HS8.2.4 | Toward a better comprehension of karst hydrogeology: multi-disciplinary approaches for water resource management and mitigating hazards in karst environment
EDI
Toward a better comprehension of karst hydrogeology: multi-disciplinary approaches for water resource management and mitigating hazards in karst environment
Co-organized by NH1
Convener: Mario Parise | Co-conveners: Hervé Jourde, Isabella Serena Liso, Jannes Kordilla, Daniel Bittner
Orals
| Mon, 24 Apr, 14:00–15:45 (CEST)
 
Room 2.15
Posters on site
| Attendance Mon, 24 Apr, 16:15–18:00 (CEST)
 
Hall A
Orals |
Mon, 14:00
Posters on site
Mon, 16:15
Karst environments are characterized by distinctive landforms and unique hydrological behaviors. Karst systems are extremely complex, heterogeneous and very difficult to manage, because their formation and evolution are controlled by a wide range of geological, hydrological, geochemical and biological processes, and are extremely variable in time and space. Furthermore, karst systems are highly vulnerable to a variety of hazards, due to the direct connection between the surface and subsurface through the complex networks of conduits and caves.
In karst, any interference is likely to have irreversible impacts and disturb the natural balance of the elements and processes. The great variability and unique connectivity may result in serious engineering problems: on one hand, karst groundwater resources are easily contaminated by pollution because of the rapidity of transmission through conduit flow, and remediation action, when possible, could be very expensive and require a long time; on the other hand, the presence of karst conduits that weakens the strength of the rock mass may lead to serious natural and human-induced hazards. The design and development of engineering projects in karst environments thus should necessarily require: 1) an enhanced understanding of the natural processes governing the initiation and evolution of karst systems through both field and modelling approaches, and 2) specific interdisciplinary approaches aimed at mitigating the detrimental effects of hazardous processes and environmental problems.
This session calls for abstracts on research from karst areas worldwide related to geomorphology, hydrogeology, engineering geology, hazard mitigation in karst environments in the context of climate change and increasing human disturbance.

Orals: Mon, 24 Apr | Room 2.15

Chairpersons: Hervé Jourde, Isabella Serena Liso, Daniel Bittner
14:00–14:05
5-minute convener introduction
14:05–14:15
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EGU23-12285
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Highlight
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On-site presentation
Impact of climate change on groundwater level dynamics and karst spring discharge of several karst systems in the Mediterranean area 
Guillaume Cinkus, Vianney Sivelle, Hervé Jourde, Naomi Mazzilli, Yves Tramblay, Bartolomé Andreo, Juan Antonio Barberá, Rachida Bouhlila, Joanna Doummar, Jaime Fernández-Ortega, Emna Gargouri-Ellouze, Valeria Lorenzi, Marco Petitta, Nataša Ravbar, Fairouz Slama, and Nico Goldscheider

Anthropogenic activities and climate change exert significant pressures on the quality and availability of water resources in karst environments, which supply drinking water to about 9.2% of the world's population. Increasing temperatures and changes in precipitation regimes will strongly impact water recharge processes. Understanding the karst hydrodynamic behaviour in the present context of climate change constitutes a major challenge for a sustainable management of karst groundwater. This study focuses on the Mediterranean area, where up to 90% of the drinking water supply depends on carbonate aquifers. The spring discharge and/or water level of six karst systems in the Mediterranean area (France, Italy, Lebanon, Slovenia, Spain and Tunisia) are simulated using precipitation-discharge reservoir modelling tools. The studied karst systems are well known and have different characteristics in terms of climatic conditions, hydrogeological properties and available data. Using different model structures, the hydrological models are first calibrated and validated over a historical period and then used to simulate spring discharge time series under various climate projections (up to 2100). To account for uncertainties in climate projection, 12 coupled GCM/RCM climate models are considered with two emission scenarios (RCP 4.5 and RCP 8.5) proposed in the framework of the CMIP5 initiative. The analysis of the forecasted spring discharge and water level time series focuses on (i) the long-term trends in the hydrological functioning of karst systems, (ii) the effects of climate change on spring discharges (intensity and duration of extreme events), and (iii) the study of uncertainties related to the exceedance of the known functioning ranges of the systems. Further discussion is also dedicated to model uncertainties in relation to model parameters and structure, climate models, and the estimation of potential evapotranspiration in future climate. This research has been conducted within the KARMA (Karst Aquifer Resources availability and quality in the Mediterranean Area) project into the PRIMA (Partnership for Research and Innovation in the Mediterranean Area) EU program.

How to cite: Cinkus, G., Sivelle, V., Jourde, H., Mazzilli, N., Tramblay, Y., Andreo, B., Barberá, J. A., Bouhlila, R., Doummar, J., Fernández-Ortega, J., Gargouri-Ellouze, E., Lorenzi, V., Petitta, M., Ravbar, N., Slama, F., and Goldscheider, N.: Impact of climate change on groundwater level dynamics and karst spring discharge of several karst systems in the Mediterranean area, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12285, https://doi.org/10.5194/egusphere-egu23-12285, 2023.

14:15–14:25
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EGU23-5147
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ECS
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On-site presentation
A Bayesian multi-model framework for structure selection and parameter estimation for lumped parameter modeling in karst hydrology. 
Vianney Sivelle, Yohann Cousquer, Hervé Jourde, and Naomi Mazzilli

Lumped parameter modeling in karst hydrology has been widely developped in the last decades. Uncertainty in model conceptualization, which often leads to one unique model structure, is frequently neglected. This issue is particularly important for karst hydrology, where hydrological systems are highly heterogenous and information about the structure is difficult to obtain. In this work, we delopped a Bayseian multi-model framework that allows to calibrate simulteanously a set of model structure and associated parameters. This constitutes a significant step forward compared with classical calibration approaches that allow (i) to provides an ensemble of predictions considering both structural and parametric uncertainties, and (ii) to avoid epistemic error due to model structure selection, wich is generally influenced by the subjective conceptualization of the karst hydrological system by the modeler. The methodology is illustred with a Bayesian inference procedure among a large range of lumped parameter model structure considered for the simulation of discharge at fontaine de Vaucluse karst spring (southern France).

