Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 1 - 50 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort ascending	Keywords
Characterization of groundwater dynamics to identify the risks of flooding of the sewerage network of the urban communities of Lens-Liévin (northern France)	G	Picot-Colbeaux	France	2023	aquifer, Groundwater, groundwater inflow, hydrodynamic modelling, piezometry, sewerage network, urban hydrogeology
Abstract The interactions between groundwater and the sewerage networks of the Lens-Liévin urban communities, located in the north of France, locally lead to non-compliance in the operation of the network and the wastewater treatment plants, questioning the city’s economic development policy. Indeed, the infiltration of groundwater inflow in the sewerage network could be the cause. Based on the piezometric measurements carried out in 2022, the surface elevation of the groundwater table is carried out using a kriging approach. The comparison of altitudes between network position and piezometry made it possible to identify the pipes most at risk of the infiltration of groundwater inflow and correspond to those indicated as non-compliant by network managers according to the national decree. Outside this period, the network vulnerability indicators are defined based on simulated piezometry by a 3D hydrodynamic model of the chalky hydrosystem (MARTHE code) established in a transient state. For two past extreme situations, the network would have been flooded at 1.20% in the dry period (1997) and up to 8.30% in the wet period (2001), highlighting the existence of a part of the network systematically flooded. Using the hydrodynamic model according to different prospective scenarios makes it possible to anticipate the actions deployed on the network to guide management and adaptation solutions. However, a modelling methodology that considers the feedback between the dynamics of the groundwater and the flows passing through the networks remains to be developed.
Regional-scale identification of recharge or discharge using remote sensing and GIS: Implications towards groundwater-surface water interactions	Kawawa	Banda	Zambia	2023	Barotse Floodplain, Groundwater-Surface water, Zambezi River, Zambia, Ecosystems
Abstract Identifying groundwater recharge and discharge areas across catchments is critical for implementing effective strategies for salinity mitigation, surface water and groundwater resource management, and ecosystem protection. This study seeks to identify potential GW-SW discharge and recharge areas around the Barotse Floodplain. The results of remote sensing analysis using the Normalised Difference Vegetation Index (NDVI) show that the vegetation is sensitive to the dynamics of groundwater level, with shallower levels (< 10 m) in the lower reaches compared to deeper levels (>10 m) in the upper catchment). These zones are further investigated and likely represent geological variability, aquifer confinement and the degree of GW-SW interactions. GW-SW interactions likely are influenced by an interplay of factors such as water levels in the groundwater and surface level and hydrogeological conditions. Based on the findings, the wetland hosts riparian vegetation species responsive to the groundwater dynamic. NDVI can thus be used as a proxy to infer groundwater in the catchment. Therefore, effective water resources management of the floodplain should be implemented through conjunctive management of groundwater and surface water.
Nitrate vulnerability assessment in the fast-growing African district of Abuja Federal Capital Territory (Nigeria)	M	Etuk	Abuja FCT, Nigeria	2023	DRASTIC-LU model, Groundwater Contamination, population growth
Abstract In the Federal Capital Territory of Abuja (Abuja FCT, Nigeria), a population growth of about 400% between 2000 and 2020 has been reported. This trend, coupled with the persisting urban sprawling, is likely to result in severe groundwater quality depletion and contamination, thus undermining one of the area’s main freshwater supplies for drinking purposes. In fact, groundwater in Nigeria and Abuja FCT provides over 70% of the drinking purposes. Results of a groundwater vulnerability assessment that compared land use data from 2000 and 2020 showed that the region had been affected by a dramatic change with an increase in urbanized (+5%) and agricultural (+27%) areas that caused nitrate concentrations to exceed the statutory limit for drinking purposes in more than 30% of the monitored wells in 2021 and 40% in 2022. Although fertilizers are generally considered the main source of nitrate contamination, results suggest a possible mixed (urban and agricultural) pollution origin and a legacy of previous nitrogen pollution sources. The comparison between the DRASTIC-LU map and nitrate concentrations shows that the highest values are found in urban/peri-urban areas, in both shallow and deep wells. This investigation is the first step of a comprehensive nitrate pollution assessment in the region, which will provide decision-makers with adequate information for urban planning given the expected population growth in the area
Combined effects of seawater intrusion and nitrate contamination on groundwater quality in the coastal agricultural area of El-Nil River, Algeria	Lamine	Boumaiza	Algeria	2023	Coastal aquifer, Groundwater Quality, nitrate contamination, Seawater Intrusion, stable isotopes
Abstract This study focuses on the coastal agricultural area of El-Nil River (Algeria), where anthropogenic activities heavily impact groundwater resources. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, δ15NNO3 and δ18ONO3), is combined with a hydrochemical facies evolution diagram and a Bayesian isotope mixing model (MixSIAR) to assess seawater contamination and distinguish the nitrate sources and their apportionment. A total of 27 groundwater samples and 7 surface water samples distributed over the entire study area were collected. Results show classic inland intrusion combined with an upstream seawater impact through the river mouth connected to the Mediterranean Sea. Results from nitrate isotopic composition, NO3 and Cl concentrations, and the MixSIAR model show that nitrate concentrations chiefly originate from sewage and manure sources. Nitrate derived from sewage is related to wastewater discharge, whereas nitrate derived from manure is attributed to an excessive use of animal manure to fertilise agricultural areas. The outcomes of this study are expected to help decision-makers prepare suitable environmental strategies for effective and sustainable water resources management in the study area.
A combined stochastic-analytical method for the assessment of climate change impact on spring discharge	Attila	Kovacs	Hungary	2023	Spring hydrograph, analytical model, Climate change, stochastic mode
Abstract This study describes a novel methodology for predicting spring hydrographs based on Regional Climate Model (RCM) projections to evaluate climate change impact on karstic spring discharge. A combined stochastic-analytical modelling methodology was developed and demonstrated on the Bukovica karst spring catchment at the Durmitor National Park, Montenegro. As a first step, climate model projections of the EURO-CORDEX ensemble were selected, and bias correction was applied based on historical climate data. The regression function between rainfall and peak discharge was established using historical data. The baseflow recession was described using a double-component exponential model, where hydrograph decomposition and parameter fitting were performed on the Master Recession Curve. Rainfall time series from two selected RCM scenarios were applied to predict future spring discharge time series. Bias correction of simulated hydrographs was performed, and bias-corrected combined stochastic-analytical models were applied to predict spring hydrographs based on RCM simulated rainfall data. Simulated climate scenarios predict increasing peak discharges and decreasing baseflow discharges throughout the 21st century. Model results suggest that climate change will likely exaggerate the extremities regarding climate parameters and spring discharge by the end of the century. The annual number of drought days shows a large variation over time. Extremely dry years are periodic, with a frequency between 5-7 years. The number of drought days seems to increase over time during these extreme years. The study confirmed that the applied methodology can successfully be applied for spring discharge prediction
First Nations Communities as Partners in Hydrogeology	Sarah	Bourke	Australia	2023	Cultural Water Values, First Nations Groundwater Connections, Social Hydrogeology
Abstract Aboriginal and Torres Strait Islander people have inhabited the lands now known as Australia for over 65,000 years. Their communities are intricately connected to the land and waters through culture and tradition. However, there are few examples of integrated water resource management that serve Aboriginal and Torres Strait Islander communities or cultural interests. This is particularly the case for groundwater. In Australia, Indigenous connections to groundwater have historically been overlooked or, in some cases, assumed not to exist. On the contrary, many Aboriginal and Torres Strait Islander cultures have longstanding physical and spiritual connections to a range of artesian and subartesian groundwater resources. These cultures also house accurate records of groundwater systems. Despite this, groundwater management in Australia remains dominated by Western scientific perspectives, and the groundwater sector poorly integrates Indigenous stakeholder concerns or knowledge into groundwater management and planning. IAH Australia has prepared and signed an Indigenous Groundwater Declaration intending to raise awareness among the groundwater community of the value of Indigenous perspectives and knowledge of groundwater systems. This Declaration can be viewed and signed at http://declaration.iah.org.au. This presentation provides examples of effective partnerships between Indigenous Communities and Government or Academic groundwater professionals. While progress has been made, challenges must be overcome to integrate Indigenous knowledge and connections into groundwater resource management.
