Conference Abstracts

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

Water resources worldwide are stressed, and the number of groundwater professionals required to manage those resources is not being generated in sufficient numbers. Groundwater educational resources must be placed in schools to generate excitement and raise awareness. Additionally, people entering the workforce need training throughout their professional careers. Oklahoma State University partnered with the U.S. National Ground Water Association to develop a framework for providing education and training programs in groundwater that allow for interactive online education at all levels. The Awesome Aquifer 360 program targets grades 5-8, allowing students to conceptually explore aquifers and the people who manage them. The Drilling Basics Online program provides a 40-hour basic safety and drilling training to recruit professionals into the groundwater industry and reinforce safe operations. These programs and future plans for the technique will be discussed.

Abstract

The use of radiogenic isotope tracers, produced through bomb testing (e.g. 3H and 14C), and the application of these isotopes is yet to be fully explored now that atmospheric abundances have returned to background levels. New isotope-enabled institutions and laboratories have recently been established in developing countries to apply isotopes in practical research. This study utilized several laboratories in South Africa and in Europe to compile a robust hydrochemical (major cations and anions) and isotope (d18O, d2H, 3H, 14C, 86Sr/87Sr) dataset of groundwater from 95 sample locations in the Maputo province of Mozambique. Groundwater is hosted in different aquifers and recharged through variable mechanisms ranging from direct infiltration of exposed alluvial soils to inter-aquifer transfer between fractured aquifer systems in the mountainous regions and the weathered bedrock in the lowlands. A combination of hydrochemistry and isotopes provided insight into the heterogeneous nature of recharge, mixing of modern and fossil groundwaters, and aquifer vulnerabilities when combined with other physical parameters in the region. However, it is also clear that grab sampling over a regional spatial extent and two sampling seasons (wet and dry) did not capture all the system variability, and more regular monitoring would uncover details in the system’s behaviour not captured in this study.

Abstract

 Predicting and quantifying the hydrogeological interference of big underground works is a complex effort. This is due to the considerable uncertainty in estimating the key geomechanical and hydrogeological parameters affecting the area of potential interference of the projects. Moreover, the pattern of involved groundwater flow systems is hardly identified, either in natural or disturbed conditions. Base tunnels through mountain ridges are particularly complex in their interactions with groundwater. Several approaches and tools have been published to predict the magnitude and distribution of water inflows inside tunnels and their impact on many receptors (springs, rivers, lakes, wells, groundwater-dependent ecosystems). The research, co-funded by Italferr Spa (Italian railway national company for tunnel design), deals with calibrating and validating these methods based on huge datasets. Main engineering companies provided data from completed base tunnel projects. In particular, in this study, the Drawdown Hazard Index (DHI) method has been calibrated with a dataset of a 15 km long sector of the Gotthard base tunnel drilled through a crystalline geological setting. The calibration involved only the Potential Inflow (PI) parameter to verify the matching between the probability of inflow and the actual output of the excavation, according to the available data in the preliminary stage of the project. An alternative tool based on a machine-learning approach was then applied to the same dataset, and a comparison was presented.

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

Streamwater and groundwater are changing in the Arctic region because of significant climate warming. Arctic amplification has intensified the melting of snow cover, glaciers and permafrost, leading to a prominent variation in the annual discharge of rivers, the groundwater occurrence, and their relationships. In high-latitude regions, evaluating groundwater flux/storage and river discharge is challenging due to a lack of hydrogeological data. Changes in river flows and groundwater discharge will alter freshwater and terrigenous material flux, with implications for freshwater and marine ecosystems. Consequently, a more timely and accurate evaluation of surface and groundwater is required. In this framework, through the ICEtoFLUX project (MUR/PRA2021/project-0027), hydrology, geophysics and geochemical-isotopic surveys have been started during 2022 in the Bayelva River catchment (W-Svalbard) from its glaciers and periglacial/proglacial systems up to the Kongsfjorden. The study aims to quantify hydrologic processes and related transport of matter (solid transport, chemical solutes flux) and investigate how subsurface and surface waters interact during active layer development. The first results suggest that electrical conductivity and total suspended solids increase from glaciers to the Bayelva monitoring station, about 1 km from the coast. Seasonal evolution of physical-chemical features was also observed. Results from geophysics data and piezometers indicate that the underground flow is spatially and temporally heterogeneous, both quantitatively and from a physicochemical-isotopic point of view. Springwater characteristics testify to a deep and well-organized groundwater flow path system. This study highlights the high complexity of these systems and their high sensitivity to the meteo-climatic regimes.

