Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 701 - 750 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort descending	Keywords
Managed Aquifer Recharge within the Greater Kruger National Park and Implementation of Recharge Scheme	Michael	Holloway	South Africa	2023	aquifer, Dolerite, Feasibility, Gneiss, Increased, Managed, recharge
Abstract West of the world-renowned conservation site, Kruger National Park, lies the larger extent of the Greater Kruger National Park within the Limpopo province. Boreholes have been drilled for decades to provide water to game lodges, large resorts, and watering holes for game viewing and livestock. The area contains both primary and secondary aquifers classified as having yields between 0.5 and 5.0 l/s, based on the geological setting, which consists of gneiss intruded by dolerite dyke swarms. A geohydrological assessment revealed that groundwater quality within the project area has an EC of 100 - 350 mS/m, linked to borehole proximity to surface water systems. The Makhutswi Gneiss and Doleritic Dyke swarms are the major controlling geology of the area, with higher-yielding boreholes close to dykes and major structural lineaments (faulted / weathered zones). A concern identified through geohydrological assessment observations is that boreholes frequently dry up after a few years, requiring deeper drilling/redrilling or drilling a new borehole. Aggressive calcium hardness in the water frequently damages equipment and increases maintenance costs. This project investigated the feasibility of increasing recharge to the aquifer with seasonal flooding/rainfall events by constructing artificially enhanced recharge locations overlaying doleritic dykes. This is expected to decrease the groundwater’s salinity and hardness, reducing operational costs. This pre-feasibility assessment has been completed, and the project has continued through a gradual implementation phase.
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).
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
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.
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.
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.
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
Groundwater potential and lateral connectivity of the Limpopo sand river system mitigating water scarcity and salinity in semi-arid Mozambique	P	Saveca	Mozambique	2023	Limpopo, aquifer connectivity, groundwater potential, salinity mitigation, sand river, semi-arid regions
Abstract In this study, we assess the potential of large riverbed aquifers in semi-arid Africa, known as sand rivers, to mitigate water scarcity and salinity for multiple-use water supply through a case study of the Limpopo River in Mozambique. Such sand river systems are widespread and still heavily underused at a regional scale, particularly in Mozambique, with the riparian vegetation currently being the primary user, though only consuming a minor fraction of available water. At a local scale, we performed geoelectrical surveys, water level measurements (in river and groundwater), as well as field physicochemical measurements and hydrochemical and isotopic sampling at 38 locations in the river channel, margins and up to 6 km away from the river, over five years. Results show that these shallow systems can be up to a kilometer wide and 15 m thick and, at some locations, can extend laterally beyond the river channel, below thin layers of clay and silt. Large areas of the sand river channel carry runoff yearly, providing optimal conditions for rapid recharge into the coarse sands with a high storage capacity. Connectivity between the river margin and channel is clearly shown at the local scale, even though sand pockets located further away appear isolated (revealed by geophysics), isotopically different and more brackish. Recharge, evapotranspiration and mixing processes are confirmed through hydrogeochemical modelling. The proven connectivity is highly relevant as groundwater is abstracted locally, promoting socio-economic development in water-scarce regions.
Sustainable establishment of localised groundwater supply systems at critical infrastructure for disaster preparedness	G	Kode	South Africa	2023	Western Cape Province, business continuity planning, critical facilities, disaster planning, localised groundwater supply systems, water resilience
Abstract Given the challenging global water outlook due to climate change and urbanisation, there is a heightened necessity for greater water resilience at critical facilities to tackle water disasters or disasters that lead to water crises. In 2017, the Western Cape Province of South Africa experienced an extended drought with the risk of acute water shortages. The Western Cape Government (WCG) developed business continuity plans and implemented a programme to ensure water supply to certain critical service delivery facilities, utilising the strategy of developing localised groundwater supply systems. The case study research of the WCG program enabled the development of an evaluation framework that assessed this strategy’s effectiveness in improving water resilience levels at critical facilities. From the lessons learnt in the WCG programme, the research also crystallised the critical success factors in sustainably implementing this strategy. The research showed that this is an effective strategy for its purposes and provides both current and future disaster preparedness planners with an improved understanding of the levels of water resilience achievable through this strategy and the methodology to achieve it best.
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.
