Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 151 - 200 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort ascending	Keywords
Radical evolution of the Geneva transboundary aquifer agreement: an example for the sustainability of TBA governance?	Gabriel	de los Cobos	Switzerland	2023	Geneva aquifer, MAR, Climate change, Governance, transboundary aquifer agreement
Abstract The Geneva aquifer is internationally recognized for its transboundary resource management agreement between Switzerland and France, described as the first groundwater management agreement in the world. Signed in 1978 and renewed in 2008, this agreement on managing a shared underground resource has long been an example for establishing other agreements worldwide, particularly by UNESCO and its hydrological program via the TBA commission of the IAH. Like many countries worldwide, Switzerland and France experienced a critical summer of 2022 concerning the use of water resources, both surface and underground. The system applied in the cross-border agreement for using the aquifer involves French participation in the costs of managing aquifer recharge (MAR), depending on the total pumping. It shows that the French part, having consumed more water to compensate for the extreme drought of 2022, has seen its bills increase considerably. Development plans show that the population of Greater Geneva will increase considerably by 2030-2040, requiring significant medium-term water availability (30% additional water). Therefore, the French institutions’ political leaders have formally asked the authorities of the canton of Geneva to review the conditions linked to the quotas and calculation methods included in the 2008 agreement. A new agreement could be a real example of positive cross-border coordination for decision-makers finding themselves in a blocked or even conflicting situation due to differences in managing a shared resource revived by the effects of climate change.
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.
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
Units for joint management of cross-border groundwater impacts in Transboundary Aquifers: An overview of concepts and methodologies	C	Morales		2023	cross-border groundwater impacts, hotspots identification, joint management units, time and space scales factor, transboundary aquifers, zoning
Abstract This study aims to contribute to the conceptual and methodological development of units of joint management in transboundary aquifers (TBAs) to prevent and mitigate cross-border groundwater impacts (GWIs) in quantity and/or quality. Joint management units are a relatively new but growing topic in the field of TBAs, and their conceptualisation and appropriate identification are still at an early stage. By reviewing the literature on the subject and elaborating on its terminology, main features, and current methodological progress, a comparison of the existing methodologies for identifying such units is analysed. On this basis, trends and recommendations for further research and application of such methodologies to the joint management of TBAs are presented. The literature on this issue is scarce and has been published mainly in the last five years. These publications lack consistency in the use of concepts and terminology. The above has led to miscommunication and semantic issues in the concept behind such units and in comprehending the particular challenges of identifying them. Still, some directions and methodologies for identifying or directly delineating these management units have been proposed in the literature. However, no analysis from these methodological attempts has been conducted; thus, there are no lessons to be learned about this progress. This research looks forward to closing these gaps and making headway toward dealing with cross-border GWIs in TBAs, thus helping countries meet international law responsibilities and maintaining stable relationships among them.
Potential land use changes and wildfires effects over the spatiotemporal distribution of groundwater recharge at a regional scale: RAPReHS indicator accounting for SDG-13 in Bolivia	Monica Ximena	Guzmán Rojo	Bolivia	2023	Climate change, groundwater recharge, SDG
Abstract Having knowledge of spatiotemporal groundwater recharge is crucial for optimizing regional water management practices. However, the lack of consistent ground hydrometeorological data at regional and global scales has led to the use of alternative proxies and indicators to estimate impacts on groundwater recharge, enabling effective management of future water resources. This study explores the impact of land use changes and wildfires on groundwater recharge at a regional scale in Bolivia, using an alternative indicator to estimate variations in groundwater recharge rates. Based on a study by de Freitas L. in 2021, the methodology developed the annual groundwater recharge reduction rate (RAPReHS) utilizing remotely sensed data from the FLDAS and TERRACLIMATE datasets. The RAPReHS employs a simplified version of the water balance equation, estimating direct vertical groundwater recharge by considering the difference between precipitation, evapotranspiration, and runoff. The methodology was upscaled to improve data processing and analysis efficiency using an open-source cloud-computing platform (Google Earth Engine) over a 20-year period. The first results reveal a strong correlation between decreasing groundwater recharge rates and natural vegetation in the eastern region. By utilizing the RAPReHS index, forest preservation strategies can be prioritized. This study is in the framework of SDG 13 (Climate Action), which aims to mitigate the impacts of climate change on the environment and society. By exploring the impact of land use changes and wildfires on groundwater recharge at a regional scale in Bolivia, this research contributes to the inclusion of groundwater in policy guidelines for sustainable water management
Well integrity assessment using fibre optic active distributed temperature sensing	M	Brown	Canada	2023	Active Distributed Temperature Sensing, fibre optic, multilevel monitoring well, well integrity
Abstract Groundwater quality and groundwater sample representativeness depend on the integrity of the water supply and monitoring wells. Well-integrity issues can occur by improper placement of grout seals behind the protective casing and/or by improper backfilling processes between ports. Multi-level monitoring systems are becoming common in the industry, providing depth-discrete groundwater samples and hydraulic head data from a single borehole. However, isolation between the monitoring intervals can be challenging when backfilled methods are used. No independent verification method exists to confirm seal placement for isolating monitoring intervals in such multi-level wells. A new approach using a hybrid fibre optic cable for adding heat, referred to as Active Distributed Temperature Sensing (A-DTS), is deployed in the annular space of a backfilled multi-level well. This new method is used to quantify the position of bentonite used as seals and sand packs that define the monitoring interval lengths and to identify issues associated with backfilling. A-DTS data from three boreholes with back-filled multilevel systems to 85 mbgs in a dolostone aquifer in Guelph, Ontario, Canada, demonstrates clear boundaries between backfill materials. In one interval, a deviation in the thermal data suggests a bridge in the bentonite seal, and this interval coincides with challenges in the backfilling from the field notes. The proposed method verifies well completion details, is repeatable and provides an efficient and effective way to assess well integrity impacting measurement uncertainty in a range of well types.
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.
Basin Water Balance modelling with the aim to make transboundary groundwater flow visible	M	Hunt	Estonia	2023	EUWaterres, Modflow6, transboundary aquifers, surface water groundwater interactions, water balance modelling
Abstract A conceptual water budget model is required to “make groundwater visible” in the shared transboundary area of Estonia and Latvia, which doesn’t face any significant water management issues. Despite having a water management agreement since 2003, it wasn’t until 2018 that cooperation on groundwater began. In the EU-WATERRES project, the water balance modelling of the ~9,500 km2 transboundary (TB) area with MODFLOW 6 was performed. Based on budget calculations, the area’s average precipitation is 203 m3 /s, with ~50% (102 m3 /s) of it discharging to the sea as surface water. The infiltration share (7%, 14.4 m3/s) is a small fraction of overall precipitation, but as an average, it forms ~14% of surface water flow, with 98% of infiltrated groundwater forming the baseflow. Modelling produced two main conclusions: surface water and groundwater form a joint system in the upper ~150 m cross-section depth, and there is no preferred regional TB flow direction due to flat topography. This makes cross-border flow highly dependent on pumping close to the border area. The results of recent studies provide valuable information on groundwater’s importance in EE-LV TB areas and a basis for simple conceptual models to make groundwater visible to the general audience and decision-makers. These findings are critical for specialists in managing water resources in the region and will inform decisions related to the use and protection of groundwater in transboundary areas.
