HS8.2.10 | Observing and understanding current and past subsurface water and energy transfers in a changing environment
EDI
Observing and understanding current and past subsurface water and energy transfers in a changing environment
Co-organized by ERE2/GI5
Convener: Victor Bense | Co-conveners: Agnès Rivière, Wei-Li Hong, Barret Kurylyk, Anne Jost, Susanne A. Benz, Ariel ThomasECSECS
Orals
| Fri, 19 Apr, 08:30–12:30 (CEST)
 
Room 3.16/17
Posters on site
| Attendance Fri, 19 Apr, 16:15–18:00 (CEST) | Display Fri, 19 Apr, 14:00–18:00
 
Hall A
Posters virtual
| Attendance Fri, 19 Apr, 14:00–15:45 (CEST) | Display Fri, 19 Apr, 08:30–18:00
 
vHall A
Orals |
Fri, 08:30
Fri, 16:15
Fri, 14:00
Groundwater's strategic importance for water, energy, and food security is growing in the face of ongoing environmental changes. It is crucial to observe and correctly interpret ongoing subsurface groundwater storage and energy transfers in the currently rapidly changing environment, in order to sustainably manage groundwater resources. For example, time-series of groundwater temperature on decadal timescales observed in piezometers provide a record of subsurface changes that have led to an improved understanding of hydrogeological processes. While such observations can be incidental and provide important insights, dedicated observatories (e.g., LTER sites; https://lternet.edu) of subsurface change (water and energy) do provide more robust, long-term, spatially detailed information on groundwater resources, to enable in-depth studies to be carried out, land-use changes to be taken into account. While observations in ad-hoc settings and at observatories can be used to understand subsurface change on the local to regional scale and over decadal to centennial timescales, a phenomenon like offshore freshened groundwater, increasingly looked as a source for potable fresh water in arid coastal zones, can only be properly understood in the context of continental scale processes over millennial time-scales.
This session aims to illustrate this diversity in subsurface observations of water and energy transport processes in aquifer systems, especially in the context of changing climate and environmental conditions. This includes extreme short-lived events such as heatwaves, floods, and droughts, but also impacts of climate change and glaciation. These events can have a significant impact on aquifer functioning and deserve special attention to understand the resilience of the aquifer. We seek contributions on advances in the characterization of subsurface flow processes based on field observations and on-site experiments possibly combined with modelling approaches. The analysis of groundwater issues related to the consequences of anthropogenic activities is of particular interest. Studies that explore innovative and multidisciplinary approaches to quantify water and energy transfers, are also welcomed. This session is partly organized through a community effort support by the COST action OFFSOURCE (https://off-source.eu/).

Orals: Fri, 19 Apr | Room 3.16/17

Chairpersons: Susanne A. Benz, Victor Bense, Ariel Thomas
08:30–08:35
Urban heat
08:35–08:45
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EGU24-16623
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ECS
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On-site presentation
Nele Hastreiter and Thomas Vienken

The presented study focuses on quantifying the impact of the anthropogenic heat input from residential buildings on the subsurface temperature regime, employing an innovative approach that combines building physics simulations with heat and groundwater flow modelling. To enhance the applicability of the approach, sensitivity analyses of various parameters that govern the heat transfer from the investigated buildings are performed. The investigated parameters took hydrogeological and meteorological conditions, building properties (including different insulation standards and building types) as well as petrophysical rock properties into account.

The findings contribute to a comprehensive understanding of the subsurface temperature regimes within densely settled areas, which is particular significant for the impact assessment of shallow geothermal applications. Results of the study show that neglecting anthropogenic heat input may lead to an underestimation of the effects of shallow geothermal applications on the underground temperatures.

How to cite: Hastreiter, N. and Vienken, T.: Anthropogenic heat input into the subsurface: Influencing factors and its importance during shallow geothermal impact assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16623, https://doi.org/10.5194/egusphere-egu24-16623, 2024.

08:45–08:55
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EGU24-1879
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ECS
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On-site presentation
Maximilian Noethen, Julia Becher, Kathrin Menberg, Philipp Blum, Simon Schüppler, Erhard Metzler, and Peter Bayer

Worldwide shallow groundwater is increasingly exposed to anthropogenic impacts. The thermal state of this important resource is affected not only by global warming but also by various local structures that release heat into the subsurface. This additional heat can accumulate and lead to local hotspots or - mostly urban - areas of elevated groundwater temperatures. The consequences of this warming for groundwater quality and ecology are widely unknown. Groundwater ecosystems are embedded in a naturally relatively stable environment, where temperature changes can affect the highly specialized, cold-stenotherm invertebrate community and meso- to psychrophilic microorganisms. In this study, we examine whether and how a groundwater temperature hotspot impacts groundwater ecology. We identified such a thermal anomaly in Hockenheim, Germany, caused by a water park with heated swimming pools and basements. The thermal impact was monitored over the course of a year by temperature data loggers in nine wells – four upstream and downstream of the structure each and one inside the basement. The same wells were sampled for chemical and microbiological parameters, such as the microbial total cell count and the cellular ATP content, as well as groundwater fauna. We additionally tested three wells in a nearby forest to obtain reference values that are mostly unaffected by anthropogenic interference. The measurements were repeated every three months in order to account for seasonal variations. The preliminary results show a local heat plume and an increase in groundwater temperatures by up to 8 K. However, there is no significant deterioration in the ecological parameters. Regarding the fauna, which generally shows low abundance due to oxygen depletion in the study area, we observed only a minor decrease within the thermally affected zone. Finally, the outcome of this study will improve our understanding of the vulnerability of groundwater ecosystems in the context of subsurface warming.

How to cite: Noethen, M., Becher, J., Menberg, K., Blum, P., Schüppler, S., Metzler, E., and Bayer, P.: Does an anthropogenically induced subsurface temperature hotspot affect groundwater ecology?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1879, https://doi.org/10.5194/egusphere-egu24-1879, 2024.

08:55–09:05
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EGU24-1319
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ECS
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On-site presentation
Ashley Patton, Peter Cleall, and Mark Cuthbert

The subsurface Urban Heat Island effect has been proposed as a shallow geothermal energy resource, however, annual near-subsurface temperature variation may result in unexpected system performance. Understanding heat transport processes in the urban subsurface is key to managing and modelling city-scale thermal regimes for geothermal energy resource development. Existing studies have focussed on analysis of repeat temperature-depth profiles rather than long-term groundwater temperature time-series. We show here how time-series analysis can complement temperature-depth profiles and offer additional insights into the controls on subsurface thermal transport processes.

Annual variations in temperature time-series from 49 boreholes in the Cardiff Geo-observatory (UK), recorded between 2014-2018, fall into several distinct shape categories. We hypothesise these shapes are indicative of the dominance of particular flow and heat transport mechanisms such that sinusoidal profiles are associated with conduction-only settings, while ‘right-skewed’ profiles denote the influence of advection. Short-lived temperature events are observed on the cooling limbs of such profiles and are correlated with groundwater level rises, indicative of recharge events. These winter temperature drops have the effect of cooling groundwater faster in winter than it is warmed in summer. The short timescales of these events suggest recharge is localised and may be controlled by preferential flow paths within the superficial deposits overlying the aquifer. While these events do have an overall cooling effect on the seasonal temperature profile, groundwater temperatures following these events recover quickly to levels near what they were before the recharge event, suggestive of the presence of local thermal non-equilibrium with the gravel aquifer. More complex behaviours observed in boreholes located close to the city’s rivers indicate recharge responses coupled with the influence of stream-aquifer interactions. Thus, temperature time-series data have potential as a tool to identify subsurface hydraulic and thermal processes, with implications for geothermal exploration and the wider field of hydrogeology.

How to cite: Patton, A., Cleall, P., and Cuthbert, M.: Identifying urban subsurface thermal and hydraulic processes from time-series groundwater temperature data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1319, https://doi.org/10.5194/egusphere-egu24-1319, 2024.