How can collective groundwater resource management solutions benefit water governance at various levels? An example in a volcanic watershed in East Java, Indonesia	E	Cut	Indonesia	2023	groundwater governance, district level, collective solutions, stakeholders, volcanic watershed, Java Indonesia
Abstract On the slopes of Mount Bromo, East Java (Indonesia), the land use of the Rejoso watershed is dominated by rice fields and sugarcane ( lowland area ), agroforestry (midstream) and horticulture and pine plantation in the upstream part. During the last three decades, some land changes driven by socio-economic development, with conversion of agroforests to rice fields, tree monoculture and horticulture, and the development of urban areas nearby, increased pressure on the watershed. Intensive irrigated rice cultivation is using groundwater from free-flowing artesian wells. Due to a lack of management, the hydraulic head and discharge of the major spring are decreasing. Rejoso watershed, like others in urban and rural areas in Indonesia, is facing challenges to guarantee sustainable integrated water resources management. Collective solutions have been implemented between 2016 and 2022 within this watershed. In the downstream, sustainable paddy cultivation and wells management with local stakeholders, aiming at improving water efficiency, have been piloted on 65 ha with 184 farmers. Water governance at the district level was re-activated and strengthened thanks to the project. Various capacity-building tools were used via radio talk shows and workshops. Members of the watershed forum of Pasuruan took some actions to reshape the structure and set up a roadmap. The implementation of collective solutions in the field was a real catalyst and serves all levels of water governance, as it is replicable. This example will be explained and illustrated after the presentation of the socio-hydrogeological context.
Groundwater and surface water interdependencies in a water-scarce arid system, Sandveld, South Africa	L	Smit	South Africa	2023	Catchment, coastal wetlands, Groundwater, Hydrogeology, Management, surface water
Abstract The largely groundwater-dependent Sandveld region’s water resources have been put under severe strain due to increased agricultural and town development and recent increased interest in mineral exploration within these catchments. The area known locally as the Sandveld consists of the coastal plain along the west coast of South Africa, bordered by the Olifants River to the north and east, the Berg River to the south and the Atlantic Ocean coastline to the west. Groundwater is considered an essential source of fresh water for the town and agricultural supply. It also plays a major role in maintaining the functionality of the natural environment, especially concerning the coastal wetlands, such as the Verlorenvlei Wetland, designated as a Wetland of International Importance (Ramsar Site). Monitoring boreholes displayed a general drop in water levels, and a decrease in surface water flow has been reported. This has resulted in the drying up of wetland areas within the catchments. This investigation focused on conceptualising the geohydrological setting and defining the groundwater-surface water interactions and interdependencies. The assessment entailed a complete review and analyses of available hydrogeological and hydrochemical data and reports obtained through Stellenbosch University, the Department of Water and Sanitation and the private consulting sector. The priority groundwater areas were delineated, and recommendations on the regional management of these aquifers were made. The research characterised the geohydrological setting and outlined the Sandveld surface water systems’ dependency on groundwater baseflow and spring flow.
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.
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.
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.
Formation of the groundwater chemical composition in the Quaternary aquifer of the coastal valley (North Sinai, Egypt)	Natalia	Vinograd	Egypt	2023	Quaternary sediments, Sinai Peninsula, fresh water, Groundwater, groundwater–rock system, mineral water, physicochemical equilibrium
Abstract The research aims to reveal possible ways of formation of the chemical composition of mineral and fresh groundwater in Quaternary sediments of the coastal plain of Northern Sinai. Statistical assessment of the distribution of various hydrochemical indicators of mineral and fresh groundwater has been carried out according to the following data samples: 1) the general population for all Quaternary deposits (164 wells); 2) the central zone (74 wells); the eastern zone (25 wells); the western zone (65 wells). The following variables were assessed: total dissolved solids (TDS) (in ppm), concentrations of major components (in epm and % epm), pH value and the depth of the sampled well (ds) (in meters). The physicochemical equilibria between the groundwater and rock–forming carbonate and sulfate minerals were calculated using the PHREEQC software. Saturation indices (SI) for groundwater of three zones in relation to various rock-forming minerals were analyzed. Correlation relationships were obtained for TDS, major components and some genetic coefficients ((Requ=(Na++K+)/ (Ca2++Mg2+); Na+/Cl-; SO4 2-/Cl-; Ca2+/SO4 2-). It was concluded that the groundwater chemical composition is defined by infiltration recharge and/or intrusion of Mediterranean seawater. Most likely, during short-term flood periods, the infiltration into aquifers significantly exceeds the evaporation. Despite the relatively high evaporation rate, the degree of groundwater metamorphization is below the saturation level in relation to sulfates and carbonates. The research is of great practical importance for assessing freshwater resources to provide potable water supply
Continental-scale mapping of groundwater yield from basement aquifers in Africa	D	MacDonald	Africa	2023	Africa, aquifer mapping, basement aquifers, groundwater yield
Abstract Crystalline basement underlies much of Africa, and the groundwater within the shallow, weathered layer provides reliable drinking water for many people. This resource is key in adapting to changing climate, particularly in providing reliable water for drinking and smallscale irrigation. However, this requires higher yields from boreholes than currently abstracted. Renewed research is required to investigate sustainable yields from this type of aquifer and how it varies spatially. Recent work on crystalline basement rocks in Africa has shown that there are a number of important geological and geomorphological controls on shallow aquifer parameters; variability of geological properties and the impact of the landscape history is likely to have a strong control. Typically, the basement has experienced high metamorphic grades, which reduces intergranular porosity. Consequently, the aquifer relies on the presence of fault/ fracture zones; and the regolith’s depth and nature, which can have significantly higher porosity and permeability than the underlying bedrock. The interaction and variability of these key factors and climatic and landuse variables are likely to impact shallow aquifer productivity strongly. Here, we report on an ongoing study by UK and African scientists to understand how to represent the variability of geological, regolith and landscape factors across African crystalline basements. In tandem, a data-driven modelling approach is being used to examine these controls’ influence on groundwater yields. Continental-scale mapping of basement groundwater yield is planned, supporting those planning further aquifer development, including the growing use of solar-powered pumps.
