Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 101 - 150 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year	Keywords
Integrated Modelling of the Hydrological Dynamics of the Semi-arid Hout-Sand Catchment, South Africa	E	Bjerre	South Africa	2023	drylands, conceptual flow model, integrated dynamic hydrological modelling, water resources, assessment and management
Abstract The interaction between dryland hydrological fluxes and the high spatial and seasonal climate variability is inherently complex. Groundwater recharge is episodic, and rivers are ephemeral. When flow occurs in the river network, water is lost through the riverbed, giving rise to focused recharge, which could be a significant part of total recharge. We have used the integrated and physically based MIKE SHE modelling system to analyze the hydrological processes and fluxes in the 7,715 km2 Hout-Sand catchment in the South African part of the Limpopo River Basin. The discharge hydrograph measured at the outlet station is highly episodic, with a small baseline flow component superimposed by high flow events in response to intense rainfall. Likewise, the groundwater hydrographs from the area are characterized by rapid increases in groundwater levels in response to high rainfall events with recurrence intervals of several years. Due to the scarcity of basic measurements and information, we used data products from satellite platforms to supplement the information on rainfall, evapotranspiration, soil moisture, land use and irrigated areas. We applied MIKE SHE to test different conceptual flow models of the catchment by calibrating the different models against direct measurements of river discharge and groundwater levels and indirect estimates of evapotranspiration and soil moisture from satellite products. By analyzing the simulated model dynamics and the resulting values for the calibration parameters, we identified the most plausible conceptual model, which then forms the basis for water resources assessment and management recommendations for the Hout-Sand catchment.
A conceptual model for methane occurrences in the Western Karoo as part of a geochemical baseline for shale gas development	Danita	Hohne	Western Cape	2023	Western Karoo, shale gas development, shallow and deep groundwater, thermogenic and biogenic methane; isotopes
Abstract Although methane occurrences have been documented in Karoo groundwater in the past, the advent of possible unconventional oil and gas extraction now made it important to determine the type and origin of this methane to assess the possibility of shallow-deep groundwater interaction. During groundwater surveys from 2016-2021, methane was detected at three sites in the Western Karoo: the Soekor sites KL1/65, QU1/65 and an unidentified shallow groundwater borehole (BHA). The Soekor wells were drilled in the 1960-1970s to depths of between 2500-3500 meters in South Africa’s search for oil. On the other hand, Borehole BHA was drilled in 1998 and only up to a depth of 298m. This study aimed to determine methane’s origin through gas and isotope analyses. To do this, groundwater, rock and soil samples were analysed to determine whether the methane is thermogenic or biogenic and its origin. We determined that methane was both thermogenic and biogenic and probably originated from different layers of the Karoo formations and that mixing occurs between deep and shallow aquifer systems at these Soekor sites. This information was used to develop a final conceptual model of what the Karoo underground system might look like and to make recommendations for establishing a groundwater baseline.
The impacts of climate change on groundwater in South Africa	Zaheed	Gaffoor	South Africa	2023	CMIP6, GRACE data, groundwater recharge potentia
Abstract Climate change is expected to have a significant impact on freshwater resources across the globe. Changes in the distribution and quantities of rainfall over the coming decade will impact various earth systems, such as vegetation, contributions to streamflow, sub-surface infiltration and recharge. While groundwater resources are expected to act as a buffer, changes in rainfall will ultimately impact the recharge process and, thus, groundwater reserves. Understanding these changes is a crucial step to adapt better and mitigate climate change’s impacts on water resources. This is valid in South Africa, where much of the population depends on groundwater as a freshwater supply. Hence, this research presents the status quo regarding climate change’s impacts on South Africa’s groundwater resources. Reviewing relevant literature, the impacts on recharge, groundwater quantity (storage changes), discharge and groundwater-surface water interactions, groundwater quality, and groundwater-dependent ecosystems are discussed. In addition, utilizing factors such as rainfall, slope and vegetation cover collected from CMIP6 climate projections, changes in groundwater recharge potential from the past through the present and future are demonstrated. The findings illustrate uncertainty over the long-term impacts of climate change on groundwater for different regions and various aquifers. However, global warming could lead to reduced recharge, which impacts groundwater reserves.
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.
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.
The application of artificial intelligence techniques to support groundwater management in Southern Africa	Z	Gaffoor	South Africa	2023	Big data analytics, Machine learning, transboundary aquifers
Abstract The beneficial groundwater use in the Southern African Development Community (SADC) is well documented. Groundwater plays a vital role in the freshwater supply mix and, in some cases, is the only source of freshwater, especially in the arid region of SADC. However, the management of this resource is hampered by numerous challenges, such as lack of data, limited tools to leverage available data, lack of resources, institutional mismanagement, and climate change, amongst others. Of these challenges, the lack of data and the tools needed to transform this data into information has consequences for the decision-making process. Hence, this research attempts to address this challenge by demonstrating the use of big data and artificial intelligence (AI) to fill data gaps with new unconventional sources and model groundwater processes to transform data into actionable information. The presentation focuses on introducing the landscape of groundwater big data in SADC, followed by a review of regional AI applications. After that, novel approaches to using AI in various aquifers across SADC are demonstrated in their applicability to support groundwater management. Finally, the challenges facing the use of AI in SADC are discussed, followed by opportunities for new research based on the current state-of-the-art AI techniques. The results illustrate that AI can be a helpful tool for supporting groundwater management in SADC. However, the need for enhanced data collection is evident for these techniques to be generally applicable.
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.
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.
