Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 1 - 50 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort ascending	Keywords
Water resource management in tectonically active volcanic regions: Towards an in-depth understanding of Mt. Fuji’s hydrogeology	Stephanie	Musy		2023	SW-GW interactions; tracers; modelling
Abstract Mt. Fuji is the iconic centrepiece of a large, tectonically active volcanic watershed (100 km2 ), which plays a vital role in supplying safe drinking water to millions of people through groundwater and numerous freshwater springs. Situated at the top of the sole known continental triple-trench junction, the Fuji watershed experiences significant tectonic instability and pictures complex geology. Recently, the conventional understanding of Mt. Fuji catchment being conceptually simple, laminar groundwater flow system with three isolated aquifers was challenged: the combined use of noble gases, vanadium, and microbial eDNA as measured in different waters around Fuji revealed the presence of substantial deep groundwater water upwelling along Japan’s tectonically most active fault system, the Fujikawa Kako Fault Zone [1]. These findings call for even deeper investigations of the hydrogeology and the mixing dynamics within large-scale volcanic watersheds, typically characterized by complex geologies and extensive networks of fractures and faults. In our current study, we approach these questions by integrating existing and emerging methodologies, such as continuous, high-resolution monitoring of dissolved gases (GE-MIMS [2]) and microbes [3], eDNA, trace elements, and integrated 3-D hydrogeological modelling [4]. The collected tracer time series and hydraulic and seismic observations are used to develop an integrated SW-GW flow model of the Mt. Fuji watershed. Climate change projections will further inform predictive modelling and facilitate the design of resilient and sustainable water resource management strategies in tectonically active volcanic regions
Securing Water Supplies – Participatory Groundwater Monitoring and Management in Botswana and Uganda	Piet Kebuang	Kenabatho	Botswana, Uganda	2023	Livelihoods and Pollution, Participatory groundwater monitoring
Abstract Groundwater resources in Africa face increasing threats of over-exploitation and pollution due to urbanization, agricultural and mining activities, yet monitoring remains challenging. Conventional approaches to monitoring groundwater at the exclusion of communities have not been successful. To overcome this, it is important to fully engage and train local communities in monitoring Groundwater Levels (GWLs), Rainfall and Water Quality (RWQ), which are important for understanding groundwater dynamics in wellfields. In this way, villagers can better understand groundwater issues and convey this information to others to cooperatively manage groundwater. A pilot program to monitor GWLs and RWQ by locals was initiated in two villages each in Botswana and Uganda to learn about its effectiveness. Through continuous stakeholder engagement, the local communities in the two case studies have been facilitated, trained and supported in monitoring groundwater and using the information collected to understand groundwater trends and their sustainability. Preliminary results indicate improvement in understanding the importance of groundwater monitoring by the communities and the implications on groundwater sustainability for improved livelihoods. This has become useful to one of the communities engaged in a village-level irrigation project which depends on groundwater resources. This project builds on a successful village-level participatory approach developed in the MARVI project (www.marvi.org.in ). It seeks to contribute to the United Nation’s 2022 call on “Groundwater: making the invisible visible” to highlight the importance of better monitoring and managing this vital resource.
Alternative approaches for integrated groundwater management in the rural basins of central Bolivia	I	Rodriguez-Levy	Bolivia	2023	Bolivia, socio-hydrogeology, Geophysics, groundwater recharge, soil water balance
Abstract Due to technical, social, and economic limitations, integrated groundwater management presents a significant challenge in developing countries. The significance of this issue becomes even more pronounced in groundwater management, as this resource is often overlooked and undervalued by decision-makers due to its status as a “hidden resource,” despite the fact that it provides multiple ecosystem services. This study aims to establish the technical hydrogeological foundation in rural basins of central Bolivia through alternative, simplified, and cost-effective methods and tools. The study includes applying geophysical techniques, such as Electrical Resistivity Tomography, to determine the conceptual hydrogeological model of a micro-basin. In addition, a soil water balance approach was applied, characterizing 24 biophysical variables to identify groundwater recharge zones, while global circulation models provided a substitute for unreliable meteorological data. Furthermore, a participatory model was developed to identify recharge areas in upper basin areas within the framework of developing a municipal policy for their protection. The participatory model included local knowledge in all stages of methodology development, considering the characteristics of the local plant communities and the spatial distribution of local rainfall. The research findings have already contributed to resolving socio-environmental conflicts in Bolivia and establishing a foundation for effective water governance by empowering local rural communities. This study has demonstrated the feasibility of using alternative, simplified, and low-cost methods and tools to establish the technical hydrogeological basis, which can inform public policies to promote sustainable groundwater management in developing countries.
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.
Dynamic groundwater modelling of Lake Sibaya	M	Maseko	South Africa	2023	Groundwater/surface-water relations, Climate change, groundwater model, land-use landcover, surface-water model
Abstract The Lake Sibaya groundwater-dependent catchment in uMhlabuyalingana (KwaZulu-Natal) has been the focus of hydrological research since the 1970s. The continuous decline in lake water levels and groundwater stores has prompted recent efforts. To increase confidence in the relative attribution of known causes of declines, an existing MODFLOW groundwater model was updated based on reviewed and extended hydrological input datasets and more accurate land-use and land cover (LULC) change data. A novel approach was used in this study, which involved running the ACRU surface-water model in distributed mode to provide dynamic recharge outputs for the groundwater model. This approach considers LULC changes, improved spatial and temporal distribution of climatic data, and land-surface hydrological processes. The refined groundwater model provided satisfactory simulations of the water system in the Lake Sibaya catchment. This study reports on the advances and limitations discovered in this approach, which was used to reassess past to current status quo model simulations for the region. The model was then used, as part of a multidisciplinary project, to assess the response of the lake water system under various LULC preferences based on inputs from local communities under two future climate scenarios (warmer wetter and warmer drier) in the current ongoing WRC project. The ultimate goal is to advise water resources management in the catchment.
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.
Determination of the best hydrogeological target for improving the success rate and productivity of boreholes in basement rocks	Younaise S. O	Adeotan	Benin	2023	basement rock aquifers, boreholes properties, hydrogeological targets
Abstract Access to safe water is not yet universal in Burkina because 30% of Burkinabes do not yet have access to drinking water. The objective of universal access to drinking water (ODD 6.1) is difficult to achieve in the context of population growth and climate change. Basement rocks underline 80% of Burkina Faso. However, about 40% of the boreholes drilled in the Burkina Faso basement rocks do not deliver enough water (Q < 0.2l/s) and are discarded. This study focuses on determining the appropriate hydrogeological target that can be searched to improve the currently low drilling success rate. We set up a well-documented new database of 2150 boreholes based on borehole drilling, pumping tests, geophysical measurements, and geological analysis results. Our first results show that the success rate at 0.2l/s (i.e. 700 l/h) is 63% at the end of the drilling against 54% at the end of borehole development: the yield of 8% of the boreholes lowers significantly after only a few hours of development. We also found that the yield of the water intakes encountered during the drilling process slightly decreases with depth; beyond 60m, it is rare (only 15% of cases) to find water occurrences. We found clear relationships between the productivity of the borehole (yield after drilling and transmissivity obtained from the pumping test) and the thickness of the weathering rocks, indicating that the appropriate target to obtain a productive borehole is a regolith of about 35 meters thick.
