Conference Abstracts

Abstract

Groundwater is increasingly being exploited in South African cities as a drought crisis response, yet there is poorly coordinated regulation of increasing urban users and usage and fragmented management of aquifers. Designing interventions and innovations that ensure sustainable management of these resources requires systems thinking, where the city is understood as an integrated, interdependent set of actors and flows of water. This paper presents a study that applied and integrated an urban water metabolism (UWM) analysis with a governance network analysis for two major South African cities facing severe drought risk, Cape Town and Nelson Mandela Bay. ‘Learning Laboratories’ in each city brought together stakeholders from various groundwater-related domains to build a shared understanding of how groundwater fits into the larger system and how various actors shape urban groundwater flows and the health of local aquifers. The UWM quantified all hydrological and anthropogenic flows into and out of each city (or urban system) to conduct an integrated mass balance. How this mass balance changes under varying climate change scenarios and land use was used as a focal point of stakeholder discussions. The governance network analysis highlighted that many state and non-state actors have a stake in shaping the quantity and quality of urban groundwater, such as regulators, service providers, water users, knowledge providers, investors in infrastructure, and emergency responders.

Abstract

Groundwater is an essential source of water worldwide. The increased reliance on groundwater has caused the mining of many aquifers, a situation compounded by climate change, rising surface-air temperature, declining precipitation, and reduced groundwater recharge in many regions. The global annual intensity of groundwater use rose from 128 to 155 m3 per capita between 1950 (when the world population was 2.5 billion people) and 2021 (when the population was 7.9 billion people) and is herein projected to rise to 178 m3 per capita by 2050 as the world’s population is projected to increase (to 9.7 billion people by 2050) throughout the rest of the 21st century and beyond. This study projects a global annual groundwater depletion of 1,008 km3 by 2050, representing a 256% rise from the estimated 2010 depletion. This projection is most likely a lower bound of the actual groundwater depletion that would be realized considering environmental flows, historical trends of global economic growth, and climate-change impacts, thus being a harbinger of rising environmental degradation (e.g., land subsidence, seawater intrusion, streamflow reduction, aridification). Measures to achieve groundwater sustainability are herein identified.

Abstract

Water and contaminant transport processes in the vadose zone through preferential flow paths can be understood using environmental and artificial tracer methods. Further improvement in tracer techniques can be achieved by applying numerical modelling techniques of both water and solute transport, accounting for additional information on water movement and the matric potential of the vadose zone. The vadose zone is often ignored as a key component linking the land surface to the groundwater table, even though it acts as a filter that removes or stores potential contaminants. The water transit time between the surface and the groundwater table is frequently investigated using artificial tracers that normally show conservative behaviour. The main advantage is that the input function can be clearly defined, even though artificial tracers can generally only be applied over a relatively small area. The research is expected to provide insight into the selection and use of environmental and artificial tracers as markers for detecting and understanding the contaminant transport processes and pathways of contaminants in altered vadose zone environments (open-pit quarry). The impact is improved characterisation of the pathways, transport and migration processes of contaminants, and residence times, leading to the development of appropriate conceptual and numerical models of vadose zone flow processes that consider various contaminant sources. The principal aim is, therefore, to systematically examine the transport mechanisms and associated pathways of different environmental and artificial tracers in an open-pit quarry.

Abstract

atural water-rock interaction processes and anthropogenic inputs from various sources usually influence groundwater chemistry. There is a need to assess and characterise groundwater quality monitoring objectives and background values to improve groundwater resource monitoring, protection and management. This study aims to determine monitoring objectives and characterise monitoring background values for all monitoring points within the Soutpansberg region. This study used long-term groundwater quality monitoring data (1995- 2022) from 12 boreholes and 2 geothermal springs. Monitoring objectives were determined from land-use activities, allocated groundwater use, and water use sectors. Monitoring background values were determined from the physio-chemical parameters from each of the 14 monitoring points. This study determined monitoring objectives and background values of all monitoring points and all physio-chemical parameters in the Soutpansberg region. This study recommends reviewing the determined monitoring objectives and background values every 5 to 10 years to assess any change in land use, groundwater use and sector and monitoring data trends.

Abstract

Global warming affects atmospheric and oceanic energy budgets, modifying the Earth’s water cycle with consequent changes to precipitation patterns. The effects on groundwater discharge are still uncertain at a global and local scale. The most critical step to assess future spring flow scenarios is quantifying the recharge-discharge connection. This research aims to predict the long-term effects of climate change on the discharge of seven main springs with long hydrologic series of discharge values located in different hydrogeological settings along the Apenninic chain (Italy). The investigated springs are strategic for either public water supply or mineral water bottling. The Apennines stretch along the Italian peninsula in a Northwest-Southeast direction, crossing the Mediterranean area that represents a critical zone for climate change due to a decreased recharge and increased frequency and severity of droughts over the last two to three decades. In this communication, the data of one of the chosen springs, called Ermicciolo (42°55’25.8”N, 11°38’29.5”E; 1020 m ASL), discharging out from the volcanic aquifer of Mount Amiata, are presented. Statistical and numerical tools have been applied to analyse the time series of recharge-related parameters in the spring’s contribution area and the spring discharge from 1939 to 2022. To estimate the impact of climate change on the Ermicciolo’s outflow, a regional atmospheric circulation model has been downscaled to the spring catchment area and used to derive the expected discharge at the 2040-2060 time span, according to the build-up data-driven model of the recharge-discharge relationship in the past.