How to cite: Sivelle, V., Cousquer, Y., Jourde, H., and Mazzilli, N.: A Bayesian multi-model framework for structure selection and parameter estimation for lumped parameter modeling in karst hydrology., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5147, https://doi.org/10.5194/egusphere-egu23-5147, 2023.

14:25–14:35
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EGU23-200
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ECS
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On-site presentation
A critical review of solute mixing and transport approaches in karstic groundwater modelling and key challenges 
Kübra Özdemir Çallı, Süleyman Selim Çallı, Daniel Bittner, Gabriel Chiogna, and Andreas Hartmann

Modelling solute mixing and transport processes is one of the key steps to effectively managing karstic groundwater resources, particularly under the threat of climate change and risk of contamination. For that reason, a considerable body of literature has been devoted to understanding and describing solute mixing and transport processes in karst aquifers. However, due to the strong multiscale heterogeneity (from microscale to aquifer scale), modelling solute mixing and transport processes in karst aquifers remains a challenging task. This presentation critically reviews the current state of knowledge and fundamental challenges in the modelling of solute mixing and transport processes in karst aquifers, thereby collocating and synthesizing the existing body of knowledge in the literature. To provide a holistic and objective picture of the state-of-the-art of the solute mixing and transport modelling, we performed a bibliometric analysis on the relevant literature for karst groundwater studies (over 2800 scientific papers). Further, with a meta-analysis of scientific papers focusing on the quantitative tracer tests, we evaluated the field-based transport parameters that are typically served for the solute mixing and transport models.

The review unveils the fundamental modelling hinges underlying a successful modelling practice for the solute mixing and transport processes in karst, thereby discussing to what extent and in what ways we are dealing with these challenges. The major modelling challenges are defined as follows: (i) Model conceptualization based on data collection and system understanding (e.g., How well is the problem of interest defined? To what extent is the domain of interest described?), ii) Model selection considering the choice of a dominant physicochemical process (e.g., How well is the process of interest represented by a set of governing equations over the problem domain?), iii) Time-variability of solute mixing and transport processes (e.g., To what extent do the parameters represent the process of interest under the different time-scales?), iv) Model parametrization considering the parameter non-uniqueness and transferability (e.g., How realistic are the model parameters? To which extent are they transferable over the same aquifer?), v) Uncertainty quantification in model results (e.g., How robust are the model results? How much are we (un)certain about our model?). Finally, we address potential research directions and knowledge gaps by encouraging the community for building a protocol for solute transport modelling in karst aquifers, as well as providing more transparent and reproducible results.

How to cite: Özdemir Çallı, K., Çallı, S. S., Bittner, D., Chiogna, G., and Hartmann, A.: A critical review of solute mixing and transport approaches in karstic groundwater modelling and key challenges, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-200, https://doi.org/10.5194/egusphere-egu23-200, 2023.

14:35–14:45
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EGU23-6413
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On-site presentation
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Dynamics of seasonal CO2 concentrations above and below the karst-water table are influenced by density-driven transport: monitoring data from a cave in the Swabian Jura and interpretation with numerical simulation models 
Holger Class, Leon Keim, Larissa Schirmer, Bettina Strauch, Kai Wendel, and Martin Zimmer

It is long known that dissolved aqueous CO2 is the key driving force of chemical reactions leading to rock corrosion, which is denoted as karstification. Accordingly, it is evident that meteoric water percolating through the biologically active vadose zone leads to replenishment of CO2 concentrations in karst water. We performed long-term measurements in a cave that show quick responses of gaseous CO2 concentrations in cave air after rain events.

More importantly, however, our research aims at highlighting a so far by the literature totally ignored process in karst research, which is density-driven dissolution of CO2 at the karst-water table. Our preliminary results indicate that this process can have high significance for hydraulic conditions where water is stagnant or at small convective base velocities (Class et al., 2021).

In our most recent work (Class et al., 2022, submitted), we monitored the influence of seasonally fluctuating gaseous CO2 concentrations in a deep karst cave on aqueous CO2 concentrations in different depths of a stagnant water column. The data indicate that density-driven enhanced dissolution at the karst-water table is the driving force for a fast increase of aqueous CO2 during periods of high gaseous concentrations in the cave, while during periods of lower gaseous concentrations the decline of aqueous CO2 is limited to shallow water depths in the order of 1m. Numerical simulations with a Navier-Stokes model and water density dependent on CO2 concentration can be used to interpret the data and, perspectively, to extrapolate to geologically relevant time scales. This can also include the dissolution of CaCO3, which is likely further increasing the relevance of density-driven dissolution at the karst-water table.

References:
H. Class, P. Bürkle, T. Sauerborn, O. Trötschler, B. Strauch, M. Zimmer: On the role of density-driven dissolution of CO2 in phreatic karst systems, Water Resources Research 57(12), e2021WR030912, 2021, doi:10.1029/2021WR030912

H. Class, L. Keim, L. Schirmer, B. Strauch, K. Wendel, M. Zimmer: Seasonal dynamics of gaseous CO2 concentrations in a karst cave correspond with aqueous concentrations in a stagnant water column, manuscript submitted, December 2022

How to cite: Class, H., Keim, L., Schirmer, L., Strauch, B., Wendel, K., and Zimmer, M.: Dynamics of seasonal CO2 concentrations above and below the karst-water table are influenced by density-driven transport: monitoring data from a cave in the Swabian Jura and interpretation with numerical simulation models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6413, https://doi.org/10.5194/egusphere-egu23-6413, 2023.

14:45–14:55
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EGU23-12506
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ECS
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On-site presentation
The role of seasonal variation of precipitation/recharge for different climates in karst genesis behaviors 
Chuanyin Jiang, Hervé Jourde, and Xiaoguang Wang

Recharge is an important factor controlling dissolution processes during speleogenesis of karst aquifers. In former studies simplified assumptions were considered, where a maximum recharge rate is assumed while its fluctuation is ignored. Under the latter assumption, the karst genesis is clearly divided into two successive processes characterized by either a hydraulic head limitation (hydraulic control) or a flow rate limitation (catchment control). In this study, we consider a karst system evolving according to a maximum recharge rate linked to the seasonal variation of precipitation, which may lead to speleogenesis processes under hydraulic control or catchment control from the beginning of the karst genesis. We found that, without considering the recharge fluctuation, the enlargement of fractures as well as the dimensions of dissolving area under a long-term evolution tends to be underestimated. Moreover, in the cases of a large catchment area, the time required to reach the final dissolution patterns tends to be underestimated (i.e., earlier breakthrough), while it tends to be overestimated in the cases of a small catchment area. In addition, the flow focusing during the karst genesis may be interrupted during dry seasons when the recharge regime is under catchment control. This may cause a stagnation in the evolution of flow channeling or even a less localized flow field. This study highlights the importance of recharge fluctuation in modeling karst genesis, which may have important engineering implications for the management of karst aquifers or the leakage risk prediction at dam sites.