How alluvial storage controls surface water – groundwater interactions in dryland intermittent and ephemeral streams: A case study from semi-arid Australia	M	Zarate	Australia	2023	Groundwater, groundwater recharge, drylands, ephemeral streams, focused recharge, intermittent, semi-arid, streamflow, surface water, water balance
Abstract Water balance partitioning within dryland intermittent and ephemeral streams controls water availability to riparian ecosystems, the magnitude of peak storm discharge and groundwater replenishment. Poorly understood is how superficial geology can play a role in governing the spatiotemporal complexity in flow processes. We combine a new and unusually rich set of integrated surface water and groundwater observations from a catchment in semi-arid Australia with targeted geophysical characterisation of the subsurface to elucidate how configurations of superficial geology surrounding the stream control the variability in streamflow and groundwater responses. We show how periods of stable stream stage consistently follow episodic streamflow peaks before subsequent rapid recession and channel drying. The duration of the stable phases increases in duration downstream to a maximum of 44±3 days before reducing abruptly further downstream. The remarkable consistency in the flow duration of the stable flow periods, regardless of the size of the preceding streamflow peak, suggests a geological control. By integrating the surface water, groundwater and geological investigations, we developed a conceptual model that proposes two primary controls on this behaviour which influence the partitioning of runoff: (1) variations in the permeability contrast between recent channel alluvium and surrounding deposits, (2) the longitudinal variations in the volume of the recent channel alluvial storage. We hypothesise optimal combinations of these controls can create a ‘Goldilocks zone’ that maximises riparian water availability and potential for groundwater recharge in certain landscape settings and that these controls likely exist as a continuum in many dryland catchments globally.
Improved hydrogeological conceptual model through additional ERT profiles in medial-distal facies of andesitic volcanic area: Case study of Pandaan, East Java, Indonesia	Arif	Fadillah	Indonesia	2023	Andesitic stratovolcanoes, Electrical Resistivity Tomography, Groundwater, Hydrogeological, conceptual model, sustainability
Abstract In Java Island, Indonesia, andesitic volcanic aquifers are the main water resource for domestic, agricultural, and industrial use. To guarantee sustainable management, a hydrogeological conceptual model is key. Electrical resistivity tomography (ERT) survey is one tool to characterize aquifer structures and extension, specifically in the medial facies of the Arjuno Welirang volcano. Fadillah et al. (2023) proposed a hydrogeological interpretation of the aquifers in the central to proximal-medial transition zone of the Arjuno Welirang volcano. This interpretation was based on geology, hydrogeology, and ERT and focused on major springs and boreholes. Nine additional ERT profiles and borehole data were collected downstream to enhance the medial facies’ understanding further. Seven ERT lines were conducted throughout the midstream part of the watershed. The results confirm the presence of two superimposed aquifers, a first unconfined aquifer made of volcanic sandstone and breccia with a vertical extension of 25 meters and a confined aquifer from 35 to 120 meters (maximum depth of investigation). This last one consists of tuffaceous breccia and volcanic sandstone and includes lava layers as well. A clayey layer with an average thickness of 10 meters constitutes the aquiclude/aquitard between those two aquifers. Furthermore, two ERT lines were conducted in the vicinity of the major spring located in the distal part of volcanic deposits, highlighting the development of a multi-layer alluvial aquifer system.
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.
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.
Groundwater overuse and water quality challenges in a large metropolitan catchment	B	Karthikeyan	India	2023	Managed aquifer recharge, megacity, persistent organic pollutants, urban catchment
Abstract Conjunctive use of surface water and groundwater plays a pivotal role in sustainably managing water resources. An increase in population, especially in the cities, increases the demand for water supply. Additional infrastructure to meet the needs and treatment techniques to remove the pollutants should be updated from time to time. Closing the urban water cycle by recycling and reusing treated sewage in the water sector can significantly reduce excessive groundwater extraction. However, this method is being implemented in only a few cities in developed countries. In the closed urban water cycle, treated sewage is discharged to rivers or other surface water bodies and used for managed aquifer recharge (MAR). Bank filtration, soil aquifer treatment and infiltration ponds are available MAR methods that augment the groundwater resources and remove pollutants during the natural infiltration process. These cost-effective natural treatment methods serve as a pre-treatment technique before public water supply to remove turbidity, algal toxins, bulk dissolved organic carbon and pathogenic microorganisms. The successful performance of these treatment methods depends on the need and feasibility for MAR, suitable hydrogeological conditions, sub-surface storage capacity of the aquifers, availability of suitable areas for MAR, type of MAR, source of recharge water, quality criteria, assessing the past, present and future climatic conditions. Case studies on groundwater resources management and water quality assessment, including for organic micropollutants from a large urban catchment in India, are presented.
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.
Groundwater recharge in sub-humid drylands under different agricultural systems	D	Mudimbu	SADC (Malawi, Zambia, Zimbabwe)	2023	groundwater recharge, basement aquifers, Southern Africa Development Community (SADC
Abstract Groundwater is a strategic long-term water resource used by an estimated 70% of the populations in sub-Saharan Africa for drinking, irrigation and a wide range of economic activities. Understanding groundwater recharge processes is key for effectively using and managing water resources. Very few studies have used direct groundwater observations to assess the impact of different farming systems on groundwater recharge processes. This study focused on assessing basement aquifer recharge in 4 instrumented catchments in Malawi (Chitedze), Zambia (Liempe and Kabeleka) and Zimbabwe (Domboshawa) within the SADC region between 2019-2022. Employing a range of methods, including direct field observations (groundwater hydrographs, precipitation data, stable isotopes, chloride mass balance and residence time tracer data), we quantify the amount of groundwater recharge as well as the timing and nature of recharge processes under both conservation and conventional tillage systems in these four study sites. Groundwater recharge was measured in most years across the study sites. The study reveals the strong climate controls on seasonal groundwater recharge volumes, the influence of low permeability layers in the unsaturated zone, and the likely magnitude of impact from different farming practices. Groundwater residence times are high (i.e. low fractions of modern recharge, interquartile range 1-5%, n=46), even in shallow piezometers, suggesting these unpumped systems may be highly stratified. The results provide an evidence-based suite of data that reveals much about key controls on groundwater recharge in basement aquifers in sub-humid drylands and will inform the development and management of such groundwater systems.
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.