Abstract

To better understand the role of groundwater contribution to baseflow and EWR in groundwater protection and allocation, groundwater contribution must be quantified. Groundwater contribution to baseflow remains a challenge. Baseflow values have been widely used as groundwater contribution to surface water, which overestimates or underestimates the role of groundwater in the ecological ecosystem sustainability. To achieve the aim of the study, which was to estimate groundwater contribution to baseflow in a perennial river system at a catchment scale of the Upper Berg catchment, three objectives were taken into consideration: 1) To describe the hydrogeology of river morphology for groundwater-surface water interaction, 2) To estimate groundwater contribution to baseflow 3) To demonstrate the use of the background condition in setting resource quality objectives. Baseflow separation method using the Lynne & Hollick and Chapman algorithms, mass balance equation using EC as the tracer, field observation, and hydrochemical analysis methods were used to determine groundwater contribution to baseflow. Based on the hydrogeological cross-section presented, the fractures and faults of the peninsula geological formation dominating the study area predicted groundwater contribution to baseflow, which was confirmed by the calculations. The mass balance equation showed that 2,397 % of the 7.9 % baseflow index calculated at G1H076 and 19,093% of the 7.2% baseflow index calculated at G1H077 was groundwater. The background condition of the Upper Berg catchment was determined to be pristine with clean water.

Abstract

Micro-electro-mechanical system (MEMs) technologies coupled with Python data analysis can provide in-situ, multiple-point monitoring of pore pressure at discrete and local scales for engineering projects. MEMs sensors are tiny, robust, inexpensive, and can provide wireless sensing measurements in many electrical and geomechanical engineering applications. We demonstrate the development of MEMs pressure sensors for pore pressure monitoring in open boreholes and grouted in piezometers. MEMs sensors with a 60 m hydraulic head range and centimetre vertical resolution were subject to stability and drawdown tests in open boreholes and in various sand and grouts (permeability 10-8 to 10-2 m/s). The resulting accuracy and precision of the MEMs sensors, with optimal calibration models, were similar to conventional pore pressure sensors. We also demonstrate a framework for estimating in-situ hydrogeological properties for analysis from vented pore pressure sensors. This framework method included Python code analysis of hourly pore pressure data at the millimetre vertical resolution, which was combined with barometric data and modelled earth tides for each borehole. Results for pore pressure analysis in confined boreholes (>50 m depth) included specific storage, horizontal hydraulic conductivity and geomechanical properties. Future improvements in the vertical resolution of MEMs pore pressure sensors and combined these two technologies will enable groundwater monitoring at multiple scales. This could include the deployment of numerous MEMs, at sub-meter discrete scale in boreholes and evaluating local site scale variations in pore pressure responses to recharge, groundwater pumping and excavations in complex sub-surface geological conditions.

Abstract

Water resources, including groundwater, are under threat globally from abstraction and pollution, making studies of water flows ever more urgent. South Africa has a growing population, a relatively dry climate and abundant mining activity, all of which increase the importance of water management. Mooiplaas Dolomite Quarry, southeast of Pretoria, has been mining metallurgical grade dolomite since 1969 and is located in the productive karst aquifers of the Malmani Subgroup, Transvaal Supergroup. The site was investigated by sampling precipitation, surface water, groundwater and mine water for hydrochemical and stable isotope analysis from 2011 to 2017, totalling over 400 samples. Nitrate levels in groundwater and mine water were marginally above drinking water limits from explosives residues, and ammonia in the nearby Hennops River was unacceptably high due to municipal sewage outfalls, but otherwise, water quality was very good. Alkalinity from rock weathering, aided by the crushing of dolomite, was the main control on water chemistry. Combined analysis of dissolved matter (TDS, nitrate, Mg, etc.) suggested that the dewatering of the mine and resultant recharge from slime dams caused an aerated zone of groundwater, which mixed with regional groundwater flowing beneath the site. Stable isotopes, with an evaporated signature from mine open water bodies, also showed how mine operations cause recharge to groundwater and subsequent seepage back into the pit lakes. The mine appears not to contaminate the regional groundwater. However, mine designs should avoid situations where process water flows via groundwater back into pits, causing excessive dewatering costs.

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.

Abstract

This study presents a novel approach for developing geologically and hydrogeologically consistent groundwater models at large valley scales. Integrating geological, geophysical, and hydrogeological data into a single model is often challenging, but our methodology overcomes this challenge by combining the Ensemble Smoother with Multiple Data Assimilation algorithm (ESMDA) with a hierarchical geological modelling approach (ArchPy). The ESMDA framework assimilates geophysical and hydrogeological field data jointly. To diminish the computational cost, the forward geophysical and groundwater responses are computed in lower-dimensional spaces relevant to each physical problem, alleviating the computational burden and accelerating the inversion process. Combining multiple data sources and regional conceptual geological knowledge in a stochastic framework makes the resulting model accurate and incorporates robust uncertainty estimation. We demonstrate the applicability of our approach using actual data from the upper Aare Valley in Switzerland. Our results show that integrating different data types, each sensitive to different spatial dimensions enhances the global quality of the model within a reasonable computing time. This automatic generation of groundwater models with a robust uncertainty estimation has potential applications in a wide variety of hydrogeological issues. Our methodology provides a framework for efficiently integrating multiple data sources in geologically consistent models, facilitating the development of hydrogeological models that can inform sustainable water resource management.

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.

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.

Abstract

This work is part of the AUVERWATCH project (AUVERgne WATer CHemistry), which aims to better characterise some Auvergne water bodies, specifically the alluvial hydrosystem of Allier River (France). Alluvial aquifers constitute worldwide a productive water resource, superficial and easily exploitable. In France, 45% of the groundwater use comes from these aquifers. The study site is a wellfield that withdraws 8.5 million m3 of water annually from an alluvial aquifer to produce domestic water for 80% of the local population. At the watershed scale, precipitations have decreased by -11.8 mm/y, air temperatures have increased by 0.06°C/y and the river flow has declined by 20.8 Mm3 /y on 2000 – 2020. In the summer period, at least 50% of the river flow is ensured by the Naussac dam (upstream catchment part), but the recent winter droughts have not allowed the dam to replenish. Thus, water stakeholders are concerned that the productivity of the wellfield could be soon compromised. Based on geological, geophysical, hydrochemical, and hydrodynamic surveys, a numerical model of the wellfield is being developed using MODFLOW. The calibration in natural flow regime is successful using a range of hydraulic conductivities going from 1×10-3 to 1×10-4 m/s (pilot points method), consistent with the pumping tests. Preliminary results show that the river entirely controls the groundwater levels at all observation points. The perspective is now to calibrate this model in a transient regime by integrating domestic water withdrawals to determine how low the river can go without affecting the wellfield productivity.

