Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 1 - 50 of 574 results
Title Presenter Name Presenter Surname Area Conference year Keywords

Abstract

Surface water has traditionally been the primary resource for water supply in South Africa. While relatively easy to assess and utilise, the surface water resource is vulnerable to climatic conditions, where prolonged periods of drought can lead to an over-exploitation and eventually water shortness and supply failure. Following the drought in 2018, more focus has been given to the groundwater resource to supplement the water supply in South Africa.

In the Saldanha Bay municipality the water supply is based on a combination of surface water and groundwater, with plans to supplement this with desalination and managed aquifer recharge (MAR) in the future. For an efficient and sustainable utilisation of the different water resources, a Water Supply Management System is developed that can be used to manage water mix from multiple resources. The system builds on top of a flexible WaterManager system developed for operation of complex water supply infrastructures, which in the study is extended by implementing operational rules for optimal management.

The operational rules provide recommendations for the day-to-day management, but also consider seasonal and long-term utilisations. To achieve this, the rules will rely on real-time monitoring data combined with results from hydrological modelling, providing estimated system response to selected scenarios to which the water supply must be resilient. In the present study the combined Water Supply Management System is developed and tested using synthetic data, which will be presented in the paper.

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.

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.

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.

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.

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.

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.

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

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

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.

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.

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.

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.

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.

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.

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.

Abstract

A Case study done in the heterogeneous Tygerberg shales underlying the northern section of the Cape flats aquifer. A well field consisting of five boreholes within a 1.6 Ha area was test pumped to determine aquifer parameters and sustainable yields for the well field. The wellfield located in a highly heterogeneous geological setting, proved to be an interesting scenario for wellfield analysis and determination of sustainable borehole yields. A variety of analytical methods were used to analyse the test pumping data including the Advance FC analysis and the Cooper Jacob Wellfield analysis, both producing different results. Through the test pumping data analysis, the wellfield could be divided into sub wellfield clusters based on drawdown interconnectivity during testing. Sub wellfield clusters were confirmed using groundwater chemistry, providing higher confidence in limiting uncertainty in long term cluster connectivity.

Abstract

Tamilo, T; Webb, S.J.

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.

Abstract

South Africa is currently considering unconventional oil and gas (UOG) extraction as an additional energy resource to improve the country’s energy security. In a water-scarce country such as South Africa, which has experienced more frequent and more intense climate extremes due to climate change, the water-related impacts of UOG extraction is a concern. The South African government is however determined to proceed with UOG development as soon as regulations to protect natural resources have been drafted. The country’s intricate governance system can however not enforce such regulations effectively, as it experiences repeated inter-departmental miscommunication, fails to collaborate with stakeholders effectively, and lacks human and financial resources for enforcement. A lack of transparency in fracking operations and between stakeholders is another challenge for enforcing UOG extraction regulations. Poor regulatory enforcement presents an obstacle for the protection of groundwater resources if fracking were to commence.

This study, therefore, focuses on addressing the enforcement challenges of UOG regulations aimed at protecting groundwater resources. It proposes the use of civic informatics on a technology platform, specifically via a mobile application (FrackSA), to assist with on-the-ground enforcement of these regulations. While many UOG mobile applications are used internationally, they mostly focus only on UOG related aspects (news, information, pricing, geological information, and fracking well information). FrackSA uses civic informatics to address both groundwater monitoring and management as well as UOG extraction operations in a single platform, to enable regulators to protect groundwater resources more effectively during UOG extraction, while simultaneously enhancing transparency in the UOG industry.