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

Aboriginal and Torres Strait Islander people have inhabited the lands now known as Australia for over 65,000 years. Their communities are intricately connected to the land and waters through culture and tradition. However, there are few examples of integrated water resource management that serve Aboriginal and Torres Strait Islander communities or cultural interests. This is particularly the case for groundwater. In Australia, Indigenous connections to groundwater have historically been overlooked or, in some cases, assumed not to exist. On the contrary, many Aboriginal and Torres Strait Islander cultures have longstanding physical and spiritual connections to a range of artesian and subartesian groundwater resources. These cultures also house accurate records of groundwater systems.

Despite this, groundwater management in Australia remains dominated by Western scientific perspectives, and the groundwater sector poorly integrates Indigenous stakeholder concerns or knowledge into groundwater management and planning. IAH Australia has prepared and signed an Indigenous Groundwater Declaration intending to raise awareness among the groundwater community of the value of Indigenous perspectives and knowledge of groundwater systems. This Declaration can be viewed and signed at http://declaration.iah.org.au. This presentation provides examples of effective partnerships between Indigenous Communities and Government or Academic groundwater professionals. While progress has been made, challenges must be overcome to integrate Indigenous knowledge and connections into groundwater resource management.

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 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

Sacred wells are found across the world yet are rarely studied by hydrogeologists. This paper will present the results of a 5-year hydrogeological study of holy wells in Ireland, a country with a relatively large number of these wells (perhaps as many as 3,000). It was shown that holy wells occur in all the main lithology and aquifer types but are more numerous in areas with extreme or high groundwater vulnerability. Water samples were collected from 167 wells and tested for up to 60 chemical parameters, including a large range of trace elements. Statistical analyses were performed to see if there were any statistically significant associations between the chemical constituents and the reputed health cures for the different well waters, and the results will be presented here. One of the issues in communicating the research findings to the general public is in explaining the small concentrations involved and the likely very small doses pilgrims at holy wells receive during their performances of faith. The spiritual dimension, including the therapeutic value of the landscape where the well is located, is likely an important aspect of the healing reputation.

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

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

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

The Lake Sibaya groundwater-dependent catchment in uMhlabuyalingana (KwaZulu-Natal) has been the focus of hydrological research since the 1970s. The continuous decline in lake water levels and groundwater stores has prompted recent efforts. To increase confidence in the relative attribution of known causes of declines, an existing MODFLOW groundwater model was updated based on reviewed and extended hydrological input datasets and more accurate land-use and land cover (LULC) change data. A novel approach was used in this study, which involved running the ACRU surface-water model in distributed mode to provide dynamic recharge outputs for the groundwater model. This approach considers LULC changes, improved spatial and temporal distribution of climatic data, and land-surface hydrological processes. The refined groundwater model provided satisfactory simulations of the water system in the Lake Sibaya catchment. This study reports on the advances and limitations discovered in this approach, which was used to reassess past to current status quo model simulations for the region. The model was then used, as part of a multidisciplinary project, to assess the response of the lake water system under various LULC preferences based on inputs from local communities under two future climate scenarios (warmer wetter and warmer drier) in the current ongoing WRC project. The ultimate goal is to advise water resources management in the catchment.

Abstract

With the revision of the European Drinking Water Directive (Directive on the quality of water intended for human consumption 2020/2184) in December 2020, the preparation of Water Safety Plans (WSP) is foreseen according to the guidelines of WHO. Within the EU Interreg Adrion MUHA project, a decision support tool (DST) has been developed to provide a holistic approach to drinking water infrastructure risk analysis. The project mainly addresses four water-related risks: accidental pollution, floods, droughts and earthquakes. The core of the DST is the inventory of hazardous events (causes, their consequences and impacts) for each component of the drinking water supply chain: (1) drinking water source - catchment area, (2) water supply system, and (3) domestic distribution system. For each identified potential hazard, the type of hazard was determined (e.g., biological, chemical, radiological, or physical hazard (including turbidity), inadequate availability of water supplied to customers, safety to personnel, external harm to third parties, including liability). The DST was tested in the partner countries (Italy, Slovenia, Croatia, Serbia, Montenegro and Greece) to verify the resilience of the measures and elaborate the WSP.