Platinum-Group-Elements and Total Organic Carbon in hyperalkaline springs at the Ronda peridotites (Malaga, Spain) as proxies of the origin of dissolved methane gas	Lucia	Ojeda	Malaga, Spain	2023	Hyperalkaline springs, Methane, Platinum-Group-Elements, Ronda peridotites, Total Organic Carbon
Abstract The serpentinization of ultramafic rocks is a process in which minerals of ferromagnesian nature (e.g., olivine) are transformed into serpentine and produce groundwater with a very high pH. In these settings, CH4 can be produced by combining H2 from serpentinization and CO2 from the atmosphere, soil, carbon-bearing rocks, or mantle, although the microbial generation of CH4, mediated by methanogens utilizing CO2, formate and/or acetate can be another source in these aquifers. In this sense, the hydrochemistry of hyperalkaline springs can provide valuable information about gas origin. The Ronda peridotites (Malaga province, Spain) are one of the world’s largest outcrops of the subcontinental mantle (~450 km2). Hyperalkaline springs (pH>10) emerging along faults present a permanent low outflow (<1 L/s), Ca2+- OH- facies and residence times exceeding 2,000 years. The fluids, poor in Mg2+ and rich in K+, Na+, Ca2+ and Cl-, also contain significant concentrations of dissolved CH4 and other hydrocarbons. Water samples have been collected from eight hyperalkaline springs and analyzed for major, minor and trace elements, including Platinum Group Elements (PGE) and Total Organic Carbon (TOC). The most mobile PGEs (Pd and Rh) are present in all the springs, indicating the existence of potential catalysts for the abiotic synthesis of CH4. High TOC concentrations are observed in some studied springs where previous analyses (i.e., bulk CH4 isotopes) have indicated a microbial CH4 origin.
Regional-scale identification of recharge or discharge using remote sensing and GIS: Implications towards groundwater-surface water interactions	Kawawa	Banda	Zambia	2023	Barotse Floodplain, Groundwater-Surface water, Zambezi River, Zambia, Ecosystems
Abstract Identifying groundwater recharge and discharge areas across catchments is critical for implementing effective strategies for salinity mitigation, surface water and groundwater resource management, and ecosystem protection. This study seeks to identify potential GW-SW discharge and recharge areas around the Barotse Floodplain. The results of remote sensing analysis using the Normalised Difference Vegetation Index (NDVI) show that the vegetation is sensitive to the dynamics of groundwater level, with shallower levels (< 10 m) in the lower reaches compared to deeper levels (>10 m) in the upper catchment). These zones are further investigated and likely represent geological variability, aquifer confinement and the degree of GW-SW interactions. GW-SW interactions likely are influenced by an interplay of factors such as water levels in the groundwater and surface level and hydrogeological conditions. Based on the findings, the wetland hosts riparian vegetation species responsive to the groundwater dynamic. NDVI can thus be used as a proxy to infer groundwater in the catchment. Therefore, effective water resources management of the floodplain should be implemented through conjunctive management of groundwater and surface water.
Investigation of Seawater Intrusion due to Group-Well- Pumping of a local coastal aquifer in Durban, South Africa.	Molla	Demlie	Durban, South Africa	2023	Eastern South Africa, Environmental Isotopes, group-well-pumping, Harbour Beds Formation, Hydrochemistry
Abstract The response of an alluvial and estuarine deposit aquifer, locally known as the Harbour Beds Formation, located in the coastal area of the Durban Metropolitan District to 48 hours of group well pumping is studied to understand its potential for groundwater supply and consequent seawater intrusion. Groundwater levels were monitored from the three pumped boreholes and piezometers. Similarly, EC, TDS and pH were monitored every hour from the boreholes and piezometers. Hydrochemical and water isotopes (2H and 18O) samples of groundwater were taken at 12, 18, 24, 36, 42 and 48 hours during pumping. The results indicate that the aquifer has a transmissivity, hydraulic conductivity and storativity of 48.97 m2/d, 1.7 m/day and 0.0032, respectively. The generally monitored EC, TDS, and pH have been fairly constant during the pumping period and didn’t show any seawater intrusion. Similarly, the hydrochemical data monitored for the three boreholes show general Na-CaHCO3-Cl-dominated groundwater throughout the pumping duration. However, uneven drawdown distribution and complex groundwater flow conditions indicate that the aquifer structure and hydraulic properties are heterogeneous. The water isotopes (2H and 18O) monitoring during the test pumping suggests spatial variability regarding water recharging the Harbour Beds aquifer. Though limited in area extent, the Harbour Beds Formation aquifer is a productive aquifer with acceptable water quality and can be a viable water source for domestic and industrial uses. However, continuous long-term monitoring of water quality and groundwater levels using data loggers is recommended to prevent induced seawater intrusion and contamination.
Coupling environmental tracers and modelling and what can they tell us about groundwater sustainability and example from the southwestern Great Artesian Basin (GAB) of Australia	A	Love	Australia	2023	Great Artesian Basin, Environmental tracers, recharge rates
Abstract Recent advances in groundwater dating provide valuable information about groundwater recharge rates and groundwater velocities that inform groundwater sustainability and management. This talk presents a range of groundwater residence time indicators (85Kr, CFCS 14C, 81Kr, 36Cl and 4 He) combined with analytical and numerical models to unravel sustainability parameters. Our study site is the southwestern Great Artesian Basin of Australia where we study an unconfined confined aquifer system that dates groundwater from modern times up to 400 kyr BP. The study area is arid with a rainfall of <200 mm/yr and evaporation in the order of 3 m/yr. Despite these arid conditions we observe modern recharge rates in the order of 400 mm/yr. This occurs via rapid ephemeral recharge beneath isolated riverbeds where the sandstone aquifer directly outcrops. Groundwater dating and stable isotopes of the water molecule indicates that this recharge comes from monsoonal activity in the north of the continent that travel some 1500 kms. Furthermore, this is restricted to recharge in the Holocene.as we move down the hydraulic gradient groundwater “ages” increase and recharge rates dramatically decrease by orders of magnitude. We conclude that there has been a significant decline in monsoonal precipitation and hence recharge in the deserts of central Australia over this time. We present a couple environmental numerical model that describes how to estimate temporal recharge rates and estimates of hydraulic conductivity from groundwater age data that can be used for groundwater management.