Offshore groundwater
09:05–09:15
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EGU24-10761
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ECS
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On-site presentation
Daniel Zamrsky, Joep J.H. van Lith, and Rens van Beek

Offshore freshened groundwater reserves have been identified in numerous regions worldwide. These reserves were often deposited during past sea level lowstands and are therefore non-renewable and slowly salinized by infiltrating seawater. However, in some cases these offshore freshened groundwater reserves can be connected to inland groundwater systems and can be recharged by fresh groundwater inflow from the landward direction. It has recently been suggested that these offshore freshened groundwater reserves could provide an additional source of fresh (and brackish) water for coastal communities that often face increasing fresh water stress. The feasibility, both economic and physical, of offshore freshened groundwater extraction is investigated in this study. To assess this feasibility from a physical point of view we built a set of 3D semi-conceptual groundwater flow models using the imod-wq code which allows us to estimate the offshore groundwater salinity development over large time scales (i.e. one glacial-interglacial cycle). The result of these large time scale models can be interpreted as estimations of the current offshore groundwater salinity conditions and thus provide a better picture of the current presence and magnitude of the offshore freshened groundwater resources in the model domain. In the next modelling stress period we introduce a set of pumping wells into the offshore domain and simulate several offshore freshened groundwater extraction scenarios. In such way we can evaluate the time it takes for these offshore freshened groundwater reserves to be fully salinized and exhausted. Additionally, we can also assess any potential negative impacts on the groundwater system in the coastal hinterland such as decreasing groundwater levels and/or increased salinization.

In the second part of our study we evaluate the economic feasibility of the offshore freshened groundwater pumping and use as additional fresh water resource for coastal communities. Several coastal areas located in south and south-east Asia (e.g. Pearl River delta) were selected since this region is identified as a region with high possibility and magnitude of offshore freshened groundwater resources. The economic parameters that are taken into account as favourable for offshore freshened groundwater exploration are (i) the overall economic development (e.g. GDP, HDI), (ii) the presence of groundwater pumping and desalination plants inland meaning the technology is already present in the region and (iii) costs of fresh water and groundwater pumping and desalination infrastructure in the region. Our study is only the first step in assessing the feasibility of offshore freshened groundwater exploration and hopefully our approach will be improved and tested in other coastal regions around the world to evaluate the full potential of these still untapped fresh groundwater resources.

How to cite: Zamrsky, D., van Lith, J. J. H., and van Beek, R.: Conceptual 3D groundwater models of offshore freshened groundwater extraction and its economic viability assessment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10761, https://doi.org/10.5194/egusphere-egu24-10761, 2024.

09:15–09:25
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EGU24-5599
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On-site presentation
Bruno Campo and Marco Antonellini

The analysis of twenty geophysical well logs covering a shelf area of about 3,500 km2 in front of the Emilia-Romagna coast (Italy), has shown apparent resistivity (ρa) values consistent with important Offshore Freshened Groundwater (OFG) reserves stored in the first 450 m of the Middle-to-Upper Pleistocene succession, and extending seaward about 60 km from the modern shoreline. Four classes with different ρa intervals (i.e., different salinities) were identified. The first three (1, 2 and 3) classes are characterized by ρa ranges of 7-28 Ω m, 4-7 Ω m and 2-4 Ω m, respectively. These values are higher than seawater resistivity (< 2 Ω m - i.e., class 4) and, based on the OFG definition (i.e., “the water stored in the sub-seafloor with a total dissolved solid concentration below that of seawater”), they have been used for OFG identification. Class 1 ρa is coherent with fresh-to-brackish water content, whereas classes 2 and 3 have been interpreted as transitional to seawater.
The correlation of offshore wells (spontaneous potential and ρa profiles) with onshore data (stratigraphic and lithological) from water wells and additional geophysical well logs, led to the stratigraphic architecture reconstruction of the Plio-Pleistocene siliciclastic succession along onshore-offshore transects, up to 60 km-long, from the Apennine front to the Adriatic shelf. The uppermost (first 450 m) Middle to Upper Pleistocene interval displays a vertical alternation of high-permeability (amalgamated and laterally continuous gravel to sand bodies) and low-permeability (mud-dominated) strata made of fluvio-deltaic, coastal and shelfal deposits. The high-permeability bodies represent the offshore extension of the onshore aquifer systems, whereas the low-permeability units make the aquitards. Along the transects, different stratigraphic intervals characterized by the four ρa classes have been identified. The highest ρa values (class 1) have been documented in the first 300 m of the succession, despite its deposition mostly occurred in deltaic to marine (i.e., saline water) conditions. This interval wedges out seawards, with ρa progressively decreasing down to class 3 values at about 35 km from the coast. Similarly, ρa decreases vertically, between about 300 and 450 m depth. Such a vertical gradual decrease may suggest that locally aquitards do not completely prevent water exchange, and transitional classes 2 and 3 likely resulted from freshwater and seawater mixing through space and time. Below 450 m depth, ρa drops to < 2 Ω m (class 4), thus defining the lowermost limit of the OFG reserves.    
Onshore-offshore reconstructions additionally revealed how OFG aquifers are actively recharged in correspondence of the Apennine front, where the topographic gradient is higher and permeable units are subaerially exposed. Their extremely high degree of amalgamation even allows the topographically-driven recharge of the deeper (and marine) strata.
The relatively shallow depth (< 350 m) of the northern Adriatic aquifers and the presence of several and abandoned oil&gas platforms in the area, provide a good opportunity to further investigate these OFG reserves that are strategic for the densely populated Emilia-Romagna coastal plain.

How to cite: Campo, B. and Antonellini, M.: Offshore freshened groundwater reserves identification as revealed by geophysical and stratigraphic data: insights from the Northern Adriatic shelf (Italy) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5599, https://doi.org/10.5194/egusphere-egu24-5599, 2024.

09:25–09:35
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EGU24-4575
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ECS
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On-site presentation
Damiano Chiacchieri, Lorenzo Lipparini, Aaron Micallef, and Elizabeth Quiroga

The work focused on the Oligo-Miocene Ragusa Formation, a known regional shallow aquifer in the Hyblean Plateau in southern Sicily, made of medium to high porosity carbonates deposited in the ramp environment, also investigated in the adjacent offshore by deep well drilling.

The main objective was to investigate if and how this known shallow onshore aquifer extend in the coastal area and possibly offshore.

A detailed methodology was defined for the quantitative use of geophysical logs from about five deep Oil & Gas wells to characterize groundwater in the Ragusa Formation in terms of pressure, piezometry and salinity distribution, as it follows:

  • A first step was the digitization of the full suite of logs required for the application of petrophysical workflow for each well analysed, for a total of about 25 km of digitized logs, such as SP (Spontaneous Potential), GR (Gamma Ray), DT (Sonic log) and Resistivity logs.
  • At the same time a synthetic lithological log for each selected well was built, to support the understanding of lithological influence of electrical logs.
  • A customised petrophysical workflow to calculate porosity and salinity (concentration of salts in TDS) was applied, considering: lithotypes, BHT (borehole temperatures), porosity (derived to DT – sonic log), pore fluid resistivity.
  • A comparison of TDS results with salinity data from DST and composite logs was performed.
  • A detailed well correlation and comparison between onshore shallow water wells and deep Oil&Gas wells, both onshore and offshore, was carried out.

By applying this petrophysical approach, it was possible to identify and quantified key indications of the presence of fresh groundwater in the Ragusa Formation carbonates both onshore and offshore in southern Sicily (Italy). Indeed, has been demonstrated that the onshore outcropping aquifer appear likely connected with the deep offshore aquifer due to positive indications in the same geological formation 10 km offshore from the coastline.

How to cite: Chiacchieri, D., Lipparini, L., Micallef, A., and Quiroga, E.: Offshore freshened groundwater identified in southern Sicily (Italy) by applying well logs petrophysical interpretation. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4575, https://doi.org/10.5194/egusphere-egu24-4575, 2024.

