Conference Abstracts

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.

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

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

Abstract

Groundwater is a critical resource in Namibia, particularly in the Kunene and Omusati Regions, which are among the driest in Sub-Saharan Africa. Hydrogeological mapping is essential to ensure this resource’s sustainable use and management. The hydrogeological map of Namibia was updated recently (2021). However, the details of a 1:1M map are too coarse for regional groundwater management. An ongoing study of groundwater potential assessment in the two regions required downscaling the information to 1:250 000. This work made use of geological maps 1:250 000 from the Geological Survey of Namibia, about 430 selected wells including 20 recent boreholes, 117 reinterpreted pumping tests, some existing reports from private companies, academic works including a PhD thesis, interviews with local water resource experts and statistical analysis of 6 500 wells from the National Groundwater Database (GROWAS II) maintained by the Ministry of Agriculture, Water and Land Reform (MAWLR). The regional hydrogeological map obtained was then associated with the recharge evaluated in a separate task of the same project to assess the available groundwater sustainability. By assessing abstraction costs and water demand, the work gives insights into areas where groundwater abstraction can be increased or restricted to ensure sustainable use. As conscientious and serious as this study may be, it does not replace a master plan but allows a global vision of the development potential of groundwater at a regional scale. This study was financed by the French Agency for Development (AFD) under a tripartite agreement (MAWLR-MEFT-AFD).

Abstract

The National Park Plitvice Lakes (NPPL) in the Republic of Croatia was declared in 1949 due to its exceptional natural beauty. However, in addition to its attraction, the NPPL also encompasses an area of significant karstic water resources in the Dinaric karst region, on the border between the Black Sea and the Adriatic Sea catchment. In some parts, groundwater connections to the Klokot Spring and Una River in Bosnia and Herzegovina have been assumed by hydrogeological research and proven by tracing tests, which confirm transboundary aquifer. Assessing transboundary aquifer systems already presents challenges in managing this area, considering not only the well-defined physical catchment. Therefore, comprehensive protection is necessary, which must reconcile people’s aspirations for spatial development with the sustainability of natural systems. Protecting karstic water resources can be achieved through separate analyses of the natural vulnerability of surface and groundwater and their integration into a comprehensive protection system. Protection should be layered through three levels: (1) protecting the area from the impact of the upstream catchment, (2) protecting surface water in the catchment that is most affected by anthropogenic influences, and (3) protecting the surrounding area from the impact of the NPPL, which with numerous visitors every year and tourist facilities, also represents significant pressure on downstream catchments. The ultimate goal is a scientifically based proposal for sustainable development of the protected area, in line with the needs of protection and spatial use, and based on an assessment of the overall risk to water resources.

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.

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

Groundwater governance and risk management in the Murray-Darling Basin in Australia (MDB) are being challenged by the increasing demand for water and the growing scarcity and variability of water supply owing to climate change. Over the past 20 years, consideration of risk related to groundwater in the MDB has evolved from concerns about the impact of groundwater extraction on surface water resources to an integrated assessment of risks to connected water resources and ecosystems. The Basin Plan includes a comprehensive framework for assessing risks to Basin water resources and ecosystems, but further scientific and policy developments are required to implement the plan. Consistent definition and improved assessment of groundwater-surface water connectivity are required, together with longer planning timeframes. Multi-year planning rules and policies must be developed to exploit opportunities for integrated management of groundwater and surface water resources and storage to manage droughts and floods. Risks to groundwater quality and groundwater-dependent ecosystems must be adequately assessed and monitored to avoid adverse impacts on communities and long-term loss of ecosystem services. Further improvements can be made in assessing cumulative risks from coal seam gas and coal mining. Additional research can be targeted towards knowledge gaps and uncertainties that pose the greatest risk to connected groundwater and surface water resources and ecosystem viability. Most importantly, further training and capacity building in water management agencies is critical to enable effective and transparent monitoring and management of Basin water resources.