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.

Abstract

Studies have examined the effects of groundwater pumping on nearby streams. Groundwater pumping affects streamflow, surface water rights, and aquatic ecosystems. This study investigates the impact of groundwater abstraction on surface water bodies. A secondary objective aims to develop a conceptual model to evaluate alternative approaches for streamflow depletion. The study area is a previous UFS/WRC test site along Modder River, Free State, South Africa. Streamflow depletion was simulated using four (4) analytical solutions, i.e., Jenkins (1968), Hantush (1964), Hunt (1999) and Hunt (2003). STRMDEPL08 analytical computer program tool is used to evaluate streamflow depletion. The aquifer parameters: distance of the boreholes to the stream; pumping periods analyzed in steady states conditions for a simulation period of 1 year; transmissivity with an average of 71 m/d; storativity of 0.02; specific yield of the aquitard range between 0.1 to 0.3; and abstraction rate of 2 l/s are defined for the hypothetical model. The average distances tested range from 10 m to 6,000 m. Pumping rate scenarios for an order of magnitude lower (0.2 l/s), 1 l/s; 4 l/s, and an order of magnitude larger (20 l/s) were simulated. Simulated graphs indicate that streamflow depletion rates are largest if the borehole is closer to the stream and decrease as the distance of the pumped borehole from the stream increases. Cumulative volume graphs for both analytical solutions decrease streamflow depletion volume

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.

Abstract

The Limpopo River Basin (LRB) is highly vulnerable to recurrent floods and droughts, significantly threatening its water and food security. Sustainable groundwater management is necessary to improve resilience. Scientists and stakeholders must collaborate to evaluate management scenarios that can identify sustainable practices. A transboundary basin-scale management instrument was developed using a multisector collaborative modelling approach to identify the role of groundwater in building resilience. The approach used an integrated hydro(geo)logical model, co-created through stakeholder workshops. The model assessed management scenarios identified during a series of local, national and transboundary stakeholders workshops, focusing on improving groundwater storage during wet periods for use during dry periods in a context of population growth and increasing groundwater reliance across the basin. Management scenarios: (1) increasing groundwater abstraction; (2) deforestation; (3) afforestation; and (4) managed aquifer recharge (MAR) using injection wells capturing excess water from major dams, rainwater harvesting through local ponds/ wells, and small water reservoirs. Analysis of scenario outputs suggested that local groundwater storage techniques, especially water harvesting and storage through small-scale water well recharge, were the most effective strategy in reducing the risk and impact of floods and drought at the basin scale. Upscaling this strategy can significantly increase groundwater levels across the basin, supporting increasing groundwater reliance. The study showed that the multisector collaborative modelling approach effectively co-creates management strategies and identifies appropriate and inclusive strategies to improve resilience in data-limiting conditions. The proposed modelling outcomes are useful in making informed decisions regarding water management and transboundary cooperation in the LRB.

Abstract

Per and Polyfluoroalkyl substances (PFAS) are ubiquitous on our planet and in aquifers. Understanding PFAS transport in aquifers is critical but can be highly uncertain due to unknown or variable source conditions, hydrophobic sorption to solid organic aquifer matter, ionic sorption on mineral surfaces, changing regulatory requirements, and unprecedentedly low drinking water standards. Thus, a PFAS toolkit has been developed to enable decision makers to collect the hydrogeologic data necessary to understand and better predict PFAS transport in aquifers for the purpose of managing water resources. This toolkit has been tested at a significant alluvial aquifer system in the western United States, which provides water for 50,000 people. Here, the toolkit has provided decision makers with the data necessary to optimize water pumping, treatment and distribution systems. The toolkit describes (1) the design and implementation of a sentinel well network to measure and track PFAS concentrations in the alluvial aquifer over time in response to variable pumping conditions, (2) data collection used to empirically derive input parameters for groundwater fate and transport models, which include the collection of paired aquifer matrix and groundwater samples, to measure PFAS distribution coefficients (Kds) and modified borehole dilution tests to measure groundwater flux (Darcy Velocity) and (3) the use of data collection techniques to reduce cross contamination, including PFAS-free, disposable bailers and a triple-rinse decontamination procedure for reusable equipment. The PRAS transport toolkit has the potential to assist decision makers responsible for managing PFAS contaminated aquifers.

Abstract

Technological advances in recent years provide a unique opportunity to adopt new instruments for groundwater monitoring to reduce operating costs, obtain higher measuring accuracy and reliability, and accomplish comprehensive real-time monitoring. Microelectromechanical system (MEMS) technology enables small and low-cost energy-saving microsensors and integration with IOT for real-time monitoring. This presentation will discuss the findings of the performance of a newly developed instrument based on a MEMS piezoresistive pressure sensor. We demonstrate a path forward for the expansion of this research. The sensor is designed to be applicable to both open and closed systems for measuring groundwater level and pore water pressure. Tests show that MEMs (0-689 kPa range) can obtain full-scale accuracy between 0.2-0.3% in groundwater level prediction. However, the measurement result mainly depends on the appropriateness of the calibration method. Regarding pore pressure measurement under sealed conditions by gravel sand and cement-bentonite grout, a full-scale accuracy between 0.3% and 0.725% is accessible, depending on the backfill material. However, it was evident that backfill materials have considerable effects on the response time and accuracy of measurement, in which a stiff and less permeable grout can increase inaccuracy and time lag in measurement. Overall, the initial results have shown a promising future for this technology in groundwater monitoring. However, more tests and analyses are still required to improve sensor design, energy consumption for IOT applications, wireless module, installation system and its specifications such as accuracy, conformance, precision, and stability.

