Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 251 - 300 of 795 results

Title	Presenter Name	Presenter Surname	Area	Conference year Sort ascending	Keywords
Hydrogeological modeling of a coastal wetland: The development of a steady-state numerical groundwater flow model for Rietvlei Wetland, Cape Town	Nathasha R	Gariremo	Cape Town	2021	Poster, coastal wetland, wetland management, groundwater budget, numerical model, wetland hydrodynamics
Abstract The Rietvlei Wetland, located in the Western Cape of South Africa is well recognised for harbouring numerous bird species, and is ranked the 6th most important coastal wetland in the South-western Cape. Researchers perceive that the wetland could be threatened by the growing drought hazards, and increased water demand in Cape Town. The extent of the effects is however unquantified and unknown. This therefore calls for extensive research and novel approaches to understand and quantify wetland hydrodynamics, to shape wetland management frameworks. Conducting thorough field work to understand wetland processes, and the use of numerical models for future prediction of black swan events are well recommended. Thus, the study aims to develop a conceptual hydrogeological model for Rietvlei Wetland, and to develop a numerical model to quantify the wetland’s groundwater budget. To achieve this, historical data was gathered, and field work which included groundwater monitoring, collection of sediment profiles and water quality analysis was undertaken. Preliminary results show that the wetland is underlain by an unconsolidated aquifer, largely overlain by different types of sand, mixed with clay and silt, and precipitation is the main source of groundwater into the wetland. A distinct relationship is seen between elevation, soil type and soil structure, such that during the peak rainy season, groundwater tends to be above the ground surface in the low-lying salt pans, dominated by clayey layers on their surfaces. These surfaces tend to crack during the dry season, facilitating preferential flow pathways at onset of rain. This information, and other historical data will be used to develop a numerical model using MODFLOW-NWT and ModelMuse. The numerical model is perceived to be the basis of groundwater modeling using open-source software for Rietvlei Wetland, and may be used for predicting the impacts of drought and increased groundwater abstraction on the wetland’s hydrodynamics.
Sharing water resources and the complexities around it: Three Case Studies from the Western Cape	Christel	Van Staden	Western Cape	2021	Water resource, De Doorns, Worcester, Drilling, Water level, Drawdown, abstraction, Irrigation, Quartzite bedding
Abstract With increasing population growth and a subsequently increased demand for food production, the agricultural sector has had to grow and develop continuously despite drought-stricken water resources in recent years. The expansion in this sector requires increasingly efficient water use management and increases in water supplies, which are often met through groundwater utilization. In the past several years the use of groundwater in the Western Cape has increased exponentially and thus has forced the sharing of resources. The question pertains to how an invisible water resource that is difficult to measure and quantify, can be shared. Issues of varying complexities can arise when submitting a water use licence application (WULA), such as historical water use debates, interactions between groundwater and surface water, seasonal stresses on resources, etc. In one case study in De Doorns, a WULA became side-tracked soon after initiation by a neighbour’s complaint that his production borehole was severely affected by the drilling of the applicant’s boreholes. In the second case study in the Hexriver Valley, a WULA was complicated by a gentleman’s agreement stating that no one in the valley is allowed to abstract groundwater from deeper than 6 m. This gentleman’s agreement stems from past disagreements regarding such practices. The final case study was not a WULA but arose out of concerns for dropping weir levels connected to a new borehole. The borehole was equipped with new casing to case off the alluvium; it was suspected to be the cause of the disturbance. The scientific method was used to evaluate the borehole’s impact on the weir. Case studies such as these will become more prevalent as the demand on water resources will increase. Hydrogeologists needs to more informed of the complexities that can and will arise in the future as a result of shared water resources.
Optimized Groundwater Monitoring Design for Managed Aquifer Recharge Using Hybrid Numerical, Geophysical and Chemical modelling approach	Clinton W	Andries	West Coast, Western Cape	2021	MAR, AHP, Monitoring network design
Abstract Israel, S; Kanyerere, T Globally, surface waters are severely unsustainably exploited and under pressure in semi-arid coastal regions, which results in increasing demand for groundwater resources. Currently, Cape Town and its neighbouring towns along the West Coast of South Africa are facing water shortage related problems. Managed Aquifer Recharge (MAR) is a nature based solution to improve groundwater security in drought prone regions such as the West Coast. The objective of this study was to design a groundwater monitoring network using a hybrid hydrochemical, geophysical and numerical modelling approach to assess and mitigate the potential impacts of MAR for the West Coast Aquifer System (WCAS). An Analytical Hierarchy Process method was used to perform a Multi-criteria analysis employed in GIS (ArcMap 10.3). The factors of importance for optimized groundwater monitoring network design were based on available data and consultations with hydrogeologists and environmental scientist at stakeholder workshops. The factors which were considered included: elevation (m), geology, density of existing boreholes (wells/km2), electrical conductivity (mS/m), water rise (m), water level decline (m), transmissivity (m/day), saturation indices and lithological thickness (m). Factors were weighted based on their level of importance for the design of the groundwater monitoring network using Analytical Hierarchy Process (AHP). Priorities were calculated from pairwise comparisons using the AHP with Eigen vector method. The Consistency Ratio (CR) calculated was 5.2% which deems the weighting coefficients statistically acceptable. The results show that high priority monitoring areas occurs in the areas where there are fresh groundwater, high borehole density, elevated topography, higher recharge rates and decline in water levels are found. The monitoring network will include boreholes from the low priority areas to ensure that hydrogeological conditions are monitored and impacts are not worsened. Geophysical, numerical and chemical modelling aspects of the methodological approach will be incorporated into the initial groundwater monitoring network design.
Sustainable rehabilitation of production boreholes: Application of ph-neutral iron(III)dissolvers by closed-circuit injection	Päivi	Puronpää-Schäfer	Finland, Germany, others	2021	Rehabilitation, maintenance, closed-cicuit injection
Abstract Clogging of existing boreholes due to natural well ageing is the most common cause of decreasing yield worldwide, also in South Africa. Maintenance plans based on systematic monitoring are required including inspection, service and rehabilitation to lengthen production times and to slow down ageing processes. Therefore a prerequisite of economical well operation is to apply the most efficient measures to secure their production capacity at the lowest possible cost. Rehabilitations by mechanical, hydraulic or impulse methods do often not lead to acceptable yield increases. Acids of all kinds have been applied to remove iron(III) and manganese(III,IV) clogging, although pH values of < 1.0 are required before any significant dissolution takes place. This treatment does not only affect substances in adjacent geology but also well construction materials and technical equipment. Alternatives for acidization were researched and developed at the Technical University of Aachen (RWTH) in 1990’s by Prof. Dr. Treskatis and Dr. Houben. Since then iron(III) and manganese(III,IV) are removed by pH-neutral reductants with 50 times greater dissolving capacity than hydrochloric acid at pH 1.0 in identical molar concentration. The closed-circuit injection technique was proved to be the only method to transfer chemical agents as far as the borehole wall in a study by Dresdner Groundwater Center on behalf of German Gas and Water Association in 2003. Low pressure circulation based on large volume flow is accomplished by means of state-of-the-art gravel washers. The application of pH-neutral dissolvers by closed-circuit injection has proved its effectiveness not only in Germany, but also in Switzerland, Austria, Netherlands, Spain, UK, UAE and Peru. Our case study documents its successful introduction in Finland 2020. Until then stand-by acidization had been the only means of battling well ageing. Research funds enabled rehabilitations in different parts of the country resulting in unexpected high yield increases.
Observation and monitoring of field parameters for springs and rivers of a Swiss alpine valley in relation to seasonality.	Cedric	Meier	Switzerland, France	2021	Monitoring, data management, data science libraries, Water security, Groundwater Sampling, training, municipal water supply
Abstract The study area is located in a Swiss alpine valley at the border between Switzerland and France and is situated in Valais. It is delimited by the hydrologic catchment of the river “La Vièze de Morgins”. The catchment area is situated in the Municipality of Troistorrents and of Monthey. Its population is approximately 4500 inhabitants. From the geological point of view, the valley “Val de Morgins” is mostly comprised of sedimentary rocks, amongst others breccia, schist, flysch, limestone, and quaternary sediments. The valley is affected by several natural hazards, such as landslides, rockfalls, and avalanches. Hydrogeologically, the valley contains few main springs that are outlets of porous and fissured aquifers. For this study, an inventory and monitoring of springs and rivers has been carried out since 2018 until April 2021. Particularly, more than 110 springs and rivers have been registered and observed during this time. The data includes GPS coordinates, photos, measurements of physical-chemical parameters and flowrates. Complementary to measurements, specific geological and topographical maps, and site information have been gathered. The analysis and interpretation of this huge set of hydrogeological data will be concluded with a new and innovative approach using different data science libraries that are implemented for the Python programming language. In this case study, groundwater sampling training is used to increase the understanding of the water quality. Four years of field measurements enable a better understanding of the parameter variability in relation to seasonality. Furthermore, new data analysis can aid the integrated resource management for the municipal water supply. The sampling and monitoring are key aspects to ensure water security, in terms of quality and volume. Additionally, it can also unlock prospective groundwater resources for municipal water supply. Case study data will also be compared with South African and other Swiss dataset of similar aquifer type.