How to cite: Jiang, C., Jourde, H., and Wang, X.: The role of seasonal variation of precipitation/recharge for different climates in karst genesis behaviors, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12506, https://doi.org/10.5194/egusphere-egu23-12506, 2023.

14:55–15:05
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EGU23-12938
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ECS
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On-site presentation
Solute transport experiments and modelling in terminal conduit of karst hydrosystems, Southern France 
Mohammed Aliouache, Pierre Fischer, Pascal Brunet, Lionel Lapierre, Benoit Ropas, Frank Vasseur, and Hervé Jourde

In the community working on karst hydrosystems, the needs for subsurface solute and contaminant transport characterization is widely acknowledge.  In former studies, several researchers addressed these needs with different approaches such as laboratory experiments, field tests, and groundwater flow and transport simulations. The main objective of such approaches is to improve knowledge of transport processes in karst hydrosystems, and propose solutions to limit the downstream hydrogeological risks (contamination of water resources). In this study, we performed a solute transport experiment in different karst aquifers, in the terminal karst conduit near the spring. We injected a dye in the karst conduit and we monitored the restitution of the tracer at three different zones downstream. In each zone, five probes were placed at different locations (middle, up, down, left and right parts of the cave) along the cross-section of the karst conduit.

Experimental data allowed to reconstruct a transient spatial distribution of concentration for each zone and a general evolution of solute plume. It also provided information about dye mixing along the karst conduit. As a next step, these results are compared to simulated results to investigate the effect of karst conduit geometry, turbulent flow and velocity profiles on concentration profiles, mixing processes and the evolution of solute plume along the conduit. Preliminary results showed that the consideration of the complex karst conduit geometry and morphology has an important effect on transport processes, with a behavior notceably different from the one obtained with numerical simulations on simplified karst conduit geometries.

How to cite: Aliouache, M., Fischer, P., Brunet, P., Lapierre, L., Ropas, B., Vasseur, F., and Jourde, H.: Solute transport experiments and modelling in terminal conduit of karst hydrosystems, Southern France, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12938, https://doi.org/10.5194/egusphere-egu23-12938, 2023.

15:05–15:15
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EGU23-5640
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On-site presentation
Degradation and loss of soil in karst terrains 
Umberto Samuele D'Ettorre, Isabella Serena Liso, Luca Pisano, Veronica Zumpano, and Mario Parise

Fragility of karst derive from a variety of reasons, starting from peculiarity of the geological, hydrogeological, and ecological features, and the facility to transform and negatively impact the environment through many anthropogenic activities. This makes karst terrains among the most endangered areas in the world, as repeatedly demonstrated in many karst areas, also with severe impacts on natural resources. Apulia, the southern-east portion of Italy, is an almost entirely karst region, where expansion of the urbanized areas, development of agricultural practices, and lack of awareness of the importance of karst resources over the last decades have determined an acceleration in the degradation of the karst environment. This is quite in contrast with the long history of the region, where past cultures and civilizations were able to live sustainably with the karst environment, without destroying or polluting its precious natural resources, in primis groundwater.

For instance, the agricultural practices marked a very bad time starting from the 1980s, when intense stone clearing (performed with the goal to obtain new land for cultivation) strongly changed the original karst landscape, which was characterized by bare karst, with slightly incised karst valleys and dolines, and a high number of caves. As a result of such an intense conversion of land cover, karst landforms were highly disturbed, many of them were canceled, and surficial erosion and loss of soil had to be often registered on the occasion of the main rainstorms. Alta Murgia, one of the main karst regions of Apulia (also included within the National Natural Park) was particularly affected, and obliteration of many karst features had to be recorded. Furthermore, the extraction activity carried out in quarries, to extract limestone rocks used for building and ornamental purposes, resulted in destruction of karst caves, against the regional laws which prescribed the need in exploring any cave found during quarrying, aimed at ascertaining any likely interest of the underground karst. Overall, these anthropogenic activities caused an high negative impact on the Alta Murgia karst, which only recently has started to become worth of specific studies from the scientific community. Quantification of the loss of soil, and of the karst landforms is not easy, but in some portions of Alta Murgia has definitely been significant.

Within projects dedicated to creating a greater awareness about local populations of the importance of living in karst, and of respecting such a natural landscape which hosts fundamental natural resources, we present in this contribution some examples of preliminary evaluations of the landscape changes observed, and of their negative impacts on karst.

 

References

Parise M., 2016, Modern resource use and its impact in karst areas – mining and quarrying. Zeitschrift fur Geomorphologie, vol. 60, suppl. X, p. 199-216.

Parise M. & Pascali V., 2003, Surface and subsurface environmental degradation in the karst of Apulia (southern Italy). Environmental Geology, vol. 44, p. 247-256.

Pisano L., Zumpano V., Pepe M., Liso I.S. & Parise M., 2022, Assessing Karst Landscape Degradation: a case study in Southern Italy. Land, vol. 11, 1842.

How to cite: D'Ettorre, U. S., Liso, I. S., Pisano, L., Zumpano, V., and Parise, M.: Degradation and loss of soil in karst terrains, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5640, https://doi.org/10.5194/egusphere-egu23-5640, 2023.