Delineating wellhead protection areas and aquifer vulnerability in the Cape Flats, South Africa	Brynn	Hunink	South Africa	2023	Aquifer vulnerability mapping, groundwater sustainability, Resource protection, Source protection, Wellhead protection areas
Abstract Prevention of threats to the quality and quantity of groundwater supply is critical to ensure its sustainability. Several African studies have shown that contamination of aquifers is primarily caused by improper placement of land-based human activities. Therefore, adequate preventative measures are required to safeguard the water quality of African aquifers to avoid long-term deterioration. Spatially explicit, 3D numerical groundwater modelling is a common methodology to assess contaminant transport. However, model development is time-consuming and complex. Contrastingly, DRASTIC-L is a 2D, GIS-based aquifer vulnerability mapping technique. The method is simple to apply, but analyses are qualitative and subjective. The study aims to compare both methods and to combine their strengths using GIS overlay. Overall, aquifer vulnerability was determined using the DRASTIC-L method, while wellhead protection areas were delineated using steady-state numerical modelling. This study focuses on the Cape Flats area due to its rapid development and growing municipal water supply supplementation needs. DRASTIC-L mapping revealed that aquifers in the Cape Flats are highly vulnerable to contamination due to the region’s unconfined hydrogeological properties, shallow water table and high-risk land use types. Moreover, groundwater vulnerability mapping combined with the delineation of wellhead protection areas allows for reduced uncertainty in the contamination potential of delineated groundwater protection zones. As a result, this study highlights the need for overall resource protection of the Cape Flats aquifers and provides insights into mapping out potential source protection areas of existing water supply wells.
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.
The pharmaceutical compounds diversity at two river bank filtration sites located in Warta River valley (Poland)	Krzysztof	Dragon	Poland	2023	pharmaceuticals compounds; river bank filtration sites
Abstract Emerging contaminants (e.g. pharmaceuticals or pesticides) are increasingly detected in aquatic environments. The most apparent contamination source of river water pollution by pharmaceuticals is sewage treatment plant stations that discharge treated sewage effluent to the rivers. The river bank filtration systems (RBF) can effectively remove these contaminants. The two RBF sites were examined for pharmaceuticals: Śrem and Gorzów waterworks. The water samples for pharmaceuticals investigation were taken from the river and four continuously pumped wells at each site. Two wells near the river were chosen at each site (40-50 m) and two at a greater distance from the river (70 m in Śrem and 110 m in Gorzów). A visible increase in pharmaceutical concentrations was observed along the river. The sum of pharmaceuticals concentration is 8151 ng/l in Śrem (upstream), while in Gorzów (downstream) concentration is 9142 ng/l. A very big differentiation in pharmaceutical occurrence was observed. In Śrem, the sum of pharmaceuticals concentration is between 657 and 3290 ng/l, while in Gorzów, despite the higher concentrations of pharmaceuticals in the river, these substances were detected only in one well located at a close distance from the river (two substances at a concentration of 92 ng/l). The research proves a very big differentiation of pharmaceutical concentration even on sites located at similar hydrogeological conditions and demonstrates the necessity of its monitoring, especially in groundwater strongly influenced by river water contamination (like at RBF sites). This work has received funding from the National Science Centre Poland (grant no. 2021/41/B/ST10/00094).
Paleo-hydrogeological reconstruction of a complex deep groundwater system in a tectonically active region	H	Levanon	Israel	2023	Dead Sea Rift, Golan Heights, Lagoonary brines, Paleo-hydrology, intrusion/backflow
Abstract The geochemical study of deep aquitard water in the southern Golan-Heights (GH), Israel, reveals the complex paleo-hydrological history affected by the intensive tectonic activity of the Dead Sea Rift (DSR). The sampled water collected from new research boreholes exhibits relatively high salinities (2,000-10,000 mg Cl/L), low Na/Cl ((HCO3 +SO4 )). δ18OV-SMOW and δDV-SMOW values are relatively depleted (~-7‰ and ~-42‰, respectively), while 87Sr/86Sr ratios are enriched compared to the host rocks. Lagoonary brines with similar characteristics (excluding the water isotopic compositions) are known to exist along the DSR. These brines formed 10-5 Ma ago from seawater that transgressed into the DSR and subsequently underwent evaporation, mineral precipitation and water-rock interactions. These hypersaline brines intruded into the rocks surrounding the DSR and based on the current study, also extended as far as the southern GH. Further, following their subsurface intrusion into the GH, the brines have been gradually diluted by isotopically depleted freshwater, leaving only traces of brines nowadays. The depleted isotopic composition suggests that the groundwater system is recharged at high elevations in the north. It is also shown that variable hydraulic conductivities in different formations controlled the dilution rates and subsequently the preservation of the entrapped brines. The paleo-hydrological reconstruction presented here shows that the flow direction has reversed over time. Brines that initially intruded from the rift have since been gradually flushed back to the rift by younger fresh groundwater.
Time scale connection of groundwater with adjacent spheres	M	Taniguchi	Japan	2023	Anthropocene, Kumamoto, adjacent spheres, social revolution, time scale
Abstract Groundwater is connected with the earth’s interior, atmosphere, ocean sphere, and human sphere. Fluid, heat, and dissolved materials are crossed over the boundaries of adjacent spheres with different time scales in dynamics. These different time scales include event scales such as earthquakes and Tsunami, seasonal scales such as precipitation seasonality, a decade or longer scales such as climate change, and human scales such as groundwater pumping, land cover/use changes, and social revolutions such as industrialization, green revolution, urbanization, and globalization in Anthropocene. This study shows two examples of groundwater connected with different time scales. The first is thermal signals preserved in groundwater by earthquake, climate change, and anthropogenic impacts with different time scales. Thermal signals in groundwater from the Kumamoto earthquake in 2016 revealed evidence of fluid flow from the earth interior and Aso mountain. The thermal signal in groundwater in Kumamoto also showed the impacts of global warming and urbanization, as well as changes in precipitation and land use. The second example is the connectivity between residence time of groundwater and groundwater consumption in social revolutions such as industrialization and urbanization in the Anthropocene, as well as World War II as an example of groundwater for emergency situations.
Evaluating Karst Drywells for Urban Stormwater Management and Aquifer Recharge	Yonatan	Ganot	Israel	2023	Drywell, karst, MAR, RQD, unsaturated zone
Abstract Drywells are extremely useful for coping with excess surface water in areas where drainage and diversion of storm flows are limited, facilitating stormwater infiltration and groundwater recharge. Drywells have been used for stormwater management in locations that receive high precipitation volumes, naturally or due to climate change; however, to date, they have not been developed in urban areas overlying karst landscapes. To test the performance of karst drywells, we constructed a pilot system for collecting, filtering, and recharging urban stormwater through drywells in karst rock. The study site is in the Judaean Mountains, an urban residential area in Jerusalem, Israel. The infiltration capacity of the drywells was evaluated using continuous and graduated water injection tests, and its effective hydraulic conductivity (K) was estimated. Drywells’ infiltration capacity was up to 22 m3 /hour (the maximum discharge delivered by a nearby fire hydrant), while monitored water levels in the drywells were relatively stable. Calculated hydraulic conductivities were in the range of K=0.1-100 m/ day, and generally, K was inversely proportional to the rock quality designation (RQD) index (obtained from rock cores during the drilling of the drywells). The pilot system performance was tested in the recent winter: during 9 days with a total rainfall of 295 mm, a cumulative volume of 45 m3 was recharged through the drywell, with a maximum discharge of 13 m3 / hour. High-conductivity karst drywells and adequate pre-treatment filtration can be valuable techniques for urban flood mitigation and stormwater recharge.