The connectedness of transboundary groundwater researchers: from network analysis to network-building	A	Fernald		2023	network analysis, network-of-networks, transboundary groundwater
Abstract The Transboundary Groundwater Resilience (TGR) Network-of-Networks project brings together researchers from multiple countries to address the challenges of groundwater scarcity and continuing depletion. Improving groundwater resilience through international research collaborations and engaging professionals from hydrology, social science, data science, and related fields is a crucial strategy enabling better decision-making at the transboundary level. As a component of the underlying data infrastructure, the TGR project applies visual analytics and graph-theoretical approaches to explore the international academic network of transboundary groundwater research. This enables the identification of research clusters around specific topic areas within transboundary groundwater research, understanding how the network evolved over the years, and finding partners with matching or complementary research interests. Novel online software for analysing co-authorship networks, built on the online SuAVE (Survey Analysis via Visual Exploration, suave.sdsc.edu) visual analytics platform, will be demonstrated. The application uses OpenAlex, a new open-access bibliographic data source, to extract publications that mention transboundary aquifers or transboundary groundwater and automatically tag them with groundwater-specific keywords and names of studied aquifers. The analytics platform includes a series of data views and maps to help the user view the entire academic landscape of transboundary groundwater research, compute network fragmentation characteristics, focus on individual clusters or authors, view individual researchers’ profiles and publications, and determine their centrality and network role using betweenness, eigenvector centrality, key player fragmentation, and other network measures. This information helps guide the project’s data-driven international networking, making it more comprehensive and efficient.
Assessment of groundwater potential of the Kalahari aquifers in Kavango East and West regions, Namibia	Anna	David	Namibia	2023	groundwater potential, Kalahari aquifers, recharge, water-balance
Abstract The Kavango West and East regions are situated in a semi-arid area northeast of Namibia and bounded by the perennial Okavango River on the northern border. Groundwater in the area is the main source of water supply for the inhabitants living further from the river. In addition, most bulk water users along the river have boreholes for their water supply. With a semi-arid climate, drought in the regions is common and inflicts devastating effects on local communities. More drought relief boreholes are being drilled to sustain communities, increasing the dependency of the inhabitants on groundwater. The complexity of the behaviour and nature of the groundwater in the regions is poorly understood, and there are no strategies to manage these aquifers properly. As a result, an attempt was made to better understand the groundwater potential by examining several hydrogeological factors involved. A basic water-balance approach was used in determining the groundwater potential of the middle and lower Kalahari aquifers. The total resource potential for the entire region is estimated at 144 447.16 x 106 m3 /a, demonstrating great resource potential with significant storage space. The greatest potential is shown in the middle Kalahari aquifers, comprising about 94% of the total resource. Groundwater recharge, as one of the hydrogeological factors, was determined using the chloride mass balance method, giving an average of 6.03 mm/a for the entire study area. If utilized sustainably, the Kalahari aquifers can sustain most communities within the two regions, especially those further from the Okavango River.
Sampling procedures for PFAS and pharmaceuticals –Recommendations vs. reality	A	Kuczyńska	Poland	2023	emerging contaminants, groundwater monitoring, sampling protocols
Abstract PFAS and pharmaceuticals in groundwater are two of many synthetic compounds currently under the attention of many researchers and environmental administration in Europe, especially in light of the revision of the EU Groundwater Directive 2006/118/EU. The two types of substances were first included in the voluntary groundwater watch list and were first formally regulated at the EU scale. This regulation implies that they will be obligatory to be monitored within national monitoring programmes for groundwater body status assessment procedures across the EU. While there is no doubt about the need to regulate the presence of these substances in groundwater, sampling procedures and QC/QA protocols may be challenging to implement as no official guidelines exist. Although scientific literature allows us to define protocols usually based on precautionary principle, these may be too difficult and expensive to implement at the national scale monitoring. This article describes a work that the Polish Geological Institute – National Research Institute undertook to define an optimal sampling process for PFAS and pharmaceuticals in groundwater. Experimentally tested factors included cleaning pumps between sampling sites, the need for using protective suits during sampling and the influence of ambient air on sample quality. Results showed that sampling protocols for PFAS and pharmaceuticals do not need to be modified concerning current protocols as these seem to be sufficient to protect groundwater samples from unintentional cross-contamination.
A Review of potential and actual groundwater recharge: Insights and implications to groundwater use	N	Tuswa	Bellville, South Africa	2023	Groundwater allocation, capture principle, semi-arid region, water resource management
Abstract Recharge is one of the most significant parameters in determining the sustainability volume of groundwater that can be abstracted from an aquifer system. This paper provides an updated overview and understanding of potential and actual groundwater recharge and its implications for informing decision-makers on efficiently managing groundwater resources. The paper argues that the issue of potential and actual recharge has not been adequately addressed in many groundwater recharge studies, and if not properly addressed, this may lead to erroneous interpretation and poor implementation of groundwater resource allocations. Groundwater recharge has been estimated using various methods, revised and improved over the last decade. However, despite numerous recharge methods, many studies still fail to distinguish that some assess potential recharge while others estimate actual recharge. The application of multiple recharge methods usually provides a wide range of recharge rates, which should be interpreted in relation to the type of recharge they represent; as a result, the wide range of recharge findings from different methods does not necessarily imply that any of them are erroneous. A precise distinction should, therefore, be made between the potential amount of water available for recharge from the vadose zone and the actual recharge reaching the water table. This study cautions groundwater practitioners against using “potential recharge values” to allocate groundwater resources to users. The results of this paper may be useful in developing sustainable groundwater resource management plans for water managers.
Pock Marks as a Nature-based solution for enhancing water availability in African marginal drylands?	D	Kibirige	South Africa	2023	Pockmarks, Groundwater, nature-based solutions
Abstract Nearly 1.9 billion people live in marginal environments, including drylands, semiarid, arid, and hyperarid environments. Obscure but ubiquitous circular pockmark depressions dot these lands. These circular depressions can range from a few meters to kilometers, and the depth of these depressions varies from a few centimeters to over 10 m. However, the genesis of the circles has been investigated among scientists for many years because of their obscure nature. Some researchers believe that termites cause fairy circles, while others believe they are caused by plants competing for water and nutrients. This study documented the Africa-wide prevalence and extent of the pockmarks for the first time, and it further classified the pockmarks according to their genesis and hydrological roles. We further investigated their relevance in serving as nature-based solutions to overcome water scarcity in dryland regions. So far, field evidence in Ethiopia and Somalia showed that these features potentially have water security significance in a) organizing surface water flows over arid/semi-arid landscapes, b) serving as the site of temporary surface water storage, and c) serving as the site of focused groundwater recharge into the underlying aquifers. This presentation will highlight the spatial prevalence, extent, and genesis model of the pockmarks across the drylands in Africa (South Africa, Namibia, Somalia, Ethiopia, Kenya, Chad, Senegal, Mali, Niger, etc.).
Quantification of river-aquifer interactions using multiple measuring methods for improved water abstraction in the Lower Vaal River catchment, South Africa	Lucky	Baloyi	South Africa	2023	baseflow, discharge areas, Hydrochemistry, multi-methods approach, stable isotopes
Abstract Previous studies have shown that river-aquifer connectivity exists. However, an integrated approach that consists of multiple measuring methods to quantify and characterise such connectivity still needs improved scientific understanding due to the underlying principles and assumptions of such methods, mainly when such methods are applied in a semi-arid environment. Three techniques (hydrogeochemistry, stable water isotopes, and baseflow separations) were applied to quantify and characterize river-aquifer interactions. The study’s objective was to improve knowledge and understanding of the implications of the results from the three methods. Field measurement, laboratory assessment, and record review were used to collect primary and secondary data. Results showed that Na- HCO3 water type dominated the upper stream, discharging onto the surface and forming stream sources. Na-HCO3 water type was an outlier when the area’s geology and land use activities were assessed. The isotope results showed that the studied aquifer had 9% recently recharged water. Being the upstream, the freshwater in such a mountainous aquifer was expected. The baseflow index (BFI) results showed that the dependency of the total river flow to aquifer discharge contributed 7.24 % in the upper stream, 7.31% in the middle stream, and 7.32% in the lower stream. These findings provided empirical evidence that hydrochemistry, stable isotopes, and baseflow separation methods provide key insights into aquifer-stream connectivity. Such findings inform choosing appropriate and relevant measures for protecting, monitoring, and allocating water resources in the catchments.