Abstract

Groundwater represents a crucial source of drinking water in the Lille metropolitan area. Despite its importance, the resource is vulnerable to the potential evolution of land use: recharge, runoff and evapotranspiration processes in a soil-sealing context and changes in cultural practices. As a result, stakeholders emphasized the importance of exploring the influence of land use on groundwater to ensure sustainable resource management and enhance territorial planning. The 3D hydrodynamic model helped manage groundwater resources, but the (MARTHE code) has a significant limitation in that it does not consider the impact of land use evolution. We propose to investigate the contribution of a hydrological distributed numerical approach incorporating land cover data in groundwater modelling compared to a global approach at the scale of a peri-urban territory. To do so, we use the HELP code by considering the temporal and spatial evolution of land use and their associated characteristics, such as vegetation and soil properties, to detail recharge and runoff over more than 20 years that we incorporate into the initial groundwater model.

The two approaches yielded comparable global water balance results. However, at the local scale, the model accounting for land use showed significantly different hydric components. Choosing the appropriate model depends on the specific research question and spatial scale, and considering land use evolution is crucial for accurate urban planning impact assessments, especially at the district level.

Abstract

Contamination of fresh groundwater aquifers by leakage of saline water (brine) from wells may result from various activities, such as salt mining, wastewater or concentrate injection and geothermal heat production. Here, the brine transport and consequences for groundwater monitoring have been explored for a wide range of brine compositions, leakage and hydrogeological conditions using numerical simulations that considered buoyancy impacts from both temperature and density differences. Results show that at close distances to the leak (up to 3-5 meters away), breakthroughs of the salt ( at 1,000 mg/L) occurred within one month of leakage in all modelled scenarios. At a radial distance of 10 meters, with a leak rate of 2 m3 /d, it took three to six months in most cases. For the leakage of relatively warm brines, the heat transport is separated from the salinity due to thermal retardation resulting in monitoring the breakthrough of heat more closely to the depth of the leakage point than the salinity breakthrough. In summary, this study indicates that the mode of dispersion of leaking geothermal brine strongly depends on the brine properties and the leakage and hydrogeological conditions. At the same time, vertical monitoring of temperature and conductivity at a limited distance from brine injection wells (<5m) appears to be a robust method for detecting a possible leak relatively quickly (within a month) and after limited contamination. The monitoring signal in the event of leakage is also sufficiently distinctive to prevent false positives.

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.

Abstract

Knowledge of the nature and extent of groundwater-dependent ecosystems (GDE) at an aquifer scale enables incorporating ecological water requirements in integrated groundwater resource management activities, including transboundary aquifer cases (TBA). This way, sustainable groundwater management and functional ecosystem services can be achieved. Therefore, understanding groundwater- ecosystems-surface water interactions is crucial for assessing resources’ resilience or susceptibility towards certain impacts. Unfortunately, this subject is widely under-researched with fragmented information, especially in southern Africa. This study was thus initiated to understand groundwater processes controlling the maintenance of Tuli-Karoo TBA (Botswana, South Africa, Zimbabwe) GDEs towards developing a model that can be utilised in impact assessments, especially in climate change. The employed approach included stable isotope analysis (mainly 2 H and 18O) for groundwater, streams, springs, rainwater, vegetation, and soil; spatial imagery and GIS classification (incl. NDVI, NDRE, NDWI); and plant moisture stress techniques. Identified GDEs in the study area (characterized by intergranular alluvium aquifer underlain by the Karoo sandstone of intergranular and fractured secondary aquifer type) are riparian vegetation, floodplain and depression wetlands, and springs. Precipitation recharged alluvium aquifer’s contribution to Limpopo River baseflow is negligible as the discharge is mainly through springs and evapotranspiration. Monitoring data scarcity and skewed availability among sharing countries hamper research and its output applicability to TBA’s entirety. Therefore, data generation, exchange, and joint databases development are crucial for sustainable comanagement of groundwater and supported ecosystems and science-based decision-making.