Hydrostratigraphic controls on groundwater arsenic enrichment in the Brahmaputra river basin aquifers	D	Aind	India	2023	aquifer composition, Arsenic, clays, Groundwater
Abstract Groundwater arsenic (As) distribution in alluvial floodplains is complex and spatially heterogeneous. Floodplain evolution plays a crucial role in the fate and mobilization of As in the groundwater. This study presents how groundwater As enrichment is controlled by the spatial disposition of subsurface sand, silt, and clay layers along an N-S transect across the Brahmaputra river basin aquifer. Six boreholes were drilled in the shallow aquifer (up to 60 m) along this transect, and 56 groundwater samples were collected and analysed for their major and trace elements, SO4, PO4, dissolved organic carbon (DOC), and dissolved oxygen (DO). Groundwater As ranges from 0.1 to 218 μg/L on the northern bank while from 0.2 to 440 μg/L on the southern bank of the Brahmaputra. Groundwater in the southern bank is highly reduced (Eh -9.8 mV) with low DO and low SO4 (2 mg/L), while groundwater in the north is less reduced (Eh 142 mV) with low DO and higher SO4 (11 mg/L). Subsurface lithologies show that the aquifer on the southern bank has a very thick clay layer, while the aquifer on the northern bank is heterogeneous and interlayered with intermediate clay layers. Depth comparison of the groundwater arsenic concentrations with subsurface lithological variations reveals that groundwater wells overlain by thick clay layers have higher arsenic, while groundwater wells devoid of clay capping have lesser arsenic. Detailed aquifer mapping could be decisive in exploring potentially safe groundwater from geogenic contamination.
Evaluating dry wells for flood management in urban catchments using integrated surface-subsurface flow models	J	Liu	Japan	2023	Drywell, flood, surface-subsurface flow model, urban catchment
Abstract Floods result in significant human and economic losses worldwide every year. Urbanization leads to the conversion of natural or agricultural land covers to low-permeability surfaces, reducing the infiltration capacity of the land surface. This amplifies the severity and frequency of floods, increasing the vulnerability of communities. Drywells are subsurface structures built in the unsaturated zone that act as managed aquifer recharge facilities to capture stormwater runoff. They are particularly well-suited for the urban environment because of their low land occupancy. In this study, we utilized an integrated surface-subsurface flow modelling approach to evaluate the effectiveness of dry wells in reducing urban runoff at a catchment scale. We developed a 3D model with HydroGeoSphere, characterizing a synthetic unconfined aquifer covered by a layer of low-permeability materials. Sensitivity analyses of land surface conditions, aquifer properties, dry well designs, and rainfall conditions were performed. Model results indicated that dry wells are more effective in reducing runoff when the land surface has a higher Manning roughness coefficient or the aquifer material has a higher hydraulic conductivity. Dry wells should be situated beneath drainage routes with high runoff flux to achieve optimal performance. Increases in dry well radius or depth enhance the infiltration capacity, but deeper dry wells can contaminate groundwater through infiltrating stormwater. Dry well performance declines with higher rainfall intensity, emphasizing the need for local rainfall intensity–duration–frequency (IDF) data to inform the design level of dry wells in specific catchments.
Global potential groundwater recharge in response to climate variability and teleconnection	C	Moeck	Norway	2023	climate variability, global, groundwater recharge, teleconnections, unsaturated zone
Abstract Periodic climate variability, such as that caused by climate teleconnections, can significantly impact groundwater, and the ability to predict groundwater variability in space and time is critical for effective water resource management. However, the relationship between climate variability on a global scale and groundwater recharge and levels remains poorly understood due to incomplete groundwater records and anthropogenic impacts. Moreover, the nonlinear relationship between subsurface properties and surface infiltration makes it difficult to understand climate variability’s influence on groundwater resources systematically. This study presents a global assessment of the impact of climate teleconnections on groundwater recharge and groundwater levels using an analytical solution derived from the Richards equation. The propagation of climate variability through the unsaturated zone by considering global-scale climate variability consistent with climate teleconnections such as the Pacific-North American Oscillation (PNA) and the El Niño/Southern Oscillation (ENSO) is evaluated, and it is shown when and where climate teleconnections are expected to affect groundwater levels. The results demonstrate the dampening effect of surface infiltration variability with depth in the vadose zone. Guidance for predicting long-term groundwater levels and highlighting the importance of climate teleconnections in groundwater management is provided. The obtained insights into the spatial and temporal variability of groundwater recharge and groundwater levels due to climate variability can contribute to sustainable water resource management.
Study on the Relationship between Water Quality and Wetland Plant Community in Huixian Karst Wetland	L	Shen		2023	Huixian Karst Wetland, Water quality, Wetland Plant Community
Abstract Huixian Karst National Wetland Park is the most typical karst wetland in the middle and low latitudes of the world and has become an internationally important wetland. The relationship between water quality and aquatic organisms in Huixian Wetland is a hot research topic in wetland ecology. This article focuses on the relationship between the current water quality situation in Guilin Huixian Karst Wetland and the growth of wetland plants. Sixteen sampling points are set up in the wetland to monitor and analyze water quality in wet, normal, and dry seasons. The Kriging index interpolation method is used to obtain a comprehensive water quality interpolation map in the survey area during normal water periods and in combination with the wetland plant survey sample data and the landscape status. A comprehensive analysis of the relationship between wetland plant growth and water quality. The results show that the centre of Huixian Wetland receives recharge from surrounding groundwater, which is greatly affected by the surrounding water quality. The comprehensive water quality is relatively good in the dry season, relatively poor in the normal season, and the worst in the wet season. Agricultural production, non-point source pollution, rural domestic sewage, and human interference affect wetland water quality, which directly affects the structure and function of plant communities and the ecological service function of wetlands.
Water impact assessment of water stewardship activities at catchment scale: the case of the Lido Catchment in West Java, Indonesia	A	Fadillah	Indonesia	2023	artificial recharge, land restoration, water access, water stewardship, sustainability
Abstract Water stewardship is achieved through a stakeholder’s inclusive process. It aims to guarantee long-term water security for all uses, including nature. Various actions can occur in the watershed’s recharge area, such as land cover restoration and artificial recharges. To measure the effectiveness of these actions, it is crucial to quantify their impact on water and communities. The common method for assessing the benefits of water stewardship activities is the volumetric water benefit accounting (VWBA) method. It allows for comparing the positive impact on water to the extracted groundwater volume for operations. We present the validation of the Positive Water Impact of DANONE Aqua operation at the Lido Site in West Java, Indonesia, within the VWBA framework. Different methods were used to evaluate three main water impact activities: (1) land cover restoration with reforestation, (2) artificial recharge with infiltration trenches and wells, and (3) water access. The curve number of the SWAT model was used to measure the reduced runoff impact of the land conservation action. The water table fluctuation method was employed to assess artificial recharge volume. The volume of pump discharge rates was used for water access. Results highlight the water impact at the Lido site, with the volumetric accounting of the three main activities. The discrepancy in the final calculation can be related to the variation in the field’s validated activities. VWBA framework is useful to validate water stewardship activities’ impact and plan further impactful actions.