Diamonds on the soles of their feet: groundwater monitoring in the Hout Catchment, Limpopo	Jacqueline	Goldin	Limpopo	2021	Citizen Science, framework, participatory methods, Rainfall, Groundwater Sampling, Data collection
Abstract We present findings from a current project in the Hout Catchment, Limpopo Province in South Africa, In grounding the discussion, we propose a citizen science framework that builds on ideas of the living lab, trust and research integrity. The idea of research integrity is not only about ethics but also about methods and we propose participatory methods that are inclusive, just and fair. We achieve trust and practices of research integrity, applying participatory action research methods which not only address the hydrological void in data by identifying water features in the catchment but also have intrinsic value, enhancing well being and brokering trust. The frame presents the idea of water literacy – where the material aspects of CS (dip-meters, rain gauges etc.) intersect with the more intangible goods that have to do with human well-being. In our application we redress the bias where the focus lies more on the natural science aspect rather than the humanities with its attention to human well-being and the recognition of difference and diversity. Considering CS within the frame of feminist philosophy, it is personally transformative with the element of ‘surprise’ that the end point is undetermined – and it focusses on diversity and difference across segments and within segments in the catchment. Participatory parity has intrinsic value (equity and a more just social context) but also extrinsic value (better data and plotting of map features for remote rural areas otherwise difficult to access). CS is a powerful emancipatory tool that is able to generate virtuous cycles of inclusion and equality. We propose a CS frame that captures the ideas of trust, the living lab, SDGs and the emancipatory notion of citizen science, narrowing the divide between the natural and social sciences and acknowledging research integrity and the opportunity for what we call ‘authentic’ learning. Also Refer Article published in the BWJVol131 https://bwa.co.za/the-borehole-water-journal/2021/12/28/south-african-groundwater-project-shows-the-power-of-citizen-science
Identifying suitable sites for Managed Aquifer Recharge within the Saldanha Bay Local Municipality, situated in the West Coast of South Africa	Ashleigh	Tomlinson	West Coast, Western Cape	2021	MAR
Abstract The West Coast in the Western Cape of South Africa is a water-scarce area. With pressure from population and industrial growth, recurring droughts and climate change, there is increasing urgency in the West Coast to protect groundwater resources. Saldanha Bay is dependent on groundwater as part of its bulk water supply system. Where the natural groundwater recharge is no longer sufficient to meet the growing groundwater needs, practices such as Managed Aquifer Recharge (MAR) can be used to ensure the sustainability of these groundwater resources. This study aims to identify areas within the Saldanha Bay Local Municipality suitable for Managed Aquifer Recharge to maximize the water available during periods of limited surface water supply. As such, the MAR study site identification requires a comprehensive geohydrological assessment of the Saldanha Bay aquifer. This includes an understanding of the quality and quantity of the source water available for recharge, the aquifer structure and hydraulic properties, the space available to store water, and the compatibility of the recharged water with the groundwater. MAR research methods included Time Domain Electromagnetic (TDEM) airborne geophysical surveys, infiltration tests, pumping tests and hydrochemical analysis. TDEM surveys provided clarity on the various aquifer geological properties. Infiltration and pumping tests shed light on the horizontal and vertical hydraulic properties of the aquifer. PhreeqC modelling outputs helped predict the outcome of the mixing between groundwater and potential MAR water resources. Geological features were delineated through TDEM surveys and inferred five suitable MAR sites where clay layers were missing. Infiltration and pumping tests showed that Langebaan Road is better suited to borehole injection, whereas Hopefield has the benefit of infiltration MAR techniques as an additional option. PhreeqC outputs exhibit that both pipeline and Berg River water show promising results as potential source water resources for MAR as compared to other resources.
The presence and concentration of antiretroviral drugs in different water bodies around the Western Cape	Phumelele	Maphumulo	Western Cape	2021	Antiretroviral, chemical formulas
Abstract This study is based on the presence and concentration of antiretroviral drugs in water bodies around the Western Cape Province in South Africa, these areas include wastewater treatment plants, water treatment plants, stormwater, and landfill boreholes. South Africa has the highest rate of HIV and AIDS in the entire world, statistics from 2018 show that 7.7 million South Africans are infected with HIV/AIDS and 68% of them are on antiretroviral treatment (UNAIDS). South Africa has the largest antiretroviral treatment program (ART) in the world, due to the lack of proper water and sanitation these drugs are deposited in the environment poorly and reach water bodies, therefore, contaminating them. This study involves the collection of samples from areas such as Mitchell’s Plain, Khayelitsha, Athlone, Cape Flats, and Atlantis around the western cape, these samples are analyzed to determine the presence of 5 antiretroviral drugs used in South Africa which are Efavirens, Lopinavir, Nevirapine, Ritonavir, and Tenofovir. Water samples are prepared for analysis by filtering 2.5ml water through a 1µm glass fiber filter, the sample is then placed into sample vials and analyzed on HPLC-QTOF/MS. Mass Hunter software is used to identify the specific ARVs in the water samples analyzed, by searching for the compounds via their chemical formulas. With a match made if their chemical formula, retention time and mass to charge ratio of the compounds correspond. Concentrations range between 0.0855ng/ml Nevapine to 4.3289ng/ml Lopinavir, this analysis has determined that all the mentioned antiretroviral drugs are indeed present in different water bodies around the identified areas within the Western Cape in varying concentrations.
eSymon - An Innovative Solution to Monitoring Data Management	Tarika	Isaac	South Africa various	2021	eSymon, Monitoring, data management, data visualization, data security
Abstract The year 2020 will forever be synonymous with the Covid-19 pandemic and the immeasurable impact it has had on all our lives. During this time, there was one avenue that reigned supreme: technology. Whether it was Zoom calls or Netflix, online consultations or video conferencing at work, technology took charge. In light of this, GCS (Pty) Ltd started exploring ways that technology could assist with the most common problem identified in the Water and Environmental sectors, which is the management of large volumes of geodata. Thus, the invention of eSymon. Monitoring of the environment usually generates a significant amount of data. If this data is not systematically stored, problems often arise with: • Limited access to historical data due to poor storage; • Different formats of stored data (if they are kept in digital form at all); • Continuity and integrity of the data; and • Security of the data. Therefore, years of historical data cannot be used or trusted. The solution was to develop eSymon, which is an acronym for Electronic Data Management System for Monitoring. eSymon is primarily designed to: • Systematically import, store, view and manipulate large volumes of monitoring data; • Provide remote and instantaneous access to site-specific information; • Allow data visualization using an interactive GIS interface; and • Create various outputs such as time series graphs, geochemical diagrams and contour maps. The main idea of the software is to have all historical data for a site on one platform and have it be accessible and functional at the touch of a button. This results in several key benefits, including saving time, providing accurate and up to date information, not having to wait for technical reports to assess trends and compliance, providing several means of data visualization and, most importantly, ensuring data security.
Latest approaches and examples illustrating the key role of numerical modelling in sustainable groundwater use in South Africa	Annalisa Sagra	Vicente	South Africa various	2021	numerical modelling, recharge
Abstract Imrie, S. Groundwater in South Africa has great potential to supplement our country’s water demands. Currently, studies show that less than 10% by volume of the Average Groundwater Exploitation Potential is abstracted on an annual basis. The 2017 drought has aided in creating awareness of the importance of this resource towards building water resilience. If managed correctly, groundwater is commonly viewed as a sustainable source. Oftentimes, the ‘sustainability’ of a groundwater resource is an ‘open-ended’ definition based on the hydrogeologist’s interpretation of aquifer pumping test data alone. This approach often discounts the cumulative impact of environmental factors (including drought and climate change) and other users on groundwater. The use of numerical groundwater models to support and inform the conceptual models provides the mechanism to bridge this gap. This paper discusses various approaches and examples of where numerical modelling plays a key role in supporting groundwater usage in a sustainable and informed manner. In particular, this includes: •Inclusion of impact from other anthropogenic activities and groundwater users, with model scenarios that show the potential impact of each on the other, as well as the combined result to groundwater (levels and water quality) •Consideration of extreme climatic events (e.g. 1 in 100-year drought and/or flood), including the use of uncertainty analysis and consideration of dynamic groundwater management, such as the possible varying of sustainable pumping rates to suit the prevailing conditions •Identification of groundwater receptors and appropriate assessment of potential impacts to those receptors from groundwater usage, including “target-audience” thinking in the post-processing and reporting of numerical model results, so as to convey clear messages to the interested and effected parties and stakeholders •Use of multiple methods and technologies to calculate and model surface water / groundwater interaction and recharge, including uncertainty analysis, and intelligent challenging of traditional methods of estimating groundwater recharge
"But is it 'pollution'?" - determining appropriate site-specific regulatory limit values for groundwater quality.	Carin	Bosman	National	2021	Groundwater Quality, WSA 108 of 1997, SANS, law, policy, Methodology
Abstract Because the quality of groundwater is influenced by the host rock through which it moves, it differs on a site-specific basis, and is often naturally brackish or even potentially harmful to people. In spite of this, many practitioners incorrectly use the SANS 241 Drinking Water Standard as “compliance requirement” to compare groundwater quality against. This standard only applies to water that has been purified to be suitable for potable purposes at a water treatment works in terms of regulations made under the Water Services Act 108 of 1997. The only circumstance in which it could be used to compare the quality of natural groundwaters against, is where such groundwater is (to be) used, for potable purposes (with or without treatment), and then only to provide guidance on the level of treatment required to facilitate suitability for such domestic use, and not to determine possible ‘unacceptable’ levels of contamination. Therefore, the comparison of groundwater quality results against the SANS 241 Drinking Water Standard is not only a scientifically flawed practice, it has no basis in law. It is furthermore a scientifically flawed practice to refer to groundwater quality as ‘good’, ‘bad’, or ‘poor’, as it reflects a judgemental anthropocentric perspective that has no place in modern discussions on judicious environmental management and monitoring. This then raises the question, what are, or should the limit values be against which groundwater quality results should be compared to determine if it has been negatively affected by anthropogenic activity to such an extent that a scientifically substantiated claim can be made that the groundwater has been ‘polluted’, an allegation with criminal liability implications? This paper aims to answer this question in the context of South African Framework law and policy, and propose a methodology to determine appropriate site-specific limit values for groundwater quality.