15:15–15:25
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EGU23-2979
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On-site presentation
Natural production of nitrate by groundwater nitrification in New Zealand karst springs 
Michael Stewart, Chris Hickey, Magali Moreau, Joseph Thomas, and Roger Young

The objective of this work is to understand the sources of nitrate in Te Waikoropupū Springs (‘the springs’) in New Zealand, and thereby contribute to their preservation. Previous work has shed light on the recharge sources of water to the springs (Stewart and Thomas, 2008), and nitrate mass balance based on this recharge model reveals the nitrate values in the recharge waters when they reach the springs. The major recharge source (from pristine forest on karst uplands) delivers much more nitrate to the springs than expected from measurements on water in its recharge area. This excess nitrate is attributed to nitrification (following mineralisation of organic-N) within the oxic karst groundwater system as the water flows to the springs.

Nitrification (bacterial conversion of ammonium to nitrate) is widespread in soils, unsaturated zones and oxic groundwater systems. Evidence showing natural production of nitrate by nitrification in the current system is given by: (1) Total nitrogen measurements: If organic-N is converted to nitrate-N along the flowpath from the Karst Uplands to the springs, there must be input of 5 kg/ha/yr of organic-N from the recharge area of 170 km2. This is within the range found by McGroddy et al. (2008) for first order streams from pristine forests in NZ. (2) 15N and 18O measurements: Nitrification produces nitrate with low values of the isotope ratios as observed for the springs, whereas denitrification would cause high values which are not observed. (3) Scientific literature: Recent papers have reported nitrification as a previously unrecognised source of nitrate in oxic karst systems. For example: Musgrove et al. (2016) showed that groundwater nitrate concentrations in the Edwards Aquifer were higher than those in the surface water recharge. They concluded that nitrification within the aquifer is the source of the extra nitrate in the groundwater.

References

McGroddy, M.E., Baisden, W.T., Hedin, L.O. 2008. Global Biogeochemical Cycles 22, GB1026.

Musgrove, M., Opsahl, S.P., Mahler, B.J., Herrington, C., Sample, L.L., Banta, J.R. 2016.  Science of the Total Environment 568, 457–469.

Stewart, M.K., Thomas, J.T. 2008. Hydrology and Earth System Sciences 12(1), 1-19.

How to cite: Stewart, M., Hickey, C., Moreau, M., Thomas, J., and Young, R.: Natural production of nitrate by groundwater nitrification in New Zealand karst springs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2979, https://doi.org/10.5194/egusphere-egu23-2979, 2023.

15:25–15:35
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EGU23-8112
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ECS
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On-site presentation
Hydrological control on cave ventilation and its effect on the heat balance of Longeaigue cave 
Claudio Pastore, Marc Luetscher, Frédéric Doumenc, Amir Sedaghatkish, Eric Weber, and Pierre-Yves Jeannin

The network of fractures and conduits crossing a karst massif drains water and air from the atmosphere deep into the massif, exchanging heat at the boundaries between rock, air and water. The thermal characteristic of the rock together with thermal processes including convection, evapo-condensation, radiation and conduction, concur to fix the cave’s temperature. The thermal length, the distance at which the external temperature fluctuations are damped, and the energy balance of the cave system depend on its geometry and the fluxes therein. Comprehensive knowledge of what modifies these thermal characteristics is of interest for e.g. low-enthalpy geothermal exploitation, mineralisation in water supplies and also for paleoclimatic studies on speleothems.

In Longeaigue cave (Val-de-Travers, Jura mountains, CH), we deployed several sensors measuring airflow and temperature along the main conduit network. The cave is mainly dry and has a lower and upper entrance leading to an intense airflow controlled by the chimney effect. The temperature oscillations observed throughout the cave are chiefly related to external temperature and airflow variations. Results from 8 monitoring stations reveal that 90% of the energy brought in by the air during ventilated periods is exchanged within the first tens of meters from the cave entrances. However, temporary interruptions of the airflow occur during periods of flooding related to rainfall and snowmelt. This situation can take place several times per year. Our observations demonstrate that the transient nature of this airflow modifies the temperature signals in the cave, affecting the cave energy balance in a differentiated way according to seasonal hydrological conditions. With the increasing winter temperatures, we anticipate a progressive shift towards a summer ventilation regime enhanced by limited summer rainfall. A positive feedback is observed on the energy balance of the cave. It is therefore of crucial importance to consider the presence of subsurface ventilation for the thermal characterisation of karstic environments, which can modify the biochemical, physical and thermal characteristics of seeping water and, in turn, impact on the interaction with the encasing rock.

How to cite: Pastore, C., Luetscher, M., Doumenc, F., Sedaghatkish, A., Weber, E., and Jeannin, P.-Y.: Hydrological control on cave ventilation and its effect on the heat balance of Longeaigue cave, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8112, https://doi.org/10.5194/egusphere-egu23-8112, 2023.

15:35–15:45
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EGU23-12973
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ECS
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On-site presentation
Seasonal pressurization of a coastal karst: the paleolithic decorated Cosquer cave (SE France) 
Pellet Hugo, Henry Pierre, Arfib Bruno, and Touron Stéphanie

The Cosquer cave is a paleolithic decorated cave, in a coastal karst linked to the sea. Stability of climatic parameters in caves is known to be one main condition for conservation of art. Hydroclimate data are measured since several years at a 5 minutes time step: karst air pressure, water level in the karst, atmospheric pressure and sea level. Data shows an unusual behaviour for a karst: the karst air pressure is nearly always higher than the atmospheric pressure. As a result, water level in the karst is below the sea level. Some rock art figures present on walls near water level undergo wash out and fading but limited thanks to the karst pressurization. A stop of this mechanism due to rising sea-level, an increase of the massif permeability or changes in climatic conditions would lead to the loss of arts near water bodies.

The cave air overpressure is related to the rock permeability that should be low. The pressure time series show that three main processes drive the cave pressure. The daily variations of the sea tide provide an assessment of the cave air volume above the pools water level. Although the cave air is confined by the rock and the seawater, there are external air inflows during short pressurization events, that can be deduced from pressure data. Then, the low cave air pressure decrease over the summer season is explained by air outflow through the rock. A bulk permeability is then calculated using Darcy law, assuming a gas permeability in a non-saturated medium. Three theoretical cases are evaluated: an equivalent porous medium, a single fracture, and a single karst conduit. The time series give an observation database to assess future changes in the pressure behaviour of this decorated paleolithic cave, and to detect water level increase and adjust conservation choices.