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.
The Atlantis Water Resource Management Scheme – Lessons in Resilience	L	Towers	South Africa	2023	adaptive management, Drought, Managed aquifer recharge, Resilience
Abstract The Atlantis Water Resource Management Scheme (AWRMS) has operated since the 1970s. It demonstrates cost-effective and wise water use and recycling through visionary town planning and Managed Aquifer Recharge (MAR), offering water security to Atlantis’s residential and industrial sectors. For the AWRMS to succeed, it required integrating its water supply, wastewater and stormwater systems. Each of these water systems is complex and requires a multidisciplinary management approach. Adding to the challenges of inter-departmental co-operation and communication within a municipal system is the complexity and vulnerability of the coastal, primary Atlantis Aquifer. A combination of operational difficulties, biofouling, vandalism and readily available surplus surface water (leading to scheme augmentation from surface water) were negative drivers to decrease the reliance on groundwater supply from the scheme’s two wellfields. In response to the 2015-2018 drought experienced in the Western Cape of South Africa, the City of Cape Town has improved assurance of supply from the scheme and successfully built resilience by upgrading knowledge and insight through improved investigative techniques, monitoring, modelling and adaptive management of the various water resources and associated infrastructure systems. An integrated and adaptive management approach is essential to ensure continued water security and resilience to the effects of on-going urban expansion, population growth and climate change. Resilience is assured by institutions, individuals and communities taking timely and appropriate decisions, while the long-term sustainability of the AWRMS depends on proper management of all actors coupled with a high level of scientific confidence.
Learning from complexity: Multi-stakeholder water resources management in the island of Santa Cruz, Galápagos (Ecuador)	Viviana	Re	Italy	2023	socio-hydrogeology, sustainability, technical cooperation, transdisciplinarity
Abstract The Galápagos Archipelago (Ecuador), traditionally considered a living museum and a showcase of evolution, is increasingly subject to anthropogenic pressures affecting the local population who has to deal with the challenges of accessing safe and sustainable water resources. Over the years, numerous national and international projects have attempted to assess the impact of human activities on both the water quality and quantity in the islands. However, the complexity of the stakeholders’ structure (i.e., multiple agents with competing interests and overlapping functions) and the numerous international institutions and agencies temporarily working in the islands make information sharing and coordination particularly challenging. A comprehensive assessment of water quality data (physico-chemical parameters, major elements, trace elements and coliforms) collected since 1985 in the Santa Cruz Island revealed the need to optimise monitoring efforts to fill knowledge gaps and better target decision-making processes. Results from a participatory approach involving all stakeholders dealing with water resources highlighted the gaps and potentials of water resources management in complex environments. Particularly, it demonstrated the criticalities related to data acquisition, sustainability of the monitoring plan and translation of scientific outcomes into common ground policies for water protection. Shared procedures for data collection, sample analysis, evaluation and data assessment by an open-access geodatabase were proposed and implemented for the first time as a prototype to improve accountability and outreach towards civil society and water users. The results reveal the high potential of a well-structured and effective joint monitoring approach within a complex, multi-stakeholder framework.
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.
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.
The connectedness of groundwater and human systems: a study of sacred wells in Ireland	Bruce	Misstear	Ireland	2023	Groundwater heritage, communication, holy wells, water and health
Abstract Sacred wells are found across the world yet are rarely studied by hydrogeologists. This paper will present the results of a 5-year hydrogeological study of holy wells in Ireland, a country with a relatively large number of these wells (perhaps as many as 3,000). It was shown that holy wells occur in all the main lithology and aquifer types but are more numerous in areas with extreme or high groundwater vulnerability. Water samples were collected from 167 wells and tested for up to 60 chemical parameters, including a large range of trace elements. Statistical analyses were performed to see if there were any statistically significant associations between the chemical constituents and the reputed health cures for the different well waters, and the results will be presented here. One of the issues in communicating the research findings to the general public is in explaining the small concentrations involved and the likely very small doses pilgrims at holy wells receive during their performances of faith. The spiritual dimension, including the therapeutic value of the landscape where the well is located, is likely an important aspect of the healing reputation.
Research-based exploration of deep groundwater within the eastern limb of the Bushveld Complex	Amy	Allwright	Bloemfontein, South Africa	2023	Bushveld Complex, Deep groundwater, deep scientific drilling
Abstract The current understanding of groundwater within the larger Bushveld Complex (BC) is evaluated to gauge the potential for deep groundwater, specifically emphasising the lesser investigated eastern limb. From the review of publicly available literature and data, geohydrological databases and statistical analyses are presented as a collation of the current understanding of groundwater in the eastern limb of the BC. Unfortunately, information on deep groundwater (> 300 m) is scarce due to the cost associated with deep drilling, mining exploration holes often neglecting hydrogeological data collection, or lack of public access to this information. Nevertheless, the conceptual model developed from the available information highlights deep groundwater’s variable and structurally controlled nature and the uncertainty associated with groundwater characterisation of the deeper groundwater systems. This uncertainty supports the need for research-based scientific drilling of the deeper fractured lithologies in the eastern limb of the Bushveld Complex. The Bushveld Complex Drilling Project (BVDP) established an opportunity to perform such research-based drilling and was funded by the International Continental Scientific Drilling Program (ICDP). While the main focus of the BVDP is to produce a continuous vertical stratigraphic sequence of the BC, there is a sub-component to collect geohydrological information. The planned borehole, 2 500 m deep, will provide an opportunity to collect information from the deeper systems within the Bushveld Complex and the underlying Transvaal Supergroup, which will inform on the connection between shallow and deeper groundwater.
From monitoring networks to near real-time groundwater forecast. A case study in Cape Town Table Mountain Aquifer, South Africa	J	Nicolas	South Africa	2023	Gardénia, MétéEau Nappes, Table Mountain Group, forecast, groundwater monitoring, modelling, near real-time
Abstract Groundwater level monitoring is essential for assessing groundwater’s availability, behaviour and trend. Associated with a modelling tool, groundwater level fluctuations can be predicted in the short to middle term using precipitation probabilities or meteorological forecasts. This is the purpose of the MétéEAU Nappes tool implemented by BRGM for the City of Cape Town (CoCT) in the Table Mountain Group Aquifer (TMGA). This case study shows how near real-time groundwater level monitoring can support the municipality in managing its future groundwater withdrawals. The TMGA is an important source of groundwater in the Western Cape region of South Africa. The upper Nardouw Sub-Aquifer of the TMGA is an unconfined aquifer recharged by rainfall. It had been monitored in the Steenbras area for over 10 years before CoCT started groundwater production from the Steenbras wellfield in 2021. The MétéEAU Nappes forecasting tool is already implemented on many observation wells of the French national piezometric network, where it is used for decision-making by the French administration. It allows, in particular, to anticipate several threshold levels of drought and take appropriate measures. It combines real-time water cycle measurement data with a groundwater level lumped model (e.g. Gardenia model) and extrapolates observations for the next 6 months from statistical meteorological scenarios completed with abstraction scenarios. This tool can help protect the Steenbras wellfield as a critical water source for CoCT in the TMGA. This study was financed by the French Agency for Development (AFD).