Abstract

Due to technical, social, and economic limitations, integrated groundwater management presents a significant challenge in developing countries. The significance of this issue becomes even more pronounced in groundwater management, as this resource is often overlooked and undervalued by decision-makers due to its status as a “hidden resource,” despite the fact that it provides multiple ecosystem services. This study aims to establish the technical hydrogeological foundation in rural basins of central Bolivia through alternative, simplified, and cost-effective methods and tools. The study includes applying geophysical techniques, such as Electrical Resistivity Tomography, to determine the conceptual hydrogeological model of a micro-basin. In addition, a soil water balance approach was applied, characterizing 24 biophysical variables to identify groundwater recharge zones, while global circulation models provided a substitute for unreliable meteorological data. Furthermore, a participatory model was developed to identify recharge areas in upper basin areas within the framework of developing a municipal policy for their protection. The participatory model included local knowledge in all stages of methodology development, considering the characteristics of the local plant communities and the spatial distribution of local rainfall. The research findings have already contributed to resolving socio-environmental conflicts in Bolivia and establishing a foundation for effective water governance by empowering local rural communities. This study has demonstrated the feasibility of using alternative, simplified, and low-cost methods and tools to establish the technical hydrogeological basis, which can inform public policies to promote sustainable groundwater management in developing countries.

Abstract

Rising shallow groundwater temperatures are observed in many cities worldwide and are expected to increase further over the next century due to anthropogenic activities and climate change. The impact of groundwater temperature increase on groundwater quality is poorly understood. This study conducted two high-spatial-resolution campaigns in Vienna (Austria, autumn 2021/ spring 2022). At 150 wells, a comprehensive parameter set (e.g. major ions, nutrients, and water stable isotopes) was analyzed in groundwater collected, and at 812 wells, the water temperature was measured. Results are compared to available long-term data on groundwater chemistry (1991-2020). In theory, temperature triggers a cascade of effects, where, finally, the depletion of dissolved oxygen (DO) causes a switch to anaerobic microbial processes and a deterioration of water quality. No direct relation between DO and water temperature was observed between 10 and 20 °C. However, many wells delivered anoxic groundwater, including the one with the highest measured temperature (27 °C). The highest temperatures were consistently observed near potential heat sources (local scale), with a rapid decrease in temperature with increasing distance from these sources. Long-term data from particular high-temperature wells revealed decreased dissolved oxygen after sudden temperature changes of > 5 K. On a regional scale, it is observed that groundwater-surface water interactions and aquifer properties play a pivotal role in oxygen availability and redox conditions. In conclusion, high-spatial-resolution sampling combined with long-term data analysis is needed to determine the impact of temperature on water quality.

Abstract

The work presented in this paper incorporates spring data for further conceptualizing the hydrogeology of northern Namibia’s so-called “Karst Area”, an area around the towns of Tsumeb, Otavi and Grootfontein. Also called the Otavi Mountainland, it can be described as a mountainous highland of parallel, east-west trending elongated valleys and ranges shaped by the underlying folded units of carbonate rocks of the Damara Supergroup. The karst aquifers are a supplementary source to the central areas of the country during drought. Most of these 35 springs are often found near hilltop crests or high up on the mountain flanks rather than lower down at the valley floors. If flows are generated locally as gravity or contact overflow springs, studying them would not add much to conceptualizing the regional groundwater flow. Fundamental insights are provided if flows arise due to hydraulic pressure from deeper down. As artesian boreholes do not occur as a rule in the Karst Area, artesian springs might indicate the presence of deeper aquifers out of reach at normal drilling depth. One such hypothesis is that the bottom of the dolomitic synclines, structurally weaker at the fold axis, had been subjected to deep-seated karstification. The work presented here investigates that possibility and argues for and against it. In addition, established concepts of groundwater flow mechanisms for the area have been revisited. A conclusion has not yet been reached, but the balance of the arguments is presented.

Abstract

Understanding and quantifying hydrology processes represent a mandatory step in semi-arid/arid regions for defining the vulnerability of these environments to climate change and human pressure and providing useful data to steer mitigation and resilience strategies. This generally valid concept becomes even more stringent for highly sensitive ecosystems, such as small islands like Pianosa. The project intends to deploy a multi-disciplinary approach for better understanding and quantifying the hydrological processes affecting water availability and their evolution, possibly suggesting best practices for water sustainability.