Open access to digital groundwater and geodata supports the green transition and the spatial planning of competing subsurface uses	Klaus	Hinsby	Denmark	2023	FAIR data, UN SDGs, digital geoinformation, digital twins, geohazards, Groundwater, resources management, subsurface, sustainability
Abstract Modern societies rely heavily on subsurface resources and need open access to accurate and standardized scientific digital data that describe the subsurface’s infrastructure and geology, including the distribution of local and regional aquifers up to a depth of five kilometres. These data are essential for assessing and reducing climate change’s impact and enabling the green transition. Digital maps, 3D and 4D models of the subsurface are necessary to investigate and address issues such as groundwater quality and quantity, flood and drought impacts, renewable geo-energy solutions, availability of critical raw materials, resilient city planning, carbon capture and storage, disaster risk assessment and adaptation, and protection of groundwater-dependent terrestrial and associated aquatic ecosystems and biodiversity. For over a decade, EuroGeoSurveys, the Geological Surveys of Europe, has been working on providing harmonized digital European subsurface data through the European Geological Data Infrastructure, EGDI. These data are invaluable for informed decision-making and policy implementation regarding the green transition, Sustainable Development Goals, and future Digital Twins in earth sciences. The database is continuously developed and improved in collaboration with relevant stakeholders to meet societal needs and facilitate sustainable, secure, and integrated management of sometimes competing uses of surface and subsurface resources.
Tracer applications in an urban MAR (Rhine) scheme: Identifying the presence of regional groundwater in a complex geological setting	Jared	van Rooyen	Switzerland	2023	Isotopes, MAR, Online monitoring, Urban Groundwater
Abstract Managed aquifer recharge (MAR) has become increasingly popular in Central Europe as a sustainable, clean, and efficient method for managing domestic water supply. In these schemes, river water is artificially infiltrated into shallow aquifers for storage and natural purification of domestic water supply, while the resulting groundwater mound can simultaneously be designed to suppress the inflow of regional groundwater from contaminated areas. MAR schemes are typically not managed based on automated optimization algorithms, especially in complex urban and geological settings. However, such automated managing procedures are critical to guarantee safe drinking water. With (seasonal) water scarcity predicted to increase in Central Europe, improving the efficiency of MAR schemes will contribute to achieving several of the UN SDGs and EU agendas. Physico-chemical and isotope data has been collected over the last 3-4 decades around Switzerland’s largest MAR scheme in Basel, Switzerland, where 100 km3 /d of Rhine river water is infiltrated, and 40 km3 /d is extracted for drinking water. The other 60 km3 /d is used to maintain the groundwater mound that keeps locally contaminated groundwater from industrial heritage sites out of the drinking water. The hydrochemical/isotope data from past and ongoing studies were consolidated to contextualize all the contributing water sources of the scheme before online noble gas and regular tritium monitoring commenced in the region. The historical and the new continuous tracer monitoring data is now used to inform new sampling protocols and create tracer-enabled/assimilated groundwater-surface water flow models, vastly helping algorithm-supported MAR optimization
Unfolding the spatial heterogeneity of the natural background level of arsenic in groundwater at the mesoscale using data from sites under remediation	L	Landi	Italy	2023	Arsenic, Natural Background Level, Heterogeneity, sites under remediation
Abstract The Natural Background Level (NBL) of contaminants in groundwater is typically determined using regional-scale monitoring networks or site-specific studies. However, regional scale values are limited in their ability to capture natural heterogeneities that affect contaminant mobility at smaller scales, potentially leading to local over- or underestimation of the natural contaminant concentration. Conversely, site-specific studies can be expensive and time-consuming, with limited use outside the specified case study. To overcome this issue, a study was conducted in a 2600 km2 area, analyzing arsenic concentration values from monitoring networks of sites under remediation as an alternative source of information. The main drawbacks of the alternative dataset were the lack of information on monitoring procedures at the remediation sites or potential anthropogenic influences on the concentration data. However, these limitations were adequately managed with a thorough data pre-treatment procedure informed by a conceptual model of the study area. The NBLs estimated with the alternative dataset were more reliable than that from the regional monitoring network, which, in the worst case (i.e., in the area with the highest geological and geochemical heterogeneity), the NBL of one order of magnitude was underestimated. As a future step, the project seeks to incorporate geological and geochemical heterogeneities as secondary variables in a geostatistical analysis to produce a continuous distribution of arsenic concentrations at the mesoscale. This would provide a useful tool for managing contaminated sites and a reproducible protocol for NBL derivation in different areas, overcoming the scale issue.