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
Well integrity assessment using fibre optic active distributed temperature sensing	M	Brown	Canada	2023	Active Distributed Temperature Sensing, fibre optic, multilevel monitoring well, well integrity
Abstract Groundwater quality and groundwater sample representativeness depend on the integrity of the water supply and monitoring wells. Well-integrity issues can occur by improper placement of grout seals behind the protective casing and/or by improper backfilling processes between ports. Multi-level monitoring systems are becoming common in the industry, providing depth-discrete groundwater samples and hydraulic head data from a single borehole. However, isolation between the monitoring intervals can be challenging when backfilled methods are used. No independent verification method exists to confirm seal placement for isolating monitoring intervals in such multi-level wells. A new approach using a hybrid fibre optic cable for adding heat, referred to as Active Distributed Temperature Sensing (A-DTS), is deployed in the annular space of a backfilled multi-level well. This new method is used to quantify the position of bentonite used as seals and sand packs that define the monitoring interval lengths and to identify issues associated with backfilling. A-DTS data from three boreholes with back-filled multilevel systems to 85 mbgs in a dolostone aquifer in Guelph, Ontario, Canada, demonstrates clear boundaries between backfill materials. In one interval, a deviation in the thermal data suggests a bridge in the bentonite seal, and this interval coincides with challenges in the backfilling from the field notes. The proposed method verifies well completion details, is repeatable and provides an efficient and effective way to assess well integrity impacting measurement uncertainty in a range of well types.
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.
Groundwater models for water resources assessment at regional, local and site scales	V	Price	England	2023	England, Groundwater/surface-water relations, numerical modelling, scale, water-resources Management
Abstract For 25 years, the UK’s Environment Agency has commissioned groundwater flow models of the main aquifers in England. These regional-scale models are regularly updated, occasionally recalibrated and used for water resources management, regulatory decisions and impact assessment of groundwater abstractions. This range of uses requires consideration of the appropriate scale of data collection and modelling and adaptation of the groundwater models, with refinement where local impacts on individual springs and seasonal streams are considered and combination and simplification for strategic national water resources planning. The Cretaceous Chalk, a soft white limestone, is the major aquifer of southern and eastern England, supplying up to 80% of the drinking water in this densely populated region. Springs and baseflow of good quality groundwater feed Chalk streams, which are a rare and valuable habitat with a high public profile, but face significant challenges in the 21st century, worsened by climate change and population growth. The modelling informs strategic planning and regulatory decisions, but the model’s scale needs to be appropriate for each issue. The presentation defines these issues and presents examples, ranging from the large-scale, strategic Water Resources East to impact assessment for individual groundwater abstractions and more bespoke local investigations, including simulation of groundwater flood risks. As the scale of investigations reduces, there is increasing importance on the accuracy of information, both temporally and spatially. Model refinement made during local investigations can be incorporated into larger-scale models to ensure that this understanding is captured.
Protecting groundwater resources in an era of geological carbon sequestration: A fractional stochastic model to predict pressure buildup due to CO2 injection into a saline aquife	H	Mbah	National	2023	Carbon Capture and Storage, CCS, CCS fractional operator, geological heterogeneity., injectivity, pressure buildup, saline aquifer
Abstract Carbon Capture and Storage (CCS) in deep saline aquifers is a viable option for Green House Gas (GHG) mitigation. However, industrial-scale scenarios may induce large-scale reservoir pressurization and displacement of native fluids. Especially in closed systems, the pressure buildup can quickly elevate beyond the reservoir fracture threshold and potentially fracture/ reactivate existing faults on the cap rock. This can create pathways, which could act as conduits for focused leakage of brine and/or CO2 up-dip and mobilization of trace elements into capture zones of freshwater wells. Careful pressure management can ensure the reservoir’s hydraulic integrity. This can theoretically be achieved through simulation with appropriate mathematical tools. This research aims to quantify pressure buildup at a CO2 injection well by applying fractional derivatives to the pressure diffusivity Differential Equation (PDE). A numerical solution has been developed to (1) predict and assess the consequence of pressure buildup within the storage formation on groundwater flow in shallow aquifers and (2) assess the impact of pressure-mobilized contaminants (CO2 , brine and/or trace elements) on the quality of usable groundwater, if there is a leakage. The efficiency of each derivative is shown to depend on the type of reservoir heterogeneity. The Caputo derivative captured the long tail dependence characteristic of fracture flow, while the ABC derivative was able to model the cross-over from matric into the fracture flow. The numerical tools presented here are useful for successful risk assessments during geo-sequestration in basins with freshwater aquifers.
Assessing the hydrogeology of springs, Heuningnes catchment, South Africa	Paula	Finini	Bellville, South Africa	2023	Spring yield, conceptual model, confirmatory analysis, volumetric analysis
Abstract Springs are examples of groundwater discharges. This paper reports on findings from cold springs groundwater discharges that have served as important water sources for sustaining domestic and agricultural supply. This study assessed the hydrogeology of springs to inform practical measures for the protection, utilization, and governance of such discharges. The research assessed the hydrogeology of springs in terms of conditions in the subsurface responsible for occurrences of springs spatially and their flow paths to the surface. Spring locations were mapped and validated for spatiotemporal assessment. The study examined the flow dynamics and hydrogeochemistry of spring discharges. In-situ and laboratory measurements of spring discharges were carried out using standard methods. Results showed that shallow and deep circulating systems of springs existed in the study area, being controlled by lithology and faults. All springs had fresh water of Na-Cl type, and rock-water interaction was the dominant geochemical process that influenced spring water chemistry. Radon-222 analysis showed high values detected in spring waters that confirmed recent groundwater seepage on the surface. The drum-and-stopwatch technique was used to estimate yield from spring discharges because it’s only effective and reliable for yields of less than 2 l/s. Results suggest that some springs were locally recharged with some regionally recharged. Based on results from estimated yield and quality, it was concluded that spring waters had low discharges. A comprehensive assessment of spring discharges should be conducted to generate large datasets to inform practical measures for protection, utilization, and governance.
Literature review on methodologies used to assess surface water and groundwater interaction	Aashna	Bissoon	South Africa	2023	Groundwater, case studies, methodologies, surface water, sustainable
Abstract A major surface water–groundwater interaction difficulty is the complex nature of groundwater resources due to heterogenic aquifer parameters. Wholistic research is needed to inform the conceptual understanding of hydrological processes occurring at surface and groundwater interfaces and their interactions at watershed scales. Sustainable water resource use and protection depend on integrated management solutions involving cross-disciplinary studies and integrated hydrological modelling. Choosing appropriate methods such as spatial and temporal scales, measurable indicators, differences in software parameters, and limitations in application often results in uncertainties. The study aims to conduct a comparative literature analysis, integrating case studies focusing on surface water–groundwater interaction. Literature reviews from case studies focus on several factors, including soils and vegetation studies, hydrochemical signatures, hydrodynamics of the main stem channels, desktop land use assessments, surface water quality profiling, conceptual hydrogeological modelling and numerical modelling in support of understanding surface water – groundwater interaction and highlight the challenges of methods used to indicate baseflow transition. This paper considers the methodologies demonstrated in the literature and their use in numerical modelling to obtain measurable indicators related to the two hydrological disciplines comprising (i) the surface water component and (ii) the groundwater component. These outcomes should be used to inform the potential future impacts on water quality from activities such as mining, irrigation, and industrial development. Water management protocols related to integrated surface water and groundwater studies for the future are critical in ensuring sustainable water management methods on a catchment scale.