Contribution of gravel pit lakes in reducing the groundwater nitrate contamination originating from agricultural land	Igor	Karlović	Croatia	2023	Varaždin aquifer, gravel pit lakes, Groundwater, groundwater remediation, Nitrate
Abstract The alluvial aquifer in the Varaždin region has a long-standing problem with high groundwater nitrate concentrations, mainly from agricultural activities. Since groundwater is used in public water supply networks, it is important to ensure its sustainable use. The aquifer is also used to exploit gravel and sand, and the increased demand for this valuable construction material causes the excavation of gravel pit lakes, making groundwater more vulnerable. Although engineered processes can remove nitrate from groundwater, natural attenuation processes should be investigated to understand the nitrogen behaviour and additional mechanisms for groundwater remediation. Previous research has shown nitrate is a conservative contaminant in the critical zone. Aerobic conditions within an aquifer system prevent significant denitrification. Thus, nitrification is the main process controlling nitrogen dynamics in groundwater. Since groundwater and gravel pit lakes are hydraulically connected, and natural nitrate attenuation exists in these lakes, an additional mechanism for groundwater remediation is possible. This work used isotope hydrochemistry and groundwater modelling to investigate gravel pit lakes as possible sites to reduce nitrate concentration in groundwater. Based on the isotopic composition of groundwater and nitrate concentrations, water balance and solute mass balance were calculated, which made it possible to estimate the nitrate attenuation rate in gravel pit lakes. The gained retardation factor was applied to the groundwater flow and nitrate transport model through several scenarios to evaluate the contribution of gravel pit lakes in reducing the groundwater nitrate concentrations
Machine learning as a tool to improve groundwater monitoring networks	D	Pacios	Spain	2023	Groundwater, Machine learning, monitoring networks, Nitrate, random forest, Spain
Abstract Machine learning techniques are gaining recognition as tools to underpin water resources management. Applications range widely, from groundwater potential mapping to the calibration of groundwater models. This research applies machine learning techniques to map and predict nitrate contamination across a large multilayer aquifer in central Spain. The overall intent is to use the results to improve the groundwater monitoring network. Twenty supervised classifiers of different families were trained and tested on a dataset of fifteen explanatory variables and approximately two thousand points. Tree-based classifiers, such as random forests, with predictive values above 0.9, rendered the best results. The most important explanatory variables were slope, the unsaturated zone’s estimated thickness, and lithology. The outcomes lead to three major conclusions: (a) the method is accurate enough at the regional scale and is versatile enough to export to other settings; (b) local-scale information is lost in the absence of detailed knowledge of certain variables, such as recharge; (c) incorporating the time scale to the spatial scale remains a challenge for the future.
Groundwater circulation and hydrogeochemical evolution in the coastal zone of Xiamen, southeast China	Y	Li	China	2023	groundwater flow, Hydrogeochemical evolution, Seawater Intrusion
Abstract This study aims to investigate the groundwater circulation and hydrogeochemical evolution in the coastal zone of Xiamen, southeast China, which can provide a reference for the development of water resources and the protection of soil and water environment in the coastal areas. A close connection between mountains and the sea characterizes the southeast coast of China. Although rainfall is abundant, the topography limits it, and water resources quickly run into the sea. Coupled with a concentrated population, water is scarce. In addition, this area’s water and sediment environment are influenced by human activities and geological conditions. Its changing trend also needs further study. Therefore, using hydrochemical analysis, isotope technology, numerical simulation and other techniques, this study took Xiamen City on the southeast coast as an example to study the groundwater circulation and the environmental evolution of water and sediment. The results show that although the aquifer is thinner, there is still deep groundwater circulation, and the seawater intrusion range of deep aquifer is much further than that of shallow aquifer. In addition to geological causes, human activities have become the main factors affecting groundwater quality, especially nitrate and lead. The nitrate content even exceeds the content of the major ionic components. Introducing land-based pollutants has also contributed to declining seawater and sediment quality in the Bay area. In general, the main pollutants in coastal areas include nutrients, heavy metals and new pollutants.
Exploring the Role of Land Use evolution in Groundwater Modeling for Sustainable Management: A Case Study of the Lille Metropolitan Area	Ryma	Aissat	France	2023	Land use change, groundwater flow modelling, groundwater sustainability, recharge, runof
Abstract Groundwater represents a crucial source of drinking water in the Lille metropolitan area. Despite its importance, the resource is vulnerable to the potential evolution of land use: recharge, runoff and evapotranspiration processes in a soil-sealing context and changes in cultural practices. As a result, stakeholders emphasized the importance of exploring the influence of land use on groundwater to ensure sustainable resource management and enhance territorial planning. The 3D hydrodynamic model helped manage groundwater resources, but the (MARTHE code) has a significant limitation in that it does not consider the impact of land use evolution. We propose to investigate the contribution of a hydrological distributed numerical approach incorporating land cover data in groundwater modelling compared to a global approach at the scale of a peri-urban territory. To do so, we use the HELP code by considering the temporal and spatial evolution of land use and their associated characteristics, such as vegetation and soil properties, to detail recharge and runoff over more than 20 years that we incorporate into the initial groundwater model. The two approaches yielded comparable global water balance results. However, at the local scale, the model accounting for land use showed significantly different hydric components. Choosing the appropriate model depends on the specific research question and spatial scale, and considering land use evolution is crucial for accurate urban planning impact assessments, especially at the district level.
A stochastic data integration approach to generate geologically consistent hydrogeological models from geophysical and hydrogeological data	A	Neven	Switzerland	2023	Hydrogeophysics; Inversion; Data-Integration; Groundwater
Abstract This study presents a novel approach for developing geologically and hydrogeologically consistent groundwater models at large valley scales. Integrating geological, geophysical, and hydrogeological data into a single model is often challenging, but our methodology overcomes this challenge by combining the Ensemble Smoother with Multiple Data Assimilation algorithm (ESMDA) with a hierarchical geological modelling approach (ArchPy). The ESMDA framework assimilates geophysical and hydrogeological field data jointly. To diminish the computational cost, the forward geophysical and groundwater responses are computed in lower-dimensional spaces relevant to each physical problem, alleviating the computational burden and accelerating the inversion process. Combining multiple data sources and regional conceptual geological knowledge in a stochastic framework makes the resulting model accurate and incorporates robust uncertainty estimation. We demonstrate the applicability of our approach using actual data from the upper Aare Valley in Switzerland. Our results show that integrating different data types, each sensitive to different spatial dimensions enhances the global quality of the model within a reasonable computing time. This automatic generation of groundwater models with a robust uncertainty estimation has potential applications in a wide variety of hydrogeological issues. Our methodology provides a framework for efficiently integrating multiple data sources in geologically consistent models, facilitating the development of hydrogeological models that can inform sustainable water resource management.
Research-based exploration of deep groundwater within the eastern limb of the Bushveld Complex	Amy	Allwright	Bloemfontein, South Africa	2023	Bushveld Complex, Deep groundwater, deep scientific drilling
Abstract The current understanding of groundwater within the larger Bushveld Complex (BC) is evaluated to gauge the potential for deep groundwater, specifically emphasising the lesser investigated eastern limb. From the review of publicly available literature and data, geohydrological databases and statistical analyses are presented as a collation of the current understanding of groundwater in the eastern limb of the BC. Unfortunately, information on deep groundwater (> 300 m) is scarce due to the cost associated with deep drilling, mining exploration holes often neglecting hydrogeological data collection, or lack of public access to this information. Nevertheless, the conceptual model developed from the available information highlights deep groundwater’s variable and structurally controlled nature and the uncertainty associated with groundwater characterisation of the deeper groundwater systems. This uncertainty supports the need for research-based scientific drilling of the deeper fractured lithologies in the eastern limb of the Bushveld Complex. The Bushveld Complex Drilling Project (BVDP) established an opportunity to perform such research-based drilling and was funded by the International Continental Scientific Drilling Program (ICDP). While the main focus of the BVDP is to produce a continuous vertical stratigraphic sequence of the BC, there is a sub-component to collect geohydrological information. The planned borehole, 2 500 m deep, will provide an opportunity to collect information from the deeper systems within the Bushveld Complex and the underlying Transvaal Supergroup, which will inform on the connection between shallow and deeper groundwater.
Hydrological processes in the Arctic catchment of Bayelva River (Western Svalbard-Norway)	Marco	Doveri	Norway	2023	Arctic hydrology, Climate change, groundwater-surface water evolution, melting water
Abstract Streamwater and groundwater are changing in the Arctic region because of significant climate warming. Arctic amplification has intensified the melting of snow cover, glaciers and permafrost, leading to a prominent variation in the annual discharge of rivers, the groundwater occurrence, and their relationships. In high-latitude regions, evaluating groundwater flux/storage and river discharge is challenging due to a lack of hydrogeological data. Changes in river flows and groundwater discharge will alter freshwater and terrigenous material flux, with implications for freshwater and marine ecosystems. Consequently, a more timely and accurate evaluation of surface and groundwater is required. In this framework, through the ICEtoFLUX project (MUR/PRA2021/project-0027), hydrology, geophysics and geochemical-isotopic surveys have been started during 2022 in the Bayelva River catchment (W-Svalbard) from its glaciers and periglacial/proglacial systems up to the Kongsfjorden. The study aims to quantify hydrologic processes and related transport of matter (solid transport, chemical solutes flux) and investigate how subsurface and surface waters interact during active layer development. The first results suggest that electrical conductivity and total suspended solids increase from glaciers to the Bayelva monitoring station, about 1 km from the coast. Seasonal evolution of physical-chemical features was also observed. Results from geophysics data and piezometers indicate that the underground flow is spatially and temporally heterogeneous, both quantitatively and from a physicochemical-isotopic point of view. Springwater characteristics testify to a deep and well-organized groundwater flow path system. This study highlights the high complexity of these systems and their high sensitivity to the meteo-climatic regimes.