09:35–09:45
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EGU24-21423
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Virtual presentation
Renée Martin-Nagle

Before extraction of offshore freshened groundwater (OFG) begins, ownership must first be determined in order to confirm the right to access, possess and distribute of the resource.  Since the geological formations sheltering OFG extend beyond the coastline, the UN Convention on the Law of Sea, which has been ratified by most countries in the world, will apply, and it provides that the nation having rights to the continental shelf where the OFG is located will have sovereign rights to the resource.  However, political boundaries do not often respect geologic formations, and some deposits of OFG will straddle national boundaries.  The Law of the Sea Convention is silent on transboundary resources, so policymakers must look to other legal principles that address governance of natural resources in order to develop a governance regime.  This presentation will summarize the applicable international law principles and will provide guidance on how transboundary OFG may be governed.

How to cite: Martin-Nagle, R.: Transboundary Offshore Freshened Groundwater: What Law Applies?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21423, https://doi.org/10.5194/egusphere-egu24-21423, 2024.

Exploring Hydrosystem functioning through Unconventional Data Sources and Long-Term Time Series Observations
09:45–09:55
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EGU24-4637
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On-site presentation
Detecting Groundwater Flow Induced by Underground Research Laboratory Excavation through Active-DTS Measurements
(withdrawn)
Yanhui Dong, Liheng Wang, and Yunmei Fu
09:55–10:05
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EGU24-13973
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ECS
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On-site presentation
Titus Kruijssen, Mike Wit, Sandra Akkermans, Joshua Leusink, Boris van Breukelen, Martine van der Ploeg, and Victor Bense

Dual porosity flow is an important mechanism for groundwater transport in fractured rock aquifers. However, quantification and characterization of fracture flow systems remains challenging, as it often involves complex procedures such as the injection of tracers. In this study we conducted single-well pumping tests in 11 uncased wells in a coastal fractured rock aquifer while monitoring in-well salinity and temperature gradients through downhole casts using a Conductivity-Temperature-Depth (CTD) logger. In this way, we aimed to observe how naturally occurring salinity gradients in the well become disturbed by induced groundwater flow to the well, and if these gradients may serve as natural tracers for fracture flow. Since natural temperature gradients in the wells are minimal, we applied point electrical heating at the bottom of the well to create a plume of slightly warmer water to migrate up the wellbore during pumping from the top. During the pumping tests in this set-up, repeated CTD casts suggest that groundwater flow to these wells is strongly focused along narrow zones and is occurring at various rates over a range of salinities and temperatures. Hence, the observed patterns in both salinity and temperature presumably reflect the presence of fracture zones, which could indeed be confirmed by downhole camera observations for some wells. Further data analysis resulted in detailed hydrogeological characterization of the 11 wells, comprising an assessment of the fracture density and hydraulic conductivity of the aquifers, as well as the origin of the inflowing water being meteoric mostly fresh water or deeper saline groundwater.

How to cite: Kruijssen, T., Wit, M., Akkermans, S., Leusink, J., van Breukelen, B., van der Ploeg, M., and Bense, V.: Turn up the heat to locate and quantify groundwater flow in fractured rock aquifers in coastal zones of the tropical island of Curaçao, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13973, https://doi.org/10.5194/egusphere-egu24-13973, 2024.

10:05–10:15
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EGU24-20169
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On-site presentation
Jasmin Raymond, Fiona Chapman, Maria Klepikova, Olivier Bour, and Renaud Soucy Laroche

The traditional territory of the Lù'àn Män Ku Dän (Kluane Lake People) is found along the Saint Elias Mountains in Yukon. It hosts the Burwash Landing community, home of the Kluane First Nation, which is one of eleven self-governing First Nations operating in tripartite with Yukon Government and Canada. Burwash Landing is primarily dependent on diesel for space heating and power generation. Cutting-edge technologies were deployed in the scope of geothermal resource assessment to evaluate the thermal state and properties of the subsurface. Active distributed temperature sensing was conducted with a composite heating and fiber-optic cable installed in the water column of two existing wells with the objective of quantifying the geothermal potential and groundwater flow along available wellbores. Heat injection tests were made in the 220 and 385 m deep wells located on the south and north side of the Denali fault, near a probable releasing bend that is favorable to permeability. Melting glacier water infiltrates in mountains and groundwater flows toward Kluane Lake, which is hypothesized to be a major groundwater discharge zone. The shallower well is at an altitude of 925 masl and intercepted 40 m of quaternary deposits before hitting fractured bedrock while the deeper well is at the valley bottom near the lake (altitude of 795 masl) and entirely drilled in quaternary deposits. Passive temperature monitoring was initially made and revealed a geothermal gradient of 34 ⁰C km-1 and 47 ⁰C km-1 in the shallow south side and deep north side wells. Heat was injected during active tests for 2 and 3 days and thermal recovery was monitored for 6 and 8 days, respectively. Temperature was measured every 25 cm at 4-minute intervals. The infinite line source equation and the superposition principle were used to analyze data and calculate a thermal conductivity profile. Nearly continuous ground thermal properties and temperature profiles were combined to assess the Earth natural heat flux, considering paleoclimate and topographic corrections. Analysis indicated a heat flux above 90 mW m‑2, thought to be favorable for geothermal resource development. Peclet number analysis was undertaken to infer horizontal groundwater flow in permeable horizons. Results are being used to develop a regional groundwater flow and heat transfer model to evaluate temperature at kilometer depth and assess the communities’ geothermal potential. This presentation will illustrate how active temperature sensing can be deployed to reduce geothermal exploration risks, acknowledging Kluane First Nation that allowed us to better understand groundwater flow in this magnificent territory.  

How to cite: Raymond, J., Chapman, F., Klepikova, M., Bour, O., and Soucy Laroche, R.: Active fiber-optic distributed temperature sensing to assess the geothermal potential and groundwater flow over the traditional territory of the Lù'àn Män Ku Dän, Yukon, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20169, https://doi.org/10.5194/egusphere-egu24-20169, 2024.

Coffee break
Chairpersons: Agnès Rivière, Anne Jost, Wei-Li Hong
10:45–10:55
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EGU24-7668
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ECS
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On-site presentation
Davide Furlanetto, Matteo Camporese, Luca Schenato, Leonardo Costa, and Paolo Salandin

Unconfined shallow aquifers are particularly exposed to the risk of contamination. Especially when exploited for drinking water production, for which water quality is of particular concern, careful monitoring of the physical processes and detailed characterization of the subsurface properties are crucial. Furthermore, the possible presence of heterogeneities, such as intricate networks of hydraulically conductive paleo-channels that are often inherent in alluvial aquifers, can establish preferential pathways. Consequently, monitoring activities in these complex environments pose serious challenges and raise the demand for advanced techniques and innovative approaches. In this context, recent advances have been made possible by employing Fiber Optics Distributed Temperature Sensing (FO-DTS). This technology combines the use of heat as a natural tracer with a detailed spatiotemporal resolution and has proven informative in a wide variety of applications. In this study, we applied downhole passive FO-DTS to a cluster of piezometers in a highly heterogeneous phreatic gravelly aquifer. The aquifer is exploited for irrigation and drinking water supply, and exhibits both natural and pumping-induced groundwater temperature fluctuations. Vertical transient water temperature profiles were acquired over a 1-month experiment. Borehole-dependent and depth-related features of the temperature measurements were ascribed to possible spatial structures having different hydraulic conductivity. The collected data were used to invert the three-dimensional saturated hydraulic conductivity field of a physics-based numerical model that couples flow and heat transport. Even without active heating, FO-DTS has demonstrated its ability to provide valuable insights at an unprecedentedly high resolution.

How to cite: Furlanetto, D., Camporese, M., Schenato, L., Costa, L., and Salandin, P.: Downhole passive fiber optics temperature monitoring for improved characterization of aquifer heterogeneities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7668, https://doi.org/10.5194/egusphere-egu24-7668, 2024.

