Conference Abstracts

All Abstracts were presented at the Groundwater Conferences

Displaying 151 - 200 of 575 results
Title Presenter Name Presenter Surname Area Conference year Keywords

Abstract

The City of Cape Town (CoCT) metropolitan municipality seeks to identify and develop alternative water resources for the augmentation of surface water to ensure more robust and sustainable water supply to the CoCT and its inhabitants. A 3-D finite-element numerical model of the Atlantis Aquifer was developed using the commercial code FEFlow 7.1 to support the assessment of the impact of groundwater abstraction from the aquifer which has been identified as one of the target zones to develop sustainable alternative water resources as part of the CoCT water reconciliation strategy. The numerical model acts as a decision support tool to assist in planning and management of the rehabilitation and potential expansion of the groundwater abstraction and managed aquifer recharge scheme. The numerical model is to be applied in determining the impact of additional abstraction as well as assess the maximum sustainable yield from the wellfields without negatively impacting on surface water sources and other groundwater dependent users. The model improves upon previous modelling work and represents the latest and most comprehensive knowledge in terms of three-dimensional aquifer geometry, location and rates of anthropogenic groundwater users, spatial distribution of recharge, hydraulic parameters and location of aquifer boundary conditions. Model parameters have been successfully calibrated under steady-state conditions to provide a realistic representation of long-term groundwater levels across the system (R2=98%). Abstraction scenarios and their impact on groundwater levels were assessed using the calibrated numerical model. Scenarios were simulated of three phases of abstraction (approximately 15, 25 and 40 Ml/d) to determine drawdown around the wellfields, the impact on spring discharge, and the possibility of saline intrusion. Model results show drawdown to be mostly confined to the associated wellfields, with minor drawdown experienced in the vicinity of Silwerstroom. Simulated hydraulic heads indicate that seawater intrusion is unlikely to occur under all scenarios.

Abstract

Conservation is most Academic Editor likely linked to the behaviour of the user to use less water and to use the water more efficiently. The actions will include fixing the leaking taps, toilets and pipes; the implementation of best practices; and awareness programs. All these activities are after the water is taken from the water resource. However, the question remains: "Can water be conserved while still in the resource?" Moreover, then further "What is Groundwater Conservation?" Conservation of groundwater is related to the use of groundwater at the right time and adopts a management style that suits the aquifer characteristics. By knowing when, where, and how much to pump an aquifer can enhance the performance and life of an aquifer. By understanding the different operating rules levels and how the rules influence each other, the optimal yield can be determined. Climate variability and change is having a significant impact on our groundwater resource and the way we are managing our aquifers. Cost to pump and treat the groundwater can be cut with benefits not just to the municipality but also to the community and environment. The paper will go into practical examples to understand the concept of groundwater conservation; to implement groundwater conservation at the local level and the benefits.

Abstract

The costs of acid mine drainage (AMD) monitoring result in the quest for alternative non-invasive method that can provide qualitative data on the progression of the pollution plume and ground geophysics was the ideal solution. However, the monitoring of AMD plume progression by ground geophysics (time-lapse electrical resistance) proves to be non-invasive but also time consuming. This gave way to a study that focuses on the modeling of different scenarios of the karstic aquifer. The models use the field parameters such as the electrical resistivity of the host rock and the target rock, depth to the target, noise level and electrode configuration in order to ensure that the model outcomes represent the field data as much as possible. This geoelectric modeling process uses Complex Resistivity Model (CRMod) and Complex Resistivity Tomography (CRTomo) to generate geoelectric subsurface images. Different resistivity values are applied to targets in order to assess the difference against the baseline model for each target scenario. The model resistivity difference is reduced to the smallest difference possible between the reference and new models in order to gauge the lowest percentage change in the model at which the background noises start to have impact on the results. The study shows that the behavior of targets (aquifer) could be clearly detected through resistivity difference tomography rather than inversion tomography. The electrode array plays a significant part in the detection of target areas and their differences in resistance because of its sensitivity. This therefore indicates that the electrode array should be chosen according to study requirements. Furthermore, the model geometry also plays a role and this can be seen with the modelling of different target sizes, alignments and shapes. Future studies that can provide a correlation between the field quantitative data from sampling and the model outcomes have the ability to add to the knowledge field of geophysical modelling therefore reducing costs associated with field based plume AMD monitoring300-500 words without references; reach your conclusions rather than only delivering promises.

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.

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.

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.

Abstract

The Western Cape has experienced a drought since 2015 and one of the regions most adversely affected by this drought was the Swartland. Towns in this region make use of water supplied by the Vo?lvlei Dam, which is the Swartland Municipality's bulk and only source of water. Groundwater exploration was undertaken to find alternative sources of water which would be used to relieve some of the pressure on surface water resources. A total of seven towns and communities were identified as high risk and most vulnerable. These include Abbotsdale, Koringberg, Malmesbury, Moorreesburg, Riebeek Kasteel, Riebeek West and Riverlands. This project posed several challenges, namely: available land, proximity to infrastructure and unfavourable geology (in terms of groundwater potential). The project had mixed results in terms of quality and yield. This paper presents the approach and results of the groundwater development.

