Understanding flooding in poljes: A modelling perspective

Mayaud, Cyril; Gabrovšek, Franci; Blatnik, Matej; Kogovšek, Blaž; Petrič, Metka; Ravbar, Nataša

doi:10.1016/j.jhydrol.2019.04.092

Cited by 33 publications

(24 citation statements)

References 40 publications

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“…The RCM projection results are in line with previous work (McGrath et al, 2005;McGrath and Lynch, 2008;Gleeson et al, 2013;Nolan et al, 2014Nolan et al, , 2017Nolan et al, , 2020Nolan, 2015, O'Sullivan et al, 2015, with enhanced temperature rises predicted by the end of the century of between 0.8 and 3 • C for the high emission scenario (RCP8.5).…”

Section: Climate Models and Methodssupporting

confidence: 90%

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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Section: Climate Models and Methodssupporting

confidence: 90%

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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“…The total outflow from Planinsko Polje is estimated to be at least of 60 m 3 /s (Šušteršič 2002). When the inflow is higher than the outflow, Planinsko Polje is flooded Mayaud et al 2019). This occurred on average for 38 days per year between 1954 and 2014 (Ravbar et al 2018).…”

Section: The Study Areamentioning

confidence: 99%

“…First works focused on enhancing the polje outflow capacities and recommended a widening of the main ponors for mitigation of floods (Putick 1889;Shaw & Čuk 2015). Later studies were focused on understanding the interaction of the polje with its surrounding aquifers (Gams 1980;Frantar & Ulaga 2015;Ravbar et al 2018;Mayaud et al 2019). Comprehensive tracing experiments carried out in the 1970s revealed the main groundwater flow directions and determined the flow velocities under different hydrological conditions.…”

Section: The Study Areamentioning

confidence: 99%

Groundwater dynamics between Planinsko Polje and springs of the Ljubljanica River, Slovenia

Blatnik¹,

Mayaud²,

Gabrovšek³

2019

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UDC 551.444(497.4) Matej Blatnik, Cyril Mayaud & Franci Gabrovšek: Groundwater dynamics between Planinsko Polje and springs of the Ljubljanica River, Slovenia Caves reaching the (epi)phreatic zone may provide the only access to groundwater in the internal parts of karst aquifers. Modern instruments enable unattended high frequency measurements of groundwater parameters in such caves. A network of distributed observation points may give new information on temporal and spatial pattern of groundwater flow. Such network, recording water level, temperature and specific electrical conductivity was established in all major ponors and active water caves of the karst aquifer between Planinsko Polje and springs of the Ljubljanica River, Slovenia. Up to three and a half years long records were analysed in view of available and relevant geological, speleological, meteorological and hydrological information, and basic hydraulic principles of the epiphreatic flow. The result of the interpretation were models of possible conduit networks of the three main flow subsystems draining Planinsko Polje. For each subsystem a hydraulic model comprising the main features of the inferred conduit network and inputs was made. The models were adjusted until their response to the typical flood situations gave a good qualitative fit to the response of the observation network. The results provide new insights into the mechanism of flood propagation through the system and its relation to the known conduit geometry. The hydraulic role of known cave passages is assessed and new flow pathways are proposed. Back-flooding within the aquifer causes an increase of head in the polje, followed by the activation of higher located ponor zones and flow pathways related to them. Hydrographs recorded in two caves located northwest from Planinsko Polje revealed pos-Izvleček UDK 551.444(497.4) Matej Blatnik, Cyril Mayaud & Franci Gabrovšek: Dinamika podzemne vode med Planinskim poljem in izviri Ljubljanice, Slovenija Jame v epifratični coni običajno predstavljajo edini dostop do podzemne vode znotraj kraškega vodonosnika. Sodobni merilniki omogočajo kakovostne zvezne meritve različnih parametrov tudi v takšnih jamah. Merilna mreža z več lokacijami znotraj izbranega vodonosnika lahko ponudi nove podatke o časovni in prostorski dinamiki toka podzemne vode. Takšna merilna mreža, z meritvami višine, temperature in elektroprevodnosti vode, je bila vzpostavljena v vseh pomembnejših ponorih in vodnih jamah na območju med Planinskim poljem in izviri Ljubljanice. Do tri in pol leta dolgi nizi podatkov so bili analizirani z vidika razpoložljivih geoloških, speleoloških, meteoroloških in hidroloških podatkov ter osnovnih hidravličnih načel o epifreatičnem toku vode. Rezultat interpretacij so poenostavljeni modeli z domnevno razporeditvijo podzemnih kanalov v treh glavnih podsistemih, ki odvajajo Planisko polje. Za vsak podsistem je bil napravljen hidravličen model z dotokom in mrežo kanalov, ki najbolje ponazarja resnično stanje. Tekom raziskave so se hidravlični modeli n...

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“…Several recent models have employed urban drainage software to model the hydraulic dynamics of conduit networks accurately (including ponors, estavelles, etc. ), particularly using SWMM (Chen and Goldscheider 2014 ), including incorporating groundwater/surface-water interactions in poljes (Mayaud et al 2019 ) and turloughs (Gill et al 2013a ; see section ‘ Semidistributed pipe network models (development in Ireland) ’).…”

Section: Introductionmentioning

confidence: 99%

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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Understanding flooding in poljes: A modelling perspective

Cited by 33 publications

References 40 publications

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

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

Groundwater dynamics between Planinsko Polje and springs of the Ljubljanica River, Slovenia

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

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