In the end, the REWAS-ADRION strategy was elaborated, aiming to increase the resilience of drinking water supplies to floods, droughts, accidental pollution, and earthquake-related failures by improving the water safety planning mechanism based on the concept of inter-agency cooperation to support water utilities, civil protection organizations, and water authorities.

Abstract

Recharge is an important factor in Water Resources Management as it is often used as a measure for sustainable groundwater abstraction and resource allocation. The recharge estimation is, however, linked to a specific time, area and conditions and then generalised over seasons and years. Current climate change estimations predict a warmer and drier future for western parts of southern Africa. Groundwater recharge estimation methods do not consider changes in climate over the short term and do not consider the longer trends of a changing climate. This article looks at the various methodologies used in recharge estimations and their application in a changing world, where rainfall period, pattern and intensity have changed, where higher temperatures lead to higher actual evapotranspiration and where there is a greater need for water resources for use in agriculture, industry and domestic use. Our study considers the implications of current recharge estimation methods over the long term for water allocation and water resources management of groundwater resources from local and aquifer catchment scale estimations.

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

The joint application of water supply system security, groundwater modelling, and multicriteria analysis (MCA) indicated the potential of Managed Aquifer Recharge (MAR) to increase water supply security in Eastern Botswana substantially. Botswana faces increased water stress due to decreased water availability as climate change exacerbates variability in rainfall and increases evaporation losses and water demand. The water supply for Eastern Botswana is based on the bulk water supply system of the North-South Carrier (NSC) connecting dams in the northeast to the main demand centres, including Gaborone. The potential of MAR to increase the water security of the NSC by storing water that otherwise would have been lost to spillover and evaporation and contribute to the provision of water during droughts was studied. Large-scale MAR in the Ntane sandstone aquifer at a wellfield by the NSC was evaluated in terms of hydrogeology and national water supply perspective. Comprehensive hydrogeological surveys and assessments included borehole injection tests and hydrogeological and geochemical modelling to evaluate risks of losing recharged water and clogging of boreholes. Probabilistic water supply system modelling analysed the impact of different MAR scenarios on the water supply security of the NSC, and an MCA tool assessed the sustainability of the different scenarios. The analysis showed that large-scale MAR is feasible, and a scheme with a capacity of 40,000 m3 /d is the most sustainable from technical, social, economic and environmental perspectives and could potentially reduce the number of months with water shortage by 50% in Gaborone.

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

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

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

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

The research aims to reveal possible ways of formation of the chemical composition of mineral and fresh groundwater in Quaternary sediments of the coastal plain of Northern Sinai. Statistical assessment of the distribution of various hydrochemical indicators of mineral and fresh groundwater has been carried out according to the following data samples: 1) the general population for all Quaternary deposits (164 wells); 2) the central zone (74 wells); the eastern zone (25 wells); the western zone (65 wells). The following variables were assessed: total dissolved solids (TDS) (in ppm), concentrations of major components (in epm and % epm), pH value and the depth of the sampled well (ds) (in meters). The physicochemical equilibria between the groundwater and rock–forming carbonate and sulfate minerals were calculated using the PHREEQC software. Saturation indices (SI) for groundwater of three zones in relation to various rock-forming minerals were analyzed. Correlation relationships were obtained for TDS, major components and some genetic coefficients ((Requ=(Na++K+)/ (Ca2++Mg2+); Na+/Cl-; SO4 2-/Cl-; Ca2+/SO4 2-). It was concluded that the groundwater chemical composition is defined by infiltration recharge and/or intrusion of Mediterranean seawater.