Abstract

Climate change is expected to have a significant impact on freshwater resources across the globe. Changes in the distribution and quantities of rainfall over the coming decade will impact various earth systems, such as vegetation, contributions to streamflow, sub-surface infiltration and recharge. While groundwater resources are expected to act as a buffer, changes in rainfall will ultimately impact the recharge process and, thus, groundwater reserves. Understanding these changes is a crucial step to adapt better and mitigate climate change’s impacts on water resources. This is valid in South Africa, where much of the population depends on groundwater as a freshwater supply. Hence, this research presents the status quo regarding climate change’s impacts on South Africa’s groundwater resources. Reviewing relevant literature, the impacts on recharge, groundwater quantity (storage changes), discharge and groundwater-surface water interactions, groundwater quality, and groundwater-dependent ecosystems are discussed. In addition, utilizing factors such as rainfall, slope and vegetation cover collected from CMIP6 climate projections, changes in groundwater recharge potential from the past through the present and future are demonstrated. The findings illustrate uncertainty over the long-term impacts of climate change on groundwater for different regions and various aquifers. However, global warming could lead to reduced recharge, which impacts groundwater reserves.

Abstract

Unicef is the WASH sector lead globally and is, present at the country level, the main counterpart of government, especially regarding the component of the water balance utilised for potable safe water supplies. This mandate means that Unicef then has a role in looking at water resources nationally and not just as individual projects, and in doing so, contributes to good water governance as an integral part of system strengthening. Ensure this is done in partnership with other ministries and stakeholders that support them through advocacy for humanitarian and developmental access and support in technical areas such as groundwater assessments and monitoring. The focus on groundwater is especially linked with the fact that groundwater plays a major role due to its buffering capacity to climate variations, easier access and global coverage. Since groundwater is the most significant component of accessible freshwater resources, it is in the interest of UNICEF to make this resource more visible to meet both development and humanitarian goals, strengthen national systems and ultimately build resilience in mitigating water scarcity to scale or at the National level. Therefore, examples will be presented where Unicef has engaged on this journey with nations such as Afghanistan, Yemen, Mozambique and Rwanda to understand their water resources better. The overall objective at the National level is to adapt the capacity to withstand and recover as quickly as possible from external stresses and shocks or build resilience.

Abstract

The City of Windhoek in Namibia has developed wellfields and a managed aquifer recharge scheme within the fractured Windhoek Aquifer to ensure a sustainable potable water supply to the city during drought. A three-dimensional numerical groundwater model of the aquifer was developed using the finite-difference code MODFLOW to determine the potential impacts of varying pump inlet depth elevations and varying production borehole abstraction rates for optimal wellfield and aquifer management. The initial steady-state numerical model was calibrated to September 2011 groundwater levels, representing the best approximation of “aquifer full” conditions (following a good rainfall period and best available data). The subsequent transient numerical model was calibrated against groundwater level fluctuations from September 2011 to August 2019, the period after steady-state calibration for which data was available (and during which monitored groundwater abstraction occurred). The calibrated transient model was used to run various predictive scenarios related to increased emergency groundwater abstraction and estimate potential impacts on the Windhoek Aquifer. These predictive scenarios assessed groundwater level drawdown and recovery, aquifer storage potential, and potential abstraction rates under different pump elevations. Model results indicated a sharp initial groundwater level drop followed by a gradual decrease as groundwater levels approached the 100 m saturated depth mark. Pumping elevations were subsequently updated with recommended abstraction rates and volumes for the entire Windhoek Aquifer. The numerical groundwater model, in association with extensive groundwater monitoring, will be used to assess/manage the long-term sustainable and optimal utilisation of the Windhoek Aquifer.

Abstract

Communities in the Lower Shire River Valley in the Chikwawa District of southern Malawi face extreme development challenges due to highly variable climate, including floods and droughts, that trap them in poverty and food insecurity. The area has been the focus of numerous studies and data collection campaigns to understand better the causes and processes associated with brackish groundwater (in alluvial aquifers) and dry boreholes. An applied groundwater assessment was performed to evaluate water supply alternatives and solutions to deliver potable water to approximately 15% of the district without water access after a multi-year campaign to reach 100%. The assessment synthesized a significant volume of water quality data collected by researchers and nongovernment organizations, larger scale geological interpretations published in segmented literature, multi-spectral satellite imagery datasets, and combined field reconnaissance to investigate areas of interest further and address pertinent data gaps. Improved understanding of geologic structure and lithology, complex aquifer recharge, and evapotranspiration processes supported identifying areas unsuitable for groundwater development and yielded recommendations for groundwater exploration and other solutions.

A high permeability zone and strong surface-groundwater connection was identified along the Gungu River. Data collected throughout the area of interest corroborated that significant freshwater recharge occurs in the alluvial aquifer, promoting an aquifer zone where freshwater and higher yields are likely. Exploratory drilling resulted in a very high-yielding freshwater well that supported the development of a piped water system serving several villages.