What is in a - groundwater - map?	Nicolette	Vermaak	South Africa various	2021	Mapping methodologies
Abstract A map is a symbolic or diagrammatic representation of an area of land or sea, showing physical features and the relationship between these elements. It often reduces a three-dimensional world to two dimensions. Maps are generally static – fixed to paper or some other medium. Maps are produced for different reasons, leading to different types of maps, e.g., roadmaps, topo-cadastral maps and the groundwater maps – with the latter the topic of this article. There is a lot of work going into maps. This includes collecting all the data, doing evaluation and analysis of the data and selecting the data to use on the map. It is not possible to present all the information on a map and maps are often a generalisation. Different kinds of groundwater maps include availability, quality, vulnerability and protection. The selection of symbols to represent the information and the rendering of the maps are important in producing understandable, useful maps, but need explanations. The success in representing the information on a map will determine the usefulness of a map, but it is still often misused. At the end of this long and tedious process where conflict management skills were well developed, you may find that the information on the map is outdated before the ink on the map is dried properly. The production of maps should be an iterative process, where new data can be incorporated as soon as it becomes available. It is an expensive process and cannot be repeated too often. This article will look at the processes that helped to shape the current series of hydrogeology maps of South Africa, and how to use it optimally while mindful of limitations. It will also briefly touch on recent research that aims to help with the production of improved groundwater maps for South Africa.
Evaluating changes in groundwater storage during the 2015-2018 drought in the Western Cape using GRACE data	Ritshidze	Nenweli	Western Cape	2021	Poster, Drought, GRACE, Groundwater storage
Abstract The frequency, intensity, and duration of droughts are increasing globally, putting severe pressure on water supply systems worldwide. The Western Cape Province suffered from a period of severe water shortages that began around January 2015 and lasted until about July 2018. During this recent drought, there was a forced reduction in water use, predominantly from the agricultural sector. Citizens also reduced water use and increasingly tapped into groundwater for their needs irrespective of whether the hydrogeology was considered favourable or not. Unmonitored and unregulated abstraction of groundwater, especially under unstable climatic conditions, poses a significant risk to the future water security of the Western Cape. We hypothesize that groundwater enabled the municipalities, residents, and industries of the Western Cape to survive the recent drought. Our aim is to evaluate the change in groundwater storage during the 2015 to 2018 drought and its subsequent recovery. To achieve this, we must gain a comprehensive understanding of the dynamics of separate components of the water cycle, as well as the overall water balance. While there is data on surface water use during the drought, the impact on groundwater resources has yet to be evaluated. However, the accurate assessment of groundwater use is difficult, especially in data-scarce regions, such as South Africa. In our study, we combine remote sensing from NASA’s Gravity Recovery and Climate Experiment (GRACE), the Global Land Data Assimilation Systems, groundwater level measurements from the National Groundwater Archive, and ancillary datasets from the City of Cape Town’s weekly water dashboard to assess the total change in groundwater storage in the Cape Town Metropolitan area and surrounding cities over an 8-year period, from 2012 to 2020. Preliminary results from GRACE data analysis show a steady decline in aquifer saturated thickness over the drought, indicative of an increase in groundwater use.
Impact of Engineered Tree Plantations on Water Transfer Through the Upper Vadose Zone and Implications on Vertical Groundwater Recharge	Hendrik	Botha	National	2021	Poster, tree plantations, impact, vertical recharge, water transfer, vadose zone, water balance
Abstract The main purpose of this paper is to present a case study where soil moisture and rainfall data were evaluated for engineered tree plantations, to understand the potential impact on vertical groundwater recharge. Soil moisture for probes within the tree plantation root zones and reference sites within the same soil types were evaluated, in context to site rainfall patterns. Water transfer from shallow to deeper soil zones for a dataset of 2 years are presented. Observations in terms of water movement in the root zone are made. A water balance is presented in the effort to conceptualise the impact on water transfer through the upper vadose zone and to quantify the significance in terms of potential vertical groundwater recharge reduction.
Assuring supply during a changing environment focussing on drought	Danita	Hohne	National	2021	Drought, community supply, operating rules
Abstract Fourie, F Communities reacted differently to the drought. In some cases, you would notice a proactive approach and good management of the wellfields. In other cases, communities have been under a misconception that they received good rainfall for a recharge which did not reflect in monitoring data, and lastly, you get the communities that are mismanaging the groundwater. Various lessons were learned from the change in the climate and environment. But a lot can be done to minimise the impact of these changes on the water supply to communities. This paper addresses the changes that we can apply to deal with the changing environment around us to provide a sustainable water supply. The changes can include relooking at operating rules to ensure better management on the aquifer and borehole level. Recharge determined during pump test must be considered periods low to no recharge. Methods to enhance the recharge to the aquifer will ensure recharge occur during low rainfall events By implementing these rules, groundwater can be sustainably managed for future use.
Transport and attenuation of microplastics in saturated sands	Sabastian	Stenzl		2021	Microplastics
Abstract Globally, cumulative plastic production since 1950 is estimated to have reached 2500 Mt of plastic. It is estimated up 60% of this plastic is either resting in landfills or the natural environment, including groundwater settings. Microplastics are small pieces of plastic ranging between 1μm – 5mm in size and have been found in every ecosystem and environment on the planet. Much of the available literature on microplastics is focused on marine environments with few in comparison focused on freshwater environments, and even fewer on groundwater settings. The aim of this study is therefore to investigate the attenuation process responsible for influencing microplastic transport in saturated sands. This research will adapt colloid transport theory and experiments to better understand the movement of microplastics through sandy media. Saturated aquifer conditions will be set up and simulated using modified Darcy column experiments adapted from Freeze & Cherry (1979). Modified microplastics will be injected into the columns as tracers and the effluent concentrations measured by Fourier-transform infrared spectroscopy (FTIR). Breakthrough curves will then be plotted using the effluent concentrations to determine the attachment efficiency (α). It is expected the attachment efficiency will vary by microplastic type and size range. The Ionic strength of the solution flowing through the column and the surface charges of both microplastics and sandy surfaces are likely to influence the degree of attenuation observed. The relationship between different types of microplastics and collector surfaces from a charge perspective and their influence on the degree of attenuation will be evaluated. Given the lack of literature, its ubiquitous presence and postulated effects on human health, this research is significant. Through this research, the transport and attenuation of microplastics through sandy aquifers can be better understood, and in the process inform future research and water resource management.
The fate and occurrence of pharmaceuticals in Cape Town’s water network	Mikyle	Cloete	Cape Town	2021	Poster, CECs, micropollutants, pathways, contamination, pharmaceuticals
Abstract Israel, S Thousands of pharmaceuticals, pesticides and microplastics are consumed and disposed of directly or indirectly into various waterbodies globally. They are collectively termed “contaminants of emerging concern” or CECs. Contaminants of emerging concerns are defined as micropollutants that are present in the environment that are not regulated and that can pose a risk to the health of both humans and wildlife. The spread of these CEC’s in water systems is not isolated to a specific place and is on the rise all over the world. This study aims to investigate the spatial and temporal distribution pattern of pharmaceuticals in Cape Town’s water network, in order to assess the occurrence, concentration levels and distribution of pharmaceuticals in various water bodies. The study focuses on the occurrence of eight pharmaceuticals which are most frequently used and occurs in various water bodies around the world, namely acetaminophen, diclofenac, carbamazepine, naproxen, rifampicin, tenofovir, progesterone, sulfamethoxazole. The research sites include six waste water treatment plants in Cape Town with receiving rivers and borehole sites nearby and downstream from the waste water treatment works. Liquid chromatography combined with mass spectrometry is the selected method used to analyse the analytes of interest in the collected samples. Preliminary results obtained during the summer period (January 2021) showed that pharmaceuticals had indeed spread from waste water treatment plants into receiving water bodies with concentrations ranging from 0.8 to ≤ 6400 ng/L in both surface and groundwater due to the inefficient removal of these compounds. Continued research will conclusively address the concentration levels as a function of time, and consider the spatial distribution and its seasonality. It can be concluded from the preliminary results, that pathways of contamination from waste water discharge points to surface water and groundwater do indeed exist for the 8 pharmaceuticals considered.
Hydrocarbon groundwater analyses: a Karoo case study	Danita	Hohne	Karoo	2021	Hydrocarbon, Water level, contamination, Artisan borehole, Methane concentration, Natural gas, Dolrites, quality, Fracturing
Abstract The South African government is considering shale gas extraction in the Karoo basin, South Africa. To protect groundwater resources, there is an urgent need to do a groundwater baseline in possible gas extraction areas. Various groundwater samples have therefore been taken at a borehole and 2 soekor wells in the Northern Cape, from 2016 to 2021. The groundwater samples were analysed for dissolved gasses, specifically focussing on methane. As laboratories became more efficient ethane was also included in later analyses. From the analyses we found that drought might influence the dissolved gas concentrations in the groundwater via pressure influences on the groundwater flow and the dissolved gas flow towards the shallow aquifers. Artesian conditions at this site are helping with the flow of dissolved gasses from deep to shallow aquifers via preferential pathways. The possibility of shallow-deep groundwater interconnections and the migration of deep methane to shallow aquifers make it important to establish a groundwater baseline in the Karoo. By focusing on boreholes and wells that are emitting methane, a better understanding of groundwater flow and interaction with geological layers can be determined. If other gasses like propane and butane can be analysed in addition to methane, more information can be gathered to determine the origins of the methane and whether it is thermogenic or biogenic.
Managed aquifer recharge - evaluating the efficiency of the unsaturated zone to reduce contaminants. A case study of Atlantis aquifer	Londiwe	Ntshangase	Atlantis	2021	MAR, contaminants removal, unsaturated zone, prevention strategies
Abstract Surface water resources are under threat of depletion and quality deterioration due to various factors such as climate change, urbanization, and population expansion. Managed aquifer recharge (MAR) is a technique that has been successfully implemented over the last 4 decades to sustain the balance between water demand and availability. The unsaturated zone, where source water is introduced during infiltration, plays a major role in the reduction of contaminants present in water before it naturally percolates and reaches the aquifer. This research aims to evaluate the removal efficiency of contaminants by the unsaturated zone. Three objectives to be accomplished are; to determine and classify the chemical composition of the source water. Secondly, to determine the hydraulic properties of the soil in the area of interest. Lastly to evaluate the contaminants removal efficiency, by tracing the quality of water at the point of recharge and discharge. The Atlantis water resource management scheme in the Western Cape will be used as a case study, in order to assess the relationship between the unsaturated zone and the reduction of contaminants. The current study argues that during the artificial recharge of aquifers, contaminants present in the source water filter through the unsaturated zone, where natural processes, as well as resident microbes, reduce their concentrations to acceptable levels. Assessing the ability of the unsaturated zone to reduce contaminants, will allow for the early warnings of contamination potential and the execution of informed prevention strategies that can be used in decision making of the management and protection of water resources. Additionally, the advanced understanding of the role that the unsaturated zone plays in eliminating contaminants can be used to account for satisfactory groundwater quality in areas where groundwater is not constantly monitored and artificial remedies are not applied.