Isotope geochemistry disentangles interactions between water and carbon cycle in Mediterranean peatland	Sebastien	Santoni	Mediterranean peatland	2023	Groundwater-Dependent Ecosystem, origin of carbon, peatland-atmosphere interface, peatland-carbon-water system, sources and sinks of carbon
Abstract This research aims to evaluate the carbon storage function of a Mediterranean peatland in changing climate conditions. The scientific strategy relies on a seasonal geochemical survey sourcing the carbon origin by considering the hydrosphere, lithosphere, biosphere, and atmosphere. This unprecedented research on a Mediterranean peatland reveals the seasonality of dissolved carbon inputs from primary production, organic matter oxidation, and time-changing recharge components within the catchment (rainwater, river water, shallow groundwater, deep groundwater). Based on the mixing proportions of all recharge water components, the study applies a reverse end-member mixing analysis to define the theoretical peat water d13CDIC value and compare it to the measured ones. The model explains 65 % of the data, demonstrating the water flow influence on peatland carbon content. In 35% of the cases, peatland processes such as primary production and organic matter oxidation drive the peat water’s carbon content. Peat organic and inorganic properties, d13CTOC, and d13CCO2 data demonstrate the role of groundwater as a CO2 source and the dominance of in situ primary production that argues in favour of carbon storage within such Mediterranean peatland. This research proves the relevance of geochemistry and isotope hydrology tools to disentangle and rank peatland water and carbon processes within peatland hydro-ecosystems. Overall, it reveals the necessity to take into account the interactions between water and carbon cycle processes, with particular consideration for groundwater as a CO2 source at the peatland-atmosphere interface, to build better models for the future evolution of the global climate.
Test-pumping derivative analysis to improve conceptual understanding and abstraction yields in a complex fractured aquifer: Steenbras Wellfield (Western Cape, South Africa)	K	de Bruin	South Africa	2023	Table Mountain Group, conceptual model, derivative analysis, fractured aquifer, groundwater resource management, recommended yield, test-pumping
Abstract Test-pumping drawdown curves do not always sufficiently indicate aquifer characteristics and geometry and should never be analysed in isolation. Using derivative analysis and flow dimension theory, inferring the regional geometries and flow characteristics of fractured aquifers that are otherwise unknown or inconclusive is possible. As the drawdown and/or pressure front propagates through the aquifer, it reaches various hydrogeological objects that influence flow regimes and imprints a sequence of signatures in the drawdown derivative curve. The conjunctive interpretation of these flow regime sequences and hydrogeological data results in a robust, well-informed conceptual model (in terms of both local groundwater flow and the aquifer), which is vital for sustainable groundwater resource management. Derivative and flow regime analysis was applied to the test-pumping data of confined and unconfined Nardouw Aquifer (Table Mountain Group) boreholes within Steenbras Wellfield (Western Cape). Major NE-SW trending folding and transtensional Steenbras-Brandvlei Megafault Zone, in association with cross-cutting faults/fractures and younger False Bay Suite dykes, make the Nardouw Aquifer (and deeper Peninsula Aquifer) hydrogeologically complex. The sequential flow regime analyses reveal domains of conceptual flow models, including open vertical fractures, T-shaped channels, double (triple) porosity models, and leaky/recharge boundary models, amongst others. Appropriate analytical flow models (type curve fitting) are then applied for accurate aquifer parameter estimations, which are used to evaluate recommended long-term yields through predictive pumping scenarios. The outcome is an improved hydrogeological understanding and enhanced conceptual model of the aquifer, which informs numerical modelling, ecological protection, and groundwater resource management.
Real-time iFLUX sensors reveal rapidly changing groundwater flow dynamics in wetland ecosystems	N	Van Putte	Poland, Belgium	2023	Internet of Things, ecohydrology, groundwater flow, sensor development, wetland conservation
Abstract Shallow groundwater dynamics play a crucial role in wetland ecosystems and are key to climate change resilience. Therefore, conserving and restoring wetland areas requires excellent knowledge of groundwater flow dynamics, which are often rapidly changing following extreme weather events and anthropogenic impacts such as groundwater extraction. Traditional methods to estimate groundwater flow require extensive modelling or rely on point measurements, missing the effect of crucial short-term events and impeding quick actions to conserve the wetlands’ ecohydrological status. Here, we present a newly developed sensor that can measure real-time groundwater flow velocity and direction. The sensor probe consists of two bidirectional flow sensors that are superimposed. It is installed in a dedicated pre-pack filter and can measure a broad range of groundwater flow velocities from 0.5 cm/ day to 2000 cm/day. With an IoT (Internet of Things) system, sensor data is wirelessly transmitted and visualized in real-time on an online dashboard. In addition, we show a selection of results from a case study in the Biebrza National Park (Poland) and a nature reserve in Damme (Belgium). In both ecosystems, we could capture changes in groundwater flow velocity and direction resulting from precipitation and evapotranspiration events. As such, we are confident that our sensors provide new insights into rapidly changing groundwater dynamics and will become an invaluable tool in ecohydrological studies worldwide, ultimately leading to more integrated management strategies to protect and conserve remaining wetlands.
Machine learning applied to pumping test analysis	A	Lukas	South Africa	2023	numerical modelling, aquifer test analysis, deep learning, derivative analysis, Machine learning
Abstract Aquifer test analysis is complex, and in many regards, the interpretation resembles an art more than a science. Under the best circumstances, aquifer test analysis is still plagued by ambiguity and uncertainty, compounded by the general lack of information on the subsurface. An approach which has seen widespread adoption in other fields that need to classify time series data is machine learning. A Python script that generates numerical groundwater flow models by interfacing directly with the modelling software produces training data for deep learning. Production yielded 3,220 models of aquifer tests with varying hydrogeological conditions, including fracture, no-flow and recharge boundary geometries. Post-processing exports the model results, and the Bourdet derivative is plotted and labelled for image classification. The image classifier is constructed as a simple three-layer convolutional neural network, with ReLU as the activation function and stochastic gradient descent as the optimizer. The dataset provided sufficient examples for the model to obtain over 99% accuracy in identifying the complexities present inside the numerical model. The classification of groundproofing data illustrates the model’s effectiveness while supporting synthetically prepared data using modern groundwater modelling software.
Aquifer storage and recovery (ASR) applications to enhance drinking water supply security in the Sultanate of Oman	Harmen	van den Berg	Oman	2023	Aquifer Storage and Recovery, Oman, desalinated seawater, drinking water supply, groundwater flow modelling, Hydrogeology, recovery efficiency
Abstract Water scarcity has driven many countries in arid regions, such as Oman, to desalinate seawater for freshwater supply. Episodic problems with seawater quality (e.g., harmful algae), extreme weather events that affect energy supply and hence the desalination process have nurtured the urgent need to store desalinated seawater (DSW) in the aquifers for use during emergency and peak demand time. Aquifer Storage and Recovery (ASR) using injection wells is a possible strategic option for Oman Water and Wastewater Services Company (OWWSC) to augment aquifer storage using excess desalinated water during low demand times. ASR strategically serves as a water supply backup to optimize production capacities against seasonal demand patterns. The technical-economic feasibility of implementing ASR schemes was investigated in Jaalan, Oman, using hydrogeological and geophysical field measurements, groundwater flow and hydraulic modelling, and economic analysis. Analysis of modelled scenarios results revealed that the Jaalan aquifer is suitable for storing and recovering about 4,000 m3 /hr in 2045. Various well field designs have been tested and optimized numerically using MODFLOW 6, showing that with 160 dual-purpose wells, 7.9 Mm3 can be injected and abstracted within the constraints defined for a robust and sustainable ASR system. Simulations with the density-dependent flow model (MF6 BUY) show that the injected volume can be fully recovered considering the drinking water quality standard. Other sites were also studied. ASR capacity was found to be site-specific, and the groundwater developments near the ASR site governed its feasibility
Paleo-hydrogeological reconstruction of a complex deep groundwater system in a tectonically active region	H	Levanon	Israel	2023	Dead Sea Rift, Golan Heights, Lagoonary brines, Paleo-hydrology, intrusion/backflow
Abstract The geochemical study of deep aquitard water in the southern Golan-Heights (GH), Israel, reveals the complex paleo-hydrological history affected by the intensive tectonic activity of the Dead Sea Rift (DSR). The sampled water collected from new research boreholes exhibits relatively high salinities (2,000-10,000 mg Cl/L), low Na/Cl ((HCO3 +SO4 )). δ18OV-SMOW and δDV-SMOW values are relatively depleted (~-7‰ and ~-42‰, respectively), while 87Sr/86Sr ratios are enriched compared to the host rocks. Lagoonary brines with similar characteristics (excluding the water isotopic compositions) are known to exist along the DSR. These brines formed 10-5 Ma ago from seawater that transgressed into the DSR and subsequently underwent evaporation, mineral precipitation and water-rock interactions. These hypersaline brines intruded into the rocks surrounding the DSR and based on the current study, also extended as far as the southern GH. Further, following their subsurface intrusion into the GH, the brines have been gradually diluted by isotopically depleted freshwater, leaving only traces of brines nowadays. The depleted isotopic composition suggests that the groundwater system is recharged at high elevations in the north. It is also shown that variable hydraulic conductivities in different formations controlled the dilution rates and subsequently the preservation of the entrapped brines. The paleo-hydrological reconstruction presented here shows that the flow direction has reversed over time. Brines that initially intruded from the rift have since been gradually flushed back to the rift by younger fresh groundwater.