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.
he complexity and importance of the intermediate vadose zone - Local-scale, Pore-scale, and Discrete Scale	Matthys A	Dippenaar	South Africa	2023	adhesion, saturated zone, capillarity, cohesion, fracture flow, moisture content
Abstract The intermediate vadose zone underlies the plant root zone and comprises soil and rock. Different soils have different hydraulic and mechanical properties, and the vertical and spatial distributions are variable at a small scale. In South Africa, except for the Cenozoic and Quaternary deserts and coastal deposits, rock forms most of the vadose zone, and the rock fractures exacerbate the complexity. The vadose zone is observed at a small scale and dictates what happens in large scale, as adhesion to mineral surfaces happens first, and cohesion between water molecules is next. The original consideration of the intermediate vadose zone was a black box approach measuring what goes in from the surface and what goes out as groundwater recharge, not accounting for the movement of the vast majority of the freshwater supplied through precipitation. That doesn’t address the preferential flow, velocity, and pore water changes in the medium. Soil science addresses the soil or plant root zone very well. This zone governs the vertical movement of water and controls the ecosystems and biodiversity. However, all evapotranspiration disappears below this zone, and capillarity and gravity both move water into and through the intermediate vadose zone. Movement is no longer solely vertical and will be affected by soil types, intergranular porosity in soil and rock, changing water content, and secondary fractures with different properties in rock. This presentation will cover concepts and advances in this field, emphasising how and why water moves in the intermediate vadose zone.
Using derivative plot analysis for diagnosing boundary conditions and flow regimes, Heuningnes, Cape Agulhas, South Africa	Abongile	Xaza	South Africa	2023	Flow regimes, boundary conditions, flow dynamics
Abstract This study focused on improving the understanding of flow regimes and boundary conditions in complex aquifer systems with unusual behavioural responses to pumping tests. In addition, the purpose was to provide a novel analysis of the hydrogeological properties of aquifers to deduce inferences about the general expected aquifer types to inform new practices for managing groundwater. In this paper, we report that using derivative analysis to improve understanding of complexities in aquifer flow systems is difficult and rarely used in groundwater hydraulics research work. Thus, we argue that if derivatives are not considered in the characterizing flow regime. The heterogeneity of aquifers, boundary conditions and flow regimes of such aquifers cannot be assessed for groundwater availability, and the decision to allocate such water for use can be impaired. A comprehensive database was accessed to obtain pumping tests and geological data sets. The sequential analysis approach alongside derivative analysis was used to systematically perform a flow dimension analysis in which straight segments on drawdown-log derivative time series were interpreted as successive, specific, and independent flow regimes. The complexity of using derivatives analyses was confirmed. The complexity of hydraulic signatures was observed by pointing out n sequential signals and noninteger n values frequently observed in the database. We suggest detailed research on groundwater flow systems using tracer methods like isotopes and numeric models must be considered, especially in multilayered aquifer systems such as the Heuningnes catchment.
How groundwater temperature is affected by climate change: a systematic review and meta-analysis	Elena	Egidio	Italy	2023	Climate change, Groundwater, groundwater temperature, review, temperature
Abstract Groundwater (GW) is a target of climate change (CC), and the effects become progressively more evident in recent years. Many studies reported the effects on GW quantity, but of extreme interest is also the assessment of qualitative impacts, especially on GW temperature (GWT), because of the consequences they could have. This study aims to systematically review the published papers dealing with CC and GWT, to determine the impacts of CC on GWT, and to highlight possible consequences. Scopus and Web of Science databases were consulted, obtaining 144 papers. However, only 45 studies were considered for this review after a screening concerning eliminating duplicate papers, a first selection based on title and abstract, and an analysis of topic compatibility through examination of the full texts. The analysed scientific production from all five continents covers 1995-2023 and was published in 29 journals. As a result of the review, GWT variations due to CC emerged as of global interest and have attracted attention, especially over the past two decades, with a multidisciplinary approach. A general increase in GWTs is noted as a primary effect of CC (especially in urban areas); furthermore, the implications of the temperature increase for contaminants and groundwater-dependent ecosystems were analysed, and various industrial applications for this increase (e.g. geothermy) are evaluated. It’s evident from the review that GWT is vulnerable to CC, and the consequences can be serious and worthy of further investigation.
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.
Delineating wellhead protection areas and aquifer vulnerability in the Cape Flats, South Africa	Brynn	Hunink	South Africa	2023	Aquifer vulnerability mapping, groundwater sustainability, Resource protection, Source protection, Wellhead protection areas
Abstract Prevention of threats to the quality and quantity of groundwater supply is critical to ensure its sustainability. Several African studies have shown that contamination of aquifers is primarily caused by improper placement of land-based human activities. Therefore, adequate preventative measures are required to safeguard the water quality of African aquifers to avoid long-term deterioration. Spatially explicit, 3D numerical groundwater modelling is a common methodology to assess contaminant transport. However, model development is time-consuming and complex. Contrastingly, DRASTIC-L is a 2D, GIS-based aquifer vulnerability mapping technique. The method is simple to apply, but analyses are qualitative and subjective. The study aims to compare both methods and to combine their strengths using GIS overlay. Overall, aquifer vulnerability was determined using the DRASTIC-L method, while wellhead protection areas were delineated using steady-state numerical modelling. This study focuses on the Cape Flats area due to its rapid development and growing municipal water supply supplementation needs. DRASTIC-L mapping revealed that aquifers in the Cape Flats are highly vulnerable to contamination due to the region’s unconfined hydrogeological properties, shallow water table and high-risk land use types. Moreover, groundwater vulnerability mapping combined with the delineation of wellhead protection areas allows for reduced uncertainty in the contamination potential of delineated groundwater protection zones. As a result, this study highlights the need for overall resource protection of the Cape Flats aquifers and provides insights into mapping out potential source protection areas of existing water supply wells.
The pharmaceutical compounds diversity at two river bank filtration sites located in Warta River valley (Poland)	Krzysztof	Dragon	Poland	2023	pharmaceuticals compounds; river bank filtration sites
Abstract Emerging contaminants (e.g. pharmaceuticals or pesticides) are increasingly detected in aquatic environments. The most apparent contamination source of river water pollution by pharmaceuticals is sewage treatment plant stations that discharge treated sewage effluent to the rivers. The river bank filtration systems (RBF) can effectively remove these contaminants. The two RBF sites were examined for pharmaceuticals: Śrem and Gorzów waterworks. The water samples for pharmaceuticals investigation were taken from the river and four continuously pumped wells at each site. Two wells near the river were chosen at each site (40-50 m) and two at a greater distance from the river (70 m in Śrem and 110 m in Gorzów). A visible increase in pharmaceutical concentrations was observed along the river. The sum of pharmaceuticals concentration is 8151 ng/l in Śrem (upstream), while in Gorzów (downstream) concentration is 9142 ng/l. A very big differentiation in pharmaceutical occurrence was observed. In Śrem, the sum of pharmaceuticals concentration is between 657 and 3290 ng/l, while in Gorzów, despite the higher concentrations of pharmaceuticals in the river, these substances were detected only in one well located at a close distance from the river (two substances at a concentration of 92 ng/l). The research proves a very big differentiation of pharmaceutical concentration even on sites located at similar hydrogeological conditions and demonstrates the necessity of its monitoring, especially in groundwater strongly influenced by river water contamination (like at RBF sites). This work has received funding from the National Science Centre Poland (grant no. 2021/41/B/ST10/00094).