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.
OFF-SOURCE: A network to address the potential use of offshore freshened groundwater as an unconventional source of potable water in coastal cities.	H	Wazaz		2023	Offshore groundwater, COST Action, scientific networking, unconventional water resources, Transboundary aquifer
Abstract One-third of the world faces water insecurity, and freshwater resources in coastal regions are under enormous stress due to population growth, pollution, climate change and political conflicts. Meanwhile, several aquifers in coastal regions extending offshore remain unexplored. Interdisciplinary researchers from 33 countries joined their effort to understand better if and how offshore freshened groundwater (OFG) can be used as a source of potable water. This scientific network intends to 1) estimate where OFG is present and in which volumes, 2) delineate the most appropriate approaches to characterise it, and 3) investigate the legal implications of sustainable exploitation of the offshore extension of transboundary aquifers. Besides identifying the environmental impact of OFG pumping, the network will review existing policies for onshore aquifers to outline recommendations for policies, action plans, protocols and legislation for OFG exploitation at the local to international levels. Experienced and early-career scientists and stakeholders from diverse disciplines carry out these activities. The Action leads activities to foster cross-disciplinary and intersectoral collaboration and provides high-quality training and funded scientific exchange missions to develop a pool of experts to address future scientific, societal, and legal challenges related to OFG. This interaction will foster new ideas and concepts that will lead to OFG characterisation and utilisation breakthroughs, translate into future market applications, and deliver recommendations to support effective water resource management. The first exchange mission explored the Gela platform carbonate reservoir (Sicily), built a preliminary 3D geometrical model, and identified the location of freshened groundwater
Analysis of Heavy Metal Sources in Groundwater and Assessment of Health Risks: An Example from the Southwest Sub-basin of the Shiqi River	Yu	Shi	China	2023	Groundwater; heavy metal elments; source analysis; health risk assessment
Abstract To explore the sources of pollution and health risk profile of heavy metal elements in groundwater,41 sets of representative groundwater samples from the southwest subbasin of the Shiqi River were examined for 10 heavy metal elements, correlation analysis and principal component analysis were used to resolve the possible sources of heavy metal contamination in groundwater. The concentration characteristics and health risk levels of the 10 heavy metals were assessed using the single factor contamination index (Pi), the Nemerow comprehensive contamination index (PN) and the health risk model. The results show that: 1) The average values of heavy metal elements of the groundwater in the study area all met the limit of class III water standard in the quality standard for groundwater; only the maximum value of Al was exceeded, followed by a large variation in the concentrations of Al, Mn and Cr. The heavy metal element with the largest average contribution was Al (65.74%). 2) The results of the single factor contamination index evaluation show that only the heavy metal element Al exceeds the level, and the results of the Nemerow comprehensive contamination index evaluation show that the study area is basically at low pollution levels and the quality of groundwater is good. 3) The results of the multivariate statistical analysis show that Zn, Co and Mn are mixed sources of geological formation and domestic waste, Al, As, and Cu are agricultural sources, Cd, Cr and Ni are industrial sources, and Hg comes from long-range atmospheric transport.
Multiple-tool approach of combining microbial markers with artificial and natural tracers to specify the origin of faecal contamination on karst groundwater catchment scale	M	Sinreich	Switzerland	2023	Karst spring, MST, Catchment, faecal indicators, toolbox, tracers
Abstract Diverse tools exist to study the transfer of contamination from its source to groundwater and related springs. A backward approach, i.e. sampling spring water to determine the origin of contamination, is more complex and requires multiple information. Microbial source tracking (MST) using host-specific markers is one of the tools, which, however, has shown to be insufficient as a stand-alone method, particularly in karst groundwater catchments. A karst spring in the Swiss Jura Mountains was studied concerning the occurrence and correlation of a set of faecal indicators, including classical parameters and bacteroidal markers. Sporadic monitoring proved the impact on spring water quality, mainly during high water stages. Additional event-focused sampling evidenced a more detailed and divergent pattern of individual indicators. A multiple-tool approach, complementing faecal indicator monitoring with artificial tracer experiments and measuring natural tracers, could specify the origin of ruminant and human faecal contaminations. Natural tracers allowed for distinguishing between water components from the saturated zone, the soil/epikarst storage, or freshly infiltrated rainwater. Additionally, the breakthrough of injected dye tracers and their remobilization during subsequent recharge events were correlated with the occurrence of faecal markers. The findings hypothesize that human faecal contamination is related to septic tanks overflowing at moderate rainfall intensities. Linkage with vulnerability assessment and land-use information can finally better locate the potential point sources. Such a toolbox provides useful basics for groundwater protection and catchment management and insight into general processes governing the fate and transport of faecal contaminants in karst environments.
Regional Scale Groundwater Monitoring Status Reporting: A mapping series within the Vanrhynsdorp aquifer system	Ashton	van Niekerk	South Africa	2023	Aquifer scale, groundwater availability, Groundwater Quality, spatial-temporal, trend analysis
Abstract A mapping series was generated using the Vanrhynsdorp aquifer system to illustrate an improved standardization groundwater monitoring status reporting, that includes a progressive conceptual site model linked with spatial and temporal groundwater monitoring network assessment on an aquifer scale. The report consists of 4 segments: Base map provides a conceptual site model of a groundwater resource unit (GRU) delineating an area of 1456 km2 representing the geology and geological structures that make up the Vanrhynsdorp aquifer system. The Groundwater Availability Map illustrated over a long-term trend analysis, the measured water levels indicate an 83% decreasing trend over an average period of 21.83 years, the water levels have declined by an average linear progression of 11.54 m (ranging 0.48-35.76 m) or 0.64 m per year, which equates to an estimated decline in storage of 218 Tm3 - 21 Mm3 within the GRU. The Groundwater EC map illustrated over the long-term analysis of an average period 24 years the average EC ranged between 57 - 791 mS/m, with certain areas tracking at a constant increasing trend beyond 1200 mS/m. The Groundwater Quality Characterization map provides EC contours and spatial Stiff diagram plots. The Stiff diagrams illustrate three aquifer water types namely, Na-Cl (Table Mountain Group Sandstones), Na-Cl with high SO4 concentration (Blouport and Aties Formation) and Na-Cl-HCO3 (Widouw Formation). These four segments of information products inform Resource Quality Objectives and the need for surveillance monitoring in conjunction with annual compliance monitoring and enforcement groundwater use audits.