Abstract

Big data analytics (BDA) is a modern and innovative platform of applications that include advanced analytical techniques such as data mining, statistical analysis, artificial intelligence, machine learning, and natural language processing. Regional data are generated through groundwater monitoring, remote sensing applications or global circulation models (GCM), however this is often too course for a local understanding. Groundwater managers rely on locally relevant information for effective operational decision making, however this is often missing. A Transboundary Aquifer (TBA) Analytic Framework was developed to match, integrate and model local hydrogeological data with regional earth-observation data using BDA. Drawing on the literature on BDA, a reference architecture for the TBA analytical framework was identified for application to various groundwater management scenarios in the Ramotswa Dolomitic Aquifer (Botswana - South Africa) and Shire Valley Alluvial Aquifer (Malawi - Mozambique). The TBA analytical framework allows for local clouds to store the local and regional structured and unstructured datasets and interconnecting these local clouds through a federated cloud infrastructure. In this regard, tools that are incorporated in the TBA analytical framework include data ingestion operators, data transformation operators, and feature extractors. Various machine learning algorithms and statistical techniques are incorporated in the TBA analytical framework to downscale the regional datasets. The downscaling involves selection of potential predictors and predictants variables based on data needs to address local groundwater management scenarios such as regulating groundwater abstraction to prevent groundwater depletion. Using the downscaled data the TBA analytical framework can be utilised to uncover patterns and statistical relationships in the datasets in order to model local groundwater processes such as cone of depression, groundwater levels forecasting, well protection zoning, amongst others.

Abstract

Extensive geological, mineralogical and geochemical research have been done on the Insizwa layered mafic sill intrusion, located in the northern part of the Eastern Cape province, South Africa. This focus is understandable in the light of its potential for Cu, Ni and PGM extraction. However, the complex is also linked to a potentially significant groundwater reserve, and is located in a populated rural area with numerous communities residing on or in close proximity to the intrusion. These communities rely on local groundwater sources and recent groundwater development projects have suggested that groundwater yield potential is higher in its host Karoo sedimentary rocks adjacent to the intrusion than farther away. The proposed research will endeavour to investigate the structural geological features that influence groundwater yield, quality and community water supply potential in the Insizwa and surrounding area to provide a baseline for integrated quantified groundwater management, to meet community needs and awareness.

Abstract

Frequently hydrogeologists are required to site boreholes in areas that are not the optimal for groundwater supply and are given budgets that don't allow rigorous science. This paper presents case studies from Windhoek (Namibia), Matatiele (Eastern Cape Province) and the greater Port Elizabeth area where high success rates and yields were achieved by adopting a no-compromise approach to budgets and target areas. In Windhoek, the aim was to locate and intercept faults at depths up to ~500 m. Following geological mapping and geophysics, angled boreholes were drilled to establish fault dips prior to successfully drilling deep production boreholes. In the Matatiele area, an extensive area was flown with airborne geophysics prior to surface geophysical surveys. In Port Elizabeth the electricity supply to a large area was temporarily cut in order to get undisturbed geophysical data. In Jeffreys Bay, the main entrance road was virtually blocked to cater for geophysical surveys. Hankey town is located in a poor groundwater area, so drilling on private land about 20 km out of town had to be negotiated in order to target an aquifer suitable for the town's supply. These are some of the examples that will be presented in the paper. In most areas drilling yields in excess of 50 L/s were achieved, and the success can be attributed to not compromising on doing rigorous science in the right areas.

Abstract

Assessment of aquifer vulnerability to contamination is receiving renewed attention due to recent extreme events as demand for groundwater as alternative sources of water supply intensifies. In this study, GIS-based modeling of the impact of land-based activities and climate variability is employed to quantify the risk to quality deterioration of groundwater resource, delineate potential areas and highlight degree of vulnerability in the Cape Flats aquifer. The study used Scenariorcp85 CMIP5 AR5 climate change datasets downscaled from GCM using WaterWorld model. The WaterWorld is physically based global model for water balance includes all data required for application with a spatial resolution at 1-square km (Mulligan, 2009). The modeling results suggest that water balance for the predominantly low-lying flat central portion receives recharge ranges from 44 to 376 mm/yr. This reflects the area precipitation ranges from 500 to 800 mm/yr. Actual evapotranspiration (mm/yr) ranges from 92 to 1,200. The cmip5rcp85worldclimhe20412060 simulation main results indicate water balance (mm/yr) for the area predict to a minimum of -1,100 and maximum of 1,100. Actual evapotranspiration (mm/yr) ranges from 67 to 1,200. This led to an increase in evapotranspiration for the area of 13 mm/yr (2.5 %) that lead to an overall decrease in the water balance of -44 mm/yr (22 %). The human influence on water quality was simulated based on the human footprint index. The risk of contamination is largely attributed to the change in urban areas, pastures and cover of bare ground. In order to address the significant spatial variability of groundwater recharge and potential contamination risk occurring throughout the area, a GIS-based approach is used. The result underscores that GIS-based models are powerful tools to integrate spatiotemporal data and make assessment possible to improve understanding of water security in light of climate and land use change scenarios.