First results pointed out as over the last decade the precipitation regime has led to a major rate of evapotranspiration and minor effective infiltration that caused a decreasing of piezometric level over several years. Quantity and chemical-isotopic features of rainfall and effective infiltration water measured/collected by a raingauge and a high precision lysimeter describe the hydrological processes at soil level and characterize the rate and seasonality of groundwater recharge. Hydrogeological and geochemical data of groundwater are highlighting the distribution and relationship among different groundwater components, including the seawater intrusion. Furthermore, the comparative analyses of continuative data monitoring in wells and weather station showed the presence of possible concentrated water infiltration processes during rainfall extreme events that induce a quick response of shallow groundwater system in terms of water level rise and decrease of electrical conductivity. Thus, elements of vulnerability of the aquifer to pollution are pointed out, as well as the possibility to provide technical solutions for enhancing water infiltration and groundwater availability.

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

Salinization is one of the main threats to groundwater quality worldwide, affecting water security, crop productivity and biodiversity. The Horn of Africa, including eastern Ethiopia, northeast Kenya, Eritrea, Djibouti, and Somalia, has natural characteristics favouring high groundwater salinity. However, available salinity data are widely scattered, lacking a comprehensive overview of this hazard. To fill this gap, machine learning modelling was used to spatially predict patterns of high salinity with a dataset of 6300 groundwater quality measurements and various environmental predictors. Maps of groundwater salinity were produced for thresholds of 800, 1500 and 2500 μS/cm. The main drivers include precipitation, groundwater recharge, evaporation, ocean proximity, and fractured rocks. The combined overall model accuracy and area under the curve of multiple runs were both ~81%. The salinity maps highlight the uneven spatial distribution of salinity, with the affected areas mainly located in arid, flat lowlands.

These novel and high-resolution hazard maps (1 km2 resolution) further enable estimating the population potentially exposed to hazardous salinity levels. This analysis shows that about 11.5 million people (~7% of the total population) living in high-salinity areas, including 400,000 infants and half a million pregnant women, rely on groundwater for drinking. Somalia is the most affected country, with an estimated 5 million people potentially exposed. The created hazard maps are valuable decision-support tools for government agencies and water resource managers in helping direct salinity mitigation efforts

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

Research on Fracking in the Karoo basin yielded results that, if not considered “unexpected”, can be considered as “should have been foreseen”. Some aspects substantially impacting research on fracking are often overlooked when undertaking scientific research on an emotional topic such as fracking. This presentation aims to provide insights and recommendations based on the experiences and outcomes of current research on hydraulic fracturing or “fracking” in the Karoo basin of South Africa. Fracking has been a subject of significant research and debate over the past decade. Topics, each with its challenges, include 1) The scale of exploration/production extent (Site specifics), 2) Importance of robust and independent research, 3) Need for stakeholder engagement and participation, 4) The complexity of environmental risks and impacts, 5) The need for a precautionary approach, 6) Regulatory and policy challenges. Several methodologies can be relied upon to compare outcomes of different aspects of fracking research in the Karoo, such as 1) Comparative analysis, 2) Meta-analysis, 3) Stakeholder mapping and analysis and 4) Data visualisation. A combination of these methodologies can be used to compare outcomes of different aspects of fracking research in the Karoo and provide insights and recommendations for future decision-making and planning. Ultimately, the decision to allow Fracking should be based on a balanced assessment of potential risks and benefits, considering long-term impacts on the environment, economy, and communities.

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.