How to cite: Hugo, P., Pierre, H., Bruno, A., and Stéphanie, T.: Seasonal pressurization of a coastal karst: the paleolithic decorated Cosquer cave (SE France), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12973, https://doi.org/10.5194/egusphere-egu23-12973, 2023.

Posters on site: Mon, 24 Apr, 16:15–18:00 | Hall A

Chairpersons: Jannes Kordilla, Isabella Serena Liso, Mario Parise
A.169
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EGU23-13275
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Highlight
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Model-based assessment of dynamic volume estimates for karst aquifers 
Steffen Birk and Mahmoud Abirifard

Karst springs frequently drain large catchment areas and thus represent important water resources. Adequate management of karst water resources requires quantitative information about the drainable water volume, i.e., the dynamic volume of the karst aquifer supplying the spring. The mathematical integration of a functional relationship fitted to the observed discharge recession curve is one approach commonly employed for this purpose. Yet, this approach implicitly assumes that the observed recession behavior can be extrapolated to longer times and lower discharge values. Here, we explore the adequacy of this approach using the numerical karst groundwater flow model MODFLOW-CFP to simulate the discharge recession of hypothetical karst aquifers. While the model scenarios represent simplified hydrogeological settings, each of them includes complexities that may be encountered in real karst aquifers. By comparing the actual dynamic volume of the modelled aquifer to the volume estimate obtained from recession analysis, we identify factors potentially affecting the accuracy of the dynamic volume estimate (Abirifard et al., J. Hydrol., 2022, https://doi.org/10.1016/j.jhydrol.2022.128286 ). It is found, for example, that a decrease of hydraulic conductivity with depth causes underestimation of the dynamic volume, whereas groundwater abstraction within the spring catchment results in an overestimation. Real-world examples where these factors likely affect the recession behavior and thus the dynamic volume estimate are identified and described.

How to cite: Birk, S. and Abirifard, M.: Model-based assessment of dynamic volume estimates for karst aquifers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13275, https://doi.org/10.5194/egusphere-egu23-13275, 2023.

A.170
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EGU23-6405
Investigating the hydrological behaviour of the Upper Pivka Valley (Slovenia) 
Cyril Mayaud, Blaž Kogovšek, Metka Petrič, Nataša Ravbar, Matej Blatnik, and Franci Gabrovšek

The Pivka River is a 20 km long stream located 40 km SW from Ljubljana (Slovenia), which disappears in the world famous Postojna Cave. While the river flows permanently on flysch rocks in the valley lower part, water is only present temporarily in the valley upper part due to the karstic nature of the aquifer located below the river. This aquifer is assumed to be linked to the larger Javorniki karst aquifer that belongs to the catchment of the Unica and Malenščica Springs, which drain water from the whole region. During high water period, the regional groundwater level rises up to 50 m, and 17 temporary lakes might appear on the valley surface. Because the hydrological situation in the Javorniki karst aquifer is assumed to affect flooding in the Pivka Valley, the interaction between both need to be understood. A network of nine automatic stations recording water level, specific electrical conductivity and water temperature at a 30 min interval has been progressively established in the valley since 2020. The three years dataset has been analysed with data collected in the water active caves of the Javorniki karst aquifer and at the Unica and Malenščica Springs. Results allowed elaborating a conceptual hydrological model of the region. They emphasized that the karst aquifer below the Upper Pivka Valley acts as an overflow of the Javorniki karst aquifer during high water periods, while it flows back into the Javorniki karst aquifer and further toward the Unica and Malenščica springs during the recession.

How to cite: Mayaud, C., Kogovšek, B., Petrič, M., Ravbar, N., Blatnik, M., and Gabrovšek, F.: Investigating the hydrological behaviour of the Upper Pivka Valley (Slovenia), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6405, https://doi.org/10.5194/egusphere-egu23-6405, 2023.

A.171
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EGU23-14082
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ECS
A method to determine the dissolution and erosion rates of marly gypsum samples from Ripon, UK 
Gabriella Williams, Elisabeth Bowman, Domenico Bau, and Vanessa Banks

Ripon is a town affected by frequent collapse sinkholes that occur due to the rapid dissolution of the underlying gypsum. This gypsum is interbedded and mixed with low solubility but easily water weakened calcareous marl. Construction sites underlain by cavities can be remediated, but if even small flow paths remain, new cavities can appear in close proximity. Dissolution rates previously determined for gypsum have either been on high purity specimens or do not consider the insoluble impurities. It is therefore important to understand the role of interbedded calcareous marls in controlling cavity distribution and growth. A method is proposed to evaluate the effect of marl impurity on gypsum dissolution rates in this area.

For the dissolution test, water is circulated through a hole drilled in a gypsum specimen from Ripon. As the gypsum dissolves, the marl could detach and settle, become suspended or also dissolve. If it remains attached, however, it could impede further gypsum dissolution. Conductivity, total dissolved solids (TDS) and pH of the water are monitored and the test continues until the conductivity has stabilised. This indicates that the water is saturated with gypsum and dissolution has ceased. The water is then evaporated to recover suspended solids, which are put through particle size distribution (PSD) sieves. The post-test specimen mass is added to the recovered solid mass and compared to the pre-test mass.

After testing, mass loss is estimated from both conductivity and TDS curves, and these are compared to measured mass loss. Changes in pH are taken to indicate dissolution of calcareous components in the marl. The conductivity curve is used to find the dissolution rate constant of the specimen, and its cross-section is visually inspected to check the dissolution pattern. The PSD is used to study transport and deposition of insoluble material. Results are combined to assess the influence of marl on gypsum dissolution and sinkhole development, which can be applied both in Ripon and elsewhere.

How to cite: Williams, G., Bowman, E., Bau, D., and Banks, V.: A method to determine the dissolution and erosion rates of marly gypsum samples from Ripon, UK, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14082, https://doi.org/10.5194/egusphere-egu23-14082, 2023.

A.172
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EGU23-1596
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ECS
Study on the relationship between geometrical features and permeabilities of fracture networks based on the spring hydrographs 
Yuan Chen, Longcang Shu, Zhe Wang, Shuyao Niu, and Zihan Ling

Identifying the hydraulic properties of fracture networks is important for groundwater management of karst aquifers which are composed of fractured rocks and cavernous conduits. Although much research has been done on the geometrical characteristics and flow calculation of discrete fracture networks, further exploration on the relativity between them is still needed. This study aims to quantitatively analyze the relationship between different geometrical features and permeabilities of fracture networks based on the spring hydrographs, which can intuitively reflect the flow velocity of karstic medium system.