Improving groundwater dynamics: A key factor for successful tidal marsh restoration.	N	Van Putte	Belgium	2023	HYDRUS, groundwater dynamics, macroporosity, tidal marsh restoration, water quality improvement
Abstract Along estuaries and coasts, tidal wetlands are increasingly restored on formerly embanked agricultural land to regain the ecosystem services provided by tidal marshes. One of these ecosystem services is the contribution to estuarine water quality improvement, mediated by tidally induced shallow groundwater dynamics from and to tidal creeks. However, in restored tidal marshes, these groundwater dynamics are often limited by compacted subsoil resulting from the former agricultural land use in these areas. Where the soil is compacted, we found a significant reduction of micro- and macroporosity and hydraulic conductivity. To quantify the effect of soil compaction on groundwater dynamics, we set up a numerical model for variably saturated groundwater flow and transport in a marsh and creek cross-section, which was parametrized with lab and field measurements. Simulated results were in good agreement with in situ measured groundwater levels. Where a compacted subsoil is present (at 60 cm depth), 6 times less groundwater and solutes seep out of the marsh soil each tide, compared to a reference situation without a compact layer. Increasing the creek density (e.g., through creek excavation) and increasing the soil porosity (e.g., by organic soil amendments) resulted in a significant increase in soil aeration depth and groundwater and solute transport. As such, these design measures are advised to optimize the contribution to water quality in future tidal marsh restoration projects.
Using the Groundwater Level Status approach for climate Impacts	Fanus	Fourie	South Africa	2023	Groundwater level; Status; water level fluctuation; risk; climate change; recharge
Abstract South Africa is known for droughts and their effect on groundwater. Water levels decrease, and some boreholes run dry during low recharge periods. Groundwater level fluctuations result from various factors, and comparing the levels can be challenging if not well understood. Fourie developed the “Groundwater Level Status” approach in 2020 to simplify the analysis of groundwater level fluctuations. Groundwater levels of two boreholes within different hydrogeological settings can thus be compared. The “Status” can now indicate the severity of the drought and thus be used as a possible groundwater restriction level indicator. The reasons for the groundwater level or the primary stress driver can only be determined if the assessment is done on individual boreholes and the boreholes according to hydrogeological characteristics. The analysis is used to identify areas of risk and inform the authorities’ management to make timely decisions to prevent damage or loss of life or livelihoods. The applicability of this approach from a borehole to an aquifer level is showcased through practical examples of the recent droughts that hit South Africa from 2010-2018.
Assessment of hydrochemistry and heavy metal contamination in the groundwater around an abandoned Copper Mine area in Klein Aub, Namibia	Shoopala	Uugulu	Namibia	2023	contamination, Copper, Heavy metal, Klein Aub
Abstract The long mining history in Namibia has resulted in numerous abandoned mines scattered throughout the country. Past research around the Klein Aub abandoned Copper mine highlighted environmental concerns related to past mining. Considering that residents of Klein Aub depend solely on groundwater, there is a need to thoroughly investigate groundwater quality in the area to ascertain the extent of the contamination. This study made considerable effort to characterise groundwater quality using a comprehensive approach of quality assessment and geostatistical analysis. Onsite parameters reveal that pH ranges between 6.82-7.8, electrical conductivity ranges between 678 - 2270 μS/cm, and dissolved oxygen ranges between 1.4 -5.77 mg/L. With an exemption of two samples, the onsite parameters indicate that water is of excellent quality according to the Namibian guidelines. The stable isotopic composition ranges from −7.26 to -5.82‰ and −45.1 to -35.9‰ for δ18O and δ2H, respectively—the groundwater plots on and above the Global Meteoric Water Line, implying no evaporation effect. Hydrochemical analyses show bicarbonate and chloride as dominant anions, while calcium and sodium are dominant cations, indicating groundwater dissolving halite and mixing with water from a recharge zone. The heavy metal pollution index of the groundwater is far below the threshold value of 100, which signals pollution; it contrasts the heavy metal evaluation index, which clustered around 3, implying that the heavy metals moderately affected groundwater. Copper, lead and Arsenic were the main contributors to the values of the indices.
Development of United Nations Framework Classification for Resources (UNFC) for Groundwater Resources Management	Peter	van der Keur		2023	SDGs, UNFC, common pool resources, subsurface geo-resources, sustainable groundwater resources management
Abstract There is an urgent need to support the sustainable development of groundwater resources, which are under increasing pressure from competing uses of subsurface geo-resources, compounded by land use and climate change impacts. Management of groundwater resources is crucial for enabling the green transition and attaining the Sustainable Development Goals. The United Nations Framework Classification for Resources (UNFC) is a project-based classification system for defining the environmental-socio-economic viability and technical feasibility of projects to develop resources and recently extended for groundwater. UNFC provides a consistent framework to describe the level of confidence in groundwater resources by the project and is designed to meet the needs of applications pertaining to (i) Policy formulation based on geo-resource studies, (ii) Geo-resource management functions, (iii) Business processes; and (iv) Financial capital allocation. To extend use in groundwater resources management, supplemental specifications have been developed for the UNFC that provide technical guidance to the community of groundwater professionals to enhance sustainable resource management based on improved decision-making. This includes addressing barriers to sustainably exploiting groundwater resources, avoiding lack of access to water and also related to ‘common pool resources’ in which multiple allocations are competing with domestic water supply (e.g. geo-energy, minerals, agriculture and ecosystems, and transboundary allocation of natural resources). UNFC for groundwater resources is designed to enhance governance to protect the environment and traditional users while ensuring socio-economic benefits to society. Consequently, it is a valid and promising tool for assessing both the sustainability and feasibility of groundwater management at local, national and international levels.
A mixing analysis to explore the distribution and behaviour of contaminants of emerging concern and regulated organic pollutants in the hydrogeological media. Case study: the endorheic catchment of the Fuente de Piedra Lagoon (Southern Spain)	M	Llamas	Southern Spain	2023	emerging contaminants, Groundwater, mixing model
Abstract An end-member mixing analysis has been conducted for the hydrogeological system of the endorheic catchment of the Fuente de Piedra lagoon (Malaga, Southern Spain). Three end-members have been considered because of the three main groundwater types related to the different kinds of aquifers found in the catchment. The model’s objective is to help understand the distribution of the organic contaminants (including contaminants of emerging concern [CECs]) detected in groundwater samples from the catchment. Results suggest that some contaminants can be related to long groundwater residence time fluxes, where contaminant attenuation can be limited due to low oxygen levels and microbial activity. The three main aquifer types are: (i) unconfined carbonate aquifers with low mineralized water corresponding to two mountain ranges with no human activities over theirs surface; (ii) an unconfined porous aquifer formed by Quaternary and Miocene deposits, exposed to pollution from anthropogenic activities (agriculture and urban sources); and (iii) a karstic-type aquifer formed by blocks of limestones and dolostones confined by a clayey, marly and evaporite matrix from Upper Triassic. The groundwater monitoring campaign for the analysis of organic contaminants was carried out in March 2018. Target organic contaminants included pharmaceuticals, personal care products, polyaromatic hydrocarbons, pesticides, flame retardants and plasticizers. For the mixing model, a dataset was built with the hydrochemistry and isotopic results (δ2 H, δ18O) from the monitoring campaign conducted in March 2018 and from campaigns carried out in previous years and retrieved from the literature.
