The hydrogeology of the Gort Lowlands

Gill, Laurence; Johnston, Paul; Morrissey, Patrick; Regan, Shane; Naughton, Owen; McCormack, Ted; Drew, David A.

doi:10.3318/ijes.2018.36.3

Cited by 7 publications

(11 citation statements)

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“…The lowland karst aquifer is fed by these sinking streams which disappear into underground fissures and conduits and then frequently reappear again in surface reaches or as turloughs in glacially formed depressions. The drainage takes the flows underground to the north-west to the Atlantic Ocean at Kinvara through a complex multi-level conduit system in this lowland network that has formed as a result of past glaciation cycles and their impact of karstification processes, as discussed previously (Naughton et al 2018). The turloughs flood in winter and store temporarily huge volumes of water, forming a key component in the hydrogeological regime.…”

Section: D Models To Simulate Groundwater/surface-water Interactionmentioning

confidence: 94%

An evaluation of semidistributed-pipe-network and distributed-finite-difference models to simulate karst systems

et al. 2020

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Several different approaches have been developed to model the specific characteristics of karst aquifers, taking account of their inherent complex spatial and temporal heterogeneities. This paper sets out the development of a semidistributed modelling approach for applications in an Irish karst context using urban drainage software. The models have proven to be very useful for different studies, with examples given for the ecohydrology of ephemeral karst lakes, extreme groundwater-flood alleviation, karst network investigation, submarine groundwater discharge, and quantification of different recharge and flow components. The limitations of the approach are also highlighted, in particular not being able to simulate diffuse infiltration and flow paths explicitly across the groundwater catchment. Hence, a more distributed, finite-difference modelling approach using MODFLOW Unstructured Grid (USG) with the newly developed Connected Linear Network (CLN) process is then compared against the semidistributed approach on the same karst catchment. Whilst it has proven difficult to achieve the same levels of model performance in simulating the spring flows in the distributed model compared to the semidistributed model, the ability to interrogate the flow paths at any point on the three-dimensional aquifer is demonstrated, which can give new insights into flows (and potential contaminant transport) through such complex systems. The influence of the proximity of highly transmissive conduits on the flow dynamics through the much-lower transmissive matrix cells in which the network is embedded has been particularly investigated.

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Section: D Models To Simulate Groundwater/surface-water Interactionmentioning

confidence: 94%

An evaluation of semidistributed-pipe-network and distributed-finite-difference models to simulate karst systems

et al. 2020

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“…Groundwater flooding in Ireland predominantly occurs within the lowland limestone areas of the west of the country (Naughton et al, 2012, Naughton et al, 2018. This flooding is governed by complex interactions between ground and surface waters, with sinking and rising rivers/streams common and surface water features absent completely in many areas (Drew, 2008).…”

Section: Study Catchmentmentioning

confidence: 99%

“…This results in surcharging of groundwater from the hydraulic network above the surface which is typically contained within low-lying topographic depressions known as turloughs, which represent the principal form of extensive, recurrent groundwater flooding in Ireland (Coxon, 1987a, Coxon, 1987b. In Ireland, the most susceptible region to groundwater flooding is the south Galway Lowlands, centred around the town of Gort, which is a lowland karst catchment covering an area of approximately 500 km 2 (Naughton et al, 2018).…”

Section: Study Catchmentmentioning

confidence: 99%

“…The lowland karst catchment is made up of two distinct, bedrock geologies with the upland mountainous areas to the east underlain by Old Red Sandstone and the lowlands in the west underlain by highly permeable karstified Carboniferous Limestone. The presence of a permeable epikarst with a welldeveloped conduit and cave system dispersed throughout the limestone portion of the catchment has given rise to a very distinct surface hydrology which large exchanges of water between the surface and subsurface across the lowlands through sinking streams, large springs and estavelles (Naughton et al, 2018). Three rivers flow off the Slieve Aughty Mountains (much of which are covered in blanket bog and forestry) providing allogenic recharge into the lowland karst and a fourth flows into the catchment from the south-west.…”

Section: Study Catchmentmentioning

confidence: 99%

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Impacts of climate change on groundwater flooding and ecohydrology in lowland karst