Assessment of hydrochemistry and heavy metal contamination in the groundwater around an abandoned Copper Mine area in Klein Aub, Namibia	Shoopala	Uugulu	Namibia	2023	contamination, Copper, Heavy metal, Klein Aub
Abstract The long mining history in Namibia has resulted in numerous abandoned mines scattered throughout the country. Past research around the Klein Aub abandoned Copper mine highlighted environmental concerns related to past mining. Considering that residents of Klein Aub depend solely on groundwater, there is a need to thoroughly investigate groundwater quality in the area to ascertain the extent of the contamination. This study made considerable effort to characterise groundwater quality using a comprehensive approach of quality assessment and geostatistical analysis. Onsite parameters reveal that pH ranges between 6.82-7.8, electrical conductivity ranges between 678 - 2270 μS/cm, and dissolved oxygen ranges between 1.4 -5.77 mg/L. With an exemption of two samples, the onsite parameters indicate that water is of excellent quality according to the Namibian guidelines. The stable isotopic composition ranges from −7.26 to -5.82‰ and −45.1 to -35.9‰ for δ18O and δ2H, respectively—the groundwater plots on and above the Global Meteoric Water Line, implying no evaporation effect. Hydrochemical analyses show bicarbonate and chloride as dominant anions, while calcium and sodium are dominant cations, indicating groundwater dissolving halite and mixing with water from a recharge zone. The heavy metal pollution index of the groundwater is far below the threshold value of 100, which signals pollution; it contrasts the heavy metal evaluation index, which clustered around 3, implying that the heavy metals moderately affected groundwater. Copper, lead and Arsenic were the main contributors to the values of the indices.
Using analytical models to examine groundwater abstraction impacts on surface water levels	N	Maluleke	South Africa	2023	groundwater-surface water interaction, streamflow depletion, model coupling
Abstract Studies have examined the effects of groundwater pumping on nearby streams. Groundwater pumping affects streamflow, surface water rights, and aquatic ecosystems. This study investigates the impact of groundwater abstraction on surface water bodies. A secondary objective aims to develop a conceptual model to evaluate alternative approaches for streamflow depletion. The study area is a previous UFS/WRC test site along Modder River, Free State, South Africa. Streamflow depletion was simulated using four (4) analytical solutions, i.e., Jenkins (1968), Hantush (1964), Hunt (1999) and Hunt (2003). STRMDEPL08 analytical computer program tool is used to evaluate streamflow depletion. The aquifer parameters: distance of the boreholes to the stream; pumping periods analyzed in steady states conditions for a simulation period of 1 year; transmissivity with an average of 71 m/d; storativity of 0.02; specific yield of the aquitard range between 0.1 to 0.3; and abstraction rate of 2 l/s are defined for the hypothetical model. The average distances tested range from 10 m to 6,000 m. Pumping rate scenarios for an order of magnitude lower (0.2 l/s), 1 l/s; 4 l/s, and an order of magnitude larger (20 l/s) were simulated. Simulated graphs indicate that streamflow depletion rates are largest if the borehole is closer to the stream and decrease as the distance of the pumped borehole from the stream increases. Cumulative volume graphs for both analytical solutions decrease streamflow depletion volume
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.
Researching Fracking in the Karoo: Summary of lessons learned	Fde	Lange	South Africa	2023	Challenges, Fracking, Independent, policy, Precautionary, Regulatory, Research, risks, scale, stakeholders
Abstract Research on Fracking in the Karoo basin yielded results that, if not considered “unexpected”, can be considered as “should have been foreseen”. Some aspects substantially impacting research on fracking are often overlooked when undertaking scientific research on an emotional topic such as fracking. This presentation aims to provide insights and recommendations based on the experiences and outcomes of current research on hydraulic fracturing or “fracking” in the Karoo basin of South Africa. Fracking has been a subject of significant research and debate over the past decade. Topics, each with its challenges, include 1) The scale of exploration/production extent (Site specifics), 2) Importance of robust and independent research, 3) Need for stakeholder engagement and participation, 4) The complexity of environmental risks and impacts, 5) The need for a precautionary approach, 6) Regulatory and policy challenges. Several methodologies can be relied upon to compare outcomes of different aspects of fracking research in the Karoo, such as 1) Comparative analysis, 2) Meta-analysis, 3) Stakeholder mapping and analysis and 4) Data visualisation. A combination of these methodologies can be used to compare outcomes of different aspects of fracking research in the Karoo and provide insights and recommendations for future decision-making and planning. Ultimately, the decision to allow Fracking should be based on a balanced assessment of potential risks and benefits, considering long-term impacts on the environment, economy, and communities.
Developing and testing a Groundwater Mapping methodology to increase drilling success rates for sustainable drinking water boreholes in African Arid and Semi-Arid Lands – the case study of Cunene Province, Angola	Daniela	Benedicto van Dalen	Angola	2023	Analytic Hierarchy Process, WASH program, groundwater mapping, remote sensing
Abstract In recent years, practical applications of vector and raster multi-layers overlay analysis to enhance outcomes of conventional hydrogeological methods for allocation of productive boreholes have been applied in arid and semi-arid lands and is currently being tested in Ethiopia, Kenya, Somalia and Angola in cooperation with UNICEF. Advanced Remote Sensing (RS) and Geographic Information Systems (GIS) techniques combined with traditional geological, hydrogeological and geophysical methods are being used for improved access to sustainable drinking water supply boreholes in the scope of a WASH program. Identifying suitable areas with a good potential for sustainable groundwater resources exploitation mainly depends on a) consistent/reliable aquifer recharge and b) favourable hydrogeological conditions for groundwater abstraction. Multi-layer analyses and attribution of layer scores to the hydrogeological information layers – aquifer recharge, aquifer class, lineaments, slope, land cover, and presence of streams – combine into a qualitative Groundwater Suitability Map, using pairwise comparison (weights) to determine their relative importance with the Analytic Hierarchy Process (AHP). Additionally, traditional field methods enhance the quality of outputs and delineate Target Areas for detailed investigations: validation of hydrogeological conceptual models, hydrogeological assessment, groundwater sampling and finally, geophysical methods. Downscaling the remote sensed information of the groundwater suitability map with field verifications is required to recommend borehole drilling sites. The engagement of stakeholders is vital for the data collection and validation of the weighting criteria analyses (AHP method), as well as for the cooperation on the ground, validation of the Target Areas selection and implementation.
