Présentations Colloques

Oral Presentation
Session 8.05: Karst aquifers
Understanding groundwater surface water dynamics within the catchment of Bell Harbour Bay, Ireland, using Infoworks ICM
Within the recent hydrological years of 2010 and 2016 the south Galway and Bell Harbour regions of western Ireland have experienced excessive groundwater (GW) flooding beyond the seasonal long-term averages. **In Ireland GW flooding occurs mainly within low lying (<100 masl) karstified Carboniferous limestone with a shallow drainage system- such aquifers underlie almost 40% of the country. Intense, protracted rainfall events quickly saturate the shallow karst aquifers resulting in extensive flooding which can inundate surrounding buildings, agricultural land and infrastructure. Climate change scenarios for Ireland predict that extreme weather events will intensify, and so, GW flooding is likely to become more significant too. In order to mitigate these extreme events, a better understanding of the dynamic of lowland karst aquifers and their responses is needed.**Based on existing conduit-dominated karst models this research aims to better characterise the role of diffuse GW recharge and slow-flow components in order to incorporate both in more reliable hydrological models. Hence, the model shall serve as a Decision Support System to understand the complex interaction of SW and GW addressing flood mitigation and contaminant transport in Irish karst aquifers. **The study area, Bell Harbour, is a 47 kmC GW flow dominated catchment which discharges at a series of intertidal and submarine springs along the Atlantic coast. Mean freshwater discharge form the springs is estimated via water balance using continuous meteorological records. The discharge estimate is then validated by monitoring salinity fluctuations in the enclosed bay. Furthermore, a semi-distributed hydrological model has been developed using InfoWorksyICM based on the results of geophysical studies in the catchment.**Using this model, it is possible to couple turbulent fast-flow components within major conduits together with the slow flow component in the matrix and fissures, as well as with seasonal GW flooding on the surface concentrating in topographic depressions, groundwater dependent terrestrial ecosystems known locally as turloughs.**