Abstract

Groundwater is an important freshwater supply that has a significant role in the economy. However, water is increasingly becoming scarce in several regions. Huai Krachao Subdistrict in Kanchanaburi Province is an example of an area that has been experiencing a severe drought for decades due to the impacts of climate change. This study was conducted to delineate the groundwater potential zones in hard-rock terrains using geographic information system (GIS) techniques. The study aims to explore deep groundwater resources in challenging areas and propose alternative methods supporting traditional groundwater exploration. This finding revealed that the groundwater potential zones were classified into high, moderate, and low potential zones based on the groundwater potential index (GWPI), integrated using the Weighted Index Overlay Analysis. The computed weights from the Analytical Hierarchy Process were acceptable and consistent. The high potential zones mainly occur in the Silurian-Devonian metamorphic rocks. The GIS-based analytical results were later prepared for detailed field investigation, including collecting well information and conducting the 2-dimensional geophysical survey. To prove the GWPI map, 9 groundwater wells were drilled in the high potential zones. Consequently, well yields obtained from the pumping-test analysis ranged from 24-40 m3 / hr, some of which are springs rich in dissolved minerals. Accordingly, a significant amount of water could meet the water demand, supplying about 1 million m3 /year. Under these circumstances, discovering new groundwater resources can support roughly 5,000 people and agricultural lands no less than 480 hectares (4.8 km2 ).

Abstract

Groundwater in flooded abandoned mines could be used for geothermal purposes using heat pumps and an open loop involving pumping and re-injection. Hydraulic conductivity values of the mined rock zones have been artificially increased. However, long-term efficiency and the possible impacts of geothermal doublets must be studied involving a series of hydrogeological challenges. Hot water would be pumped from the deep parts of the mine works, and cold water would be re-injected in a shallower gallery or shallow fractured rocks, with a seasonal flow inversion for building cooling during the hot season. Indeed, a ‘short-cut’ groundwater flow is to be avoided between the mine’s deep and shallow parts. The true geometry of the interconnected network of open galleries and shafts can be highly complex and must be conceptualized realistically to ensure that the model is feasible and reliable.

This model must involve groundwater flow and heat transport, with temperature-dependent density and viscosity, in a complex 3D heterogeneous domain of highly fractured rocks and partially collapsed exploitation zones, galleries, and shafts. Such a model is nevertheless widely recommended to design and optimize the short--, mid-, and long-term efficiency of the geothermal system and assess possible environmental impacts. An example of simulations on a synthetic case will be used for illustration and preparation work before further application in a real case study.

Abstract

Water budget assessment and related recharge in karstified and fractured mountainous aquifers suffer a large uncertainty due to variable infiltration rates related to karst features. The KARMA project (karma-project.org), funded by the European Commission, has addressed this knowledge gap. The increase in human withdrawals and the effect of climate change can modify the recharge rate and, consequently, the spring discharge. The regional aquifer of Gran Sasso mountain, Central Italy, has been investigated by monitoring spring discharge isotope composition and calculating the inflow using a GIS approach on 100x100 m cells, considering local conditions, including karst features. The results for the 2000-2022 period highlight the preferential recharge area of the endorheic basin of Campo Imperatore (up to 75% of precipitation) and a mean infiltration of about 50% of rainfall. Different methods applied for recharge evaluation (Turc, Thornthwaite and APLIS) agree with a recharge rate close to 600 mm/year. This amount roughly corresponds to the spring discharge, evidencing: i) a “memory effect” in spring discharge, which is higher than previewed during dry years; ii) a variation in discharge due to rainy and drought year distribution, frequently recorded at springs with delay (1-2 years); iii) no significant trends of spring depletion since last 20 years; iv) the risk of lowering of snow contribution to recharge due to the temperature rise. The results provide updated information to the drinking water companies and the National Park Authority for sustainable management of the available groundwater resources.

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.

Abstract

Groundwater is a vital freshwater source, and its role in meeting water demands will become pivotal under future climate change and population growth. However, groundwater supply to meet this demand is at risk as aquifers can be rapidly contaminated, and the cost of aquifer rehabilitation and/or sourcing alternative water supplies can be high. The development of groundwater protection schemes is required to ensure long-term protection of groundwater quality and sustainable groundwater supply. A groundwater protection scheme is a practical and proactive means to maintain groundwater quality and forms an additional methodology for groundwater resource management/protection. There are no legislative guidelines on establishing groundwater protection schemes in water-scarce South Africa, despite groundwater being used extensively. Three groundwater protection schemes were designed and implemented to protect abstraction from a fractured aquifer in an undeveloped natural mountain catchment and two primary aquifers within different urban settings. The approach incorporated protection zone delineation (comprising four zones), aquifer vulnerability mapping/ ranking using the DRASTIC method (with the primary and fractured aquifer systems having varying vulnerabilities), and identification of potentially contaminating activities (which also vary significantly between the urban areas overlying the two primary aquifers, and the generally undeveloped natural mountain catchment fractured aquifer is situated within). Additionally, a protection response was established to determine monitoring frequencies. Practical insights into the design and implementation of these three groundwater protection schemes can serve as a model for implementation in other African aquifer systems.

Abstract

The beneficial groundwater use in the Southern African Development Community (SADC) is well documented. Groundwater plays a vital role in the freshwater supply mix and, in some cases, is the only source of freshwater, especially in the arid region of SADC. However, the management of this resource is hampered by numerous challenges, such as lack of data, limited tools to leverage available data, lack of resources, institutional mismanagement, and climate change, amongst others. Of these challenges, the lack of data and the tools needed to transform this data into information has consequences for the decision-making process. Hence, this research attempts to address this challenge by demonstrating the use of big data and artificial intelligence (AI) to fill data gaps with new unconventional sources and model groundwater processes to transform data into actionable information. The presentation focuses on introducing the landscape of groundwater big data in SADC, followed by a review of regional AI applications. After that, novel approaches to using AI in various aquifers across SADC are demonstrated in their applicability to support groundwater management. Finally, the challenges facing the use of AI in SADC are discussed, followed by opportunities for new research based on the current state-of-the-art AI techniques. The results illustrate that AI can be a helpful tool for supporting groundwater management in SADC. However, the need for enhanced data collection is evident for these techniques to be generally applicable.