Abstract

Xu,Y; Kanyerere, T

Currently, there is little understanding of the nature and extent of groundwater-dependent ecosystems (GDEs) at catchment or aquifer scale globally, making it difficult to protect and incorporate them in integrated groundwater resources management plans. Groundwater levels fluctuations could alter groundwater accessibility patterns to GDEs, potentially resulting in groundwater quality deterioration too. The understanding of groundwater-ecosystems interactions is generally poor since most historical research has been skewed to surface water-related ecosystems. There exists a research need towards the understanding of groundwater processes that control the maintenance of GDEs at local level, through conceptual modelling. A study has been initiated in the Tuli-Karoo transboundary aquifer (TBA) – shared between Botswana, South Africa and Zimbabwe in the Limpopo Basin - to address this scientific knowledge gap because of possible cross-border negative impacts on respective groundwater resources attributed to interlinked aquifer systems’ nature between riparian countries. Ecosystems’ protective measures here are country-specific, disregarding neighbouring countries activities and based on low-flow requirements through baseflow, largely excluding terrestrial GDEs. Groundwater resource co-management agreements are also non-existent among sharing countries, warranting a collaborative approach to research. Potential GDEs in this TBA include riparian vegetation along the main stem Limpopo River and its major tributaries (Shashe and Mzingwane); terrestrial vegetation of Mopane bioregion of the Savanna Biome; and seasonal and permanent wetlands, pans and springs. Isotope analysis have ascertained dependency partly in one country and therefore extended to cover the TBA. Tuli-Karoo is characterized by shallow unconfined alluvium aquifer systems of the Karoo sandstones and basalts of shallow to medium depths. A conceptual model developed will demonstrate interactions between groundwater, surface water and ecosystems; allowing for assessments of impacts on GDEs to ensure resilience. Although TBA focused, the findings will be applicable to similar national aquifers in terms of lithology, geology, geohydrology and ecosystems types.

Abstract

In response to the drought which started in 2017, the Western Cape Government set about securing water supplies to key facilities across the province, including the Knysna Hospital. Drilling and testing of two boreholes at the facility indicated it to be viable to establish a groundwater supply of 66 KL/d from the underlying Table Mountain Group Aquifer. Iron concentrations were low and the initial water chemistry analyses pointed to concentrations below the SANS 241 aesthetic limit. However, further to the implementation and operationalization of the groundwater supply schemes, significantly elevated iron concentrations of up to 6 mg/L were observed. This contributed to the difficulty in getting the Knysna Hospital’s alternative water supply operational. Best practice requires that as little oxygen as possible gets introduced into the groundwater system; and this can be achieved by pumping the borehole continuously at the lowest rate possible. It is not always possible to do this under operational conditions when the water demand varies. To counter the iron problem in the potable water and to prevent or retard an increase in the iron concentration in the abstracted groundwater, iron treatment was added to the treatment train and a dual pumping regime was adopted. Using the variable speed drives that had been installed with the pumps, two pumping rates were adopted – with the rate controlled by the level in the treated water storage tank. When the tank level is low, the borehole is pumped at a rate of 0.9 L/s. However, when the level fills to 70%, the pumping rate is reduced to 0.35 L/s and continues pumping even if the tank is full. The modified system was brought into operation in August 2019 and has continued to meet the water demand of the hospital.

Abstract

The South African government is actively pursuing unconventional oil and gas (UOG) extraction to augment energy supplies in South Africa, but it risks damaging water quality. The Department of Water Resources and Sanitation recently released regulations to protect water resources during UOG extraction for public comment.

Regulations are one of the main tools that can be used to minimise UOG extraction impacts on water resources and enhance an environmentally sustainable economy. This tool must however be used correctly. Many states in the US and Canada have extensive regulations to protect water resources during UOG extraction but they are often ineffective, either because they were poorly drafted or because they are not properly enforced. Since South Africa is a water-scarce, groundwater-dependent country, we asked South African groundwater experts what regulations are needed and how to enforce them. Focusing on the interface between science and public policy, we critically analyse and recommend the most appropriate fracking regulations to protect groundwater resources. Additionally, we consider the enforcement mechanisms required to ensure the proper regulation of fracking.

The results from this study can assist the government in ensuring that regulations that they are currently drafting and finalising, are appropriate to protect groundwater resources, and that they would be able to enforce them effectively.

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.

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.