The Importance Of Reliable Monitoring Data	Shuaib	Dustay	National	2021	data management, numerical model, poor data
Abstract Imrie, S “Monitoring rounds”, “logging”, “quality checking”, “data collation” and “reporting” are terms all too familiar to groundwater field specialists. Yet, a full understanding of the true worth and the full lifecycle of data is often not appreciated. Field data form critical “ingredients” to groundwater conceptual and numerical models. Unfortunately, if can often be the case that the quality of field data is only tested once it has been processed and input to the model, which may be many years following collection. This case study highlights the time-consuming, budget-consuming and groundwater management difficulties that can arise from poor quality data, such as poor monitoring network designs, inconsistent data capturing, erroneous logging, poor borehole construction and gaps in data. The study area is an industrial complex with a highly contaminated groundwater system. The site is located on fractured sandstone and tillite, with major cross-cutting fault zones. The objectives of the numerical groundwater model are to assess the efficacy of the current remediation measures, likelihood of seepage due to artificial (contaminated) recharge, and prediction of the future potential contaminant plume footprint. Setbacks were encountered in the early stages of building the model. Although the site has a monitoring network of over 300 boreholes, less than 50 of these boreholes could be considered for model calibration, with those remaining including data with high uncertainty and multiple assumptions. The poor data resulted in lower calibration statistics which translated into lower model confidence levels. The modelling exercise proved useful for informing updates to the monitoring programme and identification of critical gaps where future drilling and testing will be focussed. However, the lack of reliable monitoring data led to a model of low confidence and high uncertainty, subsequently impacting the level of groundwater management, and thus impeding remediation efforts and future protection of our precious groundwater resource.
Unconventional Gas Regulations for Water Use by DWS Unconventional gas	Lebogang	Malefane	South Africa	2021	Unconventional gas, UCG, CMB, contamination, Regulations, NWA 1998
Abstract Unconventional gas development in South Africa consists of but not limited to shale gas extraction commonly known as “fracking”, Underground Coal Gasification (UCG), Coalbed Methane (CBM), to extract natural gas from geological formations is a new, rapidly expanding industry in the world and in South Africa. However, there are general concerns that these operations could have large negative impacts such as groundwater contamination. This article maps out the development of regulations for unconventional gas operations, according to Section 26(1) (9) of the National Water Act, 1998 (NWA) and read together with Government Notice 999 (Government Gazette No.: 39299, of 16 October 2015). The objectives of the published DWS regulations include, augmenting the NWA and its existing regulatory framework, providing for a step-wise process for authorising all unconventional gas operations to allow for informed decision making, to set prohibitions and restrictions for protection of water resources, and requirements for disclosure on chemicals to be used during the operations. The objectives of DWS regulations are aligned to the NEMA, and MPRDA requirements for exploration and production of these operations, and are further supplemented by the minimum information requirements for water use licensing application and as part of integrated water resource management. In conclusion, DWS proposes thoroughly consulted and fit-for-purpose regulatory framework that seeks to propose water use law and requirements for unconventional gas operations based on the National Water Act (1998). With these proposed regulations DWS ensures that it plays its critical role in the development of a regulatory framework for unconventional gas operations.
Testing Danish groundwater mapping methodologies in South Africa, Case Ladysmith, South Africa	Jan	KÜrstein	Ladysmith, South Africa, Denmark	2021	Mapping methodologies, 3D models
Abstract Vermaak, N; Fourie, F; Awodwa, A; Metcalf, D; Pedersen, PG; Linneberg, MS; Madsen, T The Strategic Water Sector Cooperation (SSC) between Denmark and South Africa is a long-term bilateral cooperation, which amongst others are contributing to the South African water sector by demonstrating and testing different Danish groundwater mapping methodologies in South Africa in order to add long term value to the South African work on optimizing the utilization of groundwater and to increase the resilience against drought. One key aspect is to develop a South African groundwater mapping methodology, based on the detailed Danish methodology and South African specialized knowledge of the South African hydrogeology. In this case, the SSC has contributed to the work done by Umgeni Water in The District Municipality of uThukela in the KwaZulu-Natal (KZN) province of South Africa. The methodology that has been used is integrated modelling using 3-geological models built in GeoScene3D and groundwater modelling, which was based on existing data from Umgeni Water and Department of Water and Sanitation (DWS). Based on the outcome of the 3-D geological voxel model both known aquifers where the boundary has been adjusted, as well as new aquifers has been outlined. Good places for drilling production boreholes have been identified, followed by groundwater modelling of sustainable abstraction rates from existing and new potential well fields. Finally, recommendations were made for new data collection and how to modify the Danish mapping approach for use in South Africa, taking the differences in geology and water management into consideration. The Danish methodology for groundwater mapping is adaptable to South African conditions but it requires Danish and South African experts works closely together. The project has also shown that integrated 3-D geological modeling and hydrological modelling can contribute to a sustainable development of groundwater in South Africa, as well as the Danish methodology for modelling and monitoring sustainable abstraction rates.4
Science-Policy Nexus: Assessing role of groundwater resource directed measures in water resources protection practice, case of Schoonspruit-Koekemoerspruit River Catchment, South Africa	Stanley	Nzama	Gauteng, North West	2021	RDM, aquifer protection, knowledge sharing, policy implementation
Abstract The argument in this paper is that improved understanding of science-policy integration, where physical bases of natural science is combined with practice in managing water resource challenges, becomes critical in translating scientific knowledge into effective and sustainability solutions linked to groundwater resource protection. Such hypothesis should be attested at locally relevant scale where water resources reside and where water utilization takes place. This paper provides a practical case-study of how science-policy integration can directly impacts groundwater resource protection practice from a local, and national perspective using strategies of groundwater resources directed measures. A combination of literature surveys, and desktop record review methods were used for the purpose of data collection from published literature and publicly accessible national databases of the Department of Water and Sanitation (DWS). Collected data were analysed using document analysis, descriptive statistics, and case study analysis methods. Based on the analysis, three types of science-policy nexus theoretical models exist in practice, namely, 1) science-policy integration, 2) policy-science integration, and 3) mixed integration. From a national perspective, the analysis showed that South Africa is able to practically apply science-policy nexus in policy implementation practice for water resources protection, and that such practice depicts a mixed integration model of the nexus. Case study analysis of the Schoonspruit-Koekemoerspruit River Catchment provided insight on how localized operationalization of groundwater resource directed measures facilitates sustained groundwater resources protection for water availability and sustainable utilization. This study provides an exemplary for collaborations between researchers and/or scientists and policy makers to ensure that science research is answering policy-relevant questions and that results from scientific work are readily available for policy implementation. In addition, there is adequate evidence to indicate that science-policy nexus can be designed and prioritized to support sustainable development agenda on groundwater resilience, and visibility at various levels.
Hydrogeological Characterization of a Methyl-Tertiary-Butyl-Ether (MTBE) Plume	Bamanye	Takashe	Saudi Arabia	2021	contamination, MTBE, TOC, remediation
Abstract The proximity of aquifer systems to sources of contamination exposes them to severe environmental threats. Pollutants that leak from petrol stations, industrial areas and landfills eventually seep through the vadose zone to reach shallow groundwater, leading to groundwater contamination. One of these pollutants is Methyl Tertiary-Butyl Ether (MTBE), which is a polar organic compound that is volatile at room temperature. As a result of its high solubility compared to other gasoline additives, MTBE can cause serious environmental issues. The aims of this study were to characterize the extent of MTBE in groundwater and characterize natural attenuation in a Saudi Arabian MTBE and methanol manufacturing company. The aims were achieved by analyzing monthly MTBE concentrations (to observe the seasonal changes of MTBE) and annual MTBE concentrations (to observe long-term changes) in 5 out of 18. Groundwater samples were collected, and in each year the MTBE, Total organic carbon (TOC) and Electrical conductivity (EC) concentrations were recorded. Because of inconsistency in the data, the results for the monthly data were from 2007 to 2010, and from 2007 to 2012 for the annual data. The results indicated a positive relationship between MTBE and TOC, and as a result TOC can be used to monitor and indicate the presence of MTBE. There was plume growth in 2 of the 5 wells (well 4 and well 14) with well 4 recording the highest MTBE concentration in all years. The reason for the high concentration might be because of spillages during truck loading. The other 3 wells showed signs of natural attenuation. Results from seasonal data suggested that temperature influences MTBE concentrations and therefore the rate of natural attenuation. There are many methods to remediate MTBE and each of them is site specific, but bioremediation was recommended for this site due to its cost-effectiveness.
Measuring Hydraulic Conductivity Across Different Scales Using Varying Methods To Develop A Hydraulic Conductivity Model	Sispho	Dlakiya	Cape Town	2021	Poster, hudraulic conductivity, methods, scales, infiltrometer, vertical infiltration
Abstract This paper describes the calibration and testing processes of three methods of measuring hydraulic conductivity (slug test, mini disk infiltrometer and particle size distribution (sieves)) across varying scales (field and lab). The methods used in the field are the slug test and sieves which were used in four different wells of the Rietvlei wetland in Cape town and the mini disk infiltrometer was used in a grid developed in one of the Nelson Mandela University Reserve salt pans. The mini disk infiltrometer and the slug test are used to determine the saturated hydraulic conductivity (Ks) of altered or unaltered soil samples under controlled conditions in a laboratory, and that is a key parameter to understand the movement of water through a porous medium. The mini disk infiltrometer requires a small volume of water and has a compact size which makes it convenient for laboratory soil specimens, especially when studying vertical infiltration. Infiltration shows a dependence on the compaction and saturation of soil while hydraulic conductivity increases with depth in a simulated aquifer.