Assessing groundwater fluxes of transboundary aquifers, using a high-resolution global groundwater model and implications on transboundary cooperation	J	Verkaik	The Netherlands	2023	Global model, transboundary aquifers, transboundary fluxes; comparative assessment
Abstract Worldwide, more than 400 transboundary aquifers (TBAs) have been identified. Only a small number of these aquifers have been assessed in detail. Consequently, little is known about (potential) transboundary impacts. Changes in transboundary groundwater fluxes can indicate potential transboundary impacts as groundwater abstractions can affect such fluxes, indicating potential risks of transboundary contamination. To our knowledge, a quantitative assessment of transboundary aquifer fluxes (TBAFs) is not available because national groundwater models (if existing) often lack a good interaction with surrounding countries. In recent years, a high-resolution global groundwater model (GGM) has been developed as part of the PCR-GLOBWB family of models, having a 5 arcmin (~1010km2 ) resolution. PCR-GLOBWB has previously been used to quantify environmental flows, assess global droughts, and assess climate impacts on global water resources. Recently the 5 arcmin GGM has been updated to 30 arcsec (~11km2 ) using high performance computing (referred to as GLOBGM). We present an application of GLOBGM to assess TBAFs of major TBAs. Results show that even though hydrogeological data are often scarce, a rough order of magnitude of the TBAFs can be assessed. TBA fluxes are compared with groundwater recharge. Although GLOBGM cannot replace assessments of TBAs based on local hydrogeological information and information on groundwater use, the analysis provides valuable information. GLOBGM can be used to quantify the relevance of TBAFs in relation to other fluxes such as from rivers or (future) abstractions. TBAF analyses can also assist in prioritising scarce funds and capacity between TBAs
Nitrate vulnerability assessment in the fast-growing African district of Abuja Federal Capital Territory (Nigeria)	M	Etuk	Abuja FCT, Nigeria	2023	DRASTIC-LU model, Groundwater Contamination, population growth
Abstract In the Federal Capital Territory of Abuja (Abuja FCT, Nigeria), a population growth of about 400% between 2000 and 2020 has been reported. This trend, coupled with the persisting urban sprawling, is likely to result in severe groundwater quality depletion and contamination, thus undermining one of the area’s main freshwater supplies for drinking purposes. In fact, groundwater in Nigeria and Abuja FCT provides over 70% of the drinking purposes. Results of a groundwater vulnerability assessment that compared land use data from 2000 and 2020 showed that the region had been affected by a dramatic change with an increase in urbanized (+5%) and agricultural (+27%) areas that caused nitrate concentrations to exceed the statutory limit for drinking purposes in more than 30% of the monitored wells in 2021 and 40% in 2022. Although fertilizers are generally considered the main source of nitrate contamination, results suggest a possible mixed (urban and agricultural) pollution origin and a legacy of previous nitrogen pollution sources. The comparison between the DRASTIC-LU map and nitrate concentrations shows that the highest values are found in urban/peri-urban areas, in both shallow and deep wells. This investigation is the first step of a comprehensive nitrate pollution assessment in the region, which will provide decision-makers with adequate information for urban planning given the expected population growth in the area
A combined stochastic-analytical method for the assessment of climate change impact on spring discharge	Attila	Kovacs	Hungary	2023	Spring hydrograph, analytical model, Climate change, stochastic mode
Abstract This study describes a novel methodology for predicting spring hydrographs based on Regional Climate Model (RCM) projections to evaluate climate change impact on karstic spring discharge. A combined stochastic-analytical modelling methodology was developed and demonstrated on the Bukovica karst spring catchment at the Durmitor National Park, Montenegro. As a first step, climate model projections of the EURO-CORDEX ensemble were selected, and bias correction was applied based on historical climate data. The regression function between rainfall and peak discharge was established using historical data. The baseflow recession was described using a double-component exponential model, where hydrograph decomposition and parameter fitting were performed on the Master Recession Curve. Rainfall time series from two selected RCM scenarios were applied to predict future spring discharge time series. Bias correction of simulated hydrographs was performed, and bias-corrected combined stochastic-analytical models were applied to predict spring hydrographs based on RCM simulated rainfall data. Simulated climate scenarios predict increasing peak discharges and decreasing baseflow discharges throughout the 21st century. Model results suggest that climate change will likely exaggerate the extremities regarding climate parameters and spring discharge by the end of the century. The annual number of drought days shows a large variation over time. Extremely dry years are periodic, with a frequency between 5-7 years. The number of drought days seems to increase over time during these extreme years. The study confirmed that the applied methodology can successfully be applied for spring discharge prediction
Development of multi-level groundwater governance systems and groundwater capacity development to support local municipalities in the Northern Cape Region	A	Tomlinson	South Africa	2023	groundwater capacity development, groundwater governance, groundwater management, groundwater management plan, standard operating procedures
Abstract The Anglo-American Municipal Capability & Partnership Program (MCPP) has partnered with the Council for Scientific and Industrial Research (CSIR) to implement programs focused on Strategic Water Management and Strategic Planning within the Gamagara and Tsantsabane Local municipalities within the Northern Cape Region. The CSIR appointed GEOSS South Africa (Pty) Ltd to assist with Municipal Groundwater Capacity Development and Support for these two municipalities. This work explores multi-level groundwater governance systems between the local municipality, government, the mining industry, and the private groundwater sector. The scope of the work focused on developing a comprehensive and practical groundwater management plan detailing the standard operating procedures for each municipality. These operating procedures have been drawn up using principles of best practice guidelines for groundwater monitoring and management but have taken site-specific details of the groundwater supply to the respective Municipalities into account. Workshops were conducted where Municipal staff were trained in basic principles pertaining to groundwater and practical skills in monitoring and managing their supply. This has proved very successful in informing Municipalities about their local groundwater system and aquifer. The capacity-building development aspect will ensure that Municipalities have the resources and the knowledge to manage their groundwater resource effectively. GEOSS has undergone several training workshops and offers weekly technical support to the two Municipalities. As the confidence of the municipal staff to manage their resource grows, their independence from the mining companies should lessen.
