An assessment of Pant-y-llyn, Wales' only turlough and comparison to Irish sites

Turloughs are ephemeral karst lakes resulting from high rainfall and, accordingly, high groundwater levels in topographic depressions in karstified limestone terrain. The ephemeral nature of turlough hydrology gives rise to a characteristic ecology as such turloughs have been designated as a Priority Habitat in the EU Habitats Directive (92/43/EEC). While there are recorded turloughs in the Republic of Ireland Pant-y Llyn is Wales’ and mainland Britain’s only recorded turlough; it is a key feature of Cernydd Carmel SSSI and SAC. A collaborative investigation was carried out between Environment Agency Wales and Countryside Council for Wales (soon to be Natural Resources Wales). The main aims of this investigation were to: - Improve the hydrogeological conceptual understanding. - Review the water chemistry of Pant-y-Llyn and the surrounding groundwater. - Compare the hydrology of Pant-y-Llyn with that of recorded Irish turloughs. - Use existing data back model the turlough hydrograph. - Provide evidence to confirm its status for the Habitats Directive. The investigation has shown that Pant y Llyn has both a water quality and hydrological cycle. For the first time comparisons with Irish turloughs allow us to put Pant y Llyn into a wider turlough typology