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

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

Abstract

The Kavango West and East regions are situated in a semi-arid area northeast of Namibia and bounded by the perennial Okavango River on the northern border. Groundwater in the area is the main source of water supply for the inhabitants living further from the river. In addition, most bulk water users along the river have boreholes for their water supply. With a semi-arid climate, drought in the regions is common and inflicts devastating effects on local communities. More drought relief boreholes are being drilled to sustain communities, increasing the dependency of the inhabitants on groundwater. The complexity of the behaviour and nature of the groundwater in the regions is poorly understood, and there are no strategies to manage these aquifers properly. As a result, an attempt was made to better understand the groundwater potential by examining several hydrogeological factors involved. A basic water-balance approach was used in determining the groundwater potential of the middle and lower Kalahari aquifers. The total resource potential for the entire region is estimated at 144 447.16 x 106 m3 /a, demonstrating great resource potential with significant storage space.

The greatest potential is shown in the middle Kalahari aquifers, comprising about 94% of the total resource. Groundwater recharge, as one of the hydrogeological factors, was determined using the chloride mass balance method, giving an average of 6.03 mm/a for the entire study area. If utilized sustainably, the Kalahari aquifers can sustain most communities within the two regions, especially those further from the Okavango River.

Abstract

Nearly 1.9 billion people live in marginal environments, including drylands, semiarid, arid, and hyperarid environments. Obscure but ubiquitous circular pockmark depressions dot these lands. These circular depressions can range from a few meters to kilometers, and the depth of these depressions varies from a few centimeters to over 10 m. However, the genesis of the circles has been investigated among scientists for many years because of their obscure nature. Some researchers believe that termites cause fairy circles, while others believe they are caused by plants competing for water and nutrients. This study documented the Africa-wide prevalence and extent of the pockmarks for the first time, and it further classified the pockmarks according to their genesis and hydrological roles. We further investigated their relevance in serving as nature-based solutions to overcome water scarcity in dryland regions. So far, field evidence in Ethiopia and Somalia showed that these features potentially have water security significance in a) organizing surface water flows over arid/semi-arid landscapes, b) serving as the site of temporary surface water storage, and c) serving as the site of focused groundwater recharge into the underlying aquifers. This presentation will highlight the spatial prevalence, extent, and genesis model of the pockmarks across the drylands in Africa (South Africa, Namibia, Somalia, Ethiopia, Kenya, Chad, Senegal, Mali, Niger, etc.).

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

Previous studies have shown that river-aquifer connectivity exists. However, an integrated approach that consists of multiple measuring methods to quantify and characterise such connectivity still needs improved scientific understanding due to the underlying principles and assumptions of such methods, mainly when such methods are applied in a semi-arid environment. Three techniques (hydrogeochemistry, stable water isotopes, and baseflow separations) were applied to quantify and characterize river-aquifer interactions. The study’s objective was to improve knowledge and understanding of the implications of the results from the three methods. Field measurement, laboratory assessment, and record review were used to collect primary and secondary data. Results showed that Na- HCO3 water type dominated the upper stream, discharging onto the surface and forming stream sources. Na-HCO3 water type was an outlier when the area’s geology and land use activities were assessed. The isotope results showed that the studied aquifer had 9% recently recharged water. Being the upstream, the freshwater in such a mountainous aquifer was expected. The baseflow index (BFI) results showed that the dependency of the total river flow to aquifer discharge contributed 7.24 % in the upper stream, 7.31% in the middle stream, and 7.32% in the lower stream. These findings provided empirical evidence that hydrochemistry, stable isotopes, and baseflow separation methods provide key insights into aquifer-stream connectivity. Such findings inform choosing appropriate and relevant measures for protecting, monitoring, and allocating water resources in the catchments.

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.

Abstract

Various electrical potential difference-audio magnetotelluric (EPD-AMT) geophysical equipment is now available in the market for groundwater exploration, and the Groundwater Detector is one of them. Due to their low cost, deeper penetration, and real-time measurement, the technology has been widely received in many developing and underdeveloped countries. However, research to understand the application of the EPD-AMT surface geophysics approach in groundwater exploration is very limited. This research gap needs urgent attention to promote the technology’s meaningful and wider application. The lack of published case studies to demonstrate the capabilities of the EPD-AMT approach is a limiting factor to its application.