Application of machine learning techniques to improve groundwater level predictions and optimization, West Coast, South Africa	N	Igwebuike	Cape Town, South Africa	2023	Groundwater Modelling, groundwater level., Machine learning, Managed aquifer recharge, Water security
Abstract Groundwater systems are complex and subject to climate change, abstraction, and land use stresses, making quantifying their impacts on aquifers difficult. Groundwater models aim to balance abstraction and aquifer sustainability by simulating the responses of an aquifer to hydrological stresses through groundwater levels. However, these models require extensive spatial data on geological and hydrological properties, which can be challenging to obtain. To address this issue, data-driven machine learning models are used to predict and optimize groundwater levels using available data. This paper argues that using machine learning to model groundwater level data improves predicting and optimizing groundwater levels for setting up a managed aquifer recharge scheme. The West Coast Aquifer System in South Africa was used as a case study. The neural network autoregression model was used for the analysis. Multiple variables such as rainfall, temperature, and groundwater usage were input parameters in the mode to facilitate predictions. Outputs from the model showed how machine learning models can enhance the interpretation of observed and modelled results on groundwater levels to support groundwater monitoring and utilization. In areas with high dependence on groundwater and where data on abstraction (use) and monitoring were scarce, results showed that feasible measures were available to improve groundwater security. Although the simulation results were inconclusive, the results provided insights into how the use of machine learning can provide information to inform setting up a managed aquifer recharge scheme.
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.
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.
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
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.
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.
Characterisation of the Lower Berg River Aquifer System, Western Cape, South Africa	A	Parker	South Africa	2023	Lower Berg River, aquifer, Discharge, Geophysics, Groundwater, Isotopes, recharge, Tritium
Abstract The Lower Berg River Aquifer System, situated in the Western Cape province of South Africa, is important to the towns that overlay it, as they rely on the aquifer for water supply, which supplements industrial development and residential growth. This aquifer system is important because surface water resources in the area are finite and fully allocated. Despite studies on the Lower Berg River Aquifer System since 1976, knowledge of the geological layers, recharge and discharge areas, and groundwater flow paths remain limited. This study aimed to provide greater insight and understanding of the aquifer to assist in better management. Investigations included a Time Domain Electromagnetic airborne geophysical survey, the assessment of groundwater levels, infiltration tests, hydrochemical analyses, and stable and radioactive isotope analyses. These methods allowed for the identification of the aquifer’s layers and extent, determination of water quality in different parts of the aquifer, delineation of flow paths through the saturated and unsaturated zones, identification of inter-aquifer flow, as well as different modes of recharge.
Investigation of Seawater Intrusion due to Group-Well- Pumping of a local coastal aquifer in Durban, South Africa.	Molla	Demlie	Durban, South Africa	2023	Eastern South Africa, Environmental Isotopes, group-well-pumping, Harbour Beds Formation, Hydrochemistry
Abstract The response of an alluvial and estuarine deposit aquifer, locally known as the Harbour Beds Formation, located in the coastal area of the Durban Metropolitan District to 48 hours of group well pumping is studied to understand its potential for groundwater supply and consequent seawater intrusion. Groundwater levels were monitored from the three pumped boreholes and piezometers. Similarly, EC, TDS and pH were monitored every hour from the boreholes and piezometers. Hydrochemical and water isotopes (2H and 18O) samples of groundwater were taken at 12, 18, 24, 36, 42 and 48 hours during pumping. The results indicate that the aquifer has a transmissivity, hydraulic conductivity and storativity of 48.97 m2/d, 1.7 m/day and 0.0032, respectively. The generally monitored EC, TDS, and pH have been fairly constant during the pumping period and didn’t show any seawater intrusion. Similarly, the hydrochemical data monitored for the three boreholes show general Na-CaHCO3-Cl-dominated groundwater throughout the pumping duration. However, uneven drawdown distribution and complex groundwater flow conditions indicate that the aquifer structure and hydraulic properties are heterogeneous. The water isotopes (2H and 18O) monitoring during the test pumping suggests spatial variability regarding water recharging the Harbour Beds aquifer. Though limited in area extent, the Harbour Beds Formation aquifer is a productive aquifer with acceptable water quality and can be a viable water source for domestic and industrial uses. However, continuous long-term monitoring of water quality and groundwater levels using data loggers is recommended to prevent induced seawater intrusion and contamination.
Groundwater 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.