Abstract

The EKK-TBA is significant in anchoring Gross Domestic Product growth and development in both countries is heavily reliant on groundwater. Recently a transboundary diagnostic analysis (TDA) and a strategic action plan (SAP) for the EKK-TBA was completed. The analysis resulted in a three-fold expansion of the EKK-TBA boundary. The new EKK-TBA boundary overlaps part of the Okavango and Zambezi River Basins and now also includes major wellfields in Botswana and Zimbabwe (Nyamandlovu and Epping Forest) as well as the Makgadikgadi Pans which act as the surface water and groundwater discharge zone.

An analysis of institutional arrangements was carried out to enhance effective and efficient management of the EKK-TBA. Noting the complexity of the EKK-TBA. the initial institutional response could potentially be the development of a bilateral agreement between Botswana and Zimbabwe for cooperation and coordination to support the management of the TBA. This agreement would seek to establish a Joint Permanent Technical Committee (JPTC) that would also co-opt in members from the two shared watercourse commissions. Such a JPTC would enable improved coordination across the varying transboundary dimensions and would align with the precepts of the Revised Protocol on Shared Watercourses. This would include such principles including sustainable utilization, equitable and reasonable utilisation and participation, prevention, and co-operation, as well as aspects of data and information exchange and prior notification.

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.

Abstract

Pietersen, KC; Musekiwa, C; Chevallier, L

Groundwater plays an integral role in the fresh water supply for both rural and urban populations of the Southern African Development Community (SADC). However, the sustainable use of groundwater is negatively impacted by persistent and recurring droughts in the region. Understanding the characteristics of drought and the risk to groundwater, will contribute towards better planning and management of water supply in the region. In this study, a novel approach is demonstrated, that uses data from the Gravity Recovery and Climate Experiment (GRACE) to map and characterise the risk to groundwater storage from drought, across the SADC region. In addition, this study also demonstrates and evaluates the inclusion of this new feature, groundwater storage sensitivity, as an additional input into a revised Groundwater Drought Risk Mapping and Management System (GRiMMS), in-order to update the SADC groundwater drought risk map developed in 2013. Specifically, the GRACE Groundwater Drought Index is calculated and used to characterise the total length, average intensity and trend, in groundwater storage drought conditions. These three factors are then combined into a new layer, groundwater storage sensitivity, and validated through comparison with groundwater level data. The groundwater storage sensitivity, which represents the risk to groundwater drought associated with groundwater storage deviations, is then included at the modular level in the GRiMMS algorithm. The inclusion of the GRACE derived groundwater storage sensitivity further highlights regions of known hydrological drought, emphasising the impact groundwater storage plays in mitigating drought risk. In conclusion, GRACE provides a unique tool that can be used to map the impact of drought across the SADC region.

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.

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.

Abstract

Delineation of groundwater resources of a given area is importance for management of groundwater resources. This is often done manually by combining various geo-scientific datasets in Geographic Information System (GIS) environment, which is time consuming and is prone to subjective bias and also suffers from other human induced uncertainties and difficult to cope with increasing volumes of data. The explosive growth of data leading to ‘rich data, but poor knowledge’ dilemma yet we have challenges to be solved. Artificial Intelligence (AI) has been successfully used in fields such as robotics, process automation in engineering, industry, medical and domestic households. Artificial Intelligence tool have the able to bridge this gap by augmenting the human capabilities in understand science far better than before. Incorporating AI into groundwater potential mapping greatly improves computation speed, reduces the subjectivity nature of manual mapping and lessens human induced uncertainties. The software platform includes artificial intelligence algorithms such as artificial neural networks, support vector machines, random forest, index-overlay and fuzzy logic.

The software platform is semi-automatic to allow the user to control some of the processes yet automating the other processes. The possible inputs to the AI for training includes; aquifer types, topographic slope, lineament and drainage density, land-use / land-cover (LULC), distance to lineaments, distance to streams and soil clay content. Yield values of selected boreholes are used as training outputs.