Abstract

Groundwater quantity and quality of shallow aquifers have deteriorated in recent years due to rapid development that has created an increased demand for drinking water, which is increasingly being fulfilled by groundwater abstraction. The study evaluates the hydrogeological framework of the Quaternary aquifer of the Kabul basin, Afghanistan, and the impact of urbanization on the groundwater resources around the Kabul city plain. Time series of Landsat satellite LCLU images indicate that the urban area increased by 40% between 2000 and 2020, while the agricultural area decreased by 32% and bare land decreased from about 67% to 52% during this period. The assumed groundwater overdraft 2019 was 301.4×103 m3 /day, while the recharge was 153.4×103 m3 /day, meaning a negative balance of about 54 million cubic meters (MCM) this year. Due to the long-term decline of water levels at 80 90 cm/year, and locally (Khairkhana, Dasht-e-Barchi) 30-50m during 2005-2019, a considerable groundwater drawdown is shown. Groundwater quality, on the other hand, reveals that chloride concentrations and salinity increased throughout the aquifer between 2005 and 2020. The nitrate concentration decreased in most Kabul Plain places over the period. In conclusion, the quantity and quality situation of urban groundwater in Kabul is worrying; urgent scientific and sustainable solutions and measures should be considered to manage this situation.

Abstract

Although methane occurrences have been documented in Karoo groundwater in the past, the advent of possible unconventional oil and gas extraction now made it important to determine the type and origin of this methane to assess the possibility of shallow-deep groundwater interaction. During groundwater surveys from 2016-2021, methane was detected at three sites in the Western Karoo: the Soekor sites KL1/65, QU1/65 and an unidentified shallow groundwater borehole (BHA). The Soekor wells were drilled in the 1960-1970s to depths of between 2500-3500 meters in South Africa’s search for oil. On the other hand, Borehole BHA was drilled in 1998 and only up to a depth of 298m. This study aimed to determine methane’s origin through gas and isotope analyses. To do this, groundwater, rock and soil samples were analysed to determine whether the methane is thermogenic or biogenic and its origin. We determined that methane was both thermogenic and biogenic and probably originated from different layers of the Karoo formations and that mixing occurs between deep and shallow aquifer systems at these Soekor sites. This information was used to develop a final conceptual model of what the Karoo underground system might look like and to make recommendations for establishing a groundwater baseline.

Abstract

Darcy Velocity (Vd) is often estimated through a single-borehole Point Dilution Tracer Test (PDTT). Vd is used in the investigation of contaminant transport and distribution in aquifers. The tracer dilution rate in groundwater is controlled by horizontal groundwater flux. However, it can be affected by other artefacts, such as diffusion and density effects. Although there are studies on tracer tests, there has not been much done to gain an understanding of how these artefacts affect the correct Vd estimation. This study, therefore, aims to investigate and provide an understanding of the influence of artefacts on the PDTT through laboratory experiments conducted using a physical model representing a porous media. A total of 18 experiments were performed with different NaCl tracer concentrations under constant horizontal groundwater flow and no-flow conditions. The study results show that the density sinking effect affects an early period of tracer dilution, which can lead to overestimation of Vd; therefore, these stages should not be used to estimate Vd. The study, therefore, proposes a way in which PDTT data should be analysed to understand the effects of artefacts on Darcy velocity estimation.

Abstract

Year-round water security is at risk as socio-economic developments lead to increasing water demands, while climate change affects water availability through higher-intensity rainfall and prolonged periods of drought. Coastal zones and deltas with often high population densities experience additional risks of salinisation and land subsidence. These developments ask for creative solutions to secure sustainable and year-round access to fresh water. The subsurface provides storage capacity to actively infiltrate freshwater, bridging the time-gap between demand and supply. Combining infiltration with extraction and desalination of brackish water prevents the salinisation of aquifers whilst providing an additional water source. We call this COASTAR. A Dutch research consortium with partners like water companies and water boards develops COASTAR. Among COASTAR results are suitability maps for Aquifer Storage and Recovery (ASR) and Brackish Water Extraction (BWE) in the coastal zone of the Netherlands. The maps are based on geohydrological factors. A quick-scan analysis was also performed to quantify the nation-wide potential extractable ASR and BWE volumes. COASTAR develops case study models and local scale pilots on ASR and BWE. For two water supply regions, an analysis has been made to geographically match development in water demand with suitability for ASR and BWE as a step in the search for strategic locations to develop ASR and BWE. The suitability maps provide guidance for initiatives’ development and practical experiences from pilot projects; this provides important information for further upscaling of COASTAR approaches.

Abstract

A hydrogeological investigation was conducted at a gold mine in the Mandiana region, northeast Guinea. The objectives of the investigation included: 1) Review the efficiency of the current dewatering system and 2) Assess potential dewatering impacts on neighbouring groundwater users. Historical and current hydrogeological information were reviewed and assessed to address the project objectives. The site geological succession contains laterites, saprolites, saprock, dolorite sill and fresh fractured bedrock below. A review of the borehole lithological logs, pump test and monitoring data confirmed that the contact zone between the saprock and the dolorite sill is the major aquifer zone with hydraulic conductivity up to 25 m/d, with a minor alluvial aquifer with hydraulic conductivity ~ 0.05 m/d. The current dewatering system is not as effective as it should be due to electrical issues causing seepage into the current pit floor. A combination of in-pit sumps and dewatering boreholes is recommended to ensure the mine pit’s dry working conditions. The neighbouring groundwater users tap into the alluvial aquifer with water levels ranging between 0-10 mbgl and are not at risk from mine dewatering impacts due to the dewatering boreholes tapping into the deeper saprock-dolorite contact zone. The shallow and deeper aquifers are hydraulically disconnected. The following is recommended: 1) Drilling of replacement dewatering boreholes and implementing continuous water level and abstraction rate monitoring, and 2) Discharge the in-pit sumps (alluvial aquifer inflow and rainfall) into the river downgradient of the mine to supplement recharge to the alluvial aquifer.