The Seven Deadly Sins of Numerical Modelling	Andries	Wilke	South Africa	2021	numerical modelling, recharge
Abstract Pope Gregory defined the seven deadly sins in order to guide the Catholic Church in the 6th century. The past 20 odd years in the industry has shown that there are several mistakes that are repeatedly made by numerical modelers. Although we all acknowledge that any numerical model is a non-unique solution, and that there exists and infinite number of solutions, there are several sins that will prevent the model from giving an accurate representation. This paper will provide the most common mistakes made in a format that is accessible to numerical modelers as well as other practitioners. Issues covered will include boundary conditions, model complexity and recharge.
Exploring Danish experiences for Groundwater mapping in South Africa	Anker Lajer	HØjberg	South Africa, Denmark	2021	mapping , fractured geology, SAGMAA, guidelines
Abstract Kürstein, J; Thorn, P; Vermaak, N; Kotzé, YL; Pedersen, PG; Linneberg, MS; Fourie, F; Magingi, A Water supply relies entirely on groundwater in Denmark. A national groundwater mapping programme was established in 2000 to protect this valuable resource. It builds on a thorough and holistic understanding of the hydrogeological settings, obtained through an extensive data collection, culminating with an identification of threats and aquifer vulnerablility. As part of the programme, new approaches, methods, and instruments have been developed, such as airborne geophysical survey by Sky-TEM that allows the mapping of large areas in a fine resolution. Another key element in the mapping is the development of three-dimensional hydrogeological and numerical models. These are used to understand the groundwater flow paths and delineate wellhead capture zones as well as infiltration areas, which, depending on the assessed vulnerability, may be subject to protective measures. The Danish mapping approach have been tested at selected South African sites through the Strategic Sector Cooperation (SSC) between Denmark and South Africa. The approach was applied in a study supporting Umgeni Water to identify groundwater resources to supply numerous villages near the town of Ladysmith. The study illustrated a high potential for adapting relevant parts of the Danish approach to South Africa, but also revealed some challenges, e.g. related to the fractured geology, where groundwater recharge can be concentrated along dykes, a process very different from what is generally observed in Denmark. The SSC has initialised the project “South African Groundwater Mapping and Assessment Approach (SAGMAA)” to share knowledge gain through the national groundwater mapping programme in Denmark with South Africa and explore the possibility of adapting elements from the Danish approach to South African conditions in a broader context. The objective of the project is to provide recommendations to South African guidelines, and the paper will present results from the comparison of approaches in the two countries and preliminary recommendations to guidelines.
Integrated approach to understanding the causes of ground subsidence in the Lyttelton Formation, Jan Smuts House: A potential case study to the greater Centurion area.	Jureya	Dildar	Centurion, Gauteng	2021	Poster, Sinkholes
Abstract The Smuts House in Centurion is under threat of subsidence due to sinkholes. These sinkholes are linked to the Malmani Dolomite Formation, a Proterozoic carbonate sequence within the Chuniespoort Group of the Transvaal Supergroup, and is subject to sinkhole development (Clay, 1981). In addition to Smuts House, the areas are populated by thousands of people meaning risk of financial damage and, in some cases, loss of property and lives (Trollip, 2006). The Jan Smuts House Museum is located in a natural park of indigenous trees and shrubs. The area is generally flat-lying; however, various ridges bisect the site in a north-south trend. A koppie (Cornwall Hill) is situated in the north. Outcrops of dolomite and chert characterise most of the study area. The two major streams in the area are that of the Sesmylspruit and Olifantspruit. This study was undertaken to examine the relationship between subsidence of the Smuts House Museum, subsurface features (geological and anthropogenic) and the local geology. Magnetic and resistivity, active seismic and ground-penetrating radar (GPR) geophysical data were collected, along with x-ray fluorescence (XRF) geochemical data and hydrogeological data.
Assessment of Concentration levels of contaminants in groundwater of Soutpansberg Region, Limpopo Province, South Africa	Lindelani	Lalumbe	Limpopo	2021	community supply, Drinking water standards, Groundwater Quality, skills transfer, knowledge sharing, health, Food security
Abstract Kanyerere, T Groundwater contribution towards improved food security and human health depend on the level of contaminants in the groundwater resource. In rural areas, many people use groundwater for drinking and irrigation purposes without treatment and have no knowledge of contaminants levels in such waters. The reason for such lack of treatment and knowledge is due to the parachute type of research which emphasizes on scientific knowledge and records only and do not develop skills and outputs on groundwater quality for improved human health and food security in communities. This study argued that parachute research type exposes groundwater users to health hazards and threaten food security of communities. Concentration levels of contaminants were measured to ascertain suitability of groundwater for drinking and irrigation use. 124 groundwater quality samples from 12 boreholes and 2 springs with physiochemical data from 1995 to 2017 were assessed. This study found high concentration levels of contaminants such F-, NO3-, Cl- and TDS in certain parts of the studied area when compared to international and national water quality standards. In general, groundwater was deemed suitable for drinking purposes in most part of the studied area. Combined calculated values of SAR, Na%, MH, PI, RSC and TDS determined that groundwater is suitable for irrigation purposes. The discussion in this paper showed that scientific knowledge generated on groundwater quality is not aimed at developing skills and outputs for improved human health and food security but rather for scientific publication and record keeping leaving communities where such knowledge has been taken devoid of knowledge and skills about the groundwater quality. In this study, it was recommended that skills and outputs on groundwater quality should be developed and shared with groundwater users through various initiatives as it will enhance the achievement of SDG’s.
An investigation of the natural groundwater recharge and discharge of the Saldanha Bay Aquifer Systems, South Africa	Aqeela	Parker	Saldanah Bay	2021	Bulk water supply, recharge, Discharge
Abstract Saldanha Bay is partially dependent on groundwater as part of their bulk water supply, as surface water resources in the area are extremely limited and fully allocated. Due to this, there is lots of pressure on the groundwater resources by industrial development and residential growth. Despite studies being conducted on these aquifer systems since 1976, they are still poorly understood especially with regards to their recharge and discharge processes. This study aimed at providing better insight and understanding on the natural groundwater recharge and discharge processes in order to assist in the better management of groundwater resources in Saldanha Bay. Recharge investigations included a Time Domain Electromagnetic airborne geophysical survey, the assessment of groundwater levels, infiltration tests, hydrochemical analyses as well as stable and radioactive isotope analyses. These methods allowed for the delineation of the geological layers and extent, determination different water quality spatially across the aquifer, determination of flow paths through the saturated and unsaturated zones, identification of inter-aquifer flow as well as different recharge processes in the area. The results of this study showed that is highly likely that the Saldanha Bay Aquifers are mainly recharged via deep flow paths from the Aurora Mountain Range and Moorreesburg region. Investigations also showed that it is unlikely that the Aquifer Systems are recharged by local rainfall due to thick unsaturated sands and low annual rainfall, except for runoff at the foot of granite hills through focused recharge processes. The Berg River, Langebaan Lagoon and the Atlantic Ocean were identified as being the main discharge zones for the area. It is recommended that further hydrogeological investigations are conducted in the Moorreesburg region in order to get a fuller picture of the regional groundwater recharge processes and flow to Saldanha Bay.
Using geophysics to detect water-hosting fractures in the Vredefort Dome: A training opportunity	Elvis	Tamilo	Gauteng	2021	Poster, Geophysics
Abstract Enslin,S; Webb, SJ The Vredefort Dome 120 km southwest of Johannesburg is a meteorite impact crater that formed at approximately 2 Ga. The region hosts farmland, and the town of Parys is situated in the northwestern part of the dome. The dome is the location of the annual Wits University/AfricaArray Geophysical Field School. The aim of the field school is to teach geoscience students several geophysical techniques while conducting scientific research in the area. A geophysical survey during the 2019 field school over an open field just outside of Parys revealed a buried fracture that hosts ground water. A 150 m long magnetic profile over the fractures shows a magnetic low (approximately 500 nT) that correlates with a low resistivity region on the inverted electrical resistivity data (dipole-dipole method). Euler deconvolution depth estimates and magnetic modelling estimate an overburden thickness of around 10 m and a similar fracture thickness. The magnetic low of the fracture is due to weathering and removal of any magnetic material in the granites in the region. Two existing boreholes that lie 618m due south and at a 10 m lower elevation have water levels of around 6.4 m. Both boreholes lie near a riverbed and vegetation, and appear to lie along an extension to the fracture. This fractures detected using geophysical methods seems to form part of a larger fracture system within the Vredefort Dome, that is linked to the formation of the dome. These fractures provide a vital source of water for the local farming community.
Test pumping derivative analysis to improve conceptual understanding in a complex aquifer: Steenbras Wellfield.	Kevin	De Bruin	Steenbras Wellfield, Cape Town	2021	flow regime analysis, flow models, test-pumping, drawdown derivative curve, hydraulic conductivity, Derivative data
Abstract Test-pumping drawdown curves are not always sufficiently indicative of aquifer characteristics and geometry. In fact, drawdown curves should never be analysed and interpreted alone. The derivative analysis (Bourdet et al., 1983) and flow dimension theory (Barker, 1988) make it possible to infer the regional geometries and flow characteristics of fractured aquifers which are otherwise often unknown or inconclusive when interpreting point-source borehole logs. The propagation of the drawdown and/or pressure front through the aquifer reaches distal hydrogeological objects which influence the flow regime and imprints signatures in the drawdown derivative curves. The conjunctive interpretation of these flow regime sequences and geological data results in a robust, well-informed conceptual model which is vital for resource management. A methodology similar to that of A. Ferroud, S. Rafini and R. Chesnaux (2018) was applied to the test-pumping data of 14 confined and unconfined Nardouw Aquifer boreholes in the Steenbras area, Cape Town, which has been under exploratory investigation since the early 2000’s. The Steenbras wellfield was developed following the major 2017-2018 Western Cape drought. The NE-SW trending open folds and dextral strike-slip Steenbras-Brandvlei Megafault Zone (with crosscutting faults and dykes) make the aquifer hydrogeologically complex. It is due to these complexities that the sequential flow regime analysis was undertaken to enhance the current conceptual understanding. The analyses reveal domains of flow models which include open vertical fracture, T-shaped channel, double(triple) porosity model, and leaky/recharge boundary amongst others. Poor data quality and noise issues are also highlighted. The outcomes of the sequential flow regime analysis allow for identification of applicable flow models for type curve fitting to avoid erroneous aquifer parameter estimations; improvement of the hydrogeological understanding of the aquifer; enhancements of the current conceptual model in order to inform on subsequent numerical modelling, groundwater resource management and ecological protection.