A combined stochastic-analytical method for the assessment of climate change impact on spring discharge	Attila	Kovacs	Hungary	2023	Spring hydrograph, analytical model, Climate change, stochastic mode
Abstract This study describes a novel methodology for predicting spring hydrographs based on Regional Climate Model (RCM) projections to evaluate climate change impact on karstic spring discharge. A combined stochastic-analytical modelling methodology was developed and demonstrated on the Bukovica karst spring catchment at the Durmitor National Park, Montenegro. As a first step, climate model projections of the EURO-CORDEX ensemble were selected, and bias correction was applied based on historical climate data. The regression function between rainfall and peak discharge was established using historical data. The baseflow recession was described using a double-component exponential model, where hydrograph decomposition and parameter fitting were performed on the Master Recession Curve. Rainfall time series from two selected RCM scenarios were applied to predict future spring discharge time series. Bias correction of simulated hydrographs was performed, and bias-corrected combined stochastic-analytical models were applied to predict spring hydrographs based on RCM simulated rainfall data. Simulated climate scenarios predict increasing peak discharges and decreasing baseflow discharges throughout the 21st century. Model results suggest that climate change will likely exaggerate the extremities regarding climate parameters and spring discharge by the end of the century. The annual number of drought days shows a large variation over time. Extremely dry years are periodic, with a frequency between 5-7 years. The number of drought days seems to increase over time during these extreme years. The study confirmed that the applied methodology can successfully be applied for spring discharge prediction
Nitrate vulnerability assessment in the fast-growing African district of Abuja Federal Capital Territory (Nigeria)	M	Etuk	Abuja FCT, Nigeria	2023	DRASTIC-LU model, Groundwater Contamination, population growth
Abstract In the Federal Capital Territory of Abuja (Abuja FCT, Nigeria), a population growth of about 400% between 2000 and 2020 has been reported. This trend, coupled with the persisting urban sprawling, is likely to result in severe groundwater quality depletion and contamination, thus undermining one of the area’s main freshwater supplies for drinking purposes. In fact, groundwater in Nigeria and Abuja FCT provides over 70% of the drinking purposes. Results of a groundwater vulnerability assessment that compared land use data from 2000 and 2020 showed that the region had been affected by a dramatic change with an increase in urbanized (+5%) and agricultural (+27%) areas that caused nitrate concentrations to exceed the statutory limit for drinking purposes in more than 30% of the monitored wells in 2021 and 40% in 2022. Although fertilizers are generally considered the main source of nitrate contamination, results suggest a possible mixed (urban and agricultural) pollution origin and a legacy of previous nitrogen pollution sources. The comparison between the DRASTIC-LU map and nitrate concentrations shows that the highest values are found in urban/peri-urban areas, in both shallow and deep wells. This investigation is the first step of a comprehensive nitrate pollution assessment in the region, which will provide decision-makers with adequate information for urban planning given the expected population growth in the area
Coupling saturated and unsaturated groundwater models to represent the effect of intensive anthropogenic activities at the regional scale	H	Kupfersberger	Austria	2023	groundwater flow model, solute/heat transport model, saturated-unsaturated zone coupling, Leibnizer Feld aquifer, FEFLOW, land use
Abstract The abstract presents a 2D modelling approach alternative to a 3D variable saturated groundwater model of solute or heat transport at the regional scale. We use FEFLOW to represent processes in the saturated zone, coupled with various models describing the unsaturated zone. The choice of the latter depends on modelling needs, i.e. simulation of the movement of seepage water and nitrate fate with respect to crop rotation patterns and dynamic characteristics of heat gradients, respectively. The flexibility of coupling specialized models of different subsurface compartments provides the opportunity to investigate the effects of land use changes on groundwater characteristics, considering the relevant drivers in sufficient detail, which is important in regions with intensive anthropogenic activities. The coupling can be operated either with (direct coupling) or without (sequential coupling) including the feedback between the saturated and the unsaturated zones depending on the depth of the groundwater table below the surface. Thus, the approach allows for reasonable computational times. The Westliches Leibnitzer Feld aquifer in Austria (43 km²; Klammler et al., 2013; Rock and Kupfersberger, 2018) will be presented as an example highlighting the needed input data, the modelling workflow and the validation against measurements.
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.
ion of multivariate statistical analysis as a support for the delineation of groundwater bodies: a case study in coastal plain areas of Campania Region (Southern Italy)	S	Stevenazzi	Southern Italy	2023	coastal aquifers, statistical analysis, volcanic areas, Water chemistry
Abstract The identification of hydrogeological boundaries and the assessment of groundwater’s quantitative and qualitative status are necessary for delineating groundwater bodies, according to the European Guidelines. In this context, this study tries to verify the current delineation of groundwater bodies (GWBs) through hydrogeochemical methods and multicriteria statistical analyses. The areas of interest are three GWBs located in the northern part of Campania Region (Southern Italy): the Volturno Plain, a coastal plain constituted of fluvial, pyroclastic and marine sediments; the Plain of Naples, an innermost plain of fluvial and pyroclastic sediments and the Phlegrean Fields, an active volcanic area with a series of monogenic volcanic edifices. Hydrogeochemical methods (i.e., classical and modified Piper Diagram) and multivariate statistical analyses (i.e., factor analysis, FA) were performed to differentiate among the main hydrochemical processes occurring in the area. FA allowed the handling many geochemical and physical parameters measured in groundwater samples collected at about 200 sampling points in the decade of the 2010s. Results reveal five hydrogeochemical processes variably influencing the chemical characteristics of the three GWBs: salinization, carbonate rocks dissolution, natural or anthropogenic inputs, redox conditions, and volcanic product contribution. Hydrogeochemical methods and FA allow the identification of areas characterised by one or more hydrogeochemical processes, mostly reflecting known processes and highlighting the influence of groundwater flow paths on water chemistry. According to the current delineation of the three GWBs, some processes are peculiar to one GWB, but others are in common between two or more GWBs.