10:55–11:05
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EGU24-17898
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ECS
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On-site presentation
New criteria for assessing local thermal nonequilibrium conditions in porous aquifers and their impact on heat transport in porous media
(withdrawn after no-show)
Wenguang Shi, Maria Klepikova, and Quanrong Wang
11:05–11:15
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EGU24-15116
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ECS
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On-site presentation
Enno de Vries and Niels Hartog

Geothermal heat production and aquifer thermal energy storage have significant potential to contribute to the energy transition. However, due to higher temperature inside the wells used, it is known that this leads to heat loss through conduction to the surrounding cooler, shallower groundwater systems. Therefore it is important to be able to anticipates such impacts to allow effective monitoring and prevention or mitigation measures when needed. However the thermal impact on groundwater systems is expected to strongly depend on local conditions. Therefore, this study focused on the impact of operational conditions (e.g. effective well temperatures and intermittency) and aquifer conditions (e.g. permeabilities and heterogeneity) on the resulting heat transport processes into the aquifer by conduction and density driven flow. To evaluate the degree and variation of impact that may occur under field conditions, the heat loss to a shallow groundwater system was simulated using a 2D axisymmetric numerical MODFLOW 6 model for a wide range of conditions considering both the impact of conduction and density-driven flow. The results of this study indicate that the total thermal impact and its distribution (up to >10 m from the hot well in 10 years) in shallow groundwater systems is strongly impacted by the induced density driven flow in the relatively permeable layers of the groundwater system. Conduction is dominant in transfer of heat from the hot well in the low permeability confining layers and for mitigating temperature differences in the groundwater system induced by buoyancy flow. Overall, this study highlights the importance of considering local conditions in assessing thermal impact by heat losses from hot well casings, to allow distinguishing these thermal impacts from those induced by leakage and to allow efficient thermal groundwater impact monitoring.

How to cite: de Vries, E. and Hartog, N.: Thermal impact on shallow groundwater systems by heat loss from hot wells: the impact of operational conditions and subsurface heterogeneity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15116, https://doi.org/10.5194/egusphere-egu24-15116, 2024.

11:15–11:25
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EGU24-19115
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ECS
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On-site presentation
Augustin Thomas, Jerome Fortin, Benoit Vittecoq, and Sophie Violette

Tidal analysis of borehole pressure has become in the recent years’ literature an essential method to follow the evolution of the hydraulic conductivity of an aquifer over time. Most traditional methods (mainly pumping or slug tests) only produce a small number of observations, and come at a greater cost. However, groundwater level tidal analysis only requires monitoring data at a sampling rate of 1 hour, data which is extensively available. These solutions are applicable provided aquifers respond to at least one tidal phenomenon among oceanic, earth or atmospheric tides.

Martinique Island, in the Lesser Antilles, is a very interesting field to study these techniques, since 16 years of piezometric level data have been recorded on this volcanic island in a monitoring network of 29 boreholes. Here we focus our study on a closely monitored study site in the Galion plain, with three boreholes, a seismometer and past conducted pumping tests and seismic surveys. We compute amplitude and phase response of aquifers to atmospheric and earth tides. Then, the response of the semi-confined aquifers to different loading sources at the tidal frequencies (between 1 and 2 cycles per day) is modelled. A careful inversion is done to obtain the characteristics of the aquifer, including aquifer transmissivity and shear modulus.

Finally, we analyse the evolutions of these inverted parameters and decipher their reversible and irreversible changes. Between earthquakes, we show the dominant effect of effective stress to control aquifer hydraulic conductivity. At the time of the earthquake, with the help of seismic stress numerical simulation, we show that seismic shear stresses are the most probable cause of aquifer properties changes both in permeability and shear modulus.

How to cite: Thomas, A., Fortin, J., Vittecoq, B., and Violette, S.: Passive characterization of aquifer permeability and shear modulus and their evolution following earthquakes using tidal signals, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19115, https://doi.org/10.5194/egusphere-egu24-19115, 2024.

11:25–11:35
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EGU24-17299
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ECS
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On-site presentation
Adisu Befekadu Kebede, Fekadu Fufa Feyessa, Thomas Hermans, and Kristine Walraevens

Groundwater monitoring is fundamental, especially for areas where there is a high dependency on groundwater use. Groundwater level (GWL) monitoring is poorly known in Ethiopia. The study focused on evaluating groundwater levels and their relation to precipitation in Ethiopia's Gilgel Gibe and Dhidhessa catchment areas. Groundwater levels (GWL), spring discharges, and rainfall data were collected from various points over the 2022/2023 hydrological year.  Rainfall varied across the region, increasing from April to September and decreasing from plateaus to lowlands with a value between 1539 mm to 1973mm annually. Groundwater levels showed significant spatial and temporal variation, influenced by precipitation and local topography.  Maximum water level varies between 17.6 and 5.75 m in the northwest, 11.6 and 6.2 m in the central part, 11.5 and 3.2 m in the east, 13.1and 4.2 m in the south. Minimum water level varies between 13.2 and 3.8 m in the northwest, 5.8 and 2.7 m in the central, 3.5 and 1.1 m in the east and 7 and 3. 6 m in the south of the study area. Groundwater level fluctuation in the automatically monitored well was 1.55m in the deep well and 3.99m in the shallow well. The spatial drop of the water table in the northwest and south is due to a hydraulic gradient to lowlands and depressions, and evapotranspiration from dense forest coverage. In the central and eastern study area, GWL is shallow and intermediate based on the positions of monitoring wells. Some wells are fully saturated during the rainy season between August and September. Shallow wells reacted swiftly to rainfall, but their levels declined in the dry season. Some wells in high elevation areas experienced minimal fluctuations due to their perched aquifer positions. Groundwater drawdown from usage in dug wells quickly recovered, suggesting potential for small-scale agricultural use. Long-term monitoring and increased data logging are recommended for future studies.

How to cite: Kebede, A. B., Feyessa, F. F., Hermans, T., and Walraevens, K.: Groundwater Level Assessment using Data logger and Manual monitoring in developing Country, southwestern Ethiopia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17299, https://doi.org/10.5194/egusphere-egu24-17299, 2024.

11:35–11:45
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EGU24-5269
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On-site presentation
Julian Klaus, Günter Blöschl, Enrico Bonanno, Barbara Glaser, Laurent Gourdol, Christophe Hissler, Luisa Hopp, Laurent Pfister, and Keith Smettem

The exchange between groundwater (GW) and surface water (SW) plays a crucial role for streamflow generation and the biogeochemical cycles within landscapes. However, accurately observing and predicting this exchange remains challenging due to the spatial heterogeneity and temporally dynamic fluxes of groundwater within the stream corridor. This presentation offers new insights into the characteristics of GW-SW interactions and hydrological processes within the hillslope-riparian-stream continuum, employing a combined experimental and modeling approach. The research builds on a comprehensive, long-term dataset obtained through baseline monitoring in the Weierbach Experimental Catchment (WEC) in Luxembourg that is a 45-hectare forested catchment. In addition to baseline monitoring, our approach involved (i) a network of 43 wells and piezometers along a selected stream reach for continuous monitoring and tracer experiments, (ii) a network of 13 wells along the riparian-hillslope interface, and (iii) ground-based thermal infrared imagery to observe spatiotemporal dynamics of surface saturation along the stream corridor. An integrated surface-subsurface hydrologic model served as a hypothesis-testing tool to examine whether surface saturation is predominantly driven by groundwater inflow or precipitation and how the relevance of the processes – surface ponding from precipitation or subsurface exfiltration – change in space and time.