Most likely, during short-term flood periods, the infiltration into aquifers significantly exceeds the evaporation. Despite the relatively high evaporation rate, the degree of groundwater metamorphization is below the saturation level in relation to sulfates and carbonates. The research is of great practical importance for assessing freshwater resources to provide potable water supply

Abstract

Globally, rivers, lakes and groundwater face complex anthropogenic water quality alterations posing risks to human health, food security and ecosystems. The World Water Quality Alliance (WWQA) forms an open, global consortium, pooling expertise on water quality science and technology innovation and providing a participatory platform for water quality assessments and co-designing tailored and demand-driven services. It addresses priority topics relevant to water governance, scalable water solutions and emerging issues in water management. The African Use Cases provided an initial testbed that puts the quality of surface water and groundwater into the context of the local 2030 Agenda and its multiple linkages across the Sustainable Development Goals. Central to the initial Africa Use Cases was the integration of in-situ, remote sensing-based earth observation and modelling data to derive the best possible current state of water quality (baseline). Of the three African Use Cases, “Cape Town’s Major Aquifer Systems” focused mainly on groundwater quality in an urban environment. One of the success factors for the Cape Town Aquifer Use Case was the ability of the team to integrate the three different data types of the triangle approach on a sub-catchment scale. This required understanding the complex surface and groundwater systems and their interaction (flow paths and fluxes) in the urban environment. A robust stakeholder engagement process and the introduction of transformative art also drove the success of the Cape Town Use Case. The outcomes of this process will be presented and discussed in this presentation.

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

Groundwater level monitoring is essential for assessing groundwater’s availability, behaviour and trend. Associated with a modelling tool, groundwater level fluctuations can be predicted in the short to middle term using precipitation probabilities or meteorological forecasts. This is the purpose of the MétéEAU Nappes tool implemented by BRGM for the City of Cape Town (CoCT) in the Table Mountain Group Aquifer (TMGA). This case study shows how near real-time groundwater level monitoring can support the municipality in managing its future groundwater withdrawals. The TMGA is an important source of groundwater in the Western Cape region of South Africa. The upper Nardouw Sub-Aquifer of the TMGA is an unconfined aquifer recharged by rainfall. It had been monitored in the Steenbras area for over 10 years before CoCT started groundwater production from the Steenbras wellfield in 2021. The MétéEAU Nappes forecasting tool is already implemented on many observation wells of the French national piezometric network, where it is used for decision-making by the French administration. It allows, in particular, to anticipate several threshold levels of drought and take appropriate measures. It combines real-time water cycle measurement data with a groundwater level lumped model (e.g. Gardenia model) and extrapolates observations for the next 6 months from statistical meteorological scenarios completed with abstraction scenarios. This tool can help protect the Steenbras wellfield as a critical water source for CoCT in the TMGA. This study was financed by the French Agency for Development (AFD).

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 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

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 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

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

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

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

There is a transboundary groundwater reservoir on the Polish–Ukrainian borderlands, which is of key importance in shaping strategic groundwater resources. Due to the particular importance of this reservoir, the two neighbouring countries are obliged to undertake joint actions to protect it. One of the main difficulties in building a common platform for the management of TBAs in the Polish-Ukrainian border area is the differences in the approach to the identification of GWB, monitoring methodologies and assessment of the condition of GWB, and the inconsistent hydrogeological databases between the two countries. A transboundary numerical groundwater flow model was developed to support internationally integrated management. The model research helped diagnose potential problems by determining the scope of the area with cross-border flows and quantifying the flows between Poland and Ukraine. In addition, the numerical model was used to define the optimal cross-border management unit and the conditions needed to exploit the Lublin–Lviv Reservoir sustainably. Abstraction on a current level slightly increased the transboundary groundwater flow from Poland to Ukraine and minimally reduced the flow in the opposite direction but did not reverse the direction of water flow at the border. The simulated drawdowns do not have a transboundary range, but negative effects on surface water resources are noticeable. Joint management should focus on a broader legal consensus, improvement of institutional relations, and integration of monitoring and groundwater status assessment systems.

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

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

The Atlantis Water Resource Management Scheme (AWRMS) has operated since the 1970s. It demonstrates cost-effective and wise water use and recycling through visionary town planning and Managed Aquifer Recharge (MAR), offering water security to Atlantis’s residential and industrial sectors. For the AWRMS to succeed, it required integrating its water supply, wastewater and stormwater systems. Each of these water systems is complex and requires a multidisciplinary management approach. Adding to the challenges of inter-departmental co-operation and communication within a municipal system is the complexity and vulnerability of the coastal, primary Atlantis Aquifer. A combination of operational difficulties, biofouling, vandalism and readily available surplus surface water (leading to scheme augmentation from surface water) were negative drivers to decrease the reliance on groundwater supply from the scheme’s two wellfields. In response to the 2015-2018 drought experienced in the Western Cape of South Africa, the City of Cape Town has improved assurance of supply from the scheme and successfully built resilience by upgrading knowledge and insight through improved investigative techniques, monitoring, modelling and adaptive management of the various water resources and associated infrastructure systems. An integrated and adaptive management approach is essential to ensure continued water security and resilience to the effects of on-going urban expansion, population growth and climate change. Resilience is assured by institutions, individuals and communities taking timely and appropriate decisions, while the long-term sustainability of the AWRMS depends on proper management of all actors coupled with a high level of scientific confidence.