Identifying water sources of Verlorenvlei using stable isotopes and hydrochemistry	Angela	Welham	Elands Bay	2023	Groundwater, rainwater, semi-arid, stable isotope, surface water, Verlorenvlei, Water chemistry, wetland
Abstract Natural processes (e.g., El Nio) and anthropogenic activities (e.g., land-use modification and groundwater abstraction) drive local and global hydrological changes. Consequently, these changes threaten the role of wetlands in the hydrological and ecological functioning of a catchment. Verlorenvlei is a vulnerable RAMSAR-listed estuarine lake located on the west coast of South Africa in Elands Bay. Since the 2015-2018 Western Cape drought, Verlorenvlei has experienced drier-than-normal conditions with less rainfall, negatively impacting the surrounding ecology. Seasonal and spatial changes of the water sources (e.g., rainfall, surface water, and groundwater) supporting the wetland and the interconnectivity between these reservoirs were investigated using O/H stable isotopes and hydrochemistry analysis. The study collected event-based rainfall (57 samples), surface water (18 samples), and groundwater (108 samples) in February, April, and June 2022. Stable isotope ratios and hydrochemistry indicate that groundwater outside the watershed (topographically and surface water delineated) supports the wetlands, suggesting that local and regional groundwater flow systems influence the Verlorenvlei. Furthermore, the Verlorenvlei is subjected to high evaporation compared to other surface waters and, in return, is reliant on baseflow supporting its hydrological functioning. The Krom Antonies and Hol sub-catchments exhibit overlapping groundwater isotope ratios and water types compared to the Verloren sub-catchment, suggesting a disproportionately high groundwater contribution from both sub-catchments into the wetland. Understanding Verlorenvlei’s water balance is necessary to improve ecological reserve determination studies to help ensure environmental and socio-economic sustainable water use
The Roussillon coastal aquifer: using multiple-point statistics and multi-model ensemble to characterize geological uncertainty impact on water resources estimation	Valentin	Dall’ Alba		2023	Coastal aquifer, Groundwater Modelling, Multi-model ensemble, Uncertainty analysis
Abstract Coastal groundwater is a vulnerable resource, estimated to sustain the water needs of about 40% of the world’s population. The Roussillon aquifer is a regional aquifer near Perpignan (southern France). It covers over 800 km2 of land and is used for irrigation, drinking water, and industrial purposes. The aquifer has experienced significant piezometric lowering in the last decades, weakening the regional resource. An important aspect of modelling the hydrodynamic of this aquifer is the need to integrate data from agriculture and drinking water abstraction, natural and anthropogenic recharge, and account for the aquifer’s complex sedimentary arrangement. An ensemble of groundwater models has been constructed to understand the spatial evolution of the saline/freshwater interface and evaluate the impact of groundwater abstraction. Three sets of physical parameter modelling approaches were used. The first is based on the direct interpolation of pumping tests. The second uses sequential indicator simulations to represent the geological uncertainty. The third is based on a detailed conceptual geological model and multiple-point statistics to represent the detailed geological structure. These models provide parameter fields that can be input for the transient state hydrodynamic simulations. Overall, the ensemble approach allowed us to understand the Roussillon plain’s hydrological system better and quantify the uncertainty on the possible evolution of the main groundwater fluxes and water resources over the last 20 years. These models can help to inform management decisions and support sustainable water resource development in the region.
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.
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.
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.
Harmonized groundwater data in International River Basins under the Water Framework Directive (2000/60/EC) – Challenges	Belinda	Flem	Norway	2023	Harmonized data; monitoring; sampling techniques; analysis
Abstract Transboundary aquifers in Europe are managed according to the Water Framework Directive (WFD) through international river basin districts (IRBD) management plans. Paragraph 11 in the WFD states that each Member State shall ensure the establishment of a programme of measures, PoM, for each river basin district, RBD, or part of an IRBD within its territory. Easy access to harmonized data from neighbouring countries part of the aquifer is essential to analyse the groundwater status and make proper PoMs. The datasets must be available in machine-readable format via an Application Programming Interface (API) and, where relevant, as a bulk download. The metadata describing the data shall be within the scope of the Infrastructure for Spatial Information in the European Community (INSPIRE) data themes set. The datasets must also be described in a complete and publicly available online documentation describing the data structure. Using a questionnaire survey of nine European countries, groundwater sampling and analysis routines are compared to evaluate if data are comparable and accessible across borders.