Alluvial aquifer modelling with MODFLOW in a case of a wellfield in a climate change context (Clermont-Ferrand, France)	Jordan	Labbe	France	2023	Alluvial aquifer, Groundwater Modelling, Climate change, water management
Abstract This work is part of the AUVERWATCH project (AUVERgne WATer CHemistry), which aims to better characterise some Auvergne water bodies, specifically the alluvial hydrosystem of Allier River (France). Alluvial aquifers constitute worldwide a productive water resource, superficial and easily exploitable. In France, 45% of the groundwater use comes from these aquifers. The study site is a wellfield that withdraws 8.5 million m3 of water annually from an alluvial aquifer to produce domestic water for 80% of the local population. At the watershed scale, precipitations have decreased by -11.8 mm/y, air temperatures have increased by 0.06°C/y and the river flow has declined by 20.8 Mm3 /y on 2000 – 2020. In the summer period, at least 50% of the river flow is ensured by the Naussac dam (upstream catchment part), but the recent winter droughts have not allowed the dam to replenish. Thus, water stakeholders are concerned that the productivity of the wellfield could be soon compromised. Based on geological, geophysical, hydrochemical, and hydrodynamic surveys, a numerical model of the wellfield is being developed using MODFLOW. The calibration in natural flow regime is successful using a range of hydraulic conductivities going from 1×10-3 to 1×10-4 m/s (pilot points method), consistent with the pumping tests. Preliminary results show that the river entirely controls the groundwater levels at all observation points. The perspective is now to calibrate this model in a transient regime by integrating domestic water withdrawals to determine how low the river can go without affecting the wellfield productivity.
Use of krypton-81 to constrain the reliability of carbon-14 in estimating groundwater ages	S	Lu	China	2023	groundwater dating, krypton-81 isotope, radiocarbon
Abstract Advances in groundwater age dating provide key information for groundwater recharge history and rates, which is of great significance for groundwater sustainable development and management. By far the, radioisotope 14C is the most frequently used in routine investigations. However, groundwater age can be misinterpreted given its dating range of up to 40 ka and its chemically active in nature. In comparison, 81Kr is less frequently used but chemically inert with a dating range of up to 1,300 ka, which overcomes the limit of 14C. Although it is not as precise as 14C when the groundwater age is younger than 40 ka, it may be helpful to determine the reliability of 14C dating results. In this study, we collected eight field samples from coastal aquifers in Nantong, China and analyzed them for 81Kr, 85Kr, and 14C. The 14C results show that all groundwater ages range from 2,400 to 35,300 years, with different correction methods yielding uncertainties of 1,500 to 3,300 years. Four of the 81Kr ages provided upper bounds, while three yielded groundwater ages which are consistent with the 14C dating results within measurement uncertainties. Interestingly, one 81Kr result gave an age of 189+11 - 12ka, whereas the corresponding corrected 14C age was less than 29,200 years. The great difference may indicate modern contamination in the sampling process or mixing between young and old groundwaters. Further investigation is needed to shed more lights in this case. Moreover, it shows the benefits of introducing 81Kr in routine hydrogeological investigations and the groundwater studies.
Platinum-Group-Elements and Total Organic Carbon in hyperalkaline springs at the Ronda peridotites (Malaga, Spain) as proxies of the origin of dissolved methane gas	Lucia	Ojeda	Malaga, Spain	2023	Hyperalkaline springs, Methane, Platinum-Group-Elements, Ronda peridotites, Total Organic Carbon
Abstract The serpentinization of ultramafic rocks is a process in which minerals of ferromagnesian nature (e.g., olivine) are transformed into serpentine and produce groundwater with a very high pH. In these settings, CH4 can be produced by combining H2 from serpentinization and CO2 from the atmosphere, soil, carbon-bearing rocks, or mantle, although the microbial generation of CH4, mediated by methanogens utilizing CO2, formate and/or acetate can be another source in these aquifers. In this sense, the hydrochemistry of hyperalkaline springs can provide valuable information about gas origin. The Ronda peridotites (Malaga province, Spain) are one of the world’s largest outcrops of the subcontinental mantle (~450 km2). Hyperalkaline springs (pH>10) emerging along faults present a permanent low outflow (<1 L/s), Ca2+- OH- facies and residence times exceeding 2,000 years. The fluids, poor in Mg2+ and rich in K+, Na+, Ca2+ and Cl-, also contain significant concentrations of dissolved CH4 and other hydrocarbons. Water samples have been collected from eight hyperalkaline springs and analyzed for major, minor and trace elements, including Platinum Group Elements (PGE) and Total Organic Carbon (TOC). The most mobile PGEs (Pd and Rh) are present in all the springs, indicating the existence of potential catalysts for the abiotic synthesis of CH4. High TOC concentrations are observed in some studied springs where previous analyses (i.e., bulk CH4 isotopes) have indicated a microbial CH4 origin.
The role of groundwater in urban resilience	Adrian	Healy	Wales	2023	Groundwater, Governance, household, Resilience, urban
Abstract The potential role of groundwater in supporting the resilience of human societies is garnering increased attention in the context of climate change. Much of this attention focuses on the resilience of the groundwater resource itself. Less attention has been given to the way that groundwater is used by society and how this may influence human-centred resilience outcomes, particularly in urban settings. In this paper, I explore how questions of scale are fundamental to the role of groundwater in the resilience of urban areas, from the scale of individual households to more regional and catchment-based notions of scale. It is these variations in the geographies of urban groundwater exploitation that provide for the challenges of groundwater governance. Drawing on the practices revealed across 5 diverse cities in sub-Saharan Africa; the paper highlights the variety of ways that groundwater promotes the resilience of urban areas to water stress. The paper finds that groundwater can accommodate a prevalence of ‘self-supply’ and market-based models as urban populations seek to counter failings in public supply provision. Whilst these actions promote the resilience of the urban setting in the short to medium term, they raise important questions for the longer-term sustainability of the resource. The paper considers the implications of these questions for the future governance of resilient groundwater resources and the role of groundwater as part of a wider strategy for urban resilience.
Unfolding the spatial heterogeneity of the natural background level of arsenic in groundwater at the mesoscale using data from sites under remediation	L	Landi	Italy	2023	Arsenic, Natural Background Level, Heterogeneity, sites under remediation
Abstract The Natural Background Level (NBL) of contaminants in groundwater is typically determined using regional-scale monitoring networks or site-specific studies. However, regional scale values are limited in their ability to capture natural heterogeneities that affect contaminant mobility at smaller scales, potentially leading to local over- or underestimation of the natural contaminant concentration. Conversely, site-specific studies can be expensive and time-consuming, with limited use outside the specified case study. To overcome this issue, a study was conducted in a 2600 km2 area, analyzing arsenic concentration values from monitoring networks of sites under remediation as an alternative source of information. The main drawbacks of the alternative dataset were the lack of information on monitoring procedures at the remediation sites or potential anthropogenic influences on the concentration data. However, these limitations were adequately managed with a thorough data pre-treatment procedure informed by a conceptual model of the study area. The NBLs estimated with the alternative dataset were more reliable than that from the regional monitoring network, which, in the worst case (i.e., in the area with the highest geological and geochemical heterogeneity), the NBL of one order of magnitude was underestimated. As a future step, the project seeks to incorporate geological and geochemical heterogeneities as secondary variables in a geostatistical analysis to produce a continuous distribution of arsenic concentrations at the mesoscale. This would provide a useful tool for managing contaminated sites and a reproducible protocol for NBL derivation in different areas, overcoming the scale issue.
A Case Study on Capacity Development in Rural Groundwater Supply in Acholiland, Northern Uganda	K	Robey	Northern Uganda	2023	Uganda, capacity development, Geophysics, handpump functionality assessments, rural groundwater supply, Water quality
Abstract Groundwater is the most important source of potable water in rural areas of Acholiland, a sub-region of northern Uganda. Installation of handpumps has been the focus of local government and international aid to provide safe drinking water in Uganda. However, non-functional handpumps are one reason for the abandonment of groundwater resources. For handpumps to be sustainable for years, appropriate siting and construction is required, as well as monitoring. This is common knowledge to specialists working in rural supply, but gaps in knowledge transfer and field skills may exist for the persons installing and maintaining handpump wells. This is a case study of a ten-day field campaign designed to train local participants who actively work in the rural groundwater supply sector. Nine non-functional handpump sites were identified for repair and hydrogeology and geophysical studies. A non-governmental organization, IsraAID, along with Gulu University implemented training by hydrogeology specialists to build local capacity. The training included handpump functionality tests, downhole inspections, electrical resistivity tomography surveys, and water quality sampling, including a novel Escherichia coli test that did not require an incubator. Functionality tests and downhole inspections provided simple but effective ways to assess handpump and well issues. Training in water quality empowered the participants to complete rapid assessments of the quality of the water and start monitoring programs. The success of the project was based on collaboration with multiple organizations focusing on the development of local capacity. The lessons learnt from this campaign should be considered for other rural groundwater supply scenarios.