We coupled the hydrological model with a hydraulic mixing-cell approach that enabled deciphering the contributions from different water sources to SW. The well network and associated artificial tracer experiments provided valuable insights into the direction of GW-SW exchange, revealing directional variability at scales of a few meters. Additionally, wells at the riparian-hillslope interface demonstrated a strong non-linearity of GW contributions to SW, influenced by GW table fluctuations. The observed and simulated surface saturation aligned well, suggesting that GW exfiltration primarily controls surface saturation in the stream corridor. Furthermore, the mixing-cell simulations revealed that subsurface water exfiltration is the dominant source for riparian surface water and intermittent streamflow, with distinct differences between stream water and riparian surface saturation. Overall, the combination of experimental techniques, hydrologic modeling, and well networks clearly improved our understanding of GW-SW interactions and revealed previously hidden exchanges in the WEC.

How to cite: Klaus, J., Blöschl, G., Bonanno, E., Glaser, B., Gourdol, L., Hissler, C., Hopp, L., Pfister, L., and Smettem, K.: Exploring the Hidden Exchanges: Groundwater-Surface Water Interactions in a Critical Zone Observatory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5269, https://doi.org/10.5194/egusphere-egu24-5269, 2024.

Geochemical
11:45–11:55
|
EGU24-2499
|
On-site presentation
Zhihua Zhou, Xiao Ren, Jun Zhong, and Xiaobo Feng

Springs offer insight into the sources and mechanisms of groundwater recharge and can be used to characterize fluid migration during earthquakes. However, few reports provide sufficient annual hydrochemical and isotopic data to compare the variation characteristics and mechanisms with both atmospheric temperature and seismic effects. As such, it is critical to obtain time series observations of stable isptopes (δ2H, δ18O and δ13CDIC) to understand the complex interactions between hydrological processes, cycle, and relationship with earthquakes. In this study, we used continuous δ2H, δ18O, δ13CDIC, and major ion data from four springs over 1 year to understand the groundwater origin, recharge sources, circulation characteristics, and coupling relationships with atmospheric temperature and earthquakes. We found that (1) the four springs are likely recharged by deep circulation of meteoric water from Bogda Mountain in the east, as well as long-distance runoff recharge from the Turpan Basin to the south. (2) atmospheric temperatures above and below 0 °C can cause significant changes in ion concentrations and water circulation depth, resulting in the mixing of fresh and old water in the aquifer, it can cause changes in δ13CDIC but it doesn’t work in δ2H and δ18O. (3) Earthquakes of magnitude ≥ 4.8 within a 66 km epicentral distance can alter fault zone characteristics (e.g., permeability) and aggravate water–rock reactions, resulting in significant changes in δ2H, δ18O, and hydrochemical ion concentrations, accompanied by limited changes in δ13CDIC. (4) Hydrogen and oxygen isotopes are the most sensitive precursory seismic indicators. The results of this study offer a reference for the establishment of long-term hydrochemical and isotopic monitoring, with the potential for use in earthquake forecasting.

This work is financially supported by the Natural Science Foundation of China (Grant No. 42373067) and by the Science for Earthquake Resilience (grant number XH23048C).

How to cite: Zhou, Z., Ren, X., Zhong, J., and Feng, X.: Response Characteristics of Hydrogen, Oxygen, and Carbon Isotope Composition to Atmospheric Temperature and Seismic Activity in Spring Water Hydrogeochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2499, https://doi.org/10.5194/egusphere-egu24-2499, 2024.

11:55–12:05
|
EGU24-17537
|
ECS
|
On-site presentation
Novel application of phosphor thermometry to investigate the heat transfer in analog porous media
(withdrawn)
Arwa Rashed, Maria Klepikova, Francesco Gomez, Benoît Fond, and Yves Méheust
12:05–12:15
|
EGU24-4855
|
ECS
|
On-site presentation
Jian Liu, Zhanli Ren, Qiang Yu, Xinyun Yan, Kai Qi, Zhen Wang, Sasa Guo, Huaping Lan, Mingxing Jia, and Yanzhao Liu

The geothermal resources in sedimentary basins have high potential for development and utilization, and have become an important research topic worldwide(Olasolo et al.,2016; Pasvanoğlu and Çelik., 2019; Duan et al.,2022). This paper focuses on the genetic mechanism and evolution process of deep geothermal water were explored through the analysis of hydrogeochemical and isotope geochemical data, which can provide technical and theoretical support for the sustainable development of geothermal fields in the Weihe basin. The study indicates that: (1)the hydrochemical type of geothermal water of Dongda geothermal field are predominantly HCO3·SO4-Na type. Meanwhile, the hydrochemical type of geothermal water of the northern Xi'an Depression are mainly SO4·HCO3-Na and SO4·HCO3·Cl-Na types. The ionic fraction is primarily influenced by the dissolution of silicate and evaporite minerals, as well as alternating cation adsorption. (2) Geothermal water is primarily recharged by atmospheric precipitation originating from the Qinling Mountains. The recharge elevation ranges from 677.94 m to 1467.65 m. (3) The Dongda geothermal field has a thermal storage temperature ranging from 50.19℃ to 80.29℃, and a depth of thermal circulation ranging from 1126.32 m to 2129.62m. Meanwhile, the northern Xi'an depression has a thermal storage temperature ranging from 73.17℃ to 109.50℃, and a depth of thermal circulation ranging from 1892.41 m to 3103.22 m. (4) The δ18O of the geothermal water in the northern Xi'an depression is more significantly shifted to the right of the atmospheric precipitation line than that of the Dongda geothermal water, indicating a significant “oxygen drift”.(5) The Dongda geothermal reservoir in the southern Xi'an Depression mainly experiences heat transfer through convection, while the geothermal reservoir in the northern Xi'an depression experiences heat transfer through conduction.

References

[1]Duan, R., Li, P., Wang, L., He, X., & Zhang, L. (2022). Hydrochemical characteristics, hydrochemical processes and recharge sources of the geothermal systems in Lanzhou City, northwestern China. Urban Climate, 43, 101152.

[2]Olasolo, P., Juárez, M. C., Morales, M. P., & Liarte, I. A. (2016). Enhanced geothermal systems (EGS): A review. Renewable and Sustainable Energy Reviews, 56, 133-144.

[3]Pasvanoğlu, S., & Çelik, M. (2019). Hydrogeochemical characteristics and conceptual model of Çamlıdere low temperature geothermal prospect, northern Central Anatolia. Geothermics, 79, 82-104.

How to cite: Liu, J., Ren, Z., Yu, Q., Yan, X., Qi, K., Wang, Z., Guo, S., Lan, H., Jia, M., and Liu, Y.: Hydrogeochemical Characteristics and Genetic Mechanisms of Geothermal Fields in the Xi'an Depression of the Weihe Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4855, https://doi.org/10.5194/egusphere-egu24-4855, 2024.

12:15–12:30

Posters on site: Fri, 19 Apr, 16:15–18:00 | Hall A

Display time: Fri, 19 Apr 14:00–Fri, 19 Apr 18:00
A.98
|
EGU24-4000
Susanne A. Benz, Dylan J. Irvine, Gabriel C. Rau, Peter Bayer, Kathrin Menberg, Philipp Blum, Rob C Jamieson, Christian Griebler, and Barret Kuryly

Groundwater, the largest reservoir of unfrozen freshwater on Earth, plays a crucial role in supporting life and ecosystems. Its thermal regimes influence various environmental processes, impacting groundwater-dependent ecosystems, geothermal potential, and groundwater quality. Despite its significance, little is known about how groundwater responds to surface warming across spatial and temporal scales. Here we present a comprehensive analysis of global groundwater temperature patterns, utilizing the latest CMIP6 scenarios.

In this study we developed the first global model of groundwater temperature patterns, combining analytical solutions to conductive heat transport with high-resolution maps of ground thermal diffusivity and geothermal gradient. This model, validated with over 8,000 groundwater temperature measurements, allows users to estimate present and future temperature depth profiles globally. Past trends show a median global groundwater temperature increase of 0.3 °C over the last two decades. When simulating projected groundwater temperatures globally, our model reveals an average warming of 2.2°C (SSP 245) to 3.8°C (SSP 585) between 2000 and 2100 at the depth of the water table. Regional variations are substantial due to climate change and water table depth variability, with mountainous regions exhibiting the lowest warming rates. These distinct regional variations emphasize important thermal controls and the need for localized analysis.