Mitigating climate change with managed aquifer recharge: 5 Case Studies	D	Hohne	South Africa	2023	Climate change; drought; MAR; nature-based solution; case studies
Abstract In the past decade, Southern Africa has experienced periods of extreme drought. This was especially true in the western Karoo in South Africa. Continuous drought and limited rainfall led to declining aquifer water levels that curtailed sustainable water supply for towns and livestock. The western Karoo is almost completely dependent on groundwater. Managed aquifer recharge (MAR) is being used to reduce the effects of droughts and mitigate climate change impacts. A good understanding of the geology and the behaviour of the aquifers is needed for implementing various MAR designs, including nature-based solutions, which are used to recharge aquifers with limited rainfall. This paper discusses 5 active MAR case studies in the Western Karoo. Here, site-specific MAR methods that use small rainfall events deliver reasonable results, whereas the implemented MAR options keep most aquifers functional. Observations at the MAR sites also showed improved water quality and less bacterial clogging. This improves the environment around the managed aquifer recharge sites. The MAR methods and designs discussed in this paper can be used on a larger scale for a town or a smaller scale for a farm. Maintenance costs are low, which makes these options cost-effective for less wealthy areas.
Netherlands National Groundwater reserves: 3D mapping and development of management policies as part of a multilevel strategy to secure water supply for disasters and the far future.	G	Nijsten	The Netherlands	2023	3-D mapping, Multi-layer governance, National fresh-salt groundwater model, Water supply strategies
Abstract The Netherlands produces about 2/3 of drinking water from groundwater. Although there is seemingly abundant groundwater, the resource needs to be carefully managed and used wisely to safeguard the resource for future generations and in case of disasters whilst also preventing negative impacts from groundwater extraction on other sectors such as nature. Provincial governments are responsible for the protection of existing groundwater abstractions for water supply against pollution. To secure groundwater resources for the future, two additional policy levels have been introduced: Provincial governments have been made responsible for mapping and protecting Additional Strategic Reserves. These allow for additional groundwater abstractions to meet growing demands in coming decades (horizon 2040/2050). The National Government is responsible for mapping and protecting the National Groundwater Reserves (NGRs) as a third level of resource protection. NGRs serve multiple goals: to protect natural groundwater capital for future generations, to provide reserves for large-scale disasters affecting water supply and to provide reserves for possible use as structural water supply in the far future (horizon 2100 and beyond). NGRs are being delineated in 3D using detailed existing geological models and the Netherlands’ national (fresh-saline) hydrological model. The dynamics of the groundwater system are analysed through scenario analyses. Reserves for potential structural use are selected such that negative impacts on nature are prevented if future abstractions are to be realised. The policies being developed must balance interests of water supply against other sectoral interests such as the green-energy transition with increased use of geothermal energy and aquifer-thermal-energy-storage.
Enhancing resilience to hydrological extremes in the Limpopo River Basin: a collaborative modelling approach	S	Mustafa	Limpopo	2023	opo River Basin, climate resilience, collaborative modelling approach, hydrological extremes and stakeholders workshops
Abstract The Limpopo River Basin (LRB) is highly vulnerable to recurrent floods and droughts, significantly threatening its water and food security. Sustainable groundwater management is necessary to improve resilience. Scientists and stakeholders must collaborate to evaluate management scenarios that can identify sustainable practices. A transboundary basin-scale management instrument was developed using a multisector collaborative modelling approach to identify the role of groundwater in building resilience. The approach used an integrated hydro(geo)logical model, co-created through stakeholder workshops. The model assessed management scenarios identified during a series of local, national and transboundary stakeholders workshops, focusing on improving groundwater storage during wet periods for use during dry periods in a context of population growth and increasing groundwater reliance across the basin. Management scenarios: (1) increasing groundwater abstraction; (2) deforestation; (3) afforestation; and (4) managed aquifer recharge (MAR) using injection wells capturing excess water from major dams, rainwater harvesting through local ponds/ wells, and small water reservoirs. Analysis of scenario outputs suggested that local groundwater storage techniques, especially water harvesting and storage through small-scale water well recharge, were the most effective strategy in reducing the risk and impact of floods and drought at the basin scale. Upscaling this strategy can significantly increase groundwater levels across the basin, supporting increasing groundwater reliance. The study showed that the multisector collaborative modelling approach effectively co-creates management strategies and identifies appropriate and inclusive strategies to improve resilience in data-limiting conditions. The proposed modelling outcomes are useful in making informed decisions regarding water management and transboundary cooperation in the LRB.
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
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.