Modelling the Impact of Groundwater Pumping on Karst Geotechnical Risks in Sete Lagoas (MG), Brazil	Paulo	Galvão	Brazil	2023	Karst hydrogeology; numerical model; water management; subsidence; overexploitation
Abstract Urban karst terrains can experience geotechnical issues such as subsidence or collapse induced/accelerated by groundwater withdrawal and civil works. Sete Lagoas, Brazil, is notable for overexploiting a karst aquifer, resulting in drying lakes and geotechnical issues. This study aims to evaluate the progression of geotechnical risk areas from 1940 to 2020 and to simulate future scenarios until 2100. Historical hydraulic head data from the 1940s (when the first pumping well was installed) to the 2000s, a 3D geological model, and a karst-geotechnical risk matrix for defining risk levels were employed to develop a calibrated Feflow numerical model. The results indicate that, before the first well in 1942, the groundwater flow direction was primarily towards the northeast. In the 1980s, due to the concentration of pumping wells in the central area, a cone of depression emerged, causing the flow directions to converge towards the centre of the cone, forming a zone of influence (ZOI) of approximately 30 km². All 20 geotechnical events recorded between 1940 and 2020 have occurred in high or considerable-risk zones where limestone outcrops or is mantled in association with the ZOI. For future scenarios, if the current global well pumping rate (Q = 144,675 m³/d) from 2020 remains constant until 2100, the high and considerable geotechnical risk zones will continue to expand. A 40% decrease in the global rate (Q = 85,200 m³/d) is necessary to achieve a sustainable state, defined by reduced and stabilized risk zones.
Harmonized groundwater data in International River Basins under the Water Framework Directive (2000/60/EC) – Challenges	Belinda	Flem	Norway	2023	Harmonized data; monitoring; sampling techniques; analysis
Abstract Transboundary aquifers in Europe are managed according to the Water Framework Directive (WFD) through international river basin districts (IRBD) management plans. Paragraph 11 in the WFD states that each Member State shall ensure the establishment of a programme of measures, PoM, for each river basin district, RBD, or part of an IRBD within its territory. Easy access to harmonized data from neighbouring countries part of the aquifer is essential to analyse the groundwater status and make proper PoMs. The datasets must be available in machine-readable format via an Application Programming Interface (API) and, where relevant, as a bulk download. The metadata describing the data shall be within the scope of the Infrastructure for Spatial Information in the European Community (INSPIRE) data themes set. The datasets must also be described in a complete and publicly available online documentation describing the data structure. Using a questionnaire survey of nine European countries, groundwater sampling and analysis routines are compared to evaluate if data are comparable and accessible across borders.
Optimizing managed aquifer recharge in coastal dunes by extracting brackish groundwater: results of a field pilot in the Netherlands	T	van Dooren	Netherlands	2023	Brackish groundwater extraction, Managed aquifer recharge, drinking water production, field pilot, coastal dunes
Abstract Faced with climate change and population growth, Dutch drinking water company Dunea is looking for additional water resources to secure the drinking water supply for the coastal city of The Hague. One of the options is to enhance the existing managed aquifer recharge (MAR) system in the coastal dunes by extracting brackish groundwater. Extracting brackish groundwater provides an additional drinking water source, can protect existing production wells from salinization, and can effectively stabilise or even grow the freshwater reserves in the coastal dunes, according to numerical groundwater modelling. To test this concept in the field, a three-year pilot commenced in January 2022 at Dunea’s primary drinking water production site, Scheveningen. Brackish groundwater is extracted at a rate of 50 m3 /h with multiple well screens placed in a single borehole within the brackish transition zone (85-105 meters below sea level). The extracted groundwater is desalinated by reverse osmosis, whilst the flow rate and quality of extracted groundwater are continuously monitored. The hydraulic effects and the dynamic interfaces between fresh, brackish and saline groundwater are monitored with a dense network of piezometers, hydraulic head loggers and geo-electrical measurement techniques. At the IAH conference, the monitoring results of the pilot will be presented. Based on the results of the field pilot and additional numerical modelling, the feasibility of upscaling and replicating the concept of brackish groundwater extraction to optimize MAR and increase the availability of fresh groundwater in coastal areas is reflected.
Coupling environmental tracers and modelling and what can they tell us about groundwater sustainability and example from the southwestern Great Artesian Basin (GAB) of Australia	A	Love	Australia	2023	Great Artesian Basin, Environmental tracers, recharge rates
Abstract Recent advances in groundwater dating provide valuable information about groundwater recharge rates and groundwater velocities that inform groundwater sustainability and management. This talk presents a range of groundwater residence time indicators (85Kr, CFCS 14C, 81Kr, 36Cl and 4 He) combined with analytical and numerical models to unravel sustainability parameters. Our study site is the southwestern Great Artesian Basin of Australia where we study an unconfined confined aquifer system that dates groundwater from modern times up to 400 kyr BP. The study area is arid with a rainfall of <200 mm/yr and evaporation in the order of 3 m/yr. Despite these arid conditions we observe modern recharge rates in the order of 400 mm/yr. This occurs via rapid ephemeral recharge beneath isolated riverbeds where the sandstone aquifer directly outcrops. Groundwater dating and stable isotopes of the water molecule indicates that this recharge comes from monsoonal activity in the north of the continent that travel some 1500 kms. Furthermore, this is restricted to recharge in the Holocene.as we move down the hydraulic gradient groundwater “ages” increase and recharge rates dramatically decrease by orders of magnitude. We conclude that there has been a significant decline in monsoonal precipitation and hence recharge in the deserts of central Australia over this time. We present a couple environmental numerical model that describes how to estimate temporal recharge rates and estimates of hydraulic conductivity from groundwater age data that can be used for groundwater management.
Regional Scale Groundwater Monitoring Status Reporting: A mapping series within the Vanrhynsdorp aquifer system	Ashton	van Niekerk	South Africa	2023	Aquifer scale, groundwater availability, Groundwater Quality, spatial-temporal, trend analysis
Abstract A mapping series was generated using the Vanrhynsdorp aquifer system to illustrate an improved standardization groundwater monitoring status reporting, that includes a progressive conceptual site model linked with spatial and temporal groundwater monitoring network assessment on an aquifer scale. The report consists of 4 segments: Base map provides a conceptual site model of a groundwater resource unit (GRU) delineating an area of 1456 km2 representing the geology and geological structures that make up the Vanrhynsdorp aquifer system. The Groundwater Availability Map illustrated over a long-term trend analysis, the measured water levels indicate an 83% decreasing trend over an average period of 21.83 years, the water levels have declined by an average linear progression of 11.54 m (ranging 0.48-35.76 m) or 0.64 m per year, which equates to an estimated decline in storage of 218 Tm3 - 21 Mm3 within the GRU. The Groundwater EC map illustrated over the long-term analysis of an average period 24 years the average EC ranged between 57 - 791 mS/m, with certain areas tracking at a constant increasing trend beyond 1200 mS/m. The Groundwater Quality Characterization map provides EC contours and spatial Stiff diagram plots. The Stiff diagrams illustrate three aquifer water types namely, Na-Cl (Table Mountain Group Sandstones), Na-Cl with high SO4 concentration (Blouport and Aties Formation) and Na-Cl-HCO3 (Widouw Formation). These four segments of information products inform Resource Quality Objectives and the need for surveillance monitoring in conjunction with annual compliance monitoring and enforcement groundwater use audits.
Vulnerability of South African water resources to emerging organic contaminants: a case study of the Witwatersrand Goldfields, Eastern Basin	L	Ligavha-Mbelengwa1	Witwatersrand Goldfields, Eastern Basin	2023	bisphenol A, caffeine, emerging organic contaminants, estrone, Groundwater
Abstract The occurrence of emerging organic contaminants (EOCs) in the aquatic environment is of no surprise since these are applied for various purposes daily. This study investigated the changes in EOCs concentrations in the water between 2019 and 2020. During rainy seasons, samples were collected from dams and surrounding boreholes in the Eastern Basin of the Witwatersrand Goldfields. During the first and second laboratory analyses, 24 and 11 analytes were screened in the water samples. The findings indicated that in 2020, compounds such as caffeine, sulfamethoxazole, atrazine and metolachlor displayed detection frequency exceeding 2019. This indicates that the occurrence of these compounds in the aquatic system has increased within a year. Whilst carbamazepine was still traced in 12 sites as previously observed in 2019, compounds estradiol, estrone, bisphenol A and ibuprofen were traced in fewer sites than they were detected in 2019. Compounds 4-nonylphenol, methylparaben, caffeine and atrazine were detected in all the samples analysed for 2019 and 2020, respectively. Antiretrovirals (ARVs) were analysed once and were detected in most sites, with efavirenz registering the highest (12/18) detection frequency. Assessing the occurrence of EOCs in boreholes according to the depth indicated that bisphenol A and estrone were traced in greater concentrations in deep than shallow aquifers, whilst the opposite was observed for atrazine. This study showed groundwater susceptibility to contamination by EOCs, with concentrations of most compounds increasing with time due to their high usage and improper sewer systems in the area.