Micro pore-pressure sensor (MEMs) and analysis technologies – towards a future of multi-scale groundwater monitoring	W	Timms	Australia	2023	multi-scale, pore pressure, sensors, analysis
Abstract Micro-electro-mechanical system (MEMs) technologies coupled with Python data analysis can provide in-situ, multiple-point monitoring of pore pressure at discrete and local scales for engineering projects. MEMs sensors are tiny, robust, inexpensive, and can provide wireless sensing measurements in many electrical and geomechanical engineering applications. We demonstrate the development of MEMs pressure sensors for pore pressure monitoring in open boreholes and grouted in piezometers. MEMs sensors with a 60 m hydraulic head range and centimetre vertical resolution were subject to stability and drawdown tests in open boreholes and in various sand and grouts (permeability 10-8 to 10-2 m/s). The resulting accuracy and precision of the MEMs sensors, with optimal calibration models, were similar to conventional pore pressure sensors. We also demonstrate a framework for estimating in-situ hydrogeological properties for analysis from vented pore pressure sensors. This framework method included Python code analysis of hourly pore pressure data at the millimetre vertical resolution, which was combined with barometric data and modelled earth tides for each borehole. Results for pore pressure analysis in confined boreholes (>50 m depth) included specific storage, horizontal hydraulic conductivity and geomechanical properties. Future improvements in the vertical resolution of MEMs pore pressure sensors and combined these two technologies will enable groundwater monitoring at multiple scales. This could include the deployment of numerous MEMs, at sub-meter discrete scale in boreholes and evaluating local site scale variations in pore pressure responses to recharge, groundwater pumping and excavations in complex sub-surface geological conditions.
The impact of storage and hydrogeological conditions on the design and recovery performance of small-scale urban ASR systems	Niels	Hartog	The Netherlands	2023	Urban Groundwater, Managed aquifer recharge, Aquifer Storage and Recovery, MAR, ASR
Abstract Aquifer storage and recovery (ASR) can play a vital role in sustaining water availability to cope with increasing weather extremes. In urban areas, ASR systems may provide flooding risk mitigation and support urban greenery. However, such systems are often relatively small and therefore, their recovery performance depends more strongly on site-specific storage conditions such as dispersion and displacement by ambient groundwater flow. In this study, we evaluated the impact of these factors by adapting and developing analytical solutions and numerical modelling, with recently established Urban ASR systems as a reference for a wide range of realistic field conditions. We validated the accuracy and usefulness of the analytical solutions for performance anticipation. Results showed that a simple, analytically derived formula describing dispersion losses solely based on the dispersion coefficient (α) and the hydraulic radius of the injected volume (Rh) provided a very good match for all conditions tested where α/Rh<0.2. An expansion of the formula to include the development of recovery efficiency with subsequent cycles (i) was also derived and in keeping with simulation results. Also, displacement losses were found to be significant at groundwater flow velocities that are typically considered negligible, particularly as displacement and dispersion losses disproportionally enforced each other. For specific conditions where the displacement losses are dominant, using a downgradient abstraction well, effectively resulting in an ASTR system, might be beneficial to increase recovery efficiencies despite increased construction costs and design uncertainty.
A methodology for uncertainty quantification of dewatering volumes under the context of open-cast mining	C	Rivera Villarreyes		2023	FEFLOW, Groundwater Modelling, mining, PEST, PESTPP
Abstract Groundwater modelling at the mine sites involves assumptions from the geological model, mining stages, parametrization, and fractures, among others. Modelling work mainly focuses on calibrating against historical measurements before operations (pre-mining) or afterwards (transient calibration). Calibration is carried out mainly with gradient-based algorithms. However, the majorlimitation is the number of model runs, since the number of parameters can easily reach hundreds or more. PEST has become the common tool for parameter estimation. The Jacobin calculation required for the Levenberg Marquardt algorithm requires several model runs. This, a limited factor for the calibration and, subsequently, uncertainty quantification. The next generation of PEST, named PESTPP, is gained popularity in the groundwater community. The great advantage of PESTPP,, compared to the classical PEST, is its new module, Iterative Ensemble Smoother (IES). PESTPP-IES covers both parameter estimation and uncertainty quantification in one goal. Its empirical formulation of the Jacobian matrix reduces the number of runs; thus, the numerical bottleneck can be significantly reduced. PESTPP-IES has been extensively tested in an open-pit mine at the geological complex conditions in the Peruvian Andes. The work involves the task of model simplification, e.g., from a regional model to a detailed local pit model, calibration and uncertainty quantification of pit dewatering volumes. Detailed model was kept calibrated based on hydraulic-head measurements, and dewatering volumes were predicted. All these consider transient changes in the mining plan within the same FEFLOW model. Results validate the methodology and practicability in mining applications.
A non-anthropocentric perspective on groundwater quality and a proposed system for groundwater quality classification and regulation	Carin	Bosman	KZN	2023	Groundwater Quality, groundwater quality classification system, regulation, water quality standards
Abstract In many countries, groundwater quality is measured against drinking water limit values or standards. While that makes sense from a water supply perspective, it is not a scientifically correct yardstick to use to classify groundwater resources or even to determine whether groundwater has been “polluted”. Using this incorrect anthropocentric yardstick has led in some cases to legal action against industries, with significant liability implications, whilst the industry’s activities did not at all influence the quality of the groundwater but were reflecting the conditions under which the lithology of the aquifer was deposited. A case study in KZN demonstrating this will be discussed. We are, therefore, in a situation where regulatory decisions regarding groundwater quality and the regulation of the potential impact of human activities on groundwater systems are unfair, not scientifically credible, and not legitimate. This situation hampers the effective management and regulation of groundwater use and the prevention of detrimental impacts on groundwater, even saline groundwater systems. This paper argues that it is necessary to develop a groundwater quality classification system that will categorise aquifers based on their natural quality, not just from the perspective of their usefulness as a potable supply source but would recognise the important role that aquifers with more saline natural qualities play in maintaining ecosystems that require such salinity for its survival. It concludes by considering international approaches and proposing aspects to consider in developing such a system for groundwater regulation.
Water allocation and economic analysis for developing groundwater resources	P	Tungkidwanichakul	Thailand	2023	Epanet, WUSMO, groundwater management
Abstract Thailand has been grappling with a water scarcity problem every year, leading to insufficient water supply for consumption in many areas. To tackle this issue, groundwater is developed from large sources, making water allocation and economic analysis essential for measuring investments in water supply projects. This research study analyzes the water allocation for consumption and irrigation, including the water sent to hospitals, in two areas, Si Somdet & Roi Et Province and Nong Fai. The study uses the WUSMO program to analyze irrigation water and the EPANET program to analyze the entire water allocation system. The expected results include the appropriate allocation of water for maximum benefit, considering both delivery time and the amount of water to ensure adequate delivery. The study provides a guideline for effective and sustainable water allocation and management, including appropriate and sufficient water costs for managing the water distribution system in both areas. The results show that a water rate of 19 baht per cubic meter in Si Somdet & Roi Et Province results in a B/C value of 1.04 and an EIRR of 6.48%, while a water tariff of 15 baht per cubic meter in Nong Fai results in a B/C of 1.01 and an EIRR of 6.16%. The study highlights the importance of regular analysis of water allocation and cost-effectiveness of projects to ensure sustainable and efficient water management for the people.