Understanding informal institutions’ role in groundwater management – Lessons from borderland communities	Kevin	Pietersen	Africa	2023	groundwater governance, informal institutions, transboundary aquifers
Abstract Across Africa, given the pressing challenges of climate change and widespread water, food and livelihood insecurity and poverty, there is an ever-increasing expanding role for groundwater in resilience building, especially in borderland communities. This situation is being investigated in several projects and geographies. This paper’s groundwater management analysis was based on literature reviews, key informant interviews (KIIs), and focus group discussions (FGDs) in selected case study areas throughout sub-Saharan Africa. The KIIs included representatives of water management institutions, community leaders, international development partners, the private sector and non-governmental organisations (NGOs) involved in the use or management of groundwater. The FGDs occurred in borderland communities in Ethiopia, Kenya, and Somalia (with these three countries sharing borders) and Mozambique, South Africa and Zimbabwe (with these three also sharing borders). The findings show that informal institutions such as clan, tribal or ethnic affiliations dictate access to natural resources such as groundwater in borderlands. These same Institutions also play a significant role in conflict resolution in the borderland areas. In addition, informal institutions play an essential role in groundwater management and should also be recognised – in engagements and formal water policies and legislation. Formal organisations, institutions and government structures should strengthen their focus on ensuring that discussions and decisions include informal role players. Further developing and enforcing conventions, land-use plans, and bylaws governing access to and use of groundwater should ensure engagement and co-creation of solutions towards effective water resource management.
Integrated Modeling to Simulate Groundwater and Surface Water Interaction in the Letaba River Catchment, Limpopo Province, South Africa	Masilo	Mohale	South Africa	2023	Catchment., Groundwater, HydroGeoSphere, interaction, surface water
Abstract The current study investigates the spatial patterns and temporal dynamics of the groundwater and surface water interactions for integrated water resource management practices. This follows the results of the groundwater flow conceptual and numerical models developed for the Middle Letaba sub-catchment, indicating that groundwater and surface water interactions play a fundamental role in determining the hydrological water balance. The study area is an example of a fully allocated surface water resource in the northeastern part of South Africa, extensively developed for domestic use and agricultural farming. As a result of the semi-arid nature of the climate, limited surface water resources and increasing water demand, the situation has contributed to groundwater as the only dependable source of water supply for various uses. However, in the last few decades, periodic water level measurements in several boreholes indicated a continuous drop in the piezometric surface over time. This study utilised HydroGeoSphere to simulate water flow processes in a fully integrated and physically based model. The results of the steady-state groundwater flow simulation indicated that recharge from the rainfall and river leakages are the most important components of the inflows that control the availability of groundwater. Water resources management scenarios suggest a continuous decline in water level, which strongly influences the groundwater flow dynamics and future availability of fresh water. Regular monitoring and management of groundwater level and abstraction are required to avoid overexploitation and possible groundwater contamination due to the strong interaction between surface water and groundwater.
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.
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.
Application of the multi-method approach to assess river aquifer interaction in Upper Berg catchment, Western Cape, South Africa	A	Umunezero	South Africa	2023	aseflow, EWR, Groundwater contribution, background condition, filtering base-flow separation method, hydrological cross-section
Abstract To better understand the role of groundwater contribution to baseflow and EWR in groundwater protection and allocation, groundwater contribution must be quantified. Groundwater contribution to baseflow remains a challenge. Baseflow values have been widely used as groundwater contribution to surface water, which overestimates or underestimates the role of groundwater in the ecological ecosystem sustainability. To achieve the aim of the study, which was to estimate groundwater contribution to baseflow in a perennial river system at a catchment scale of the Upper Berg catchment, three objectives were taken into consideration: 1) To describe the hydrogeology of river morphology for groundwater-surface water interaction, 2) To estimate groundwater contribution to baseflow 3) To demonstrate the use of the background condition in setting resource quality objectives. Baseflow separation method using the Lynne & Hollick and Chapman algorithms, mass balance equation using EC as the tracer, field observation, and hydrochemical analysis methods were used to determine groundwater contribution to baseflow. Based on the hydrogeological cross-section presented, the fractures and faults of the peninsula geological formation dominating the study area predicted groundwater contribution to baseflow, which was confirmed by the calculations. The mass balance equation showed that 2,397 % of the 7.9 % baseflow index calculated at G1H076 and 19,093% of the 7.2% baseflow index calculated at G1H077 was groundwater. The background condition of the Upper Berg catchment was determined to be pristine with clean water.
Balancing qualitative and quantitative issues of the groundwater extraction at the drinking water production site of Velm (Central Belgium)	S	Van den Broeck	Belgium	2023	Belgium, Drinking water, Drought, Pollution, sustainability, time series analysis
Abstract Recent findings allow a better insight into the interaction between two aquifers and their vulnerabilities at the groundwater extraction site of Velm, which produces drinking water for around 55,000 households. The shallow aquifer that is exploited is situated in the Formation of Hannut. This aquifer is vulnerable to pollution, especially from the agricultural lands close to the extraction site and is sensitive to natural recharge. In this case, the groundwater is captured in a basin via a naturally occurring spring flow. The second aquifer is situated in the Cretaceous at 50 to 100 m below the surface and is pumped by four wells. The drinking water quality is guaranteed by mixing and treating these two waters. To optimize the central decalcification and the pollution risks, the production volume in the deep aquifer was increased from 2017 to 2021 at the expense of the shallow aquifer. This led to a decrease in the available volumes of the shallow aquifer, which indicated a leakage from the shallow to the deeper aquifer, which was unexpected. Groundwater modelling and time series analysis have been used to assess the impact of the increased production volumes and the longer dry periods. Based on this data, a maximum production volume of 1,000,000 m3 /year is considered best for the cretaceous aquifer. With this extraction rate in the Cretaceous, it is possible to supply sufficient drinking water and limit the impact on the Formation of Hannut.