Research on different hydrogeological settings is paramount as part of the efforts to improve the practical understanding of the application of the EPD-AMT geophysical approach in groundwater exploration. This study shares field experience from applying the EPD-AMT Groundwater Detector geophysical technique to explore groundwater in dolomite, granite, and Karoo sandstone hardrock aquifers in Southern Africa.

Abstract

This study focused on improving the understanding of flow regimes and boundary conditions in complex aquifer systems with unusual behavioural responses to pumping tests. In addition, the purpose was to provide a novel analysis of the hydrogeological properties of aquifers to deduce inferences about the general expected aquifer types to inform new practices for managing groundwater. In this paper, we report that using derivative analysis to improve understanding of complexities in aquifer flow systems is difficult and rarely used in groundwater hydraulics research work. Thus, we argue that if derivatives are not considered in the characterizing flow regime. The heterogeneity of aquifers, boundary conditions and flow regimes of such aquifers cannot be assessed for groundwater availability, and the decision to allocate such water for use can be impaired. A comprehensive database was accessed to obtain pumping tests and geological data sets. The sequential analysis approach alongside derivative analysis was used to systematically perform a flow dimension analysis in which straight segments on drawdown-log derivative time series were interpreted as successive, specific, and independent flow regimes. The complexity of using derivatives analyses was confirmed. The complexity of hydraulic signatures was observed by pointing out n sequential signals and noninteger n values frequently observed in the database. We suggest detailed research on groundwater flow systems using tracer methods like isotopes and numeric models must be considered, especially in multilayered aquifer systems such as the Heuningnes catchment.

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.

Abstract

The work presented relates to the influence of regional scale dykes in groundwater flow in karst aquifers of northern Namibia’s Otavi Mountainland around the towns of Tsumeb, Otavi and Grootfontein. The aquifers are well studied and are an important water source locally and for populated central areas of the country during drought. The area has parallel, eastwest trending elongated valleys and ranges shaped by the underlying synclines and anticlines of folded carbonate units of the Damara Supergroup. The role of the regional scale dolerite dykes that cut across the dolomitic aquifers has not been fully appreciated till recently. Aeromagnetic data is effective in mapping the dykes in detail. The dykes trend in a north-easterly to northerly direction into the Otavi Platform carbonate rocks. The dykes are normally magnetised with the odd remanent dyke. They consist mainly of dolerite, although in some cases are described as tectonic with hydrothermal magnetite and no dolerite material. The dykes appear to focus southwest of the Otavi Mountainland near the Paresis Alkaline Intrusive (137Ma). Examination of existing hydrogeological data reveals different characteristics of the dykes that influence groundwater flow, forming: a) conduits that enhance flow along contact zones, b) barrier to flow with compartmentalization and c) partial barrier to flow. An advantage has been taken of the understanding gained to manage mines’ dewatering and pumped water management. Future water resources management and contaminant studies will need to recognise the compartmentalised nature of the aquifer

Abstract

The occurrence of emerging organic contaminants (EOCs) in the aquatic environment is of no surprise since these are applied for various purposes daily. This study investigated the changes in EOCs concentrations in the water between 2019 and 2020. During rainy seasons, samples were collected from dams and surrounding boreholes in the Eastern Basin of the Witwatersrand Goldfields. During the first and second laboratory analyses, 24 and 11 analytes were screened in the water samples. The findings indicated that in 2020, compounds such as caffeine, sulfamethoxazole, atrazine and metolachlor displayed detection frequency exceeding 2019. This indicates that the occurrence of these compounds in the aquatic system has increased within a year. Whilst carbamazepine was still traced in 12 sites as previously observed in 2019, compounds estradiol, estrone, bisphenol A and ibuprofen were traced in fewer sites than they were detected in 2019. Compounds 4-nonylphenol, methylparaben, caffeine and atrazine were detected in all the samples analysed for 2019 and 2020, respectively. Antiretrovirals (ARVs) were analysed once and were detected in most sites, with efavirenz registering the highest (12/18) detection frequency. Assessing the occurrence of EOCs in boreholes according to the depth indicated that bisphenol A and estrone were traced in greater concentrations in deep than shallow aquifers, whilst the opposite was observed for atrazine. This study showed groundwater susceptibility to contamination by EOCs, with concentrations of most compounds increasing with time due to their high usage and improper sewer systems in the area.