Groundwater flow paths dictate terrestrial carbon inputs into a groundwater-dominated stream	Y	Xie	China	2023	Groundwater discharge; groundwater flowpaths; dissolved carbon; environmental tracers
Abstract Groundwater discharge is crucial for transporting terrestrial carbon into streams and rivers, but the effects of groundwater flow paths on terrestrial carbon inputs are poorly understood. Here, we investigated environmental tracers (EC, Cl-, 2H, 18O, 220Rn, and 222Rn) and carbon concentrations in riparian groundwater, streambed groundwater, and stream water over six groundwater-stream monitoring sites. Significantly high 220Rn and 222Rn activities in the stream and endmember analysis results of the environmental tracers reveal that vertical groundwater discharge from the streambed (VGD) and lateral groundwater discharge from the riparian zone (LGD) is of equal importance for the stream. We quantified VGD by modelling the detailed 222Rn and Cl- profiles at the streambed and then combined differential flow gauging to estimate LGD. VGD (2.9 ± 1.4 m2 d-1) prevailed in relatively wide and shallow channels, while LGD (2.6 ± 2.6 m2 d-1) dominated narrow and deep channels. Carbon measurements indicate that LGD had the highest CO2, CH4, DIC, and DOC, while VGD had relatively higher CO2 but lower CH4, DIC, and DOC than stream water. Our findings suggest that LGD is the primary carbon source for the stream, while VGD mainly dilutes the stream (except CO2). Finally, we observed that groundwater discharge and temperature overrode metabolism in controlling stream carbon dynamics, implying the importance of groundwater discharge for understanding stream carbon cycling. Overall, this study identified the impacts of groundwater flow paths on carbon exchanges between terrestrial and stream ecosystems.
How alluvial storage controls surface water – groundwater interactions in dryland intermittent and ephemeral streams: A case study from semi-arid Australia	M	Zarate	Australia	2023	Groundwater, groundwater recharge, drylands, ephemeral streams, focused recharge, intermittent, semi-arid, streamflow, surface water, water balance
Abstract Water balance partitioning within dryland intermittent and ephemeral streams controls water availability to riparian ecosystems, the magnitude of peak storm discharge and groundwater replenishment. Poorly understood is how superficial geology can play a role in governing the spatiotemporal complexity in flow processes. We combine a new and unusually rich set of integrated surface water and groundwater observations from a catchment in semi-arid Australia with targeted geophysical characterisation of the subsurface to elucidate how configurations of superficial geology surrounding the stream control the variability in streamflow and groundwater responses. We show how periods of stable stream stage consistently follow episodic streamflow peaks before subsequent rapid recession and channel drying. The duration of the stable phases increases in duration downstream to a maximum of 44±3 days before reducing abruptly further downstream. The remarkable consistency in the flow duration of the stable flow periods, regardless of the size of the preceding streamflow peak, suggests a geological control. By integrating the surface water, groundwater and geological investigations, we developed a conceptual model that proposes two primary controls on this behaviour which influence the partitioning of runoff: (1) variations in the permeability contrast between recent channel alluvium and surrounding deposits, (2) the longitudinal variations in the volume of the recent channel alluvial storage. We hypothesise optimal combinations of these controls can create a ‘Goldilocks zone’ that maximises riparian water availability and potential for groundwater recharge in certain landscape settings and that these controls likely exist as a continuum in many dryland catchments globally.
Time scale connection of groundwater with adjacent spheres	M	Taniguchi	Japan	2023	Anthropocene, Kumamoto, adjacent spheres, social revolution, time scale
Abstract Groundwater is connected with the earth’s interior, atmosphere, ocean sphere, and human sphere. Fluid, heat, and dissolved materials are crossed over the boundaries of adjacent spheres with different time scales in dynamics. These different time scales include event scales such as earthquakes and Tsunami, seasonal scales such as precipitation seasonality, a decade or longer scales such as climate change, and human scales such as groundwater pumping, land cover/use changes, and social revolutions such as industrialization, green revolution, urbanization, and globalization in Anthropocene. This study shows two examples of groundwater connected with different time scales. The first is thermal signals preserved in groundwater by earthquake, climate change, and anthropogenic impacts with different time scales. Thermal signals in groundwater from the Kumamoto earthquake in 2016 revealed evidence of fluid flow from the earth interior and Aso mountain. The thermal signal in groundwater in Kumamoto also showed the impacts of global warming and urbanization, as well as changes in precipitation and land use. The second example is the connectivity between residence time of groundwater and groundwater consumption in social revolutions such as industrialization and urbanization in the Anthropocene, as well as World War II as an example of groundwater for emergency situations.
Risk-corrected contaminant detection probability of monitoring well networks for flow towards pumping wells in heterogeneous aquifers	T	Sarris	New Zealand	2023	Contaminant transport, Dispersion, Groundwater Contamination, Heterogeneity, monitoring networks, Risk corrected detection rate
Abstract A groundwater monitoring network surrounding a pumping well (such as a public water supply) allows for early contaminant detection and mitigation where possible contaminant source locations are often unknown. This numerical study investigates how the contaminant detection probability of a hypothetical sentinel-well monitoring network consisting of one to four monitoring wells is affected by aquifer spatial heterogeneity and dispersion characteristics, where the contaminant source location is randomized. This is achieved through a stochastic framework using a Monte Carlo approach. A single production well is considered, resulting in converging non-uniform flow close to the well. Optimal network arrangements are obtained by maximizing a weighted risk function that considers true and false positive detection rates, sampling frequency, early detection, and contaminant travel time uncertainty. Aquifer dispersivity is found to be the dominant parameter for the quantification of network performance. For the range of parameters considered, a single monitoring well screening the full aquifer thickness is expected to correctly and timely identify at least 12% of all incidents resulting in contaminants reaching the production well. Irrespective of network size and sampling frequency, more dispersive transport conditions result in higher detection rates. Increasing aquifer heterogeneity and decreasing spatial continuity also lead to higher detection rates, though these effects are diminished for networks of 3 or more wells. Earlier detection, critical for remedial action and supply safety, comes with a significant cost in terms of detection rate and should be carefully considered when a monitoring network is being designed.
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.
Application of Nanofiltration Membrane for Removal of VOCs and Heavy Metals in Groundwater, Ratchaburi, Thailand	Chunintorn	Chamathong	Ratchaburi, Thailand	2023	Heavy metals, Nanofiltration membrane, VOCs
Abstract he Namphu and Rangbua subdistricts in Ratchaburi province, in western Thailand, are affected by groundwater contamination. According to site characterization results, the aquifer has been contaminated with volatile organic compounds and heavy metals since 2014. Membrane filtration technology is an alternative method for treating groundwater to produce safe drinking water for household use. Nanofiltration membrane is a relatively recent development in membrane technology with characteristics that fall between ultrafiltration and reverse osmosis (RO). This study aimed to determine the hydrochemistry of contaminated groundwater and examine the efficiency of nanofiltration membranes for removing pollutants in groundwater and the potential implementation of the membrane. The membrane module used in this study is cylindrical in shape of 101.6 cm long and 6.4 cm in diameter, and the membrane surface charge is negative with monovalent rejection (NaCl) of 85-95%. The filtration experiments were conducted at a pressure of 0.4-0.6 MPa, which yielded flow rates of approximately 2 L/min. To examine the nanofiltration membrane efficiency, groundwater samples were extracted from four monitoring wells and were used as feed water. According to laboratory results, the nanofiltration maximum removal efficiencies for 1,2-dichloroethylene, vinyl chloride, benzene, nickel, and manganese were 97, 99, 98, 99, and 99%, respectively. However, the treatment efficiency depends on several factors, including pretreatment requirements, influent water quality and the lifespan of the membrane. Further research should be conducted to determine the maximum concentration of VOCs and heavy metals in the feed water before applying this treatment method to a large scale.