Machine learning spatial prediction modelling of groundwater salinity in the Horn of Africa	Michael	Berg	Switzerland	2023	Djibouti, Eritrea, Ethiopia, Kenya, Salinity hazard maps, Somalia, affected population, drinking water resources, Groundwater, Machine learning, random forest modelling
Abstract Salinization is one of the main threats to groundwater quality worldwide, affecting water security, crop productivity and biodiversity. The Horn of Africa, including eastern Ethiopia, northeast Kenya, Eritrea, Djibouti, and Somalia, has natural characteristics favouring high groundwater salinity. However, available salinity data are widely scattered, lacking a comprehensive overview of this hazard. To fill this gap, machine learning modelling was used to spatially predict patterns of high salinity with a dataset of 6300 groundwater quality measurements and various environmental predictors. Maps of groundwater salinity were produced for thresholds of 800, 1500 and 2500 μS/cm. The main drivers include precipitation, groundwater recharge, evaporation, ocean proximity, and fractured rocks. The combined overall model accuracy and area under the curve of multiple runs were both ~81%. The salinity maps highlight the uneven spatial distribution of salinity, with the affected areas mainly located in arid, flat lowlands. These novel and high-resolution hazard maps (1 km2 resolution) further enable estimating the population potentially exposed to hazardous salinity levels. This analysis shows that about 11.5 million people (~7% of the total population) living in high-salinity areas, including 400,000 infants and half a million pregnant women, rely on groundwater for drinking. Somalia is the most affected country, with an estimated 5 million people potentially exposed. The created hazard maps are valuable decision-support tools for government agencies and water resource managers in helping direct salinity mitigation efforts
Recharge under review: Implications for Water Resources Management	Nicolette	Vermaak	South Africa	2023	Recharge; groundwater availability; groundwater management
Abstract Recharge is an important factor in Water Resources Management as it is often used as a measure for sustainable groundwater abstraction and resource allocation. The recharge estimation is, however, linked to a specific time, area and conditions and then generalised over seasons and years. Current climate change estimations predict a warmer and drier future for western parts of southern Africa. Groundwater recharge estimation methods do not consider changes in climate over the short term and do not consider the longer trends of a changing climate. This article looks at the various methodologies used in recharge estimations and their application in a changing world, where rainfall period, pattern and intensity have changed, where higher temperatures lead to higher actual evapotranspiration and where there is a greater need for water resources for use in agriculture, industry and domestic use. Our study considers the implications of current recharge estimation methods over the long term for water allocation and water resources management of groundwater resources from local and aquifer catchment scale estimations.
Coupling saturated and unsaturated groundwater models to represent the effect of intensive anthropogenic activities at the regional scale	H	Kupfersberger	Austria	2023	groundwater flow model, solute/heat transport model, saturated-unsaturated zone coupling, Leibnizer Feld aquifer, FEFLOW, land use
Abstract The abstract presents a 2D modelling approach alternative to a 3D variable saturated groundwater model of solute or heat transport at the regional scale. We use FEFLOW to represent processes in the saturated zone, coupled with various models describing the unsaturated zone. The choice of the latter depends on modelling needs, i.e. simulation of the movement of seepage water and nitrate fate with respect to crop rotation patterns and dynamic characteristics of heat gradients, respectively. The flexibility of coupling specialized models of different subsurface compartments provides the opportunity to investigate the effects of land use changes on groundwater characteristics, considering the relevant drivers in sufficient detail, which is important in regions with intensive anthropogenic activities. The coupling can be operated either with (direct coupling) or without (sequential coupling) including the feedback between the saturated and the unsaturated zones depending on the depth of the groundwater table below the surface. Thus, the approach allows for reasonable computational times. The Westliches Leibnitzer Feld aquifer in Austria (43 km²; Klammler et al., 2013; Rock and Kupfersberger, 2018) will be presented as an example highlighting the needed input data, the modelling workflow and the validation against measurements.
An Overview of long-term groundwater development and management – 20 years of Hermanus wellfields	Kornelius	Riemann	South Africa	2023	Monitoring, groundwater management, wellfield development
Abstract Hermanus was originally supplied from springs and groundwater until the De Bos Dam was built in the 1950s. Due to increasing water demand, the municipality commenced wellfield development in 2002. The first wellfield comprised 3 boreholes, of which one borehole was later decommissioned due to reduced yield. Three additional boreholes were drilled recently to ensure abstraction capacity within the licence limits. A second wellfield was developed in the Hemel-en-Aarde Valley north of Hermanus. To ensure the sustainable management of the shared resource and minimise environmental impacts, a monitoring committee was established with all relevant roleplayers, other users, civil society, environmental groups and various commenting and regulatory authorities. A comprehensive monitoring network was established to assist with the scheme’s management and ensure that environmental impacts are minimized. The long-term monitoring (up to 20 years) shows that the groundwater abstraction from the Gateway Wellfield does not impact the environment and other users or increase the risk of saline intrusion. Identified impacts have been mitigated with the assistance of the monitoring committee. The municipality aims to provide at least half of the town’s water demand from groundwater and establish conjunctive use operation between surface water from the De Bos Dam and groundwater from these wellfields. The wellfields ensured sufficient water for the municipality when De Bos Dam’s water levels declined significantly during the Western Cape droughts in 2011 and 2017. The presentation will provide examples of the long-term monitoring records and trends.
From monitoring networks to near real-time groundwater forecast. A case study in Cape Town Table Mountain Aquifer, South Africa	J	Nicolas	South Africa	2023	Gardénia, MétéEau Nappes, Table Mountain Group, forecast, groundwater monitoring, modelling, near real-time
Abstract Groundwater level monitoring is essential for assessing groundwater’s availability, behaviour and trend. Associated with a modelling tool, groundwater level fluctuations can be predicted in the short to middle term using precipitation probabilities or meteorological forecasts. This is the purpose of the MétéEAU Nappes tool implemented by BRGM for the City of Cape Town (CoCT) in the Table Mountain Group Aquifer (TMGA). This case study shows how near real-time groundwater level monitoring can support the municipality in managing its future groundwater withdrawals. The TMGA is an important source of groundwater in the Western Cape region of South Africa. The upper Nardouw Sub-Aquifer of the TMGA is an unconfined aquifer recharged by rainfall. It had been monitored in the Steenbras area for over 10 years before CoCT started groundwater production from the Steenbras wellfield in 2021. The MétéEAU Nappes forecasting tool is already implemented on many observation wells of the French national piezometric network, where it is used for decision-making by the French administration. It allows, in particular, to anticipate several threshold levels of drought and take appropriate measures. It combines real-time water cycle measurement data with a groundwater level lumped model (e.g. Gardenia model) and extrapolates observations for the next 6 months from statistical meteorological scenarios completed with abstraction scenarios. This tool can help protect the Steenbras wellfield as a critical water source for CoCT in the TMGA. This study was financed by the French Agency for Development (AFD).
Investigation of Seawater Intrusion due to Group-Well- Pumping of a local coastal aquifer in Durban, South Africa.	Molla	Demlie	Durban, South Africa	2023	Eastern South Africa, Environmental Isotopes, group-well-pumping, Harbour Beds Formation, Hydrochemistry
Abstract The response of an alluvial and estuarine deposit aquifer, locally known as the Harbour Beds Formation, located in the coastal area of the Durban Metropolitan District to 48 hours of group well pumping is studied to understand its potential for groundwater supply and consequent seawater intrusion. Groundwater levels were monitored from the three pumped boreholes and piezometers. Similarly, EC, TDS and pH were monitored every hour from the boreholes and piezometers. Hydrochemical and water isotopes (2H and 18O) samples of groundwater were taken at 12, 18, 24, 36, 42 and 48 hours during pumping. The results indicate that the aquifer has a transmissivity, hydraulic conductivity and storativity of 48.97 m2/d, 1.7 m/day and 0.0032, respectively. The generally monitored EC, TDS, and pH have been fairly constant during the pumping period and didn’t show any seawater intrusion. Similarly, the hydrochemical data monitored for the three boreholes show general Na-CaHCO3-Cl-dominated groundwater throughout the pumping duration. However, uneven drawdown distribution and complex groundwater flow conditions indicate that the aquifer structure and hydraulic properties are heterogeneous. The water isotopes (2H and 18O) monitoring during the test pumping suggests spatial variability regarding water recharging the Harbour Beds aquifer. Though limited in area extent, the Harbour Beds Formation aquifer is a productive aquifer with acceptable water quality and can be a viable water source for domestic and industrial uses. However, continuous long-term monitoring of water quality and groundwater levels using data loggers is recommended to prevent induced seawater intrusion and contamination.
Groundwater Flow Modeling for Investigation of Exploitation Induced Land Subsidence	Alper	Elçi	Italy	2023	MODFLOW, Mediterranean, earth observation, land subsidence, over-exploitation
Abstract This paper presents the results of groundwater flow modelling studies that were conducted within the scope of the PRIMA RESERVOIR project. The project’s main goal is to develop an innovative methodology to mitigate land subsidence due to excessive groundwater exploitation in water-stressed Mediterranean watersheds. This objective is achieved by integrating earth-observation-derived land subsidence rates with a coupled implementation of numerical groundwater flow and geomechanical modelling. MODFLOWbased 3-D transient flow models were constructed for the four pilot sites (the coastland of Comacchio in Italy, the Alto Guadalentín aquifer in Spain, the Gediz River basin alluvial aquifer in Turkiye and the Azraq basin in Jordan) that have different hydrogeological properties and pose different challenges concerning water management. Models were calibrated and run for similar simulation periods (2013-2021) to obtain hydraulic head drawdowns and changes in groundwater storage. Land subsidence at these sites was evaluated using Advanced Differential Radar Interferometry (A-DInSAR) on image stacks from the Sentinel-1 satellite. Subsidence rates were then compared to hydraulic head drawdown rates to identify groundwater pumping-induced subsidence areas. The comparison for all study areas suggested that locations of maximum displacements do not necessarily coincide with areas that display the largest head drawdown calculated by the flow models. Other triggering factors, such as the thickness of compressible materials, are also related to high subsidence areas.