Our work sheds light on the importance of understanding groundwater warming patterns, identifying 'hot spots' that may pose risks to both ecosystems and human well-being. In this study we also offer a specific focus on Europe, providing averages to enhance regional relevance and address emerging challenges in groundwater quality and habitat preservation.

How to cite: Benz, S. A., Irvine, D. J., Rau, G. C., Bayer, P., Menberg, K., Blum, P., Jamieson, R. C., Griebler, C., and Kuryly, B.: The impact of our warming climate on global groundwater temperatures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4000, https://doi.org/10.5194/egusphere-egu24-4000, 2024.

A.99
|
EGU24-499
Tao Wang, Chenming Zhang, Ling Li, and Yajuan Yin

More than 60% of the global population lives in coastal areas, especially within 100 km from the coastlines, relying mostly on shallow groundwater resources. Seawater intrusion and submarine groundwater discharge (SGD) occur in the coastal aquifer systems, threatening these critical freshwater resources. Salinity seawater and fresh groundwater complexly interact with each other via SGD and SI. The SGD drives the discharge of not only a large volume of freshwater, but also terrestrial geochemical substances into the ocean through a mixing zone between discharging freshwater and recirculating seawater. The flux of SGD may be even greater than that of surface water through rivers and estuaries. For example, the SGD was estimated to be ~40 % and 80 %~160 % of the river water discharging flux into the South Atlantic Bight and Atlantic Ocean, respectively, and as a major source of dissolved organic matter and nutrients to Arctic coastal waters and the Mediterranean Sea.

A few hydrological models, including MARUN, SEAWAT, SUTRA, and PHT3D, are commonly used for SGD studies. The recently developed TOUGHREACT is robust in simulating coupled hydrodynamic, thermodynamic, and geochemical processes. From TOUGH2 (Transport Of Unsaturated Groundwater and Heat, version 2), a multi-dimensional numerical model for simulating coupled transport of water, vapor, non- condensable gas, and heat in porous and fractured media. However, TOUGHREACT is rarely used for SGD analysis, despite it being a well-rounded model with wide applications. Additionally, relevant studies on the iron (Fe) precipitation during SGD have focused predominantly on its spatial distribution and the adsorption of dissolved species, and studies on the genesis and geochemical evolution are scarce.

Therefore, we developed a systematic method using TOUGHREACT to simulate the hydrological processes in STEs and benchmarked the estimations; and then we numerically explored the groundwater flow and salt transport dur SGD by considering the influencing factors of tidal amplitude, freshwater head, seawater diffusion coefficient, and beach slope ratio. Consequently, by employing TOUGHREACT simulation, we analyzed the formation and spatiotemporal distribution of the Fe precipitation in the shallow beach aquifer due to the mixing of freshwater and seawater, and identified the key influencing factors during SGD.

The results show that, freshwater-derived Fe2+ is oxidized by O2(aq) in seawater during SGD, then precipitates as Fe (hydr)oxides (Fe(OH)3) to form an Fe precipitation zone. Fe(OH)3 tends to accumulate in the freshwater side of the mixing zone, whereas Fe(OH)3 precipitation in the seaward side of the mixing zone is inhibited by locally high H+ concentrations. The Fe(OH)3 first precipitates in the shallow aquifer, then extends to deeper layers over time, which is attributed to the increase in the residence time with the depth of both freshwater and seawater. The spatial distribution, and particularly, the extent of the iron curtain are influenced by the water flux and the concentration ratio of O2(aq) to Fe2+. These results are beneficial for better understanding the formation and distribution of iron curtains, and shed light on enhancing the understanding of the hydrogeochemical processes in subterranean estuaries.

How to cite: Wang, T., Zhang, C., Li, L., and Yin, Y.: Simulating the Hydro-Geo-Chemical Processes during Submarine Groundwater Discharge by TOUGHREACT, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-499, https://doi.org/10.5194/egusphere-egu24-499, 2024.

A.100
|
EGU24-21334
Interpreting Thermal Tracer Data in Carbonate Aquifers: Sensitivity Analysis and Identification of Ranges for Significant Heat Transfer Parameters
(withdrawn)
Oleg Glumov, Aleksandr Rastorguev, and Maria Klepikova
A.101
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EGU24-1650
|
ECS
Anthropogenic activities alter the process of submarine groundwater discharge in coastal area
(withdrawn)
Dongsheng Li, Zhongfang Liu, Yunduo Zhao, Ergang Lian, Yue Zhang, and Zijun Wu
A.102
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EGU24-7016
Chuen-Fa Ni, Thanh Quynh Duong, Chia-Yu Hsu, Nguyen Thai Vinh-Truong, and Yu-Huan Chang

Understanding the dynamics of water and mass interactions in the coastal area is essential to quantify the influences of near-shore land use on the coastal aquifers and water environment. The study aims to integrate innovative experiments and modeling techniques to assess the heat and water exchanges in the coastal aquifer of the Taoyuan Tableland in northwestern Taiwan. The site-specific hydraulic and heat tracer tests are conducted to obtain flow and heat transfer properties for the specific aquifer layers at the site. We then used the SEAWAT numerical model to quantify the freshwater and seawater interactions. The model calibration relies on the groundwater levels and quality obtained from monitoring wells installed perpendicular to the shoreline. The experimental results show that the active heat tracer tests could significantly improve the identification of aquifer layers along a well and allow for the estimations of high-resolution natural groundwater flux toward the sea. The estimated flow rate based on the heat tracer test is approximately 0.2 m/day per unit depth. The numerical model shows good agreement with the observed water levels in wells. In the study area, the location of the seawater/groundwater mixing interface is estimated at approximately 350m seaward from the shoreline, which suggests the submarine groundwater discharge zone for the site. The vertical profile model shows that the flow rate for the 100m depth aquifer varies from 51 to 60 m3/day per unit width, depending on the tidal variations and upstream groundwater levels. The results show a large flow rate discrepancy between experimental and numerical approaches, which the resolution scales of the approaches might induce in the calculations. The water levels obtained from the fully opened screen wells might mix the flow responses in different aquifer layers.

How to cite: Ni, C.-F., Duong, T. Q., Hsu, C.-Y., Vinh-Truong, N. T., and Chang, Y.-H.: Characterization of near-shore fresh water and seawater interactions-the scale issues drawn from the experimental and numerical approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7016, https://doi.org/10.5194/egusphere-egu24-7016, 2024.

A.103
|
EGU24-19219
Victor Bense and Barret Kurylyk

Temperature-depth profiles in the central part of the Netherlands collected over the past 7 years in a large number of piezometers document a regional increase in groundwater temperatures to depths of upto ~100 meters. This rise is congruent to observed increases in air temperature, related to climatic change. For some locations the data collected recently can be compared to similar observations done in the 1970-80s. Our observations show that the magnitude and rate of increase in groundwater temperature strongly vary by location and across depth. In part these differences can be explained by contrasts in land-surface conditions, but our analysis demonstrates that varying groundwater flow conditions also play an important role in explaining the observed patterns. Moreover, we show that an analysis of the transience in the temperature-depth profile can yield quantitative estimate of groundwater flow rates and subsurface hydraulic properties when combined with observations of hydraulic head gradients. We conclude that the current rising trends in groundwater temperature should provide a significant opportunity for the hydrogeological community to quantitatively analyze groundwater flow systems worldwide.

How to cite: Bense, V. and Kurylyk, B.: Drifting groundwater temperatures in the Netherlands: opportunities for hydrogeological analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19219, https://doi.org/10.5194/egusphere-egu24-19219, 2024.