Variable-scale conceptual framework for shallow groundwater systems in the low-relief, water-limited Canadian Boreal Plains	K	Hokanson	Canada	2023	Groundwater-surface water interactions, long-term study, recharge, spatiotemporal scales, subsurface connectivity
Abstract Case studies illustrate a conceptual framework for shallow groundwater flow systems’ temporal and spatial variability with groundwater-surface water interactions in the Boreal Plains of Canada. The framework was developed using a twenty-year hydrometric dataset (e.g., climatological and streamflow data, hydraulic heads, vertical hydraulic head gradients, geochemical and isotopic signatures). The region is characterized by low-relief glacial landscapes, with a mosaic of forestlands and peatlands, and a subhumid climate, resulting in spatially heterogeneous storage and transmission properties, variable recharge and evapotranspiration potentials, and highly complex patterns of water movement. Two primary spatiotemporal scales were examined to create a holistic, variable-scale conceptual model of groundwater movement: the large scale (e.g., glacial landforms, regional topography, decadal climate cycles) and the small scale (e.g., individual landcover, local hummocks, annual moisture deficits). Water table behaviour, evapotranspiration rates, and runoff were controlled by a hierarchy of interactions between hydrological processes occurring at different spatiotemporal scales; however, the specific order of controls depends on the hydrogeological setting. The case studies, supported by empirical and numerical modelling, demonstrate that smaller-scale heterogeneities in geology and recharge can dominate over topographic controls, particularly in areas with high conductivity or hummocky terrain, where the climate, geology, and topographic relief are similar. Many hydrogeological studies rely on surface topography as a first‐order control; however, with field observations and modelling, this conceptual framework demonstrates the need to consider the potential dominance of subsurface characteristics and processes, plus climate, especially in landscapes with low recharge and low relief.
Tracing an arenitic aquifer by DNA-labelled nano particles	Alessandro	Gargini	Italy	2023	nanotechnology; DNA-labelled nano particles; arenite; groundwater; tracer test; Northern Apennines
Abstract The results of a full field application of a DNA-based nano tracer in an arenitic aquifer are presented along with the comparison with the breakthrough of a classical tracer injected in parallel. DNA is encapsulated into amorphous silica spheres (nanoparticles), protecting the molecule from chemical and physical stresses. The main advantages of using DNA with classical tracers, like ionic or fluorescent, are the lower detection concentration and the chance to perform multi-tracer tests with many distinct signatures of injection. To the authors’ best knowledge, this is the first tracing adopting nano-particles on full field conditions in a sedimentary fractured aquifer. Preliminary tests in the lab were performed adopting either deionized water or groundwater collected at the experimental site: a set of nanoparticles at a known concentration was dissolved by adding a buffered fluoride solution, and DNA was then quantified by qPCR reaction (SYBR green). The hydrogeological setting is represented by a Miocenic marine arenitic aquifer (Pantano formation) outcropping extensively in Northern Apennines (Italy) and the main groundwater reservoir for public water supply through the uptake of many perennial springs. The main purpose of the tracing was to verify the transmissive capacity of fractures with high aperture (15-20 cm) identified by optical and acoustic televiewers inside an 80 m deep borehole. The injection was performed inside the borehole, and the tracer’s recovery was between 5-15 m, both in the uptake points of two perennial springs and in another borehole drilled nearby.
Evaluation of the impact of artificial recharge of groundwater by river replenishment in the North China Plain using a numerical model	Qichen	Hao	China	2023	artificial recharge, groundwater management, river water replenishment, the North China Plain
Abstract Since 2018, the North China Plain has started a large-scale ecological water replenishment project for rivers and lakes, with 17.5 billion cubic meters total from the South–North Water Transfer Project and other water sources. It is a key question of how much water infiltration into aquifers will affect groundwater and how to characterize and evaluate this effect quantitatively. The groundwater numerical model of the Beijing-Tianjin- Hebei region as the main part of the North China Plain was established using a numerical simulation method, and the groundwater level variation under the replenishment condition was simulated and predicted. By comparing the two scenarios, the relative rise method of groundwater level was proposed to characterize the influence of river water infiltration on groundwater level, and the unstructured grid method was used to refine cells near the river to improve simulation accuracy. Simulation results show that the groundwater level around some rivers has risen significantly in the past four years, especially in the alluvial fan regions with better infiltration properties. Accordingly, at the Piedmont alluvial fan region, there is also a large influence range on groundwater level. The maximum influence distance is more than 10km (0.1m relative rise of groundwater level was taken as the influential boundary). According to the prediction, if the water replenishment project continues, the range of influence can continue to expand, but the expansion rate will slow down due to the reduction of the hydraulic gradient.
Electromagnetic measurements in the Netherlands using an All Terrain Vehicle to rapidly characterize groundwater salinity and clay distribution in 3D	Jan	Gunnink	Netherlands	2023	3d-mapping, clay distribution, groundwater salinity
Abstract Electromagnetic (EM) techniques were used to map groundwater salinity and clay layers in the Netherlands. The EM method used the so-called time domain system, is towed behind an ATV and is therefore called towed TEM. The results revealed a detailed 3-dimensional insight into the subsurface’s sequence of clay and sandy layers. Also, shallow saline groundwater, far from the coast, has been detected related to a subsurface salt dome. The rapid, non-destructive data acquisition makes the tTEM a unique tool. Electromagnetic (EM) techniques detect electrical conductivity contrasts in the subsurface with depth. EM data can often be interpolated into a 3D model of electrical conductivity. Expert knowledge of the regional geohydrologist, together with existing (borehole) data, is paramount for the interpretation. The towed Transient Electro-Magnetic system (tTEM) is developed to acquire data up to 60-80m depth by driving a transmitter and a receiver behind an ATV. With a speed of 10-15 km/h, measurements are collected every 5m. On fields, the distance between lines is typically 20m, resulting in a dense network of data that is inverted into 1D resistivity models, showing the variation of conductivity with depth. Interpolating 1D resistivity models into a 3D model allows for further interpretation in terms of geology, lithology, and groundwater quality. The tTEM technique bridges the gap between point measurements and more expensive and lower-resolution airborne EM data collection. The technique is sensitive to disturbance by man-made conducting infrastructure.
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.
Groundwater resource assessment and delineation of resource unit for the Komati catchment within the Inkomati Usuthu Management Catchment area – Mpumalanga Province, South Africa	Collen	Monokofala	South Africa	2023	Catchment scale integrated surface water and groundwater studies
Abstract The recent uncertainties in rainfall patterns have resulted in shortages in the availability of water resources, posing significant risk to the sustainability of all living organisms, livelihoods and economic prosperity. The fact that hidden groundwater resources in semi-arid regions present a challenge to understanding and managing the resources. Various groundwater studies have been undertaken; however, the quantification is generally over-simplified due to a limited understanding of the groundwater flow regime and consideration being mostly given to water supply. Thus, the data is often not comprehensive enough and generally limited in determining how much groundwater is available to supply rural areas. The Komati catchment area is dominated by coal mining in the upper reaches and irrigation and agriculture in the lower reaches, with human settlements competing for these water resources. Five significant dams in the Komati catchment are constructed to deal with the increasing water demand for commercial agriculture in the region. However, given uncertain weather patterns, the water mix approach is imperative. This study focused on understanding the groundwater potential, characterised the aquifer system, delineated the groundwater resource units, quantified baseflow and calculated the groundwater balance that can be used as a guide for the groundwater management protocol for the catchment area. The box model approach (surface-groundwater interaction) was used to characterize the groundwater regime and understand the spatial distribution of the aquifer types, water quality and significant aquifers of interest to protect this important resource.