An Overview of long-term groundwater development and management – 20 years of Hermanus wellfields	Kornelius	Riemann	South Africa	2023	Monitoring, groundwater management, wellfield development
Abstract Hermanus was originally supplied from springs and groundwater until the De Bos Dam was built in the 1950s. Due to increasing water demand, the municipality commenced wellfield development in 2002. The first wellfield comprised 3 boreholes, of which one borehole was later decommissioned due to reduced yield. Three additional boreholes were drilled recently to ensure abstraction capacity within the licence limits. A second wellfield was developed in the Hemel-en-Aarde Valley north of Hermanus. To ensure the sustainable management of the shared resource and minimise environmental impacts, a monitoring committee was established with all relevant roleplayers, other users, civil society, environmental groups and various commenting and regulatory authorities. A comprehensive monitoring network was established to assist with the scheme’s management and ensure that environmental impacts are minimized. The long-term monitoring (up to 20 years) shows that the groundwater abstraction from the Gateway Wellfield does not impact the environment and other users or increase the risk of saline intrusion. Identified impacts have been mitigated with the assistance of the monitoring committee. The municipality aims to provide at least half of the town’s water demand from groundwater and establish conjunctive use operation between surface water from the De Bos Dam and groundwater from these wellfields. The wellfields ensured sufficient water for the municipality when De Bos Dam’s water levels declined significantly during the Western Cape droughts in 2011 and 2017. The presentation will provide examples of the long-term monitoring records and trends.
Basin-scale transfer of nitrate pollution from groundwater to surface water in an intensively irrigated system	M	Rotirot	Italy	2023	Cl/Br ratio, Irrigation return flow, Po Plain, boron, dilution, stable isotopes
Abstract Basin-scale studies addressing the transfer of pollutants among groundwater and surface water bodies are essential to support local authorities in the sustainable management of freshwater resources. This work revealed that, in the hydro-system of the Oglio River basin (Northern Italy), nitrate pollution in groundwater, originated by overfertilization, is transferred downstream to surface water bodies via outflow through lowland springs and baseflow to gaining rivers. Downstream groundwater is unaffected due to reducing conditions that facilitate denitrification. It follows that efficient measures to reduce nitrate pollution in surface water bodies should not be applied solely to rivers/streams but, instead, they should include the upstream groundwater body. The work aimed at understanding nitrate pollution dynamics in an intensively irrigated hydro-system, focusing on the role played by the complex interaction among irrigation water, surface water and groundwater. The study relied on nitrate concentration, Cl/Br ratio, stable isotopic composition of water, nitrate and boron in groundwater, river, lake, spring, and rainwater samples. Results highlighted a well-defined spatial distribution of nitrate concentrations in groundwater, mainly driven by irrigation practices: (1) where groundwater-fed irrigation is done, return flow promotes high nitrate concentrations (>50 mg/L) due to groundwater recirculation; (2) where intensive surface-water-irrigation is practised, fed by low-nitrate river water, return flow generates lower nitrate concentrations (<50 mg/L) due to dilution. This work highlighted the importance of a holistic approach jointly investigating surface water, groundwater, and irrigation water when nitrate pollution is examined at a basin scale.
Machine learning as a tool to improve groundwater monitoring networks	D	Pacios	Spain	2023	Groundwater, Machine learning, monitoring networks, Nitrate, random forest, Spain
Abstract Machine learning techniques are gaining recognition as tools to underpin water resources management. Applications range widely, from groundwater potential mapping to the calibration of groundwater models. This research applies machine learning techniques to map and predict nitrate contamination across a large multilayer aquifer in central Spain. The overall intent is to use the results to improve the groundwater monitoring network. Twenty supervised classifiers of different families were trained and tested on a dataset of fifteen explanatory variables and approximately two thousand points. Tree-based classifiers, such as random forests, with predictive values above 0.9, rendered the best results. The most important explanatory variables were slope, the unsaturated zone’s estimated thickness, and lithology. The outcomes lead to three major conclusions: (a) the method is accurate enough at the regional scale and is versatile enough to export to other settings; (b) local-scale information is lost in the absence of detailed knowledge of certain variables, such as recharge; (c) incorporating the time scale to the spatial scale remains a challenge for the future.
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.
Findings from nearly three decades of groundwater monitoring in an area of intensive agriculture: Sandveld, West Coast, South Africa	Julian E	Conrad	Western Cape	2023	groundwater monitoring agricultural impact
Abstract The Sandveld (Western Cape, South Africa) is a critical potato production area on the national production scale, especially for table potatoes. As the area is situated on the continent’s West Coast, it is a dry area of low rainfall (less than 300 mm /a). The bulk of the irrigation water for agriculture in the region is derived from groundwater. Approximately 60 Mm3 /a of groundwater is abstracted for irrigation of potatoes in the broader Sandveld, assuming a 4-year rotation cycle. The abstraction of groundwater is a sensitive issue in the Sandveld as groundwater also plays a critical role in supplying water to towns in the area, water for domestic use, and it also plays a critical role in sustaining sensitive ecosystems (such as the coastal lake Velorenvlei). The groundwater resources have been monitored for nearly thirty years now. The results indicate areas where a slow but consistent decline in groundwater levels and groundwater quality is occurring. The trends can also predict when the aquifers will become depleted, and the groundwater will become too saline for use. This is critical information for management interventions to be implemented now to protect the area from irreversible damage.