Intraplate tectonic setting of the southwestern Cape, South Africa: Analysis of the TrigNet geodetic record	Lechelle	Goslin	Cape Town	2021	TMG, augmentation, wellfields, mega-fault structures, TrigNet, seismo-geodetic monitoring
Abstract In response to the serious 2015-2018 “Day Zero” drought, the City of Cape Town implemented large-scale augmentation of the Western Cape Water Supply System from deep groundwater resources within the Table Mountain Group (TMG) fractured aquifers. Several planned TMG wellfields target the Steenbras-Brandvlei Mega-fault Zone (SBMZ), the northern segment of which hosts the Brandvlei hot spring (BHS) – the hottest (~70°C) and strongest (~4 million m3/yr) in the Western Cape. Considering its possible “neohydrotectonic” origin, the BHS may mark the site of a major palaeo-earthquake, suggesting that SBMZ structures are prone to failure in the current crustal stress regime. Despite the “stable” intraplate tectonic setting, the SW Cape has experienced historic large (magnitude >6) earthquakes. Therefore, a better hydrogeological and seismotectonic understanding of the regional “mega-fault” structures is needed. The South African TrigNet array of continuously recording Global Navigational Satellite System (GNSS) stations can be used to measure surface deformation related to confined aquifer depressurisation and vertical compression during groundwater abstraction. Time-series data from 12 TrigNet stations were used to establish a monitoring baseline for the SW Cape. Observed vertical motions range from slow subsidence to variable slow uplift with superimposed cyclical uplift/depression patterns of seasonal and multi-year variability. Baseline deformation/strain rates were calculated using 27 station pair lengths, ranging between compressive (-0.47 nanostrains/yr) and extensive limits (+0.58 ns/yr), indicating a rigid intraplate setting. Anomalous high strain rates (> 10 ns/yr), associated with three stations, are probably due to station mount/foundation issues, rather than neo-seismic activity. Regional results show that seismo-geodetic monitoring is an important tool for understanding fractured aquifer compressibility and hydroseismicity, the latter of which may potentially be induced by large-scale TMG groundwater abstraction and/or natural earthquakes in the Western Cape. A local seismo-geodetic monitoring system is therefore being established at Steenbras Wellfield for further observations and analysis.
Analyzing the effects of episodic groundwater recharge caused by extreme events in a semi-arid region: a case study in Beaufort West, South Africa.	Aarifah	Williams	Beaufort West	2021	recharge
Abstract On a global scale, groundwater is seen as an essential resource for freshwater used in both socioeconomic and environmental systems; therefore forming a critical buffer when droughts occur. Due to its location in a dry and semi-arid part of South Africa, Beaufort West relies on groundwater as a crucial source of fresh water. Thus, proper management of their groundwater resources is vital to ensure its protection and preservation for future generations. Although fluctuations have occurred over the years, groundwater levels in the area have progressively dropped due to abstraction in well fields. However, in 2011, an episodic flooding event resulted in extreme groundwater recharge with groundwater levels North-East of Beaufort West recovering tremendously. This led to the overall groundwater levels of Beaufort West becoming relatively higher. The general flow of groundwater in the town, which is from the Nuweveld Mountains in the North to the town dyke in the South, is dictated by dykes occurring in the area. This study aims to expand on the understanding of episodic groundwater recharge around extreme climatic conditions of high precipitation events in a semi-arid region. This was done by analyzing historical data for the Gamka Dam spanning over 30 years; estimating recharge in the Beaufort West well fields caused by the flooding event; as well as studying the hydrogeological setting and lineaments in the area. It was found that sufficiently elevated recharge around the observed flooding event only occurred in areas where the correct climatic (precipitation, evaporation), geological and geographical conditions were met. Ultimately, gaining a better understanding of these recharge events should aid in the assessment of the groundwater development potential of Beaufort West.
Update of regional groundwater flow models for the Vaal Gamagara SD1 and SD2 wellfields	Martin	Holland	Northern Cape	2021	Demand, exploitation potential, Simulations, CRD, Production rates, Prediction scenario, adaptive management
Abstract Wiegmans, FE The increasing water demand for the Northern Cape Province resulted in the detailed assessment of the exploitation potential of three groundwater development target areas namely SD1, SD2 and SD4, largely underlain by karst aquifers. Since 2014 the implementation of the wellfields was delayed pending authorisation. The potential impact on the groundwater resources was raised by several stakeholders as part of the process, resulting in the re-assessment of the SD1 and SD2 wellfields. The model update considered crucial data retrieved from several groundwater level loggers from April 2014 to December 2019. As a precursor to the model update the Cumulative Rainfall Departure (CRD) curves for the relevant rainfall stations for the study areas was updated. While for most sites a good relationship between rainfall and groundwater fluctuations was observed. A poor response of groundwater levels in comparison to the observed CRD curve suggests abstractions more than the recharge of the aquifer. Metered groundwater use is for most parts not available but was estimated based on the hydrocensus data. Once the models demonstrated to reproduce past behaviour, they were used to forecast the future behaviour. More importantly was to assess whether the 2014 proposed abstraction rates still held true after the re-calibration of the model. Several simulations were carried out iteratively to identify the optimal pumping rates and the temporal variability of the withdrawal period considering the impact on the groundwater resource. Based on the results the 2014 proposed production rates were reduced from 751,608 m3/month to 597,432 m3/month representing a 2019 mitigated (optimised) proposed abstraction scenario. The case study is an excellent example of adaptive groundwater management informed by crucial datasets and scenario modelling.
The onset of iron biofouling in boreholes in and around Cape Town	Roger	Parsons	Cape Town	2021	Iron biofouling, Drought, Monitoring
Abstract Iron biofouling in boreholes drilled into the Table Mountain Group has been documented, with groundwater abstracted for the Klein Karoo Rural Water Supply Scheme and irrigation in the Koo Valley hampered by clogged boreholes, pumps and pipes. A similar phenomenon has been experienced at some boreholes drilled and operationalised by the Western Cape Government in response to the onset of the crippling drought in 2017. Monitoring of groundwater levels and pumping rates has yielded data showing a gradual decrease in groundwater level as the pumping rate reduced in response to the pump becoming biofouled, with possibly the same negative impact on the borehole itself. Methods are available to rehabilitate the boreholes (mechanical scrubbing, chemical treatment and jetting), but it seems difficult to destroy the bacteria and re-occurrence of biofouling appears inevitable. In the absence of better solutions, current experience suggests an annual borehole maintenance and rehabilitation budget of R 100 000 per borehole is required. This paper presents three case studies of boreholes drilled into the Malmesbury Group and Table Mountain Group and explores possible triggers of biofouling and its manifestation in the monitoring data.
Groundwater monitoring of South Africa through numerical model	Akhona	Maqhubela	Sutherland	2021	Monitoring, numerical modelling, GRACE, SG measurements, MODFLOW, SAGOS
Abstract Monitoring groundwater storage is conducted in the study. World Health Organisation estimates, about 55 million people affected by drought yearly. However, Surface water holds 0.3 percent of the freshwater, and groundwater holds 30.1 percent of the freshwater. Hence, monitoring groundwater storage is vital. Though the GRACE (Gravity Recovery And Climate Experiment) satellite provides global-scale groundwater data, but does not provide any information about changes in groundwater flow systems and has uncertainties, due to large noise produced. A correlation has to be established between gravity changes and groundwater storage variations through a program that simulates the flow of groundwater. The relationship between developed numerical models and data derived from superconducting gravity is imperative. This study is conducted in South African Geodynamic Observatory Sutherland (SAGOS) area at Sutherland, South Africa. The study aims to develop a numerical geohydrological model to monitor subsurface variations in water distribution through superconducting gravimeters (SG) records. The interpretation of the SG measurements to directly compare to one another at a higher resolution is considered in the study, through the correlation of the developed model and installed superconducting gravimetric residual data. A numerical groundwater flow model is developed using model muse on MODFLOW. Assigned boundary conditions, fractured rocks were activated by the model. Hydraulic conductivities were simulated for any layer, including storage coefficient. Hence, hydraulic conductivity is an important aspect of the study. In conclusion, gravity is an excellent tool for measuring groundwater recharge within the immediate vicinity of the SAGOS. This implies that gravity can aid in monitoring groundwater recharge and discharge in semi-arid areas. The application of the hydrological model at various scales comparing the Superconducting Gravimeter and GRACE satellite data is paramount to improve modelling groundwater dynamics. The consideration of developing numerical hydrological to monitor groundwater storage will add much value to missing information.