We simulated rainfall-discharge processes of a karst area with different distributions of random fracture networks using a numerical model developed based on a laboratory experiment. The results of plenty of simulation show that the total length of fracture networks and relative density of fractures are most related to the peak values of spring discharge with the Pearson correlation coefficients of over 0.8, indicating that these two geometrical parameters can reflect the permeability of random fracture networks best, followed by the fractal dimension and number of intersection points. However, the connectivity of fracture networks also depends on whether there is one or more fractures that go through the entire study area, which greatly promote water movement and solute transport in the fractured rocks. Another factor that impacts the permeability of fracture networks is uniformity of distribution of fractures, in that a drastic propagation that occurs in a small area with clusters of fractures could not represent the overall permeability of fracture networks. Additionally, the surrounding rock matrix with ultralow hydraulic conductivity has a positive and significant impact on the water transmission capacity of fracture networks, showing that the strong water blocking effect of matrix pushes the groundwater movement towards fractures with high delivery capacity.  

This study utilized the spring hydrographs to evaluate the permeability of fracture networks for convenience compared to the calculation of equivalent permeability coefficient, while the latter is more accurate and representative. The above findings can enhance the understanding of properties of fracture networks, benefit targeted observations of detailed structures of fractured rocks and then improve the efficiency of groundwater management in karst areas.  

How to cite: Chen, Y., Shu, L., Wang, Z., Niu, S., and Ling, Z.: Study on the relationship between geometrical features and permeabilities of fracture networks based on the spring hydrographs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1596, https://doi.org/10.5194/egusphere-egu23-1596, 2023.

A.173
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EGU23-12875
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ECS
Coupled CFD-DEM Modelling of subsidence and canyon formation in an evaporite karst system 
Djamil Al-Halbouni, Lars Ruepke, Monica Giona Bucci, Torsten Dahm, and Aaron Micallef

Surface stream-channels and subsurface conduits form the connecting interface between on- and offshore groundwater in the coastal transition zone. Rapid canyon formation occurs due to erosion and dissolution of material rapid retrogressive growth, slope failure, and subsidence, thus posing important geohazards in coastal areas.

We here focus on the formation of canyon systems with theatre shaped heads as found along the Dead Sea. Underlying their recent development is a dynamic evaporite karst system fed by channelized groundwater flow with subrosion processes and subsequent discharge into the lake. We use a 3D hydromechanical modelling approach to derive information on the hydromechanics and feedback between changing fluid pathways, deformation and the formation of stream-channel morphologies under varying conditions. We use a hydrogeological setup consisting of (A) a layered alluvial fan system alternating between mechanically weak, salt/rich clay-silt material and mechanically stronger, compound alluvial sandy-gravel sediments, (B) a pronounced lateral border between the former Dead Sea lakebed and the alluvial fans, (C) a Darcy-flow type fresh-water inflow through tubes at different depths and (D) a natural hydraulic gradient of 30 m/km. We hereby couple simple computational fluid dynamics with distinct elements to simulate subrosion processes as observed for the Dead Sea shore.

We found that the shape of the canyon, and particularly the morphology of canyon heads, is (1) intrinsically linked to the geologic material conditions, i.e. the stratigraphy of the subsurface, (2) the nature (3D tube network) of the karst system and (3) the hydraulic gradient conditions. This study hence gives further insight into the role of the hydromechanical conditions that drive the formation of canyons and subsidence in unconsolidated material and shows the applicability of this approach to derive morphometrics in similar coastal environments.

How to cite: Al-Halbouni, D., Ruepke, L., Giona Bucci, M., Dahm, T., and Micallef, A.: Coupled CFD-DEM Modelling of subsidence and canyon formation in an evaporite karst system, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12875, https://doi.org/10.5194/egusphere-egu23-12875, 2023.

A.174
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EGU23-4134
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Highlight
Sinkholes evolution in coastal settings: some examples from Southern Italy 
Mario Parise and Isabella Serena Liso

The southernmost sector of Apulia Region can be described as a karst peninsula surrounded by the Adriatic and the Ionian Seas. The process of seawater intrusion, together with groundwater outflow, mainly coming out at the coastline, produces a water mixing that enhances the solution of soluble carbonate rocks. The effect of these processes can be observed along the coastline, characterized by several areas interested by sinkhole development and evolution. In some cases, they have become famous touristic attraction as at Grotta della Poesia, visited every summer by thousands of tourists; in other cases they represent spectacular sites of high ecological values, since they host peculiar ecosystems, with many fauna and flora species. At several sites along the Apulian coasts, sinkhole evolution form elongated bays, completely protected from sea waves, as in the sector between Fasano and Brindisi. Along this coastal stretch, field surveys revealed different sinkholes stages that can be described as successive phases in the development of bays: from opening of individual collapse sinkholes, typically at distance lower than 20 m from the coastline, to evolution in elongated sinkholes deriving from coalescence of nearby features, eventually leading to the final stage, with formation of protected bays, which main elongation depends upon the main discontinuity systems in the rock mass, and the main direction of sea storms as well. These examples highlight the importance of sinkhole processes in predicting the future evolution of the coast, and may be of help to local authorities for the most proper management of such a fragile environment.

How to cite: Parise, M. and Liso, I. S.: Sinkholes evolution in coastal settings: some examples from Southern Italy, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4134, https://doi.org/10.5194/egusphere-egu23-4134, 2023.

A.175
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EGU23-13530
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ECS
Dynamics of sinkhole and uvala development on the eastern shore of the Dead Sea, 1980-2022 
Hanna Z. Schulten, Robert A. Watson, Djamil Al-Halbouni, Osama Al-Rabayah Al-Rabayah, Fayez Abdulla, and Eoghan P. Holohan

The Dead Sea is a hypersaline terminal lake whose level has been declining due to anthropogenic stresses since the 1960s. At its eastern shore, near Ghor-Al-Haditha in Jordan, over 1200 collapse sinkholes have been mapped roughly parallel to the shoreline from the 1980s until 2017. This mapping also documented five larger karstic depressions (uvalas), that formed in close spatial-temporal association with the sinkholes, and demonstrated that sinkhole and uvala formation during this period has migrated laterally, both in the direction of shoreline retreat (from east to west) and parallel with the shoreline from south to north.