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.
Delineating wellhead protection areas and aquifer vulnerability in the Cape Flats, South Africa	Brynn	Hunink	South Africa	2023	Aquifer vulnerability mapping, groundwater sustainability, Resource protection, Source protection, Wellhead protection areas
Abstract Prevention of threats to the quality and quantity of groundwater supply is critical to ensure its sustainability. Several African studies have shown that contamination of aquifers is primarily caused by improper placement of land-based human activities. Therefore, adequate preventative measures are required to safeguard the water quality of African aquifers to avoid long-term deterioration. Spatially explicit, 3D numerical groundwater modelling is a common methodology to assess contaminant transport. However, model development is time-consuming and complex. Contrastingly, DRASTIC-L is a 2D, GIS-based aquifer vulnerability mapping technique. The method is simple to apply, but analyses are qualitative and subjective. The study aims to compare both methods and to combine their strengths using GIS overlay. Overall, aquifer vulnerability was determined using the DRASTIC-L method, while wellhead protection areas were delineated using steady-state numerical modelling. This study focuses on the Cape Flats area due to its rapid development and growing municipal water supply supplementation needs. DRASTIC-L mapping revealed that aquifers in the Cape Flats are highly vulnerable to contamination due to the region’s unconfined hydrogeological properties, shallow water table and high-risk land use types. Moreover, groundwater vulnerability mapping combined with the delineation of wellhead protection areas allows for reduced uncertainty in the contamination potential of delineated groundwater protection zones. As a result, this study highlights the need for overall resource protection of the Cape Flats aquifers and provides insights into mapping out potential source protection areas of existing water supply wells.
The pharmaceutical compounds diversity at two river bank filtration sites located in Warta River valley (Poland)	Krzysztof	Dragon	Poland	2023	pharmaceuticals compounds; river bank filtration sites
Abstract Emerging contaminants (e.g. pharmaceuticals or pesticides) are increasingly detected in aquatic environments. The most apparent contamination source of river water pollution by pharmaceuticals is sewage treatment plant stations that discharge treated sewage effluent to the rivers. The river bank filtration systems (RBF) can effectively remove these contaminants. The two RBF sites were examined for pharmaceuticals: Śrem and Gorzów waterworks. The water samples for pharmaceuticals investigation were taken from the river and four continuously pumped wells at each site. Two wells near the river were chosen at each site (40-50 m) and two at a greater distance from the river (70 m in Śrem and 110 m in Gorzów). A visible increase in pharmaceutical concentrations was observed along the river. The sum of pharmaceuticals concentration is 8151 ng/l in Śrem (upstream), while in Gorzów (downstream) concentration is 9142 ng/l. A very big differentiation in pharmaceutical occurrence was observed. In Śrem, the sum of pharmaceuticals concentration is between 657 and 3290 ng/l, while in Gorzów, despite the higher concentrations of pharmaceuticals in the river, these substances were detected only in one well located at a close distance from the river (two substances at a concentration of 92 ng/l). The research proves a very big differentiation of pharmaceutical concentration even on sites located at similar hydrogeological conditions and demonstrates the necessity of its monitoring, especially in groundwater strongly influenced by river water contamination (like at RBF sites). This work has received funding from the National Science Centre Poland (grant no. 2021/41/B/ST10/00094).
Radical evolution of the Geneva transboundary aquifer agreement: an example for the sustainability of TBA governance?	Gabriel	de los Cobos	Switzerland	2023	Geneva aquifer, MAR, Climate change, Governance, transboundary aquifer agreement
Abstract The Geneva aquifer is internationally recognized for its transboundary resource management agreement between Switzerland and France, described as the first groundwater management agreement in the world. Signed in 1978 and renewed in 2008, this agreement on managing a shared underground resource has long been an example for establishing other agreements worldwide, particularly by UNESCO and its hydrological program via the TBA commission of the IAH. Like many countries worldwide, Switzerland and France experienced a critical summer of 2022 concerning the use of water resources, both surface and underground. The system applied in the cross-border agreement for using the aquifer involves French participation in the costs of managing aquifer recharge (MAR), depending on the total pumping. It shows that the French part, having consumed more water to compensate for the extreme drought of 2022, has seen its bills increase considerably. Development plans show that the population of Greater Geneva will increase considerably by 2030-2040, requiring significant medium-term water availability (30% additional water). Therefore, the French institutions’ political leaders have formally asked the authorities of the canton of Geneva to review the conditions linked to the quotas and calculation methods included in the 2008 agreement. A new agreement could be a real example of positive cross-border coordination for decision-makers finding themselves in a blocked or even conflicting situation due to differences in managing a shared resource revived by the effects of climate change.
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.