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.

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.

Abstract

The City of Cape Town (CCT) initiated its “New Water Programme” in 2017 (during the major 2015-2018 “Day Zero” drought) to diversify its bulk water supply, thereby improving longterm water security and resilience against future droughts. This includes bulk groundwater abstraction from the major fractured Peninsula and Nardouw Aquifers of the Table Mountain Group (TMG) in the mountain catchments east of the CCT. The TMG aquifers are essential in sustaining groundwater-dependent ecosystems associated with the Cape Floral Kingdom – a global biodiversity (but also extinction) hotspot with exceptional endemic diversity. A strong geoethical, “no-regrets” approach is therefore required to develop TMG wellfield schemes for the CCT (and other towns/cities in the Western/Eastern Cape) to reduce the risk of any negative ecological and environmental impacts while still enhancing the drought resilience of the city, providing water for future urban growth, and meeting Sustainable Development Goals 6 and 11.

To this extent, the CCT has developed an extensive regional (and local, in terms of Steenbras Wellfield) environmental monitoring network, incorporating a range of in-situ and remote sensing-based measurements across the Earth’s “Critical Zone” – this includes current groundwater, surface water, ecological, soil and meteorological monitoring stations, and future seismo-geodetic monitoring. An ongoing ambition is to include this CCT TMG monitoring network into the “Greater Cape Town Landscape”, which is currently in development as one of six national South African landscapes under the “Expanded Freshwater and Terrestrial Environmental Observation Network” (EFTEON) platform being hosted by the South African Environmental Observation Network.

Abstract

The aquifers in the Chao Phraya River basin region were abundant in groundwater. Lately, the groundwater level has been declining due to agricultural activities. While in the wet season, these areas frequently suffered from flooding due to lower elevation than their surroundings. The Managed Aquifer Recharge (MAR) methods were applied to ease problems by constructing artificial recharge wells which can detain stormwater runoff and let it gradually infiltrate into the aquifer directly. For decades, the Department of Groundwater Resources started the MAR project to alleviate groundwater depletion and flooding over specific areas. However, most of the projects in the past lacked follow-up results and evaluation. Thus, later projects attempted to study recharge processes to evaluate the volume of recharged water through structures and calculate the infiltration rate through filter layers within the structures.

Recently, the field experiments of artificial groundwater recharge were conducted as 8-hour and 20-day experiments with shallow recharge wells in the Chao Phraya River basin regions. These two types of experiments provided similar results. The average recharge rates of 8-hour and 20-day experiments are 2.22 m3/hr and 2.57 m3/hr, respectively. Recharge rates of each well were independently distinct depending on sedimentation characteristics, aquifer thickness, and volume of dry voids. During the test, the recharge well continuously encountered the problem of sediment clogging due to using untreated water from neighbouring streams and ponds. This clogging issue needed to be treated regularly to maintain the efficiency of the recharge well.

Abstract

To explore the sources of pollution and health risk profile of heavy metal elements in groundwater,41 sets of representative groundwater samples from the southwest subbasin of the Shiqi River were examined for 10 heavy metal elements, correlation analysis and principal component analysis were used to resolve the possible sources of heavy metal contamination in groundwater. The concentration characteristics and health risk levels of the 10 heavy metals were assessed using the single factor contamination index (Pi), the Nemerow comprehensive contamination index (PN) and the health risk model. The results show that: 1) The average values of heavy metal elements of the groundwater in the study area all met the limit of class III water standard in the quality standard for groundwater; only the maximum value of Al was exceeded, followed by a large variation in the concentrations of Al, Mn and Cr. The heavy metal element with the largest average contribution was Al (65.74%). 2) The results of the single factor contamination index evaluation show that only the heavy metal element Al exceeds the level, and the results of the Nemerow comprehensive contamination index evaluation show that the study area is basically at low pollution levels and the quality of groundwater is good. 3) The results of the multivariate statistical analysis show that Zn, Co and Mn are mixed sources of geological formation and domestic waste, Al, As, and Cu are agricultural sources, Cd, Cr and Ni are industrial sources, and Hg comes from long-range atmospheric transport.

Abstract

Italian urban areas are characterized by centuries-old infrastructure: 35% of the building stock was built before 1970, and about 75% is thermally inefficient. Besides, between 60% and 80% of buildings’ energy consumption is attributed to space heating. Open-loop Groundwater Heat Pumps (GWHPs) represent one of the most suitable solutions for increasing the percentage of energy consumption from Renewable Energy Sources (RES) in cities such as Turin city (NW Italy). However, allowing the diffusion of GWHPs cannot be disregarded by the knowledge about hydrogeological urban settings. As the thermally affected zone (TAZ) development could affect energetically adjacent systems, the TAZ extension must be well-predicted to guarantee the systems’ long-term sustainable use. Different buildings of the Politecnico di Torino are cooled during the summer by 3 different GWHP systems. To investigate possible interactions with other neighbouring plants and to preserve the water resource by capturing its positive and productive aspects from an energy point of view, a complex urban-scale numerical model was set up for comprehensively analysing the impact of the geothermal plants on the shallow aquifer. Different simulation scenarios have been performed to define possible criteria for improving the energy functionality of the groundwater resource. Besides, the extent of the TAZ generated was defined as a function of the specific functioning modes of the different GWHP systems. Numerical simulations, legally required by competent authorities, represent a fundamental tool to be applied for defining hydrogeological constraints derived from the GWHPs diffusion in Italian cities.