Stable Isotope Techniques for the Evaluation of Water Sources for Domestic Supply in Stellenbosch, South Africa	Jared	Van Rooyen	Stellenbosch	2021	Poster, stable water isotopes, Monitoring, Monitoring, urban water supply
Abstract During 2017-2018, the City of Cape Town, South Africa faced an unprecedented drought crisis with the six main water storages supplying Cape Town falling to a combined capacity of just under 20%. With the threat of severe water shortages looming, various additional water sources were examined to supplement the municipal water supply network. These were focussed on groundwater, desalination and treated effluent. However, private citizens and businesses also made plans to avoid shortages, resulting in numerous uncontrolled water sources competing with the municipal supply network. Throughout the crisis, groundwater was considered the most important alternative urban water supply source but also the most vulnerable to contamination through accidental and uncontrolled return flows from the municipal network, private residences and agricultural industries. This project aims to constrain the water supply network in the Stellenbosch municipality and monitor the augmentation of groundwater into the network using stable isotopes. Long term monitoring points have been established at 35 tap water sites, 20 private wells as well as at the supply reservoirs that feed the municipal network. Preliminary data show’s distinct isotopic signals associated with each supply reservoir as well as in the local groundwater. The data also shows significant return flow into the alluvial aquifer system during warmer months when private stakeholder’s water consumption is at its highest. Groundwater is expected to supplement this urban supply network in the latter part of 2021 and will likely disrupt the current distribution of stable isotopes in the network, providing further insight into the potential return flow into the local groundwater system.
A changing environment focussing on drought	Fanus	Fourie	Northern Cape	2021	Drought, community supply, groundwater behaviour, Pumping
Abstract The western part of South Africa is experiencing a prolonged drought. In many cases, the effects of drought have been noticed since 2011, putting the western part of the Northern Cape under severe stress to provide water to the communities. In the past 10 years, rainfall has also decreased, and in most cases, the catchments did not receive rain to help with the recharge of groundwater. Various lessons were learned from the change in the climate and environment. But a lot can be done to minimise the impact of these changes on the water supply to communities. This paper addresses what we are noticing in the environment that impacts the way we think groundwater behaves. The changes include the change in rainfall: patterns, lines, and type of rainfall. The collapsing of boreholes with water strikes closing when being over-pumped occurs more often in the last 3 years. Pump test recommendation changes with water level change – deployment output. A combination of the factors mentioned puts more stress on groundwater resources, and a mindset change is needed to give assurance of future supply to the communities.
Development and testing of a hydrogeological multilevel sampling device and analysis of water chemistry through hydrochemical parameters	Lesedi	Sipuka	Western Cape	2021	Poster, Groundwater Sampling, Hydrochemistry
Abstract This study investigates and elaborates the development and testing of a multilevel sampling device. The primary purpose of this device is to achieve multilevel sampling in a well simultaneously, producing samples that are representative of the in situ groundwater. The device has been designed to have four different depths from which extraction of groundwater samples can be performed. Testing of the device involves a two-part process. A laboratory based testing and field based testing. The laboratory testing was done in a simulated well where three water tests were performed; normal tap water, salt water and hot boiling water. The field based testing was done on existing boreholes in the Rietvlei Wetland Reserve in the Western Cape. In the two processes involved, hydrochemical parameters were used to test for the efficiency of the device in terms of its working performance and to furthermore analyse the water chemistry which enables us to determine the water quality.
Assessment of the state of potable water supply system in selected communities ofVhemb District Municipality, Souh Africa	Tuwani	Malima	South Africa	2021	community supply, local municipality, main source, Groundwater Quality, distance to source, reliability
Abstract Water is regarded as a source of life and access to potable water supply delivery remains the building block to improving and maintaining the community member’s health and productive life. The demand for water supply has been increasing due to population growth and climate change phenomena. Hence, there is need to assess the current state of potable water supply system in selected rural areas of Vhembe District Municipality (VDM), South Africa. About 14 villages in VDM were visited to assess the state of water supply. Interview were held with three municipal officials who deals with water supply systems and 14 focus group discussions were held in each village with the communities and their leaders. 448 head of households, 14 councillors completed the questionnaires on potable water supply situation in their area. The results indicated that the main sources of water supply are boreholes followed by tap water from dams. In areas where the two sources are not available, the rivers, fountain and the water tankers were also the main sources. In terms of water usage, the boreholes recorded the highest responses of 45% from households, followed by the tap water from dams at 35%, 4% from rivers, 5% from fountain and 10% from water tankers. In addition, about 53.6% of participants collect water once a week from the main source (boreholes and tap water from dams). Rural communities of Vhembe District Municipality were not satisfied with the quantity, distance and reliability of boreholes. Therefore, this article recommended that the municipality, communities, councillors and traditional leaders should work together in addressing the pressing water issues. Part of which include provision of more sources of water to complement growing population. In addition, village water committees need to be established to assist in water provision management.
Application Of Drastic In Studying The Vulnerability Of The Greater Durban Area's Groundwater To Pollution, Eastern South Africa	Hlengiwe	Msweli	Greater Durban	2019	Aquifer vulnerability to pollution, DRASTIC index, GIS, Durban, South Africa
Abstract Groundwater is vulnerable to contamination from various anthropogenic sources. The degree of groundwater vulnerability can be assessed using various methods, which are grouped into three major categories: index-and-overlay methods, process-based computer simulations and statistical analyses. This study attempts to produce a groundwater vulnerability map of the eThekwini Metropolitan District Municipality using the index-and-overlay method of DRASTIC in a GIS environment for the first time. The advantage of this method is that it provides relatively simple algorithms or decision trees to integrate large amount of spatial information into maps of simple vulnerability class es and indices. The main objective of the study is to identify areas of high groundwater contamination potential based on hydrogeological conditions so that management interventions are undertaken timely. DRASTIC is a groundwater vulnerability assessment method based on the intrinsic property of groundwater systems to human or natural impacts. It uses seven hydrogeological parameters, namely, Depth to groundwater, net Recharge, Aquifer media, Soil media, Topography, Impact of the vadose zone and hydraulic Conductivity of the aquifer. These DRASTIC parameters characterize the hydrological setting and are known to control the vulnerability of aquifers to surface derived pollutants. Various studies show that depth to groundwater and impact to vadose zone impose larger impact on aquifer vulnerability followed by recharge, topography and soil media. The application of DRASTIC to the greater Durban area resulted in vulnerability index values in the range from 71 to 168. Based on these index values, greater Durban area is classified into zones of low, moderate and high vulnerability of groundwater to pollution. The low vulnerability areas (Drastic Index. DI: 71-114) are located in the northern region around Magangeni which are underlain by the intergranular and fractured aquifer due to essentially deep groundwater table (>25 m), vadose zone sediments, low hydraulic conductivity and recharge rate. The moderately vulnerable areas (DI: 114-127) cover more than 50% of the study area that is underlain by fractured and Intergranular, and fractured aquifers. The moderate vulnerability areas are located in the western region (Hammarsdale and Kloof), northern region (Mount Edgecombe and Tongaat) and southern region (Amanzimtoti). The moderate vulnerability pattern is mainly due to variation in the hydraulic conductivity of the aquifer and the vadose zone and less by the recharge and the depth to groundwater. The region around central Durban, the Bluff area, Yellowwood Park and areas along the coast that are underlain by intergranular aquifer are mapped as "hotspots" characterized by high vulnerability to groundwater pollution (DI: 127-168) and needs immediate management intervention.
The Impact Of Angled Survey Lines On ERT Surveys Using The Wenner (?) Array	Unarine	Mukhwathi		2019	ERT
Abstract The electrical resistivity tomography (ERT) method has become one of the most commonly used geophysical techniques to investigate the shallow subsurface, and has found wide application in geohydrological studies. The standard protocols used for 2D ERT surveying assume that the survey lines are straight; however, due to the presence of infrastructure and other surface constraints it is not always possible to conduct surveys along straight lines. Previous studies have shown that curved and angled survey lines could impact on the recorded ERT data in the following ways: 1) the true geometric factors may differ from the assumed geometric factors and thus affect the calculated apparent resistivities, 2) the depths of investigation may be overestimated, and 3) the recorded apparent resistivities may be representative of the subsurface conditions at positions laterally displaced from the survey line. In addition, previous studies have shown that although the errors in the apparent resistivities may be small even for large angles and curvatures, these errors may rapidly increase in magnitude during inversion. In this paper we expand on the previous work by further examining the influence of angled survey lines on ERT data recorded with the Wenner (?) array. We do this by: 1) calculating the changes in the geometric factors and pseudo-depths for angled survey lines, 2) forward and inverse modelling of ERT datasets affected by angled survey lines, and 3) examining the impact of angled survey lines on real ERT datasets recorded across different geological structures.
Groundwater development for Municipal water supply in response to drought of 2015 to 2019.	Dale	Barrow	Western Cape	2019	Drought, TMG
Abstract The geographic positioning of the Western Cape results in a Mediterranean climate - receiving majority of its rainfall during the winter months. A demand on the water supply throughout the year is typically met by storing water from winter rainfall in large dams. The Western Cape experienced a significant drought between 2015 and 2019. As a result, the supply dams have not been filled to capacity and drastic water restrictions had to be implemented. In the search for alternative water sources, groundwater exploration became a priority. Groundwater development projects were implemented rapidly in attempt to alleviate the implications caused by severe water restrictions and ultimately prevent running out of water. As a local groundwater institution, GEOSS got involved in several fast-tracked groundwater development projects for Department of local government, local municipalities, as well as other industrial and agricultural corporations. For obtaining the required water volumes, alternative measures were implemented. Previously under developed aquifers were targeted. In certain instances, in order to target the Table Mountain Group Aquifer (TMG), horizontal exploration drilling was conducted. The results of exploration and drilling yielded valuable learnings in terms of relevant hydrostratigraphy within the study areas. Additionally, there were learnings in terms of managing projects of this nature. In fast-tracked projects, careful management of the contractors, data collation (and storage) and public perception is critical to the success of the project. In this paper on water supply development for Municipalities, the various components of groundwater development are detailed along with relevant learnings from the recent emergency drought response measures.
