.
Figures & Tables
Groundwater in the Celtic Regions: Studies in Hard Rock and Quaternary Hydrogeology
This book covers a diverse range of hydrogeological environments that occur in the Celtic regions of Britain and Ireland. These include hard rock aquifers of Lower Palaeozoic and Precambrian age, generally dominated by fracture flow within a shallow zone of weathering; Carboniferous Limestone aquifers, often characterized by conduit flows in karstic systems; dual-porosity Permo-Triassic sandstone aquifers; and Quaternary deposits, many of which form shallow granular aquifers. The papers presented here address a number of current issues common to the Celtic regions, including: groundwater protection policies, groundwater management in karst aquifers, groundwater development in Quaternary aquifers, groundwater evaluation in data-scarce aquifers and groundwater supplies to small island communities.