A.104
|
EGU24-21278
|
ECS
An-Yi Hsu, Chuen-Fa Ni, Chia-Yu Hsu, and Yu-Huan Chang

 With the increasing economic development in coastal areas, the problem of coastal degradation has emerged. To facilitate subsequent planning of water resources management, it is essential to determine the coastal aquifer's dynamic exchange with ocean. In this research, our objective is to integrate innovative experiments and modeling techniques to assess the heat and water exchanges in the coastal aquifer of the Taoyuan Tableland in northwestern Taiwan. Specific hydraulic and heat tracer tests are conducted at this location to obtain the flow and heat transfer characteristics of the layered flow. In subsequent steps, we employed the MODFLOW and MT3DMS numerical model to simulate the influence of interactions between freshwater and seawater on the temperature field of the coastal aquifer. The calibration of the model is based on the groundwater levels and the temperature acquired from monitoring wells which installed near the coastline at the TAICOAST observation station. The experimental results show that the thermal responses from the active heat tracer test can match with the core sample and calculate the groundwater flux toward the sea. Significant thermal responses are observed vertically in the observation well near the heating well, ranging from the water level to a depth of 12 m, with BW08 being the observation well showing the maximum thermal response. The simulation of numerical model aligns well with the observed water levels and temperature in wells. The simulation provides a three dimensional depiction of the groundwater flow direction, which was used to calculate the velocity of groundwater flow and estimates thermal conductivity at this site. The results reveal the dynamic impacts of tidal variations on the coastal aquifer with high spatial resolution provides the valuable insights into understanding the groundwater discharge in the coastal aquifer system. 

How to cite: Hsu, A.-Y., Ni, C.-F., Hsu, C.-Y., and Chang, Y.-H.:  Using thermal tracer tests and numerical models to evaluate the layered flow characteristic in a coastal aquifer system , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21278, https://doi.org/10.5194/egusphere-egu24-21278, 2024.

A.105
|
EGU24-13147
Agnès Rivière, Marine Dangeard, Ludovic Bodet, Ramon Sanchez Gonzalez, and Alexandrine Gesret

Quantifying the water and heat fluxes at the interface between surface water (SW) and groundwater (GW) is a key issue for hydrogeologists to consider for safe yield and good water quality. However, such quantification with field measurements is not straightforward because the SW-GW changes depend on the boundary conditions and the spatial description of the hydrofacies, which aren't well known and are usually guessed by calibrating models using standard data like hydraulic heads and river discharge. We provide a methodology to build stronger constraints to the numerical simulation and the hydrodynamic and thermal parameter calibration, both in space and time, by using a multi-method approach. Our method, applied to the Orgeval Critical Zone Observatory (France), estimates both water flow and heat fluxes through the SW-GW interface using long-term hydrological data, time-lapse seismic data, and modeling tools. We show how a thorough interpretation of high-resolution geophysical images, combined with geotechnical data, provides a detailed distribution of hydrofacies, valuable prior information about the associated hydrodynamic property distribution. The temporal dynamic of the WT table can be captured with high-resolution time-lapse seismic acquisitions. Each seismic snapshot is then thoroughly inverted to image spatial WT variations. The long-term hydrogeological data (such as hydraulic head and temperature) and this prior geophysical information are then used to set the parameters for the hydrogeological modeling domain. The use of the WT geometry and temperature data improves the estimation of transient stream-aquifer exchanges.

How to cite: Rivière, A., Dangeard, M., Bodet, L., Sanchez Gonzalez, R., and Gesret, A.: Assessing Surface Water and Groundwater Interactions Using Long-Term Hydrological and Time-Lapse Seismic Data in the Orgeval Critical Zone Observatory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13147, https://doi.org/10.5194/egusphere-egu24-13147, 2024.

A.106
|
EGU24-17913
Anne Jost, Gurpreet Dass, Fanny Picourlat, Shuaitao Wang, Laurence Lestel, David Eschbach, Nicolas Flipo, and Agnès Ducharne

Human activities have significantly influenced the hydrological functioning of wetlands since they were first settled, often with the aim of reducing their perceived inconvenient wetness. Reconstructing these historical developments and understanding their impacts on hydrosystems is essential to inform strategies for the sustainable management and conservation of these vital resources. We take the example of the upper Seine valley upstream of Paris, within the vast Bassée floodplain, to illustrate and quantify how the many artificial changes it has undergone over the centuries may have had a reciprocal effect on groundwater resources. We have identified three main types of land development, ranging from hydraulic works to direct groundwater abstraction, including land use changes associated with the extraction of alluvial sands and gravels that give rise to the gravel pit lakes that are particularly prominent in the study area. Our approach is based on a detailed cartographic reconstruction of each of these influences, feeding into a hydrogeological model of the plain. We outline the main principles behind its conception and then quantify the relative impacts of anthropogenic pressures on the aquifer system budget and water table depth.

How to cite: Jost, A., Dass, G., Picourlat, F., Wang, S., Lestel, L., Eschbach, D., Flipo, N., and Ducharne, A.: Exploring historical anthropogenic influences on groundwater in the alluvial plain of the Upper Seine River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17913, https://doi.org/10.5194/egusphere-egu24-17913, 2024.

A.107
|
EGU24-12404
Citizen-science approach to long-term observation of aquifer response to meteorological forcings
(withdrawn)
Masaki Hayashi and Md Shihab Uddin
A.108
|
EGU24-19596
The subsurface thermal regime alteration brought by groundwater pumping 
(withdrawn)
Maria Klepikova, Victor Bense, Olivier Bour, Tanguy Le Borgne, and Nicolas Guiheneuf
A.109
|
EGU24-9552
|
ECS
Eva Kaminsky, Gregor Laaha, Cornelia Steiner, Eszter Nyéki, Constanze Englisch, Christian Griebler, and Christine Stumpp

In numerous cities worldwide, a rise in surface temperatures had been observed, contributing to the so-called "urban heat island effect". This effect leads to extended and hotter periods of warm weather within urban areas not only above but also below ground. The heat in the subsurface can be used for shallow geothermal energy, but it requires knowledge of spatial and temporal variations in groundwater temperature for efficient and environmentally friendly utilization of groundwater for heating and cooling. In the course of the 'Heat below the City' project, we have compiled spatial high-resolution data and developed groundwater temperature maps for the city of Vienna targeting the coldest and warmest annual conditions. Borehole temperature profiles were recorded in October 2021 and April 2022. This enabled the identification of distinct urban heat islands. Additionally, available long-term data (2001-2020) was used to conduct annual temperature trend analyses and extreme value assessments to evaluate temperature changes over time. In Vienna, an average annual temperature increase, considering all significant trends, of 0.9 ± 0.1 K/decade was observed for air, soil and shallow groundwater between 2001 and 2021. However, the increase is non-linear and, over the last decade, the change has accelerated with an increase of 1.4 ±0.2 K/decade (only significant trends taken into account). The current annual mean temperature is 14.1 °C (2021/ 2022) with individual warmer urban heat islands and locally heated locations of up to 30.6°C. Trends in extreme temperatures (represented by the lower/upper 10th percentile air, soil and groundwater temperature in quantile regression) generally show the strongest increase in the lower 10th percentile temperatures for all air and soil temperatures. But this varies site-specifically in shallow groundwater, where urban infrastructure and the interaction between surface and groundwater, in addition to climate change, influence groundwater warming. Potentially, those urban heat islands with increasing trends in groundwater temperatures have great potential for heat utilization, but should not be used for extraction of cold. These findings emphasize the importance of spatial and temporal high-resolution data and highlight the necessity for site-specific aquifer characterization for a sustainable use of shallow geothermal energy for heating and cooling.

How to cite: Kaminsky, E., Laaha, G., Steiner, C., Nyéki, E., Englisch, C., Griebler, C., and Stumpp, C.: Spatio-temporal distribution of subsurface urban heat islands – Insights from shallow groundwater temperature monitoring in Vienna, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9552, https://doi.org/10.5194/egusphere-egu24-9552, 2024.