Data-Driven approach to groundwater level prediction for improving water resource management: the Brenta aquifer system case study (Veneto, Italy)	Linda	Franceschi	Italy	2023	Foothill aquifer system, Climate change, groundwater management, predictive models
Abstract In the context of climate change, this work aims to model the piezometric levels of the foothill aquifer located in the middle-high Brenta river plain (Veneto, Italy) to support managing a groundwater system that provides drinking water for most of the Veneto Region. Using a Data-Driven approach, predictive Multiple Linear Regression Models were developed for the piezometric level at different wells, and scenarios of groundwater level evolution were achieved under dry periods. Results highlighted the high sensitivity of the aquifer to climate extremes, as well as the need to plan actions for mitigating the effects on such a strategic water supply system. Groundwater hosted in the foothill aquifer represents an important resource. However, these systems are highly sensitive to the variation of Meteo-climatic regimes. At the same time, the exploitations can lead to excessive groundwater drawdown and consequent threats of water scarcity. The Data-Driven approach adopted using long time series of meteorological, hydrometric and piezometric data can represent a valid example in these terms. The groundwater level evolution has been well-reproduced by these models. The equations describing models show the close dependence of groundwater from the Brenta River and the high sensitivity of the aquifer to meteo-climate regimes. Given this sensitivity, the forecast of groundwater level evolution under a dry period, similar to 2022, was performed. Results point out a progressive drawdown of groundwater level. These predictive models can be useful for local authorities to maintain these levels over specific critical values.
Protecting groundwater resources in an era of geological carbon sequestration: A fractional stochastic model to predict pressure buildup due to CO2 injection into a saline aquife	H	Mbah	National	2023	Carbon Capture and Storage, CCS, CCS fractional operator, geological heterogeneity., injectivity, pressure buildup, saline aquifer
Abstract Carbon Capture and Storage (CCS) in deep saline aquifers is a viable option for Green House Gas (GHG) mitigation. However, industrial-scale scenarios may induce large-scale reservoir pressurization and displacement of native fluids. Especially in closed systems, the pressure buildup can quickly elevate beyond the reservoir fracture threshold and potentially fracture/ reactivate existing faults on the cap rock. This can create pathways, which could act as conduits for focused leakage of brine and/or CO2 up-dip and mobilization of trace elements into capture zones of freshwater wells. Careful pressure management can ensure the reservoir’s hydraulic integrity. This can theoretically be achieved through simulation with appropriate mathematical tools. This research aims to quantify pressure buildup at a CO2 injection well by applying fractional derivatives to the pressure diffusivity Differential Equation (PDE). A numerical solution has been developed to (1) predict and assess the consequence of pressure buildup within the storage formation on groundwater flow in shallow aquifers and (2) assess the impact of pressure-mobilized contaminants (CO2 , brine and/or trace elements) on the quality of usable groundwater, if there is a leakage. The efficiency of each derivative is shown to depend on the type of reservoir heterogeneity. The Caputo derivative captured the long tail dependence characteristic of fracture flow, while the ABC derivative was able to model the cross-over from matric into the fracture flow. The numerical tools presented here are useful for successful risk assessments during geo-sequestration in basins with freshwater aquifers.
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.
Making the Invisible Visible: Do Aquifers Have Agency?	Adrian	Healy	Wales	2023	agency, Groundwater, more-than-human, social, socio-hydrogeology
Abstract In the social sciences, there has been a ‘posthuman’ turn, which seeks to emphasise the role of non-human agents as co-determining social behaviours. In adopting a ‘more-than-human’ approach, the academy seeks to avoid claims of human exceptionalism and extend the social to other entities. In this paper, we explore the extent to which the more-than-human approach might be applied to groundwater and aquifers and the implications that this may have for groundwater science. The role of groundwater in complex adaptive socio-ecological systems at different scales is increasingly well-documented. Access to groundwater resources positively influences societal welfare and economic development opportunities, particularly in areas where surface waters are scarce. The potential adverse effects of human activities on the quantity or quality of groundwaters are also widely reported. Adopting a ‘properties’ approach, traditional social science perspectives typically describe aquifers as structuring the agency of human actors. To what extent might aquifers also have agency, exhibited in their capacity to act and exert power? Drawing on insights from 5 cities across sub-Saharan Africa, we argue for the agency of aquifers in light of their capacity to evoke change and response in human societies. In doing so, we draw on the concept of the more-than-human to argue for a more conscious consideration of the interaction between the human and non-human water worlds whilst acknowledging the critical role played by researchers in shaping these interactions.
Literature review on methodologies used to assess surface water and groundwater interaction	Aashna	Bissoon	South Africa	2023	Groundwater, case studies, methodologies, surface water, sustainable
Abstract A major surface water–groundwater interaction difficulty is the complex nature of groundwater resources due to heterogenic aquifer parameters. Wholistic research is needed to inform the conceptual understanding of hydrological processes occurring at surface and groundwater interfaces and their interactions at watershed scales. Sustainable water resource use and protection depend on integrated management solutions involving cross-disciplinary studies and integrated hydrological modelling. Choosing appropriate methods such as spatial and temporal scales, measurable indicators, differences in software parameters, and limitations in application often results in uncertainties. The study aims to conduct a comparative literature analysis, integrating case studies focusing on surface water–groundwater interaction. Literature reviews from case studies focus on several factors, including soils and vegetation studies, hydrochemical signatures, hydrodynamics of the main stem channels, desktop land use assessments, surface water quality profiling, conceptual hydrogeological modelling and numerical modelling in support of understanding surface water – groundwater interaction and highlight the challenges of methods used to indicate baseflow transition. This paper considers the methodologies demonstrated in the literature and their use in numerical modelling to obtain measurable indicators related to the two hydrological disciplines comprising (i) the surface water component and (ii) the groundwater component. These outcomes should be used to inform the potential future impacts on water quality from activities such as mining, irrigation, and industrial development. Water management protocols related to integrated surface water and groundwater studies for the future are critical in ensuring sustainable water management methods on a catchment scale.
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.
Securing Water Supplies – Participatory Groundwater Monitoring and Management in Botswana and Uganda	Piet Kebuang	Kenabatho	Botswana, Uganda	2023	Livelihoods and Pollution, Participatory groundwater monitoring
Abstract Groundwater resources in Africa face increasing threats of over-exploitation and pollution due to urbanization, agricultural and mining activities, yet monitoring remains challenging. Conventional approaches to monitoring groundwater at the exclusion of communities have not been successful. To overcome this, it is important to fully engage and train local communities in monitoring Groundwater Levels (GWLs), Rainfall and Water Quality (RWQ), which are important for understanding groundwater dynamics in wellfields. In this way, villagers can better understand groundwater issues and convey this information to others to cooperatively manage groundwater. A pilot program to monitor GWLs and RWQ by locals was initiated in two villages each in Botswana and Uganda to learn about its effectiveness. Through continuous stakeholder engagement, the local communities in the two case studies have been facilitated, trained and supported in monitoring groundwater and using the information collected to understand groundwater trends and their sustainability. Preliminary results indicate improvement in understanding the importance of groundwater monitoring by the communities and the implications on groundwater sustainability for improved livelihoods. This has become useful to one of the communities engaged in a village-level irrigation project which depends on groundwater resources. This project builds on a successful village-level participatory approach developed in the MARVI project (www.marvi.org.in ). It seeks to contribute to the United Nation’s 2022 call on “Groundwater: making the invisible visible” to highlight the importance of better monitoring and managing this vital resource.