Abstract

In the social sciences, there has been a ‘posthuman’ turn, which seeks to emphasise the role of non-human agents as co-determining social behaviours. In adopting a ‘more-than-human’ approach, the academy seeks to avoid claims of human exceptionalism and extend the social to other entities. In this paper, we explore the extent to which the more-than-human approach might be applied to groundwater and aquifers and the implications that this may have for groundwater science. The role of groundwater in complex adaptive socio-ecological systems at different scales is increasingly well-documented. Access to groundwater resources positively influences societal welfare and economic development opportunities, particularly in areas where surface waters are scarce. The potential adverse effects of human activities on the quantity or quality of groundwaters are also widely reported. Adopting a ‘properties’ approach, traditional social science perspectives typically describe aquifers as structuring the agency of human actors. To what extent might aquifers also have agency, exhibited in their capacity to act and exert power? Drawing on insights from 5 cities across sub-Saharan Africa, we argue for the agency of aquifers in light of their capacity to evoke change and response in human societies. In doing so, we draw on the concept of the more-than-human to argue for a more conscious consideration of the interaction between the human and non-human water worlds whilst acknowledging the critical role played by researchers in shaping these interactions.

Abstract

The basis of a hydrogeological conceptual model is the comprehensive characterisation of the groundwater system. This ranges from discrete hydraulic feature analysis to local-scale testing to integrated regional-scale aquifer system conceptualisation. Interdisciplinary data integration is critical to each level of characterisation to gain a realistic, yet simplified representation of the hydrogeological system based on various data sources. Incorporation of geological datasets, including (but not limited to) structural and lithological mapping, geotechnical core logs and geophysical surveys, in conjunction with a tailored selection of hydraulic testing techniques, are often underutilised by hydrogeologists. Yet, the contribution of these alternative hydraulic datasets cannot be overstated.

A recent hydrogeological assessment and feasibility study forming part of the planned expansion project for a base-metal mine in the Northern Cape, South Africa, offers an ideal, practical example. The localised nature of the project area and the inherently complex geological setting required a more detailed conceptual model and hydrostratigraphic domaining approach. Highly heterogeneous stratigraphy and strong structural aquifer controls necessitated characterisation by reviewing, testing and analysing various datasets. Exploratory core datasets, hydraulic aquifer tests, geological and downhole geophysical datasets, and statistical Rock Quality Designation—hydraulic conductivity relationships were interpreted to produce meaningful, refined hydraulic process identifications. A comprehensive local groundwater framework, discretised into various hydrostratigraphic units and structural domains with specified hydraulic parameters, was incorporated to provide a novel, more robust conceptual understanding of the unique hydrogeological system.

Abstract

Annually, UNICEF spends approximately US$1B in water, sanitation and hygiene programming (WASH), approximately half of which is spent in humanitarian contexts. In emergencies, UNICEF supports the delivery of water, sanitation and hygiene programming under very difficult programming contexts – interruptions to access, power supply and a lack of reliable data. Many of these humanitarian situations are in contexts where water scarcity is prevalent and where the demand and competition for water are increasing, contributing to tension between and within communities. While water scarcity is not new to many of these water-scarce areas, climate change is compounding the already grave challenges related to ensuring access to safe and sustainable water services, changing recharge patterns, destroying water systems and increasing water demand. Incorrectly designed and implemented water systems can contribute to conflict, tension, and migration. Ensuring a comprehensive approach to water security and resilient WASH services can reduce the potential for conflict and use water as a channel for peace and community resilience. This presents an enormous opportunity for both humanitarian and development stakeholders to design water service programmes to ensure community resilience through a four-part approach: 1. Groundwater resource assessments 2. Sustainable yield assessments (taking into consideration future conditions) 3. Climate risk assessments 4. Groundwater monitoring/early warning systems UNICEF promotes this approach across its WASH programming and the sector through technical briefs, support and capacity building.