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

Floods result in significant human and economic losses worldwide every year. Urbanization leads to the conversion of natural or agricultural land covers to low-permeability surfaces, reducing the infiltration capacity of the land surface. This amplifies the severity and frequency of floods, increasing the vulnerability of communities. Drywells are subsurface structures built in the unsaturated zone that act as managed aquifer recharge facilities to capture stormwater runoff. They are particularly well-suited for the urban environment because of their low land occupancy. In this study, we utilized an integrated surface-subsurface flow modelling approach to evaluate the effectiveness of dry wells in reducing urban runoff at a catchment scale. We developed a 3D model with HydroGeoSphere, characterizing a synthetic unconfined aquifer covered by a layer of low-permeability materials. Sensitivity analyses of land surface conditions, aquifer properties, dry well designs, and rainfall conditions were performed. Model results indicated that dry wells are more effective in reducing runoff when the land surface has a higher Manning roughness coefficient or the aquifer material has a higher hydraulic conductivity. Dry wells should be situated beneath drainage routes with high runoff flux to achieve optimal performance. Increases in dry well radius or depth enhance the infiltration capacity, but deeper dry wells can contaminate groundwater through infiltrating stormwater. Dry well performance declines with higher rainfall intensity, emphasizing the need for local rainfall intensity–duration–frequency (IDF) data to inform the design level of dry wells in specific catchments.

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

The abstract presents a 2D modelling approach alternative to a 3D variable saturated groundwater model of solute or heat transport at the regional scale. We use FEFLOW to represent processes in the saturated zone, coupled with various models describing the unsaturated zone. The choice of the latter depends on modelling needs, i.e. simulation of the movement of seepage water and nitrate fate with respect to crop rotation patterns and dynamic characteristics of heat gradients, respectively. The flexibility of coupling specialized models of different subsurface compartments provides the opportunity to investigate the effects of land use changes on groundwater characteristics, considering the relevant drivers in sufficient detail, which is important in regions with intensive anthropogenic activities. The coupling can be operated either with (direct coupling) or without (sequential coupling) including the feedback between the saturated and the unsaturated zones depending on the depth of the groundwater table below the surface. Thus, the approach allows for reasonable computational times. The Westliches Leibnitzer Feld aquifer in Austria (43 km²; Klammler et al., 2013; Rock and Kupfersberger, 2018) will be presented as an example highlighting the needed input data, the modelling workflow and the validation against measurements.

Abstract

The geochemical study of deep aquitard water in the southern Golan-Heights (GH), Israel, reveals the complex paleo-hydrological history affected by the intensive tectonic activity of the Dead Sea Rift (DSR). The sampled water collected from new research boreholes exhibits relatively high salinities (2,000-10,000 mg Cl/L), low Na/Cl ((HCO3 +SO4 )). δ18OV-SMOW and δDV-SMOW values are relatively depleted (~-7‰ and ~-42‰, respectively), while 87Sr/86Sr ratios are enriched compared to the host rocks. Lagoonary brines with similar characteristics (excluding the water isotopic compositions) are known to exist along the DSR. These brines formed 10-5 Ma ago from seawater that transgressed into the DSR and subsequently underwent evaporation, mineral precipitation and water-rock interactions. These hypersaline brines intruded into the rocks surrounding the DSR and based on the current study, also extended as far as the southern GH. Further, following their subsurface intrusion into the GH, the brines have been gradually diluted by isotopically depleted freshwater, leaving only traces of brines nowadays. The depleted isotopic composition suggests that the groundwater system is recharged at high elevations in the north. It is also shown that variable hydraulic conductivities in different formations controlled the dilution rates and subsequently the preservation of the entrapped brines. The paleo-hydrological reconstruction presented here shows that the flow direction has reversed over time. Brines that initially intruded from the rift have since been gradually flushed back to the rift by younger fresh groundwater.

