Groundwater flooding in Irish karst: The hydrological characterisation of ephemeral lakes (turloughs)

SummaryEphemeral karst lakes (turloughs) are wetlands at the interface between groundwater and surface water, and are a characteristic feature of the Irish karst landscape. They are transient lakes resulting from a combination of high rainfall and, accordingly, high groundwater levels in topographic depressions in karstified limestone terrain. Turloughs are a valuable example of a Groundwater Dependent Terrestrial Ecosystem (GWDTE), providing a habitat for many floral and faunal species of both national and international importance. The extensive, recurring groundwater floods that originate at turloughs also represent the primary form of groundwater flooding found in Ireland. This study addresses the need for a comprehensive study of turlough hydrology based on quantitative hydrological and topographic parameters. In doing so it takes the first step towards the goals of ensuring the conservation status of these protected ecosystems, as well as providing a basis for determining the hazards associated with groundwater flooding in Ireland. The hydrodynamics of turloughs have been elucidated through the measurement of relevant hydrological parameters, the mapping of topography within turlough basins, and the analysis and interpretation of extensive hydrological datasets over a 3 year period. From this analysis a conceptual understanding of the hydrological operation of turloughs has been developed and the characteristic hydrological diversity of these habitats has been quantified.

► The flooding behaviour of ephemeral karst lakes (turloughs) was characterised. ► Hydrological and topographic data was collected over a 3 year period for 21 turloughs. ► Turloughs did not form natural hydrological types but were spread across a continuum. ► Turlough inflow and outflow showed strong links with rainfall and stage respectively. ► A conceptual understanding of turlough hydrological operation has been developed.