Groundwater-dependent ecosystem dynamics in transboundary aquifer settings - a case study in the Tuli-Karoo aquifer	Kwazikwakhe	Majola	South Africa	2023	Groundwater-Dependent Ecosystem, Interactions, Transboundary aquifer
Abstract Knowledge of the nature and extent of groundwater-dependent ecosystems (GDE) at an aquifer scale enables incorporating ecological water requirements in integrated groundwater resource management activities, including transboundary aquifer cases (TBA). This way, sustainable groundwater management and functional ecosystem services can be achieved. Therefore, understanding groundwater- ecosystems-surface water interactions is crucial for assessing resources’ resilience or susceptibility towards certain impacts. Unfortunately, this subject is widely under-researched with fragmented information, especially in southern Africa. This study was thus initiated to understand groundwater processes controlling the maintenance of Tuli-Karoo TBA (Botswana, South Africa, Zimbabwe) GDEs towards developing a model that can be utilised in impact assessments, especially in climate change. The employed approach included stable isotope analysis (mainly 2 H and 18O) for groundwater, streams, springs, rainwater, vegetation, and soil; spatial imagery and GIS classification (incl. NDVI, NDRE, NDWI); and plant moisture stress techniques. Identified GDEs in the study area (characterized by intergranular alluvium aquifer underlain by the Karoo sandstone of intergranular and fractured secondary aquifer type) are riparian vegetation, floodplain and depression wetlands, and springs. Precipitation recharged alluvium aquifer’s contribution to Limpopo River baseflow is negligible as the discharge is mainly through springs and evapotranspiration. Monitoring data scarcity and skewed availability among sharing countries hamper research and its output applicability to TBA’s entirety. Therefore, data generation, exchange, and joint databases development are crucial for sustainable comanagement of groundwater and supported ecosystems and science-based decision-making.
Alternative approaches for integrated groundwater management in the rural basins of central Bolivia	I	Rodriguez-Levy	Bolivia	2023	Bolivia, socio-hydrogeology, Geophysics, groundwater recharge, soil water balance
Abstract Due to technical, social, and economic limitations, integrated groundwater management presents a significant challenge in developing countries. The significance of this issue becomes even more pronounced in groundwater management, as this resource is often overlooked and undervalued by decision-makers due to its status as a “hidden resource,” despite the fact that it provides multiple ecosystem services. This study aims to establish the technical hydrogeological foundation in rural basins of central Bolivia through alternative, simplified, and cost-effective methods and tools. The study includes applying geophysical techniques, such as Electrical Resistivity Tomography, to determine the conceptual hydrogeological model of a micro-basin. In addition, a soil water balance approach was applied, characterizing 24 biophysical variables to identify groundwater recharge zones, while global circulation models provided a substitute for unreliable meteorological data. Furthermore, a participatory model was developed to identify recharge areas in upper basin areas within the framework of developing a municipal policy for their protection. The participatory model included local knowledge in all stages of methodology development, considering the characteristics of the local plant communities and the spatial distribution of local rainfall. The research findings have already contributed to resolving socio-environmental conflicts in Bolivia and establishing a foundation for effective water governance by empowering local rural communities. This study has demonstrated the feasibility of using alternative, simplified, and low-cost methods and tools to establish the technical hydrogeological basis, which can inform public policies to promote sustainable groundwater management in developing countries.
Formation of the groundwater chemical composition in the Quaternary aquifer of the coastal valley (North Sinai, Egypt)	Natalia	Vinograd	Egypt	2023	Quaternary sediments, Sinai Peninsula, fresh water, Groundwater, groundwater–rock system, mineral water, physicochemical equilibrium
Abstract The research aims to reveal possible ways of formation of the chemical composition of mineral and fresh groundwater in Quaternary sediments of the coastal plain of Northern Sinai. Statistical assessment of the distribution of various hydrochemical indicators of mineral and fresh groundwater has been carried out according to the following data samples: 1) the general population for all Quaternary deposits (164 wells); 2) the central zone (74 wells); the eastern zone (25 wells); the western zone (65 wells). The following variables were assessed: total dissolved solids (TDS) (in ppm), concentrations of major components (in epm and % epm), pH value and the depth of the sampled well (ds) (in meters). The physicochemical equilibria between the groundwater and rock–forming carbonate and sulfate minerals were calculated using the PHREEQC software. Saturation indices (SI) for groundwater of three zones in relation to various rock-forming minerals were analyzed. Correlation relationships were obtained for TDS, major components and some genetic coefficients ((Requ=(Na++K+)/ (Ca2++Mg2+); Na+/Cl-; SO4 2-/Cl-; Ca2+/SO4 2-). It was concluded that the groundwater chemical composition is defined by infiltration recharge and/or intrusion of Mediterranean seawater. Most likely, during short-term flood periods, the infiltration into aquifers significantly exceeds the evaporation. Despite the relatively high evaporation rate, the degree of groundwater metamorphization is below the saturation level in relation to sulfates and carbonates. The research is of great practical importance for assessing freshwater resources to provide potable water supply
The impact of groundwater temperature on water quality in the urban aquifer of the city of Vienna	E	Kaminsky	Vienna	2023	groundwater temperature, groundwater-surface water interaction, trends, Water chemistry
Abstract Rising shallow groundwater temperatures are observed in many cities worldwide and are expected to increase further over the next century due to anthropogenic activities and climate change. The impact of groundwater temperature increase on groundwater quality is poorly understood. This study conducted two high-spatial-resolution campaigns in Vienna (Austria, autumn 2021/ spring 2022). At 150 wells, a comprehensive parameter set (e.g. major ions, nutrients, and water stable isotopes) was analyzed in groundwater collected, and at 812 wells, the water temperature was measured. Results are compared to available long-term data on groundwater chemistry (1991-2020). In theory, temperature triggers a cascade of effects, where, finally, the depletion of dissolved oxygen (DO) causes a switch to anaerobic microbial processes and a deterioration of water quality. No direct relation between DO and water temperature was observed between 10 and 20 °C. However, many wells delivered anoxic groundwater, including the one with the highest measured temperature (27 °C). The highest temperatures were consistently observed near potential heat sources (local scale), with a rapid decrease in temperature with increasing distance from these sources. Long-term data from particular high-temperature wells revealed decreased dissolved oxygen after sudden temperature changes of > 5 K. On a regional scale, it is observed that groundwater-surface water interactions and aquifer properties play a pivotal role in oxygen availability and redox conditions. In conclusion, high-spatial-resolution sampling combined with long-term data analysis is needed to determine the impact of temperature on water quality.
Springs of the Otavi Mountainland. Could they teach us something significant?	B	van Wyk	Namibia	2023	karst, Namibia, Otavi Mountainland, springs, conceptual model, groundwater flow
Abstract The work presented in this paper incorporates spring data for further conceptualizing the hydrogeology of northern Namibia’s so-called “Karst Area”, an area around the towns of Tsumeb, Otavi and Grootfontein. Also called the Otavi Mountainland, it can be described as a mountainous highland of parallel, east-west trending elongated valleys and ranges shaped by the underlying folded units of carbonate rocks of the Damara Supergroup. The karst aquifers are a supplementary source to the central areas of the country during drought. Most of these 35 springs are often found near hilltop crests or high up on the mountain flanks rather than lower down at the valley floors. If flows are generated locally as gravity or contact overflow springs, studying them would not add much to conceptualizing the regional groundwater flow. Fundamental insights are provided if flows arise due to hydraulic pressure from deeper down. As artesian boreholes do not occur as a rule in the Karst Area, artesian springs might indicate the presence of deeper aquifers out of reach at normal drilling depth. One such hypothesis is that the bottom of the dolomitic synclines, structurally weaker at the fold axis, had been subjected to deep-seated karstification. The work presented here investigates that possibility and argues for and against it. In addition, established concepts of groundwater flow mechanisms for the area have been revisited. A conclusion has not yet been reached, but the balance of the arguments is presented.
Characterisation of the Lower Berg River Aquifer System, Western Cape, South Africa	A	Parker	South Africa	2023	Lower Berg River, aquifer, Discharge, Geophysics, Groundwater, Isotopes, recharge, Tritium
Abstract The Lower Berg River Aquifer System, situated in the Western Cape province of South Africa, is important to the towns that overlay it, as they rely on the aquifer for water supply, which supplements industrial development and residential growth. This aquifer system is important because surface water resources in the area are finite and fully allocated. Despite studies on the Lower Berg River Aquifer System since 1976, knowledge of the geological layers, recharge and discharge areas, and groundwater flow paths remain limited. This study aimed to provide greater insight and understanding of the aquifer to assist in better management. Investigations included a Time Domain Electromagnetic airborne geophysical survey, the assessment of groundwater levels, infiltration tests, hydrochemical analyses, and stable and radioactive isotope analyses. These methods allowed for the identification of the aquifer’s layers and extent, determination of water quality in different parts of the aquifer, delineation of flow paths through the saturated and unsaturated zones, identification of inter-aquifer flow, as well as different modes of recharge.