The software was tested using data gathered for the area surrounding Maluti-a-Phong in the Free State Province of South Africa. The area was chosen because of recent drought which has hit the country and local municipalities are searching for groundwater resources for building wellfields to supply local communities with fresh water. The groundwater potential map of the area was validated using borehole yield values of boreholes which were not used for modelling. Good correlation values as high as 0.85 was obtained between model values and borehole yield. The final groundwater potential map was divided into four zones; very good, good, poor and very poor. Based on this study, it is concluded that the high groundwater potential zones can be target areas for further hydrogeological studies.

The usage of the software proved to be efficient in minimising the time, labour and money needed to map large areas. The results of which can be used by local authorities and water policy makers as a preliminary reference to narrowed down zones to which local scale groundwater exploration can be done. AI should be viewed as augmented intelligence as it aid the decision-making process rather than replacing it. Data-driven approaches should also be knowledge-guided for efficient results.

Abstract

Groundwater in the Steenkoppies compartment of the Gauteng and North West dolomite aquifer is extensively used for agricultural practices that can potentially lead to groundwater storage depletion, threatening groundwater sustainability in the compartment. Groundwater levels represent the response of an aquifer to changes in storage, recharge, discharge, and hydrological stresses. Therefore, groundwater levels are useful for identifying limits and unacceptable impacts on an aquifer and using this information to implement sustainable groundwater management decisions. The use of machine learning techniques for groundwater modelling is relatively novel in South Africa. Conventionally, numerical techniques are used for groundwater modelling. Unlike traditional numerical models, machine learning models are data-driven and learn the behaviour of the aquifer system from measured values without needing an understanding of the internal structure and physical processes of an aquifer. In this study, Neural Network Autoregression (NNAR) was applied to obtain groundwater level predictions in the Steenkoppies compartment of the Gauteng and North West Dolomite Aquifer in South Africa. Multiple variables (rainfall, temperature, groundwater usage and spring discharge) were chosen as input parameters to facilitate groundwater level predictions. The importance of each of these inputs to aid the prediction of groundwater levels was assessed using the mutual information index (MI). The NNAR model was further used to predict groundwater levels under scenarios of change (increase or decrease in recharge and abstraction). The results showed that the NNAR could predict groundwater levels in 18 boreholes across the Steenkoppies aquifer and make predictions for scenarios of change. Overall, the NNAR performed well in predicting and simulating groundwater levels in the Steenkoppies aquifer. The transferability of the NNAR to model groundwater levels in different aquifer systems or groundwater levels at different temporal resolutions requires further investigation to confirm the robustness of the NNAR to predict groundwater levels.

Abstract

The Council for Geoscience has a corporate responsibility in rural development projects as part of the South African government initiative in food and water security. Geophysical surveys were carried out at Elizabeth Conradie School in Kimberley, Northern Cape Province South Africa aimed on siting production boreholes to supply the school with water. Traditional geophysical techniques including magnetic, electromagnetic and resistivity were used to locate groundwater bearing structures. The magnetic method was used to locate intrusive magnetic bodies (i.e. Dolerites), while electromagnetic and resistivity were used to map conductivity and resistivity distribution associated with the subsurface geology.

The magnetic method delineated possible groundwater bearing structures which may be related to dolerite dykes and sills. The electromagnetic method appears to have identified shallow fresh dolerite sill. The resistivity method was good in identifying areas of low resistivity which might be related to fractures and/or faults. The high resistivity values might be related to dolerite dykes or sill.

The results of the study showed that geophysical methods are useful non-intrusive tools for mapping groundwater resource. The 1:250 000 scale geological reconnaissance map used to constrain the geophysical interpretation is at a bigger scale when compared to the geophysical interpretation resolution. Considering this and also the ambiguity and none uniqueness in geophysical interpretation, results need to be consolidated by a local scale hydrogeological mapping and drilling results.

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

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.