Abstract

The devastating socioeconomic impacts of recent droughts have intensified the need for improved drought monitoring in South Africa (SA). This study has shown that not all indices can be universally applicable to all regions worldwide, and no single index can represent all aspects of droughts. This study aimed to review the performance and applicability of the Palmer drought severity index (PDSI), surface water supply index (SWSI), vegetation condition index (VCI), standardised precipitation index (SPI), standardised precipitation evapotranspiration index (SPEI), standardised streamflow index (SSI), standardised groundwater index (SGI), and GRACE (Gravity Recovery and Climate Experiment)-based drought indices in SA and provide guidelines for selecting feasible candidates for integrated drought monitoring. The review is based on the 2016 World Meteorological Organization (WMO) Handbook of Drought Indicators and Indices guidelines. The PDSI and SWSI are not feasible in SA, mainly because they are relatively complex to compute and interpret and cannot use readily available and accessible data. Combining the SPI, SPEI, VCI, SSI, and SGI using multi-index or hybrid methods is recommended. Hence, with best fitting probability distribution functions (PDFs) used and an informed choice between parametric and non-parametric approaches, this combination has the potential for integrated drought monitoring. Due to the scarcity of groundwater data, investigations using GRACE-based groundwater drought indices must be carried out. These findings may contribute to improved drought early warning and monitoring in SA.

Abstract

Test-pumping drawdown curves do not always sufficiently indicate aquifer characteristics and geometry and should never be analysed in isolation. Using derivative analysis and flow dimension theory, inferring the regional geometries and flow characteristics of fractured aquifers that are otherwise unknown or inconclusive is possible. As the drawdown and/or pressure front propagates through the aquifer, it reaches various hydrogeological objects that influence flow regimes and imprints a sequence of signatures in the drawdown derivative curve. The conjunctive interpretation of these flow regime sequences and hydrogeological data results in a robust, well-informed conceptual model (in terms of both local groundwater flow and the aquifer), which is vital for sustainable groundwater resource management. Derivative and flow regime analysis was applied to the test-pumping data of confined and unconfined Nardouw Aquifer (Table Mountain Group) boreholes within Steenbras Wellfield (Western Cape). Major NE-SW trending folding and transtensional Steenbras-Brandvlei Megafault Zone, in association with cross-cutting faults/fractures and younger False Bay Suite dykes, make the Nardouw Aquifer (and deeper Peninsula Aquifer) hydrogeologically complex. The sequential flow regime analyses reveal domains of conceptual flow models, including open vertical fractures, T-shaped channels, double (triple) porosity models, and leaky/recharge boundary models, amongst others. Appropriate analytical flow models (type curve fitting) are then applied for accurate aquifer parameter estimations, which are used to evaluate recommended long-term yields through predictive pumping scenarios. The outcome is an improved hydrogeological understanding and enhanced conceptual model of the aquifer, which informs numerical modelling, ecological protection, and groundwater resource management.

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

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

Integrated geophysical methods can be useful tools in mapping the subsurface characteristics likely to control groundwater occurrence and hence are useful in identifying potential drill targets in different aquifer formations in Southern Africa. This study applied hydrogeophysical methods (natural, electrical, and electromagnetic) to identify potential groundwater-bearing targets within the Kalahari sand aquifers in Namibia and the crystalline basement aquifer system in Namibia and South Africa. The results suggest that hydrogeophysical assessments in Kalahari sandstone aquifers could clearly show that the system exhibits a well-defined layered aquifer formation likely recharged from surface water. On the other hand, crystalline basement formations could be combined with geological observations and used to identify groundwater controls like lineaments and depths to fractured zones. The magnetic method, horizontal and vertical frequency domain electromagnetic geophysical methods presented herein managed to delineate the main dykes and lineament features associated with groundwater occurrence in typical crystalline basement aquifers, while the natural magneto telluric investigations managed to delineate the deep and shallow aquifer formation in Kalahari sandstone aquifer formation. The study also advocates for integrating geophysical methods with local and regional geology for groundwater evaluation to provide a more detailed approach to resource assessment in some of the vulnerable aquifer systems in Southern Africa. Results from this study are useful for technical groundwater management and promoting the utilization of groundwater as a climate-resilient strategy in Southern Africa.