Morrissey¹,

Nolan²,

McCormack³

et al. 2020

Preprint

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Abstract. Lowland karst aquifers can generate unique wetland habitats which are caused by groundwater fluctuations that result in extensive groundwater-surface water interactions (i.e. flooding). However, the complex hydrogeological attributes of these systems often present difficulty in predicting how they will respond to changing climatological conditions. Extremely fast aquifer recharge processes and flow through well-connected conduit networks in such karst systems make them very susceptible to surcharge conditions – i.e. groundwater-surface water interaction (flooding) – and therefore vulnerable to changes in the sequence and intensity of precipitation patterns. This study investigates the predicted impacts of climate change on a lowland karst catchment by employing a semi-distributed karst model populated with output from high-resolution regional climate models for Ireland. The lowland karst catchment is located on the west coast of Ireland and is characterised by a well-developed karstified limestone aquifer which discharges to the sea via intertidal and submarine springs. Annual above ground flooding associated with this complex karst system has led to the development of unique wetland habitats in the form of ephemeral lakes known as turloughs, however extreme flooding of these features causes widespread damage and disruption in the catchment. This analysis has shown that mean, 95th and 99th percentile flood levels are expected to increase by significant proportions for all future emission scenarios. The frequency of events currently considered to be extreme is predicted to increase, indicating that more significant groundwater flooding events seem likely to become far more common. The seasonality of annual flooding is also predicted to shift later in the flooding season which could have far reaching consequences in terms of ecology and land use in the catchment. The impacts of increasing mean sea levels were also investigated, however it was found that anticipated rises had very little impact on groundwater flooding due to the marginal impact on ebb tide outflow volumes. Overall, this study highlights the vulnerability of lowland karst systems to future changing climate conditions mainly due to the extremely fast recharge which can occur in such systems. The study presents a novel and highly effective methodology for quantifying the potential impact of climate change in lowland karst systems by coupling karst hydrogeological models with the output from high resolution climate simulations.

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“…The phenomenon of groundwater flooding in general has become more reported as a natural hazard in recent decades following extensive damage to property and infrastructure across Europe in the winter of 2000-2001(Finch et al, 2004Pinault et al, 2005;Hughes et al, 2011). Significant groundwater flooding also occurred in the UK at Oxford ( 2007) and at Berkshire Downs and Chilterns (2014) and in Galway, Ireland, in 2009(Naughton et al, 2017. Groundwater flooding occurs when the water table rises above the land surface flooding areas often for prolonged periods (often many weeks or months).…”

Section: Introductionmentioning

confidence: 99%

Impacts of climate change on groundwater flooding and ecohydrology in lowland karst

Morrissey

Nolan

McCormack

et al. 2021

Hydrol. Earth Syst. Sci.

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Abstract. Lowland karst aquifers can generate unique wetland ecosystems which are caused by groundwater fluctuations that result in extensive groundwater–surface water interactions (i.e. flooding). However, the complex hydrogeological attributes of these systems, linked to extremely fast aquifer recharge processes and flow through well-connected conduit networks, often present difficulty in predicting how they will respond to changing climatological conditions. This study investigates the predicted impacts of climate change on a lowland karst catchment by using a semi-distributed pipe network model of the karst aquifer populated with output from the high spatial resolution (4 km) Consortium for Small-scale Modelling Climate Lokalmodell (COSMO-CLM) regional climate model simulations for Ireland. An ensemble of projections for the future Irish climate were generated by downscaling from five different global climate models (GCMs), each based on four Representative Concentration Pathways (RCPs; RCP2.6, RCP4.5, RCP6.0 and RCP8.5) to account for the uncertainty in the estimation of future global emissions of greenhouse gases. The one-dimensional hydraulic/hydrologic karst model incorporates urban drainage software to simulate open channel and pressurised flow within the conduits, with flooding on the land surface represented by storage nodes with the same stage volume properties of the physical turlough basins. The lowland karst limestone catchment is located on the west coast of Ireland and is characterised by a well-developed conduit-dominated karst aquifer which discharges to the sea via intertidal and submarine springs. Annual above ground flooding associated with this complex karst system has led to the development of unique wetland ecosystems in the form of ephemeral lakes known as turloughs; however, extreme flooding of these features causes widespread damage and disruption in the catchment. This analysis has shown that mean, 95th and 99th percentile flood levels are expected to increase by significant proportions for all future emission scenarios. The frequency of events currently considered to be extreme is predicted to increase, indicating that more significant groundwater flooding events seem likely to become far more common. The depth and duration of flooding is of extreme importance, both from an ecological perspective in terms of wetland species distribution and for extreme flooding in terms of the disruption to homes, transport links and agricultural land inundated by flood waters. The seasonality of annual flooding is also predicted to shift later in the flooding season, which could have consequences in terms of ecology and land use in the catchment. The investigation of increasing mean sea levels, however, showed that anticipated rises would have very little impact on groundwater flooding due to the marginal impact on ebb tide outflow volumes. Overall, this study highlights the relative vulnerability of lowland karst systems to future changing climate conditions, mainly due to the extremely fast recharge which can occur in such systems. The study presents a novel and highly effective methodology for studying the impact of climate change in lowland karst systems by coupling karst hydrogeological models with the output from high-resolution climate simulations.

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The hydrogeology of the Gort Lowlands

Cited by 7 publications

References 0 publications

An evaluation of semidistributed-pipe-network and distributed-finite-difference models to simulate karst systems

An evaluation of semidistributed-pipe-network and distributed-finite-difference models to simulate karst systems

Impacts of climate change on groundwater flooding and ecohydrology in lowland karst

Impacts of climate change on groundwater flooding and ecohydrology in lowland karst

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