Abstract

McGibbon, D; Riemann, K

The Cape Flats Aquifer Management Scheme (CFAMS) includes both abstraction of groundwater and managed aquifer recharge (MAR) as part of the City of Cape Towns (CoCT) New Water Programme to diversify their bulk water supply and build resilience against future droughts. Since the project was initiated in early 2018, over 250 boreholes have been drilled for exploration, monitoring, abstraction, and MAR. Rotary mud drilling was used for most of the drilling due to its suitability in unconsolidated geological material, typical of the CFA. As effective as rotary mud drilling is for large scale development, it lacks in accuracy for detailed geological interpretation used for borehole siting and design (gravel pack and screen aperture size and screen position). This is due to the mixing of material and the circulation of the drilling mud washing away fine sediment which can skew grain size analysis results and obscure the vertical position and thickness of thin confining clay or organic rich lenses. The clay and organic rich layers can cause surface flooding during injection as they act as confining layers which effects borehole design and more importantly siting of MAR boreholes. To overcome this, two additional drilling techniques were explored, sonic and air core. Air core was disregarded early on due to the air creating a cavity in the underlying unconsolidated sediments. Sonic drilling, however, was successful in retrieving a continuous undisturbed core log through high resonant energy that liquefies the sediments, which are then brought to surface in a core barrel. The undisturbed continuous nature of the log allows for accurate grain size analysis and detailed vertical geological logging which can be used for facies analysis to interpret the paleoenvironment and predict the lateral extent of clay or organic rich layers that influence borehole siting, design, and the 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Abstract

Lourens, PJ

West of the world-renowned conservation site, Kruger National Park, lies the larger extent of the Greater Kruger National Park within the Limpopo province. Boreholes have been drilled here in the last few decades to century for the provision of water supply to game lodges, large resorts, watering holes for game viewing and also historically for agriculture and livestock. The area contains both primary and secondary aquifers classified as having yields between 0.5 and 5.0 l/s, based on the geological setting which consist of gneiss intruded by dolerite dyke swarms. A geohydrological assessment of the area revealed that groundwater quality within the project area is characterised as having an EC of 100 - 450 mS/m, which seems to link to borehole proximity to surface water systems. The Makhutswi Gneiss and Doleritic Dyke swarms are the major controlling geology of the area, with higher yielding boreholes located in close proximity to dykes and major structural lineaments (faulted / weathered zones) of the Gneiss. A major concern identified through geohydrological assessment and hydrocensus observations is that boreholes frequently dry up after a few years and require either deeper drilling / redrilling or drilling a new borehole and that the very aggressive calcium hardness in the water frequently damages equipment and leads to overall higher maintenance costs. This project investigates the feasibility of increasing recharge to the aquifer with seasonal flooding / rainfall events by constructing artificially enhanced recharge locations overlaying several doleritic dykes. This is expected to decrease the salinity and hardness of the groundwater, which will reduce operational costs. Water security will also be increased through enhanced long-term sustainability of the groundwater by balancing some of the current annual abstraction.

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.

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.

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.

Abstract

Saldanha Bay Local Municipality appointed Skytem to conduct an airborne geophysical 3D aquifer mapping survey. As part of improving the sustainable management of the groundwater resources and exploring the options of Managed Aquifer Recharge, a better understanding of the aquifers is required. The Skytem technology unlocked a rich understanding of the subsurface geology and the groundwater contained in it.

Before the main survey commenced, a trial survey was conducted to investigate the quality of the data that may be expected from the main survey. The trial survey was conducted over the existing water supply wellfield where there were existing groundwater data including borehole lithology from drilling and ground geophysics. Consequently, the main survey commenced and consisted of the following:
1) Magnetic survey providing information regarding bedrock composition and where it changes due to faults or deposition,
2) Time Domain Electromagnetic survey providing conductivity/resistivity of the subsurface,
3) Detailed elevation along flight paths, and
4) 50Hz signal to understand where interferences can be due to power lines.

The survey interpretation showed the following important aquifer characteristics that will be useful for future management of the aquifer system:
1) Bedrock elevation and paleo topography, 2) Areas with different bedrock composition, 3) Geological faults in the bedrock, 4) Bedrock below the surface, 5) Areas with thick dry sand, 6) Clay layer extent and area without clay, 7) Areas with different water quality, and 8) Areas with very high concentrations of salt.

The survey output and interpretations are regarded as very useful for the update of the conceptual models for the area. Data can now be used to update the numerical models and improve the management of the wellfields.