A.110
|
EGU24-9518
|
ECS
Development of hydro geophysical techniques to characterize water fluxes in the vadose zone of karstified and porous heterogeneous aquifers
(withdrawn)
Harmya Thadathummal Sathyan, Nele Hastreiter, Peter Dietrich, Martin Sauter, and Irina Engelhardt
A.111
|
EGU24-12406
|
ECS
Zaga Trisovic, Matthew O'Regan, Sophie ten Hietbrink, Beata Szymczycha, Arunima Sen, Aivo Lepland, Jochen Knies, and Wei-Li Hong

We investigate submarine groundwater transmissivity within Svalbard fjord sediments, where offshore freshened groundwater (OFG) was confirmed through analyses of dissolved chloride concentration and water isotope signatures (δ18O and δ2H). The analyses are comprised of physical, mechanical, and chemical attributes of three cores recovered from Tempelfjorden and Hornsund fjords. Multi-Sensor Core Logger (MSCL) analyses provide high-resolution physical characteristics of the sediment cores, including bulk density, p-wave velocity, magnetic susceptibility, and electrical resistivity. These are integrated with X-ray computed tomography (CT) images, acquired with a Geotek rotating X-ray CT system (RXCT), to identify sedimentary facies, which are used to investigate internal core structures. Discrete measurements of grain density and grain size are used to calculate sediment porosity and to estimate the permeability. Our results indicate a heterogeneous sediment matrix with frequent drop stones and ice-rafted debris interlayered with finer-grained materials. We hypothesize that the sediment matrix packaging and configuration is an important control for the sediment permeability and thus for freshened groundwater transmissivity in the sediments of these fjords. This work is not only relevant for characterizing groundwater transmissivity in Svalbard's fjords but also will contribute to ongoing geological modeling efforts. Our findings pave the way for hydrogeological simulations, enhancing our understanding of OFG occurrence, emplacement mechanisms, and OFG volumes over successive glacial cycles.

How to cite: Trisovic, Z., O'Regan, M., ten Hietbrink, S., Szymczycha, B., Sen, A., Lepland, A., Knies, J., and Hong, W.-L.: Investigating Submarine Groundwater Transmissivity in Svalbard Fjord Sediments through the Analyses of Physical Properties and Chemical Composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12406, https://doi.org/10.5194/egusphere-egu24-12406, 2024.

A.112
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EGU24-19836
|
ECS
Ariel Thomas, Daniel Zamrsky, Kamaldeen Omosanya, Mark Person, Joshu Mountjoy, and Aaron Micallef

Offshore freshened groundwater (OFG) represents a globally distributed subsurface resource with potential applications in water management, oil recovery, and environmental studies. Despite growing interest, the understanding of OFG systems, including their geometry, distribution, and emplacement dynamics, remains limited. In this study, we address these gaps by employing a novel 3D geostatistical modeling approach, focusing on the Canterbury Bight, a passive siliciclastic margin with proven OFG resources. Our methodology integrates high-resolution 2D seismic lines and borehole data, allowing us to capture the geological heterogeneity of the passive margin. Unlike traditional static models, our 3D approach considers the evolving stratigraphic architecture over multiple sea-level cycles, offering a more comprehensive understanding of OFG systems. Key findings include the successful incorporation of isostatic shifts and decompaction into our model, resulting in OFG distributions closely resembling those observed in the Canterbury Bight. We emphasize the importance of infilled buried channels and paleo-topographic highs in promoting OFG emplacement, shedding light on distribution patterns not easily explained by current seafloor topography or hydraulic heads. Our study advances the field by demonstrating how a 3D consideration of continental margin evolution significantly influences numerical estimations and improves the characterization of OFG resources. These findings contribute to a better understanding of OFG systems and provide valuable insights for future research and resource management.

How to cite: Thomas, A., Zamrsky, D., Omosanya, K., Person, M., Mountjoy, J., and Micallef, A.: Offshore freshened groundwater emplacement in an evolving siliciclastic margin (Canterbury Bight, New Zealand): A 3D modeling approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19836, https://doi.org/10.5194/egusphere-egu24-19836, 2024.

A.113
|
EGU24-20229
Hocine Henine, Julien Tournebize, Cedric Chaumont, Arnaud Blanchouin, Agnès Rivière, and Rémi Clément

Subsurface drainage practice is widely used in agriculture to eliminate temporary winter waterlogging of hydromorphic soils. Soil surface saturation is mainly due to the presence of an underlying layer (~1m deep) with a high clay content, considered as semi-impermeable. Generally, deep infiltration under this layer has been neglected in many hydrological studies. However, considering the variations in the ground water table levels, the recharge is mainly due to the deep infiltration. Understanding the dynamic of this infiltration is very important both for the quantitative management of groundwater resources and for the protection of its quality. Indeed, this infiltration can transfer spreading products (fertilizers and pesticides) used in agriculture, mainly the water-soluble molecules.

To understand the dynamic of the deep infiltration, hydrological and geophysical monitoring using ERT (Electrical Resistivity Tomography) method was set up on the drained experimental plot of Boissy le Châtel (Orgeval Observatory, in France). The water balance at the scale of the experimental plot highlighted the contribution of the deep infiltration to the groundwater table rise at the beginning of fall season.

Time-lapse geophysical survey coupled with water content monitoring on a 1.5m vertical profile showed the movement of a rewetting front from the soil surface towards deep layers during this very short transition period, which follows a precipitation event. After this period, during the intense drainage season, the deep infiltration below the drains continues (in the order of 0.12 mm/day compared to 2mm/day for subsurface drained flow) despite the rise of the water table to the surface layer. However, it is difficult to monitor its pathway using the passive ERT method, less sensitive to electrical resistivity variations in the range of soil water content close to saturation.

How to cite: Henine, H., Tournebize, J., Chaumont, C., Blanchouin, A., Rivière, A., and Clément, R.: Characterization of deep infiltrations in subsurface drained agricultural system, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20229, https://doi.org/10.5194/egusphere-egu24-20229, 2024.

Posters virtual: Fri, 19 Apr, 14:00–15:45 | vHall A

Display time: Fri, 19 Apr 08:30–Fri, 19 Apr 18:00
vA.16
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EGU24-12160
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ECS
Rene Bodjrenou

The validation of hydrogeological distributed models in western african countries is limited by the quality and availability of point station data measured in-situ. Climate models, satellite and reanalysis data have been suggested to overcome this limit. Here, we assessed the quality of ERA5 reanalysis on water table depth (WTD), and soil water content (SWC) over the Benin basins at spatial scale and monthly time scale. The single-levels version with 0.25° x 0.25° resolution (ERA5) and the land surface version with 0.1° x 0.1° resolution (namely LAND) were compared with point station data using the correlation performance evaluators and the Mean Absolute Error (MAE). The results showed that ERA5 and LAND reanalysis present well the water planes of Benin (WTD =0m). Outside wetlands areas, both reanalyses slight overestimation the WTD (MAE of ERA5=4.73m vs. LAND=3.13m. The SWC between 0-7 cm; 7-28cm and 28-100cm presented on both reanalyses are well in line with observations for all stations and on a monthly scale (correlation sometimes > 0.85 for LAND and 0.83 for ERA5). We recommend the use of LAND for validation of hydrogeological distributed models in Benin. Correcting the variables of these reanalyses could improve their performance.

How to cite: Bodjrenou, R.: Assessment of water table depth and soil water content Estimates from ERA5 reanalysis in Benin (West Africa), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12160, https://doi.org/10.5194/egusphere-egu24-12160, 2024.

vA.17
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EGU24-10700
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ECS
Exploring the potential of the north-eastern Adriatic basin to host freshened groundwater using onshore-offshore 3D hydrogeological modelling.
(withdrawn)
Cristina Corradin, Ariel T. Thomas, Angelo Camerlenghi, Luca Zini, Michela Giustiniani, Martina Busetti, Laura Foglia, Claudia Bertoni, and Aaron Micallef