Here, we use new, high-resolution optical satellite imagery from the Pleiades and PNEO satellites, to show that over 500 new sinkholes have formed between 2018-2022. Furthermore, three new uvalas have developed to the north in accordance with the appearance of the sinkholes. Our study indicates quantitatively that the coalescence of sinkholes to form larger compound sinkholes is a subsequent stage of uvala development. New mapping confirms a previously established link between sinkhole size distribution and the mechanical properties of the sedimentary materials in which they form, with holes formed in salt-dominated morphologies being smaller in diameter than those in alluvium and lacustrine mudflats. Initial comparison to local meteorological records has shown that a temporal link between periods of high rainfall and enhanced sinkhole formation is not readily apparent at the resolution of the sinkhole mapping. Moreover, as previous studies had hypothesized, growth of the sinkhole population and the uvalas continues towards the north and is diminished to the south. Our results help to inform hazard monitoring and mitigation strategies at Ghor Al-Haditha: for example, presently growing areas of surface depressions are within 130 meters of a 700-meter-long stretch of the western main highway connecting the north and south of Jordan. Therefore, we suggest that infrastructure such as the highway continue to be monitored in light of the observed subsidence.

How to cite: Schulten, H. Z., Watson, R. A., Al-Halbouni, D., Al-Rabayah, O. A.-R., Abdulla, F., and Holohan, E. P.: Dynamics of sinkhole and uvala development on the eastern shore of the Dead Sea, 1980-2022, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13530, https://doi.org/10.5194/egusphere-egu23-13530, 2023.

A.176
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EGU23-13664
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ECS
Indicator Kriging approach for the assessment of groundwater nitrate pollution in the Salento aquifer (Southern Italy) 
Gaetano Daniele Fiorese, Maria Rosaria Alfio, and Gabriella Balacco

Groundwater, being the largest distributed freshwater supply, plays a central role in sustaining ecosystems and enabling human adaptation to climate change. The strategic importance of freshwater for global water and food security will intensify as the frequency of extreme weather events such as floods and droughts events. Many aquifers are severely stressed due to unsustainable management of the water resource that compromises its quantity and quality.

Today, nitrate pollution is the most common form of groundwater contamination worldwide. Many Mediterranean regions present worrying concentrations of nitrate in groundwater and are consequently one of the most polluted territories across the world. Nitrate monitoring is fundamental since excessive concentrations in water resources may affect the quality of crops and causes several human health disorders. For this purpose, this study aimed to deal with the evolution in space and time of nitrate concentrations in the coastal karst aquifer of Salento (Puglia, Southern Italy), whose water demand for drinking and irrigation purposes relies on groundwater. The intrinsic vulnerability of this territory is critical due to its complex geomorphological and structural characteristics, the presence of saltwater beneath freshwater, intensive exploitation, and climate change.

Several different chemical surveys from 1995 to 2021 were organized into two-time datasets to focus on the spatio-temporal evolution of nitrate concentrations. The geostatistical Indicator Kriging (IK) method was used for this purpose. This is a spatial interpolation technique aimed at estimating the conditional cumulative distribution function of a variable at an unsampled location. Indicator Kriging analyses were performed for a direct estimation of the local conditional probabilities of nitrate concentrations for the two reference periods using sampled available wells. Probability maps representing the spatial distribution of water quality have been obtained as result. Results highlight a critical situation in terms of nitrate pollution, as most of the territory has experienced an increase over the past 25 years, progressively affecting large areas.

How to cite: Fiorese, G. D., Alfio, M. R., and Balacco, G.: Indicator Kriging approach for the assessment of groundwater nitrate pollution in the Salento aquifer (Southern Italy), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13664, https://doi.org/10.5194/egusphere-egu23-13664, 2023.

A.177
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EGU23-12574
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ECS
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Multi-disciplinary approach for assessing the impact of a flood event in a shallow karst cavity (Pindal Cave, Spain) 
Tamara Martin-Pozas, Soledad Cuezva, Fernández-Cortés Ángel, María González-Pumariega, Elsa Duarte, Marco de la Rasilla, Juan Carlos Cañaveras, David Benavente, Cesáreo Sáiz-Jiménez, and Sergio Sánchez-Moral

Pindal Cave (Asturias, Spain) and its Paleolithic art have been part of the UNESCO World Heritage List since 2008. The importance of this Paleolithic art led to a research project that deals with deciphering the relationships between environmental conditions and microbial activity in natural underground ecosystems and its application to the design of conservation strategies.

The Pindal karstic system develops in a calcareous massif (Carboniferous) modeled in the form of an erosional marine terrace (rasa) by coastal morphogenetic processes. This marine terrace level is located at an elevation of 30-68 meters above current sea level and constitutes the preferred catchment area for runoff water from another higher level (140-170 m) developed on quartzite layers with very low permeability (Ordovician). The cave is the main endokarstic feature of the system. On the surface of the 30-68 m rasa there are numerous exokarstic structures of sinkhole and polje type. On one of the sinkholes, located almost vertically to the cave, a cattle farm was installed in 1995.

Between October 19 and 23, 2019, an extreme episode of rainfall occurred in the area with a cumulative total of 209 l/m2. This event caused a strong accumulation of water in the aforementioned sinkhole that finally collapsed, flooding the cave for several days. Immediately after the cave had been drained, environmental measurements and sediment samplings were carried out at various points in order to determine the changes caused in the underground ecosystem. In the most affected area by the flood, changes in humidity and temperature of air and sediments were recorded for several months. Biogeochemical data indicated that the sediments deposited as a result of the flooding presented high values of available organic matter, nitrogen, phosphorus and potassium, much higher than those of the innermost areas did not directly affect by the flooding. The comparative microbiological study of sediment samples revealed that the flood produced very significant changes in the microbial composition of sediments: the appearance of the bacterial phyla Bacillota and Bacteroidota, including groups of opportunistic bacterial pathogens (Corynebacterium, Thauera, Clostridiales) and the almost complete disappearance of Rokubacteriales and Nitrospirota. Bacillota and Bacteroidota are common in the intestinal tract of mammals and are dominant in liquid and solid samples of manure from dairy farms. Overall, the results conclude that the sediments dragged into the cave were accompanied by residues from livestock farming and indicate the high degree of vulnerability of this type of cave. Although livestock activity finally ceased in 2021, we continue analyzing environmental parameters, waters, sediments and microbial populations to evaluate their evolution in the medium-long term.