Netherlands National Groundwater reserves: 3D mapping and development of management policies as part of a multilevel strategy to secure water supply for disasters and the far future.	G	Nijsten	The Netherlands	2023	3-D mapping, Multi-layer governance, National fresh-salt groundwater model, Water supply strategies
Abstract The Netherlands produces about 2/3 of drinking water from groundwater. Although there is seemingly abundant groundwater, the resource needs to be carefully managed and used wisely to safeguard the resource for future generations and in case of disasters whilst also preventing negative impacts from groundwater extraction on other sectors such as nature. Provincial governments are responsible for the protection of existing groundwater abstractions for water supply against pollution. To secure groundwater resources for the future, two additional policy levels have been introduced: Provincial governments have been made responsible for mapping and protecting Additional Strategic Reserves. These allow for additional groundwater abstractions to meet growing demands in coming decades (horizon 2040/2050). The National Government is responsible for mapping and protecting the National Groundwater Reserves (NGRs) as a third level of resource protection. NGRs serve multiple goals: to protect natural groundwater capital for future generations, to provide reserves for large-scale disasters affecting water supply and to provide reserves for possible use as structural water supply in the far future (horizon 2100 and beyond). NGRs are being delineated in 3D using detailed existing geological models and the Netherlands’ national (fresh-saline) hydrological model. The dynamics of the groundwater system are analysed through scenario analyses. Reserves for potential structural use are selected such that negative impacts on nature are prevented if future abstractions are to be realised. The policies being developed must balance interests of water supply against other sectoral interests such as the green-energy transition with increased use of geothermal energy and aquifer-thermal-energy-storage.
Groundwater recharge in sub-humid drylands under different agricultural systems	D	Mudimbu	SADC (Malawi, Zambia, Zimbabwe)	2023	groundwater recharge, basement aquifers, Southern Africa Development Community (SADC
Abstract Groundwater is a strategic long-term water resource used by an estimated 70% of the populations in sub-Saharan Africa for drinking, irrigation and a wide range of economic activities. Understanding groundwater recharge processes is key for effectively using and managing water resources. Very few studies have used direct groundwater observations to assess the impact of different farming systems on groundwater recharge processes. This study focused on assessing basement aquifer recharge in 4 instrumented catchments in Malawi (Chitedze), Zambia (Liempe and Kabeleka) and Zimbabwe (Domboshawa) within the SADC region between 2019-2022. Employing a range of methods, including direct field observations (groundwater hydrographs, precipitation data, stable isotopes, chloride mass balance and residence time tracer data), we quantify the amount of groundwater recharge as well as the timing and nature of recharge processes under both conservation and conventional tillage systems in these four study sites. Groundwater recharge was measured in most years across the study sites. The study reveals the strong climate controls on seasonal groundwater recharge volumes, the influence of low permeability layers in the unsaturated zone, and the likely magnitude of impact from different farming practices. Groundwater residence times are high (i.e. low fractions of modern recharge, interquartile range 1-5%, n=46), even in shallow piezometers, suggesting these unpumped systems may be highly stratified. The results provide an evidence-based suite of data that reveals much about key controls on groundwater recharge in basement aquifers in sub-humid drylands and will inform the development and management of such groundwater systems.
How can collective groundwater resource management solutions benefit water governance at various levels? An example in a volcanic watershed in East Java, Indonesia	E	Cut	Indonesia	2023	groundwater governance, district level, collective solutions, stakeholders, volcanic watershed, Java Indonesia
Abstract On the slopes of Mount Bromo, East Java (Indonesia), the land use of the Rejoso watershed is dominated by rice fields and sugarcane ( lowland area ), agroforestry (midstream) and horticulture and pine plantation in the upstream part. During the last three decades, some land changes driven by socio-economic development, with conversion of agroforests to rice fields, tree monoculture and horticulture, and the development of urban areas nearby, increased pressure on the watershed. Intensive irrigated rice cultivation is using groundwater from free-flowing artesian wells. Due to a lack of management, the hydraulic head and discharge of the major spring are decreasing. Rejoso watershed, like others in urban and rural areas in Indonesia, is facing challenges to guarantee sustainable integrated water resources management. Collective solutions have been implemented between 2016 and 2022 within this watershed. In the downstream, sustainable paddy cultivation and wells management with local stakeholders, aiming at improving water efficiency, have been piloted on 65 ha with 184 farmers. Water governance at the district level was re-activated and strengthened thanks to the project. Various capacity-building tools were used via radio talk shows and workshops. Members of the watershed forum of Pasuruan took some actions to reshape the structure and set up a roadmap. The implementation of collective solutions in the field was a real catalyst and serves all levels of water governance, as it is replicable. This example will be explained and illustrated after the presentation of the socio-hydrogeological context.
Application of machine learning techniques to improve groundwater level predictions and optimization, West Coast, South Africa	N	Igwebuike	Cape Town, South Africa	2023	Groundwater Modelling, groundwater level., Machine learning, Managed aquifer recharge, Water security
Abstract Groundwater systems are complex and subject to climate change, abstraction, and land use stresses, making quantifying their impacts on aquifers difficult. Groundwater models aim to balance abstraction and aquifer sustainability by simulating the responses of an aquifer to hydrological stresses through groundwater levels. However, these models require extensive spatial data on geological and hydrological properties, which can be challenging to obtain. To address this issue, data-driven machine learning models are used to predict and optimize groundwater levels using available data. This paper argues that using machine learning to model groundwater level data improves predicting and optimizing groundwater levels for setting up a managed aquifer recharge scheme. The West Coast Aquifer System in South Africa was used as a case study. The neural network autoregression model was used for the analysis. Multiple variables such as rainfall, temperature, and groundwater usage were input parameters in the mode to facilitate predictions. Outputs from the model showed how machine learning models can enhance the interpretation of observed and modelled results on groundwater levels to support groundwater monitoring and utilization. In areas with high dependence on groundwater and where data on abstraction (use) and monitoring were scarce, results showed that feasible measures were available to improve groundwater security. Although the simulation results were inconclusive, the results provided insights into how the use of machine learning can provide information to inform setting up a managed aquifer recharge scheme.
Assessing the hydrogeology of springs, Heuningnes catchment, South Africa	Paula	Finini	Bellville, South Africa	2023	Spring yield, conceptual model, confirmatory analysis, volumetric analysis
Abstract Springs are examples of groundwater discharges. This paper reports on findings from cold springs groundwater discharges that have served as important water sources for sustaining domestic and agricultural supply. This study assessed the hydrogeology of springs to inform practical measures for the protection, utilization, and governance of such discharges. The research assessed the hydrogeology of springs in terms of conditions in the subsurface responsible for occurrences of springs spatially and their flow paths to the surface. Spring locations were mapped and validated for spatiotemporal assessment. The study examined the flow dynamics and hydrogeochemistry of spring discharges. In-situ and laboratory measurements of spring discharges were carried out using standard methods. Results showed that shallow and deep circulating systems of springs existed in the study area, being controlled by lithology and faults. All springs had fresh water of Na-Cl type, and rock-water interaction was the dominant geochemical process that influenced spring water chemistry. Radon-222 analysis showed high values detected in spring waters that confirmed recent groundwater seepage on the surface. The drum-and-stopwatch technique was used to estimate yield from spring discharges because it’s only effective and reliable for yields of less than 2 l/s. Results suggest that some springs were locally recharged with some regionally recharged. Based on results from estimated yield and quality, it was concluded that spring waters had low discharges. A comprehensive assessment of spring discharges should be conducted to generate large datasets to inform practical measures for protection, utilization, and governance.
Digging Deeper: Exploring the socio-environmental impacts of sand mining in Southern Africa	D	Walker	Southern Africa	2023	extraction industry, Governance, interdisciplinarity, livelihoods
Abstract Sand mining in southern Africa is on the rise, fuelled largely by rapid urbanisation. This creates a range of societal and biophysical challenges and supports livelihoods in regions with high unemployment. Relevant scientific studies are scarce. This study explores the impacts of sand mining from ephemeral rivers on Botswana, South Africa and Mozambique communities through field visits, interviews, modelling, remote sensing and legislative analysis. What was expected to be a hydrogeology project focussing on water resources identified a broader range of issues that should be considered. Initial results uncovered a range of negative biophysical impacts, including alteration of hydrological regimes, which in turn affect groundwater recharge and exacerbate drought and flood risks, destruction of riparian vegetation, increased erosion, damage to infrastructure (including bridges and roads), reduced water quality, and the spread of invasive plant species. Equally important are the range of social impacts, such as drowning people and livestock, loss of agricultural land, increased traffic, dust, noise and crime. Complex governance arrangements influence these social and environmental challenges. The findings highlight the need to adopt an inter- and trans-disciplinary approach that considers linkages between human and natural systems. This approach is essential for finding sustainable solutions for the provision of construction materials that limit detrimental impacts on water resources, ecosystems and livelihoods.