Building evidence through hydrogeological survey and monitoring for the conjunctive development and management of water resources in Kunzila catchment area – Amhara Region, Ethiopia	Daniela	Benedicto van Dalen	Ethiopia	2023	catchment management, Conjunctive use, groundwater monitoring, participatory landscape Approach
Abstract Deploying a participatory approach for surveying the complex geohydrological system and defining the status of the groundwater resources in the Kunzila catchment area has crucial importance towards conjunctive use of its water and land resources for sustainable economic growth, social well-being, and environmental protection. Several initiatives are being undertaken to pilot the ‘Integrated Landscape Management and WASH’ project in this community to implement evidence-based approaches. A comprehensive hydrogeological study has been carried out to understand the hydrogeological system, propose ecosystem restoration measures, identify suitable locations for drilling boreholes and design a groundwater and surface water monitoring network. The first results pointed out the central area of the catchment as holding the best potential for groundwater abstraction, a productive Late Quaternary basalt aquifer. As this area is in use by private floriculture farms, several other borehole locations were sited to meet the domestic and livelihood demand across the watershed. In addition to the drinking water supply goals, the project proposed catchment intervention for soil and water conservation based on the Landscape Approach and 3R measures implementation - Retain, Recharge, Reuse. Such measures include but were not limited to riparian vegetation restoration, terracing and contour bunds, agroforestry, controlled grazing, etc. A telemetric monitoring network has been designed and installed to support the conjunctive management of shallow and deep groundwater water resources, streams and Lake Tana, together with a functional dashboard for data registrations and sharing. The monitoring program gauges the impact of groundwater abstraction and the quality parameters.
Thermal energy storage in old flooded mines: how to tackle the hydrogeological issues	Alain	Dassargues	Belgium	2023	doublets, energy storage, flooded mines, geothermal system, heat transport, modelling, old mines, open geothermal energy
Abstract Groundwater in flooded abandoned mines could be used for geothermal purposes using heat pumps and an open loop involving pumping and re-injection. Hydraulic conductivity values of the mined rock zones have been artificially increased. However, long-term efficiency and the possible impacts of geothermal doublets must be studied involving a series of hydrogeological challenges. Hot water would be pumped from the deep parts of the mine works, and cold water would be re-injected in a shallower gallery or shallow fractured rocks, with a seasonal flow inversion for building cooling during the hot season. Indeed, a ‘short-cut’ groundwater flow is to be avoided between the mine’s deep and shallow parts. The true geometry of the interconnected network of open galleries and shafts can be highly complex and must be conceptualized realistically to ensure that the model is feasible and reliable. This model must involve groundwater flow and heat transport, with temperature-dependent density and viscosity, in a complex 3D heterogeneous domain of highly fractured rocks and partially collapsed exploitation zones, galleries, and shafts. Such a model is nevertheless widely recommended to design and optimize the short--, mid-, and long-term efficiency of the geothermal system and assess possible environmental impacts. An example of simulations on a synthetic case will be used for illustration and preparation work before further application in a real case study.
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.
Hydrogeological assessment for sourcing regionally significant freshwater supplies in southern Malawi	Jonas	Bernasconi	USA	2023	Brackish Groundwater, development, Lower Shire River Valley, Malawi, Satellite Imagery/Field Survey, Water Quality Data Clustering
Abstract Communities in the Lower Shire River Valley in the Chikwawa District of southern Malawi face extreme development challenges due to highly variable climate, including floods and droughts, that trap them in poverty and food insecurity. The area has been the focus of numerous studies and data collection campaigns to understand better the causes and processes associated with brackish groundwater (in alluvial aquifers) and dry boreholes. An applied groundwater assessment was performed to evaluate water supply alternatives and solutions to deliver potable water to approximately 15% of the district without water access after a multi-year campaign to reach 100%. The assessment synthesized a significant volume of water quality data collected by researchers and nongovernment organizations, larger scale geological interpretations published in segmented literature, multi-spectral satellite imagery datasets, and combined field reconnaissance to investigate areas of interest further and address pertinent data gaps. Improved understanding of geologic structure and lithology, complex aquifer recharge, and evapotranspiration processes supported identifying areas unsuitable for groundwater development and yielded recommendations for groundwater exploration and other solutions. A high permeability zone and strong surface-groundwater connection was identified along the Gungu River. Data collected throughout the area of interest corroborated that significant freshwater recharge occurs in the alluvial aquifer, promoting an aquifer zone where freshwater and higher yields are likely. Exploratory drilling resulted in a very high-yielding freshwater well that supported the development of a piped water system serving several villages.
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.
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.
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.
Integrating reductive dehalogenase enzyme production into reactive transport modelling to simulate chloroethene biodegradation in groundwater pollution plumes	Diego	Di Curzio		2023	Biodegradation; Chloroethenes plume; Reactive Transport Modeling; Enzyme-Based Kinetics; Reductive dehalogenase enzymes; Groundwater
Abstract Degradation of chloroethene in groundwater primarily occurs via microbially-mediated reductive dechlorination (RD). Anaerobic organohalide-respiring bacteria (OHRB) use chloroethenes as electron acceptors to gain energy. They produce reductive dehalogenase enzymes (RDases) to perform this function by transcription of functional genes into mRNA and translation to proteins (metabolic regulation). However, how hydrodynamics and hydrogeochemistry control the metabolic efficiency of OHRB in biodegrading chloroethene is essential for effective bioremediation design yet an under-investigated topic. For this reason, we implemented a virtual experiment (1D reactive transport model) to investigate the effects of site conditions on transcription-translation and, hence, biodegradation processes within chloroethene plumes. In the model, RD was simulated using Enzyme-Based Kinetics, explicitly mimicking the production of RDases via metabolic regulation, calibrated on microcosm experimental data gained from literature. Features of an actual contaminated site (Grindsted, Denmark) were then used to set up the virtual experiment. Here, chloroethene leaked from a former pharmaceutical factory migrates through a sandy aquifer and gets discharged into the Grindsted stream. Preliminary results show that substrate (electron donors) limiting conditions caused by competing electron acceptors and dispersion and high flow rates represent the key factors controlling biodegradation via RDase production.
