Characterisation of karst hydrogeology in Western Ireland using geophysical and hydraulic modelling techniques

Study region: Bell Harbour. A sub-catchment of karst landscape, the Burren, in Western Ireland. Study focus: Bell Harbour is difficult to investigate using traditional hydrogeological techniques due to its complex mixture of upland, lowland and coastal karst, with ephemeral lakes and submarine/intertidal discharges. This study uses electrical resistivity tomography and discrete conduit network modelling to characterise the hydrogeology of the catchment by determining flow pathways and their likely hydraulic mechanisms. New hydrological insights for the region: Results suggest two primary pathways of northwards groundwater flow in the catchment, a fault which discharges offshore, and a ∼2 m diameter karst conduit running underneath the catchment lowlands against the prevailing geological dip. This conduit, whose existence was suspected but never confirmed, links a large ephemeral lake to the coast where it discharges intertidally. Hydraulic modelling indicates that the conduit network is a complex mixture of constrictions with multiple inlets and outlets. Two ephemeral lakes are shown to be hydraulically discontinuous, either drained separately or linked by a low pressure channel.