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

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

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

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.

Abstract

The serpentinization of ultramafic rocks is a process in which minerals of ferromagnesian nature (e.g., olivine) are transformed into serpentine and produce groundwater with a very high pH. In these settings, CH4 can be produced by combining H2 from serpentinization and CO2 from the atmosphere, soil, carbon-bearing rocks, or mantle, although the microbial generation of CH4, mediated by methanogens utilizing CO2, formate and/or acetate can be another source in these aquifers. In this sense, the hydrochemistry of hyperalkaline springs can provide valuable information about gas origin. The Ronda peridotites (Malaga province, Spain) are one of the world’s largest outcrops of the subcontinental mantle (~450 km2). Hyperalkaline springs (pH>10) emerging along faults present a permanent low outflow (<1 L/s), Ca2+- OH- facies and residence times exceeding 2,000 years. The fluids, poor in Mg2+ and rich in K+, Na+, Ca2+ and Cl-, also contain significant concentrations of dissolved CH4 and other hydrocarbons. Water samples have been collected from eight hyperalkaline springs and analyzed for major, minor and trace elements, including Platinum Group Elements (PGE) and Total Organic Carbon (TOC). The most mobile PGEs (Pd and Rh) are present in all the springs, indicating the existence of potential catalysts for the abiotic synthesis of CH4. High TOC concentrations are observed in some studied springs where previous analyses (i.e., bulk CH4 isotopes) have indicated a microbial CH4 origin.

Abstract

Identifying groundwater recharge and discharge areas across catchments is critical for implementing effective strategies for salinity mitigation, surface water and groundwater resource management, and ecosystem protection. This study seeks to identify potential GW-SW discharge and recharge areas around the Barotse Floodplain. The results of remote sensing analysis using the Normalised Difference Vegetation Index (NDVI) show that the vegetation is sensitive to the dynamics of groundwater level, with shallower levels (< 10 m) in the lower reaches compared to deeper levels (>10 m) in the upper catchment). These zones are further investigated and likely represent geological variability, aquifer confinement and the degree of GW-SW interactions. GW-SW interactions likely are influenced by an interplay of factors such as water levels in the groundwater and surface level and hydrogeological conditions. Based on the findings, the wetland hosts riparian vegetation species responsive to the groundwater dynamic. NDVI can thus be used as a proxy to infer groundwater in the catchment. Therefore, effective water resources management of the floodplain should be implemented through conjunctive management of groundwater and surface water.

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.

Abstract

To increase the security of groundwater resources, managed aquifer recharge (MAR) programs have been developed and implemented globally. MAR is the intentional recharge and storage of water in an aquifer, which will be recovered later. It was previously known and implemented as Artificial Recharge (AR). In South Africa, the documented practice dates back 40 years. There are five main MAR methods: Well-Shaft-Borehole, Spreading-induced bank infiltration, In-channel modifications, and Runoff harvesting. Two regional-scale MAR suitability maps for the Spreading Method (SM) and the Well-Shaft-Borehole (WSB) Method were compiled for South Africa, using the Geographic Information System combined with Multi-Criteria Decision Analysis (GIS-MCDA) methodology. Parameters used to compute the maps included the nature of the different aquifers, groundwater level, water quality (EC), distance to river, terrain slope, mean annual rainfall, land cover, soil moisture availability and clogging (Fe-iron content). To create a suitability map, the parameters were combined using the weighted overlay method and the Analytic Hierarchy Process (AHP – specifically the pairwise comparison). The site suitability maps indicated that most areas in South Africa are suitable for the Spreading and Well-Shaft-Borehole methods. The results were verified with the location of existing MAR schemes and were found to agree. However, these maps are not applicable for siting projects at a local scale but can serve as a guide and screening tool for site-specific studies looking for highly suitable or target areas for MAR implementation

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.