Combined effects of seawater intrusion and nitrate contamination on groundwater quality in the coastal agricultural area of El-Nil River, Algeria	Lamine	Boumaiza	Algeria	2023	Coastal aquifer, Groundwater Quality, nitrate contamination, Seawater Intrusion, stable isotopes
Abstract This study focuses on the coastal agricultural area of El-Nil River (Algeria), where anthropogenic activities heavily impact groundwater resources. A multi-tracer approach, integrating hydrogeochemical and isotopic tracers (δ2HH2O, δ18OH2O, δ15NNO3 and δ18ONO3), is combined with a hydrochemical facies evolution diagram and a Bayesian isotope mixing model (MixSIAR) to assess seawater contamination and distinguish the nitrate sources and their apportionment. A total of 27 groundwater samples and 7 surface water samples distributed over the entire study area were collected. Results show classic inland intrusion combined with an upstream seawater impact through the river mouth connected to the Mediterranean Sea. Results from nitrate isotopic composition, NO3 and Cl concentrations, and the MixSIAR model show that nitrate concentrations chiefly originate from sewage and manure sources. Nitrate derived from sewage is related to wastewater discharge, whereas nitrate derived from manure is attributed to an excessive use of animal manure to fertilise agricultural areas. The outcomes of this study are expected to help decision-makers prepare suitable environmental strategies for effective and sustainable water resources management in the study area.
Aquifer storage and recovery (ASR) applications to enhance drinking water supply security in the Sultanate of Oman	Harmen	van den Berg	Oman	2023	Aquifer Storage and Recovery, Oman, desalinated seawater, drinking water supply, groundwater flow modelling, Hydrogeology, recovery efficiency
Abstract Water scarcity has driven many countries in arid regions, such as Oman, to desalinate seawater for freshwater supply. Episodic problems with seawater quality (e.g., harmful algae), extreme weather events that affect energy supply and hence the desalination process have nurtured the urgent need to store desalinated seawater (DSW) in the aquifers for use during emergency and peak demand time. Aquifer Storage and Recovery (ASR) using injection wells is a possible strategic option for Oman Water and Wastewater Services Company (OWWSC) to augment aquifer storage using excess desalinated water during low demand times. ASR strategically serves as a water supply backup to optimize production capacities against seasonal demand patterns. The technical-economic feasibility of implementing ASR schemes was investigated in Jaalan, Oman, using hydrogeological and geophysical field measurements, groundwater flow and hydraulic modelling, and economic analysis. Analysis of modelled scenarios results revealed that the Jaalan aquifer is suitable for storing and recovering about 4,000 m3 /hr in 2045. Various well field designs have been tested and optimized numerically using MODFLOW 6, showing that with 160 dual-purpose wells, 7.9 Mm3 can be injected and abstracted within the constraints defined for a robust and sustainable ASR system. Simulations with the density-dependent flow model (MF6 BUY) show that the injected volume can be fully recovered considering the drinking water quality standard. Other sites were also studied. ASR capacity was found to be site-specific, and the groundwater developments near the ASR site governed its feasibility
Hydrological processes in the Arctic catchment of Bayelva River (Western Svalbard-Norway)	Marco	Doveri	Norway	2023	Arctic hydrology, Climate change, groundwater-surface water evolution, melting water
Abstract Streamwater and groundwater are changing in the Arctic region because of significant climate warming. Arctic amplification has intensified the melting of snow cover, glaciers and permafrost, leading to a prominent variation in the annual discharge of rivers, the groundwater occurrence, and their relationships. In high-latitude regions, evaluating groundwater flux/storage and river discharge is challenging due to a lack of hydrogeological data. Changes in river flows and groundwater discharge will alter freshwater and terrigenous material flux, with implications for freshwater and marine ecosystems. Consequently, a more timely and accurate evaluation of surface and groundwater is required. In this framework, through the ICEtoFLUX project (MUR/PRA2021/project-0027), hydrology, geophysics and geochemical-isotopic surveys have been started during 2022 in the Bayelva River catchment (W-Svalbard) from its glaciers and periglacial/proglacial systems up to the Kongsfjorden. The study aims to quantify hydrologic processes and related transport of matter (solid transport, chemical solutes flux) and investigate how subsurface and surface waters interact during active layer development. The first results suggest that electrical conductivity and total suspended solids increase from glaciers to the Bayelva monitoring station, about 1 km from the coast. Seasonal evolution of physical-chemical features was also observed. Results from geophysics data and piezometers indicate that the underground flow is spatially and temporally heterogeneous, both quantitatively and from a physicochemical-isotopic point of view. Springwater characteristics testify to a deep and well-organized groundwater flow path system. This study highlights the high complexity of these systems and their high sensitivity to the meteo-climatic regimes.
Potential land use changes and wildfires effects over the spatiotemporal distribution of groundwater recharge at a regional scale: RAPReHS indicator accounting for SDG-13 in Bolivia	Monica Ximena	Guzmán Rojo	Bolivia	2023	Climate change, groundwater recharge, SDG
Abstract Having knowledge of spatiotemporal groundwater recharge is crucial for optimizing regional water management practices. However, the lack of consistent ground hydrometeorological data at regional and global scales has led to the use of alternative proxies and indicators to estimate impacts on groundwater recharge, enabling effective management of future water resources. This study explores the impact of land use changes and wildfires on groundwater recharge at a regional scale in Bolivia, using an alternative indicator to estimate variations in groundwater recharge rates. Based on a study by de Freitas L. in 2021, the methodology developed the annual groundwater recharge reduction rate (RAPReHS) utilizing remotely sensed data from the FLDAS and TERRACLIMATE datasets. The RAPReHS employs a simplified version of the water balance equation, estimating direct vertical groundwater recharge by considering the difference between precipitation, evapotranspiration, and runoff. The methodology was upscaled to improve data processing and analysis efficiency using an open-source cloud-computing platform (Google Earth Engine) over a 20-year period. The first results reveal a strong correlation between decreasing groundwater recharge rates and natural vegetation in the eastern region. By utilizing the RAPReHS index, forest preservation strategies can be prioritized. This study is in the framework of SDG 13 (Climate Action), which aims to mitigate the impacts of climate change on the environment and society. By exploring the impact of land use changes and wildfires on groundwater recharge at a regional scale in Bolivia, this research contributes to the inclusion of groundwater in policy guidelines for sustainable water management