Modelling groundwater flooding in a lowland karst catchment

Morrissey, Patrick; McCormack, Ted; Naughton, Owen; Johnston, Paul; Gill, Laurence

doi:10.1016/j.jhydrol.2019.124361

Cited by 31 publications

(43 citation statements)

References 27 publications

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“…Considering that flood levels within turloughs are generally not normally distributed (Morrissey et al, 2019), the non-parametric Kolmogorov-Smirnov statistical test was employed to test for statistical significance of projected changes. The Kolmogorov-Smirnov null hypothesis states that the past and future data are from the same continuous distribution.…”

Section: Discussionmentioning

confidence: 99%

“…Karst Groundwater Model A semi-distributed pipe network model of the Gort lowlands has been developed using urban drainage software (Inforworks ICM by Innovyze). This model simulates both 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 (Morrissey et al, 2019). The model receives input from the four rivers as a time-varying discharge which is computed separately using observed river gauging data provided by the Office of Public Works (OPW) utilising established stage-discharge rating curves (Gill et al, 2013a).…”

Section: Figure 2: Rcm Ensemble Projections Of Winter Rainfall (%) Imentioning

confidence: 99%

“…found to represent the catchment with a very high degree of accuracy (NSE & KGE > 0.97). The full model setup and calibration/validation process is presented in Morrissey et al (2019). The RCM rainfall and evapotranspiration data, described above, were then used to run the groundwater flow model for each of the historical and future periods covering 25 simulation periods in total (5 past & 19 future).…”

Section: Figure 2: Rcm Ensemble Projections Of Winter Rainfall (%) Imentioning

confidence: 99%

“…Daily rainfall and evapotranspiration totals were output from the RCM models in all cases and these values were used as input to the RR and karst models described below. When hourly totals were required to run the model the daily total was simply evenly distributed over the 24 hour period (this had no impact on the model accuracy see Morrissey et al (2019) for further details). The OPW have specified the required allowances in flood parameters which should be made for planning purposes in Ireland (OPW, 2019) for the "Mid-Range" and "High-End" Future Scenarios (MRFS & HEFS).…”

Section: Figure 2: Rcm Ensemble Projections Of Winter Rainfall (%) Imentioning

confidence: 99%

“…Chen et al (2018) conducted a study into the effects of climate change on alpine karst using GCM data, however the results are not relevant to lowland karst with significant groundwater-surface water interactions and associated eco-hydrological habitats (groundwater fed wetlands). In order to assess the future risks relating to groundwater flooding and ecohydrology in lowland karst, it is imperative to understand the complex hydrological processes governing groundwater flow in karst bedrock and how it will likely be altered in the future (Morrissey et al, 2019). In this context, various forms of numerical models are usually applied to describe the hydrological processes in karst catchments (Fleury et al, 2009, Gill et al, 2013a, Hartmann et al, 2013, Hartmann, 2017, Mayaud et al, 2019, which can accurately simulate the groundwater flow and flooding processes which typically occur.…”

Section: Introductionmentioning

confidence: 99%

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

Morrissey¹,

Nolan²,

McCormack³

et al. 2020

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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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Section: Discussionmentioning

confidence: 99%

Section: Figure 2: Rcm Ensemble Projections Of Winter Rainfall (%) Imentioning

confidence: 99%

Section: Figure 2: Rcm Ensemble Projections Of Winter Rainfall (%) Imentioning

confidence: 99%

Section: Figure 2: Rcm Ensemble Projections Of Winter Rainfall (%) Imentioning

confidence: 99%

Section: Introductionmentioning

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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Ecohydrological metrics for vegetation communities in turloughs (ephemeral karstic wetlands)

et al. 2021

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A 28‐year hydrological record on four intermittent wetlands (turloughs) in a hydraulically linked karst area in the west of Ireland was used to assess ecohydrological metrics for different vegetation communities. A methodology using a combination of continuous water level monitoring and high resolution topographic surveying was used to develop a detailed hydrological model of the karst network, from which water levels at any point within the turloughs can be defined at any time during the 28‐year period (1989 to 2017). The flood conditions experienced across the spatial distributions for different vegetation communities (as mapped by a field survey) have then been collated and presented as statistical distributions for flood duration, flood depth, flood frequency and mean temperature/global radiation at the time of year in spring when the flood waters start to recede. Analysis of these four turloughs has revealed distinct differences between vegetation communities, from Eleocharis acicularis communities at the turlough base typically experiencing 6 to 7 months of inundation per year compared to the limestone pavement community at the top fringes of the turloughs only flooded from 1 to 2 months per year. An approach that used Sentinel‐2 satellite data to provide an assessment of whether there have been changes in the spatial distribution of the communities is also presented. Such metrics can be evaluated alongside other variables such as water quality (particularly nutrients), soil type and land‐use, in order to understand the habitat requirements for such plant communities and their associated ecological systems.

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