Investigation The Effect Of Excess Pumping On The Groundwater Salinity In Semi-Arid Aquifers Using Predicted Future Scenarios	Mohammed	Seyam		2019	Hydrological Modeling, Groundwater Quality, Salinity, Prediction scenario
Abstract The groundwater quality in semi-arid aquifers can be deteriorated very rabidly due to many factors. The most important factor affecting the quality of groundwater quality in Gaza Strip aquifer is the excess pumping that resulting from the high population density in the area. The goal of this study to investigate the future potential deterioration in groundwater salinity using scenario analysis modeling by artificial neural networks (ANN). The ANN model is utilized to predict the groundwater salinity based on three future scenarios of pumping quantities and rates from the Gaza strip aquifer. The results shows that in case the pumping rate remains as the present conditions, chloride concentration will increase rapidly in most areas of the Gaza Strip and the availability of fresh water will decrease in disquieting rates by year 2030. Results proved that groundwater salinity will be improved solely if the pumping rate is reduced by half and it also will be improved considerably if the pumping rate is completely stopped. Based on the results of this study, an urgent calling for developing other drinking water resources to secure the water demand is the most effective solution to decrease the groundwater salinity.
Hydrogeological Mapping in the Kuruman River Catchment of Northern Cape Province, South Africa	Olma	Makonto	Northern Cape	2019	Poster, mapping
Abstract Hydrogeological mapping was first attempted in Kuruman River Catchment, Northern Cape Province, South Africa. The main geology underlying the area of study includes sediments of the Kalahari Group, limestone and dolomite of the Transvaal Supergroup, lavas of the Ventersdorp Supergroup, and Archaean granite and gneiss. The main objective of this study was to produce hydrogeological maps on a scale of 1/100 000. Demarcation of different aquifer types was done by analyzing factors that control groundwater occurrence. These factors include lithology, geological features such as fault and lineaments, groundwater levels, and groundwater chemistry. Four types of aquifers were identified: o - Intergranular aquifer, associated with alluvial and pluvial deposits. o - Intergranular and fractured aquifer, associated with weathered igneous and sedimentary rock. o - Fractured aquifer, dominated by basal formations. o - Karst aquifer, associated with the dolomitic formations. The groundwater quality in the four demarcated aquifers was assessed to determine the current groundwater status. Groundwater chemistry was measured by collecting groundwater samples from boreholes. Physical parameters such as pH, temperature and electrical conductivity were measured in-situ using an Aquameter instrument. The samples taken were analysed at MINTEK laboratory using Inductively Coupled Plasma Mass Spectrometry, Ion Chromatography, and Spectrophotometer for cations, anions and alkalinity respectively. The results obtained indicated sodium chloride water type in fractured aquifer, while calcium carbonate water type was identified in intergranular aquifer, karst aquifer, and intergranular and fractured aquifer. In conclusion, high concentration of Nitrate, Magnesium, and Calcium was seen in all the four aquifers. High concentration of nitrate is due to stock farming, whereas high concentration of Magnesium and Calcium is due to geology. Moreover, high concentration of mercury due to mining activities was picked in intergranular aquifers, karst aquifers, and intergranular and fractured aquifers.
The Relationship Between Groundwater Governance And Management At Local Municipal Level.	Fanus	Fourie	National	2019	Governance, Management
Abstract The terms 'Management' and 'Governance' are used interchangeably when referring to groundwater such as policy, protection, operations, financial systems and infrastructure. Governance and management are not separate scales of action, but different processes. Both processes can take place together at local, regional, national or global scales. (Seward 2015). The influences from the different levels of government are also linked. Governance and management can in most case not be split into two blocks and handled separately. The degree of governance vs management differs per level of government from institution to institution. The line between governance and management is thus very flexible between the different areas/location or aquifers where groundwater is being used and protected. Some functions, responsibilities and roles are very difficult to place under governance or management alone and can fall under both. The term 'Implementation Governance' was created to describe the overlap of functions, and this also links closely to the term 'Local Level Governance' that focuses on governance at the local municipal level. The paper describes the relationship between governance and management functions at different government levels and illustrates it through five scenarios/examples of the different government organisations at the municipal level.
Assessing The Temporal Change In Hydro-Geochemical Properties Of Fly Ash When Disposed Into Opencast Coal Mines In Mpumalanga, South Africa	Angelo	Johnson	Mpumalanga	2019	hydrochemical, fly ash
Abstract This study focus on the feasibility of coal ash backfill into historical and future, acid generating coal mines. However, there is limited knowledge of how South African ash would behave in these acidic opencast mines. Therefore the aim is to improve the understanding of the change in hydro-geochemical properties of coal ash with reference to acid mine drainage (AMD). Fly ash from two power stations in Mpumalanga were assessed in the laboratory. The hydraulic properties of ash were determined through the use of Darcy up flow column tests, where ash was continuously leached with natural AMD. The influent and effluent was monitored for pH, EC and metal concentrations to investigate the chemical changes in the AMD, flowing through ash. The laboratory results exhibited decreasing trends in K over time, from 10-1 m/d to 10-3 m/d. These changes in hydraulic conductivity are initially subjected to the pozzolanic bindings that formed during the curing phase of the experiment. Subsequently, secondary mineralization occurs induced by calcium rich minerals which are deposited in the flow paths, causing a further decrease in K towards 10-2 m/d. Lastly, the Fe (>130 mg/L) and SO4 (>2000 mg/L) concentrations in the AMD together with the low pH = 2.5 causes a clogging effect at the front face of the ash columns, ultimately causing the K to decrease towards 10-3 m/d. Calcium was the dominant cation that leached out and sulphate the dominant anion, which was due to high concentrations in both the ash and AMD. It was observed that most of the leachate water was of a better quality than the influent AMD water quality. Based on the research findings, an ash monolith deposited at the decanting position of an opencast mine may have positive impacts. Ultimately, reducing AMD decant volumes and improving water quality.
Conceptual Hydrogeological Modelling Of The Thyspunt Area, Eastern Cape, South Africa.	Moneri Joel	Modiba	Thyspunt, Eastern Cape	2019	modelling
Abstract A conceptual hydrogeological and numerical groundwater flow modelling study is being undertaken around and within the proposed ESKOM Thyspunt Nuclear Site, located 120 km west of Port Elizabeth. The study aims to improve the understanding of the prevailing hydrogeological condition around the Thyspunt area. The area is characterized by folded and jointed geological conditions. The local geology comprises the Table Mountain Group (TMG) and the Bokkeveld Group rocks of the Cape Supergroup, and Quaternary to recent sand deposits of the Algoa Group. The study area receives mean annual precipitation (MAP) of 922.6 mm. The mean annual estimated evapotranspiration is 821 mm and the average annual recharge rate estimated using the Water Table Fluctuation method is about 71 mm. A robust conceptual hydrogeological model is developed through detailed aquifer characterisation including pumping test analyses, determination of groundwater occurrence, storage, and flow, hydrogeochemical and environmental isotope analyses. Groundwater occurs within intergranular of the Algoa Group and fractured quartzitic aquifers of the TMG. The depth to groundwater ranges from 4.5 to 28.9 m below ground level (b.g.l.) and though the local groundwater flow is complex, the general groundwater flow direction is from west to east, towards the Indian Ocean. The upper unconfined intergranular Algoa aquifer and the deeper semi-confined fractured TMG aquifer are characterised by wide range of hydraulic properties, including aquifer thickness (2.2 - 22.0 m and 18.0 - 138 m), hydraulic conductivity ( 4.5 - 19.1 m/d and 8.9x10-3 -1.58 m/d), transmissivity (108.3 - 275 m2/d and 0.4 - 44.0 m2/d), specific yield (1.5x10-2 - 0.1) and storativity (5.0x10-5 - 5.9x10-3), respectively. The main hydrochemical facies of groundwater in the shallow Algoa is Ca-Mg-HCO3 type and groundwater circulating in the deep TMG aquifers are Na-Cl type. Environmental isotope signatures (?2H, ?18O) results indicate groundwater - surface water interactions
Sustainable Groundwater Supply Potential Of The D41L And Major Dolomitic Sub-Catchments For Water Security In Gasegonyana Local Municipality	Collen	Monokofala	Gasegonyana Local Municipality	2019	supply, local municipality
Abstract South Africa has a looming water supply crisis, with 98% of its surface water already developed, demand outstripping supply in most catchment areas (WRC, 2015). Based on current usage trends, South Africa is expected to face a water deficit of 17% by 2030, and this shortage will only be worsened by climate change (WWF, 2017) which is mainly characterized by prolonged period of drought. There are many challenges facing the sustainability of groundwater, among others there are issues such as climate change, human errors in data handling, over abstraction due increasing water demand, damage of borehole infrastructure in remote areas and poor groundwater management systems. Groundwater resources within the D41L quaternary catchment occurs in abundance. Aquifers in the area are classified as karst and fractured dolomite aquifers with a median yield of >5 L/s. These aquifers are compartmentalized by several impervious dykes that sub-divide the D41L area into sub-catchments and smaller sub-compartments. With the probable impacts of extended drought period in the Gasegonyana Local Municipal area, increased water demands and density of abstraction points in some sub-catchments/sub-compartments the water resources have become stressed and at risk of being over-exploited. To sustainably and secure future water supply in the region, it has become essential that a comprehensive assessment is undertaken of the sustainable water supply potential of the D41L and delineate various groundwater resource units (GRU's). The paper highlights why is it imperative to conduct the groundwater feasibility studies on a regional scale in order to protect the sole aquifer resource for semi-desert areas such as Gasegonyana municipal zone. Secondly, the importance use of appropriate geophysical techniques which include regional gravity surveys on dolomitic aquifers with emphases to sustainability on exploitable resources as these karst aquifers are highly vulnerable to over-abstraction if not properly investigated. Groundwater water potential and large aquifer zones were delineated explicitly with the regional gravity results and exploration drilling of these zones proved to be sustainable compared to existing boreholes that were drilled in limited/smaller dolomitic compartments. The predictive scenario of the groundwater assessment confirms that the water demand could be achieved with half of the simulated abstraction rates while an increase in water demand should be managed accordingly by distributing the yields of the borehole between the existing boreholes and the newly drilled production boreholes. The study results will ensure sustainability of water supply in the region and the document will assist the town planners and stakeholders to manage high population growth in a groundwater secure zone, and it will mitigation against climate change impact for the municipality.