Research funded by PID2019-110603RB-I00 – SUBSYST project and PID2020-114978GB-I00

How to cite: Martin-Pozas, T., Cuezva, S., Ángel, F.-C., González-Pumariega, M., Duarte, E., de la Rasilla, M., Cañaveras, J. C., Benavente, D., Sáiz-Jiménez, C., and Sánchez-Moral, S.: Multi-disciplinary approach for assessing the impact of a flood event in a shallow karst cavity (Pindal Cave, Spain), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12574, https://doi.org/10.5194/egusphere-egu23-12574, 2023.

A.178
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EGU23-4013
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ECS
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Strategies for karst groundwater flow characterization in remote, mountainous, snowmelt-dominated catchments 
Sara Lilley and Masaki Hayashi

The Front Ranges of the Canadian Rockies are home to extensive carbonate assemblages that host karst aquifers. New caves and karst springs have recently been discovered in the mountains from Banff, Alberta extending all the way to the United States border, although little research has been conducted on them due to the challenging terrain. In this study, we focus on the Watridge Karst Spring, which is located on a forested hillside in a mountain range that reaches an elevation of 3400 m. This perennial spring can discharge up to 3000 L/s. Karst catchments in these snowmelt-dominated, glacierized areas have sparse vegetation, heavy snowfall, and high hydraulic gradients, leading to efficient groundwater infiltration. As a result, the hydrochemistry of these springs often exhibits strong and rapid fluctuations. The effects of rapid conduit flow are expressed at the Watridge Karst Spring by an increase in discharge followed by a lagged decrease in electrical conductivity (EC), occurring over a diurnal-scale and a longer-scale (e.g., episodic snowmelt or heavy storm). This research aims to use hydrologically relevant metrics to understand the recharge, flow paths, and storage capacity of the aquifer. 
Particularly, we used signal processing of the fluctuations in discharge, EC and air temperature to estimate groundwater response time, defined here as the lag time between a hydrologic event and a resulting change in hydrochemistry. Response time can be used to approximate celerity in the case of discharge, and velocity in the case of EC. Additionally, automatic water sampling allowed for the observation of rapid changes in major ion chemistry.
The results yielded an estimated groundwater conduit velocity on the order of 0.1 m/s that steadily decreases with diminishing flow. It was also found that a distinct shift in the EC signal phase and an associated change in mineral dissolution marks the drainage of an overflow conduit path. This is supported by dye tracer experiments of up to 14 km distance where a maximum velocity of 0.14 m/s has been recorded. Our results show that continuous hydrochemical monitoring of discharge and meteorological conditions at a high-temporal resolution can be used as a first step in characterizing conduit system response. For alpine karst springs with strong hydrochemical fluctuations, this strategy may limit the need to conduct tracer tests involving laborious field work in remote, mountainous locations.

How to cite: Lilley, S. and Hayashi, M.: Strategies for karst groundwater flow characterization in remote, mountainous, snowmelt-dominated catchments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4013, https://doi.org/10.5194/egusphere-egu23-4013, 2023.

A.179
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EGU23-5031
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Distribution and characteristics of glaciokarst on the island of Gotland, Baltic Sea - its role on groundwater recharge and sensitive wetland ecosystems 
Mikael Erlström, Peter Dahlqvist, Krister Mild, Daniel Sopher, Magnus Martinsson, Anders Glimskär, Anders Jacobson, Björn Holgersson, Frans Lundberg, and Jakob Léven

 

Glaciokarst is widespread in the Silurian carbonate bedrock on the Island of Gotland. Grikes and limestone pavements are the most common karst features. Although, less well documented, caves and subsurface channels also contribute to the complex hydrogeology in the bedrock. The karst is interpreted to have been formed, primarily, before the Pleistocene when the landscape was covered with acidic organic soils. Glacial erosion and postglacial karstification have also played significant roles in sculpturing the epikarst morphology we see today. The study presents quantitative and qualitative characterization of karst within several pilot areas on the island of Gotland. High resolution aerial photographs were acquired over the pilot areas using a drone. These images were then analysed in GIS-software to provide a statistical evaluation of length, width, and relative area with karst. As well as providing a statistical understanding of the occurrence and geometry of karst, the results also help to clarify the impact of karst on the sensitive and limited groundwater resources on Gotland. Since a large part of the carbonate bedrock surface is barren or covered by thin quaternary deposits the epikarst provides important pathways for the percolation of meteoric water and recharge to the groundwater. It also locally provides guided pathways for surface runoff. Furthermore, the study demonstrates that the presence of karst often is in conjunction with sensitive ecosystems such as temporary wetlands. Extensive development of grikes and limestone pavements also provide conditions for periodically hanging aquifers, which not only promotes groundwater recharge but also the formation of unique habitats for a variety of often threatened ecosystems. This study, which includes both biologists and earth scientists highlights the importance of the identification of catchment areas and mapping of karst. It also emphasises that investigations into the hydrogeology (including aspects such as groundwater recharge, surface runoff and subsurface transport pathways) is essential for a better understanding of wetland dynamics and their protection. The presence of karst and spreading of contaminations in the ground is also discussed. The work summarizes early results from a collaboration between authorities working with Natura 2000 karst habitats and geological classification and mapping of karst.

How to cite: Erlström, M., Dahlqvist, P., Mild, K., Sopher, D., Martinsson, M., Glimskär, A., Jacobson, A., Holgersson, B., Lundberg, F., and Léven, J.: Distribution and characteristics of glaciokarst on the island of Gotland, Baltic Sea - its role on groundwater recharge and sensitive wetland ecosystems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5031, https://doi.org/10.5194/egusphere-egu23-5031, 2023.