Abstract

Diverse tools exist to study the transfer of contamination from its source to groundwater and related springs. A backward approach, i.e. sampling spring water to determine the origin of contamination, is more complex and requires multiple information. Microbial source tracking (MST) using host-specific markers is one of the tools, which, however, has shown to be insufficient as a stand-alone method, particularly in karst groundwater catchments. A karst spring in the Swiss Jura Mountains was studied concerning the occurrence and correlation of a set of faecal indicators, including classical parameters and bacteroidal markers. Sporadic monitoring proved the impact on spring water quality, mainly during high water stages. Additional event-focused sampling evidenced a more detailed and divergent pattern of individual indicators. A multiple-tool approach, complementing faecal indicator monitoring with artificial tracer experiments and measuring natural tracers, could specify the origin of ruminant and human faecal contaminations. Natural tracers allowed for distinguishing between water components from the saturated zone, the soil/epikarst storage, or freshly infiltrated rainwater. Additionally, the breakthrough of injected dye tracers and their remobilization during subsequent recharge events were correlated with the occurrence of faecal markers. The findings hypothesize that human faecal contamination is related to septic tanks overflowing at moderate rainfall intensities. Linkage with vulnerability assessment and land-use information can finally better locate the potential point sources. Such a toolbox provides useful basics for groundwater protection and catchment management and insight into general processes governing the fate and transport of faecal contaminants in karst environments.

Abstract

Stable isotopes of the water are widely used in volcanic contexts to identify the recharge area, thanks to a strong orographic effect. Such data help improve the study areas’ conceptual model, especially to identify flow paths through the volcanic edifice. The most common pattern considered is a high to medium-elevation recharge area on a flank of the volcano, feeding both local perched aquifers and a deep basal aquifer. This is quite common for “shield volcanoes”, with the flank comprising a thick accumulation of lava flows. On composite volcanoes, especially in a volcanic arc context, the large diversity of lithologies (effusive/ destructive events dynamics) along the flanks may create a compartmented aquifers system. The Arjuno-Welirang-Ringgit volcanic complex (East Java) has been studied to elaborate a hydrogeological conceptual model. Stable isotopes of the water show significant results in identifying the recharge areas of several aquifers that are outflowing at a similar range of elevation. These results help to propose a water flow pattern from the recharge areas to the main springs with juxtaposed and superposed aquifers. This also leads to constraining the geometry of the aquifers and concluding that one volcanic complex with several recharge areas can feed juxtaposed aquifers. These results also highlight the need to adapt the study scale to each “point of interest” in the volcanic context, as each spring shows a different flowing pattern, preferential recharge elevation, and surface area. These are mandatory data to propose an adapted groundwater management.

Abstract

South Africa faces serious water scarcity challenges not only because it is a semi-arid country but also due to climate change. One of the most significant effects of climate change is an increase in temperature, which inevitably increases evaporation. Increased evaporation directly reduces the availability of surface water resources. Groundwater is less susceptible than surface water resources to evaporation and thus offers resilience against the impacts of climate change. Many South African cities, communities, and farmers depend on groundwater for domestic or other socio-economic purposes. This implies that groundwater resources which are currently or potentially utilisable should be identified, and suitable legal measures should be implemented to protect these resources from potential risks of harm or damage posed by anthropogenic activity. First, This article evaluates the effectiveness of the country’s existing regulatory framework to effectively protect South Africa’s groundwater resources and finds that the framework can be improved significantly. Secondly, it explores regulatory opportunities within the existing legal framework to strengthen South Africa’s groundwater governance regime, including using land use planning instruments to facilitate the implementation of groundwater protection zones

Abstract

Managed Aquifer Recharge (MAR) provides an integrated water governance solution that improves water security for communities and farmers by storing water in aquifers and managing groundwater extractions to ensure water supplies are available during droughts. Quantitative analysis of levelised costs and benefit-cost ratios (BCRs) of 21 MAR schemes from 15 countries and qualitative assessment of additional social and environmental benefits demonstrates the benefits of MAR compared to water supply alternatives. Cost-benefit analysis provides a systematic method for comparing alternative water infrastructure options. Levelised cost is a widely accepted method of comparing MAR with alternative water infrastructure solutions when market valuations of water are unavailable.

The benefits of MAR can be estimated by the cost of the cheapest alternative source of supply or the production value using water recovered from aquifer storage. MAR schemes recharging aquifers with natural water using infiltration basins or riverbank filtration are relatively cheap with high BCRs. Schemes using recycled water and/or requiring wells with substantial drilling infrastructure and or water treatment are more expensive while offering positive BCRs. Most MAR schemes have positive or neutral effects on aquifer conditions, water levels, water quality, and environmental flows. Energy requirements are competitive with alternative sources of supply. This analysis demonstrates strong returns to investment in the reported MAR schemes. MAR provides valuable social and environmental benefits and contributes to sustaining groundwater resources where extraction is managed.

Abstract

Kinsevere Mine is an open pit copper mine located within the Central African Copper Belt, experiencing common water challenges as mining occurs below the natural water table. The site’s conceptual model is developed and updated as one of the tools to manage and overcome the water challenges at and around the mining operations. The natural groundwater level mimics topography but is also affected by the operations. The pits act as sinks. The water table is raised below the waste dumps due to recharge in these areas, and the general groundwater flow direction is to the east. The site is drained by the Kifumashi River, located to the north of the site. Water levels from dewatering boreholes and natural surface water bodies define the site’s piezometric surface. The geological model is adopted to define the aquifers and groundwater controls. The Cherty Dolomites, a highly fractured Laminated Magnesite Unit, contribute the highest inflows into the mine workings. The Central Pit Shear Zone acts as a conduit and compartment for groundwater between Mashi and Central Pits. Hydraulic tests have been conducted over the years, and these data are used to estimate possible aquifer property values. The high-yielding aquifer on the west is dewatered using vertical wells, and the low-yielding breccia on the east is depressurized using horizontal drain holes. The site’s water management strategy is reviewed and improved through refinement of the conceptual model.