Monitor and determine local groundwater impacts from increased mining activities in the Kalahari iron manganese field of the Northern Cape, South Africa.	Gawie	van Dyk	South Africa	2023	aquitards, environmental impacts on groundwater, increased water demand, Monitoring, primary aquifers, reduced recharge
Abstract The Kalahari iron manganese field (KIMF) in the Northern Cape, South Africa, was historically exploited by only three mines, with Hotazel the only town and the rest of the area being largely rural, with agricultural stock/ game farming the major activity. Since 2010, mining activities have increased to more than 10 operational mines with increased water demand and environmental impacts on groundwater. The area is within catchments of the Matlhwaring, Moshaweng, Kuruman and Gamogara rivers that drain to the Molopo River in the Northern Cape. All the rivers are non-perennial, with annual flow occurrence in the upstream areas that reach this downstream area once every 10 years. The area is semi-arid, with annual evaporation nearly five times the annual precipitation. The precipitation is less than 300mm, with summer precipitation in the form of thunderstorms. Vegetation is sparse, consisting mainly of grasslands, shrubs and some thorn trees, notably the majestic camel thorns. The Vaal Gamagara Government Water Supply Scheme imports 11 Ml/d or 4Mm3 /a water for mining and domestic purposes in the KIMF section. The area is covered with Kalahari Group formation of 30 to 150 m thick with primary aquifers developed in the basal Wessels gravels and Eden sandstones for local use. The middle Boudin clay forms an aquitard that isolates and reduces recharge. Water levels range from 25 to 70m, and monitoring indicates local dewatering sinks and pollution. This study will report on the water uses, monitoring and observed groundwater impacts within the current climatic conditions.
Understanding the influence of Artefacts on the Darcy Velocity Estimations from Point Dilution Tracer Tests	S	Mofokeng	South Africa	2023	Contaminant transport, Darcy velocity, Groundwater, horizontal groundwater flow, point, dilution tracer test
Abstract Darcy Velocity (Vd) is often estimated through a single-borehole Point Dilution Tracer Test (PDTT). Vd is used in the investigation of contaminant transport and distribution in aquifers. The tracer dilution rate in groundwater is controlled by horizontal groundwater flux. However, it can be affected by other artefacts, such as diffusion and density effects. Although there are studies on tracer tests, there has not been much done to gain an understanding of how these artefacts affect the correct Vd estimation. This study, therefore, aims to investigate and provide an understanding of the influence of artefacts on the PDTT through laboratory experiments conducted using a physical model representing a porous media. A total of 18 experiments were performed with different NaCl tracer concentrations under constant horizontal groundwater flow and no-flow conditions. The study results show that the density sinking effect affects an early period of tracer dilution, which can lead to overestimation of Vd; therefore, these stages should not be used to estimate Vd. The study, therefore, proposes a way in which PDTT data should be analysed to understand the effects of artefacts on Darcy velocity estimation.
Managed Aquifer Recharge as a strategy for increased water supply security in Eastern Botswana	J	Strömgren	Botswana	2023	Botswana, MAR, Groundwater Modelling, multi-criteria analysis, probabilistic water supply system modelling, Water security
Abstract The joint application of water supply system security, groundwater modelling, and multicriteria analysis (MCA) indicated the potential of Managed Aquifer Recharge (MAR) to increase water supply security in Eastern Botswana substantially. Botswana faces increased water stress due to decreased water availability as climate change exacerbates variability in rainfall and increases evaporation losses and water demand. The water supply for Eastern Botswana is based on the bulk water supply system of the North-South Carrier (NSC) connecting dams in the northeast to the main demand centres, including Gaborone. The potential of MAR to increase the water security of the NSC by storing water that otherwise would have been lost to spillover and evaporation and contribute to the provision of water during droughts was studied. Large-scale MAR in the Ntane sandstone aquifer at a wellfield by the NSC was evaluated in terms of hydrogeology and national water supply perspective. Comprehensive hydrogeological surveys and assessments included borehole injection tests and hydrogeological and geochemical modelling to evaluate risks of losing recharged water and clogging of boreholes. Probabilistic water supply system modelling analysed the impact of different MAR scenarios on the water supply security of the NSC, and an MCA tool assessed the sustainability of the different scenarios. The analysis showed that large-scale MAR is feasible, and a scheme with a capacity of 40,000 m3 /d is the most sustainable from technical, social, economic and environmental perspectives and could potentially reduce the number of months with water shortage by 50% in Gaborone.
Mine dewatering case study at a gold mine in Mandiana Region, Eastern Guinea	Angelo	Johnson	Eastern Guinea	2023	mine dewatering, Monitoring
Abstract A hydrogeological investigation was conducted at a gold mine in the Mandiana region, northeast Guinea. The objectives of the investigation included: 1) Review the efficiency of the current dewatering system and 2) Assess potential dewatering impacts on neighbouring groundwater users. Historical and current hydrogeological information were reviewed and assessed to address the project objectives. The site geological succession contains laterites, saprolites, saprock, dolorite sill and fresh fractured bedrock below. A review of the borehole lithological logs, pump test and monitoring data confirmed that the contact zone between the saprock and the dolorite sill is the major aquifer zone with hydraulic conductivity up to 25 m/d, with a minor alluvial aquifer with hydraulic conductivity ~ 0.05 m/d. The current dewatering system is not as effective as it should be due to electrical issues causing seepage into the current pit floor. A combination of in-pit sumps and dewatering boreholes is recommended to ensure the mine pit’s dry working conditions. The neighbouring groundwater users tap into the alluvial aquifer with water levels ranging between 0-10 mbgl and are not at risk from mine dewatering impacts due to the dewatering boreholes tapping into the deeper saprock-dolorite contact zone. The shallow and deeper aquifers are hydraulically disconnected. The following is recommended: 1) Drilling of replacement dewatering boreholes and implementing continuous water level and abstraction rate monitoring, and 2) Discharge the in-pit sumps (alluvial aquifer inflow and rainfall) into the river downgradient of the mine to supplement recharge to the alluvial aquifer.
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.