Abstract

In the recent drought of the Cape, Drakenstein Municipality sought to improve its water security and supply through including groundwater into the municipal water supply network. After a desktop assessment of the geology and hydrogeology of the municipal area, it was initially proposed that groundwater development target the Table Mountain Group Aquifer (TMGA), which lies along and within the eastern boundary of the municipal border and is expected to yield 2 - 5 L/s/borehole. The alternate aquifers of the area are in the bedrock shales of the Malmesbury Group and the crystalline granites of the Cape Granite Suite. These are both categorized to have expected yields of 0.1 - 0.5 L/s/borehole. It was then decided that despite the substantially higher estimate potential of targeting the TMGA further away from the towns, investigations would focus on exploration on municipal land closer to local infrastructure, to limit on the costs of the additional infrastructure that would be required to get the water to the towns. This resulted in the exploration being predominantly focused on inferred bedrock faulting in the Malmesbury Group within Paarl; and the contact of the Malmesbury Group to the Wellington Pluton granite in Wellington, as well as part of the Wellington- Piketberg Fault. While several boreholes drilled in exploration in both the Malmesbury Group and the Cape Granite Suite confirmed the generally low yield expectations (< 1 L/s), surprisingly high yielding boreholes were drilled in the town of Paarl. Initial exploration of the potential fault was done in 2017 with electromagnetic and resistivity profiling to look for subsurface changes that may be associated with fracture zones. After the results of these surveys seemed to show some change in geophysical properties in the subsurface where a fault was inferred, exploration drilling along some of these profiles was conducted. In particular, exploration drilling at the Boy Louw Sportsfield in Paarl intersected water strikes from 60 - 90 mbgl in excess of 20 L/s blow yields. After a 3-day yield test with a further day for recovery in early 2018, a production wellfield was planned. Production drilling involved drilling larger diameter boreholes that would allow for higher flow rate pump installations than the typical 127 mm (PVC sleeved) to 165 mm inner diameter boreholes found in the region. Drilling depths of 100 - 150 mbgl were reached, by which depths airlift yields were exceeding 20 L/s as expected from the initial exploration drilling. Wellfield testing of the boreholes was performed by conducting two separate simultaneous borehole pumping tests at 38 L/s and 44 L/s, during which all available boreholes in the wellfield were monitored for water level changes. Based on the data analyses of these tests, the sustainable yield of the wellfield was initially estimated to be up to 60 L/s. As there was still some uncertainty regarding the high yields in a geological environment which was typically much lower yielding, two operational recommendations were put in place. The first was that the boreholes be equipped with pumps capable of adjusting flow rates as well as water level monitoring infrastructure to allow for informed management of the resource. The water level monitoring was also to be installed in the exploration boreholes to monitor the drawdown outside of the production boreholes. The second was that a one-month step-wise start to production should occur. During this period the wellfield was to start with a week of continuous pumping at a lower rate than estimated as sustainable, with increasing rates each week. This was recommended in such a way as to bridge the gap between the cumulative wellfield test rates and the cumulative wellfield recommended rate of abstraction and allow for any final optimizations to be made to this rate.While the first recommendation of monitoring infrastructure and variable rate pump installations was adhered to, in May 2019 the wellfield was abstracted from at the full initial recommendation of 60L/s. After a week of abstraction, three of the production boreholes were performing as expected fromthe wellfield test results, while one of the production boreholes had begun to drawdown more rapidly than expected. It was noted that this began to occur at a lower depth than what was reached during the 2018 wellfield tests. The rate of the individual borehole was reduced and abstraction continued for another two weeks with the new wellfield total of 54 L/s. The drawdown data of the borehole in question during the May 2019 abstraction was then re-analysed within the context of the wellfield, and with the increased drawdown data, to produce final wellfield production recommendations. As with all sustainable yield testing of boreholes, the choice of available drawdown is critical to the success of the analysis. In the Boy Louw Wellfield, it is likely that had higher abstraction rates been used during the wellfield testing, greater drawdowns may have revealed the inflection point in one of the production boreholes. Accounting for this in the initial analyses would have resulted in a more accurate initial wellfield recommendation. Additionally, the recommendations of a step-wise start to production would have likely revealed the same thing. While one of the production boreholes is now recommended to be operated at less than 50% of its initial recommendation due to the more recent identification of an inflection point, the total abstraction rate is still 90% of the initial wellfield tests' analyses recommendation. Against all odds, this allows an abstraction rate of 54 L/s from 4 production boreholes within a geological setting previously characterized as 0.1 - 0.5 L/s/borehole. Based on these results, it is recommended that future wellfield developments can adopt a similar methodology of iteratively increasing the development of a wellfield through scientific principles and testing. Wellfield testing should aim to cause sufficient drawdown in the production boreholes, as well as identify and quantify the cumulative interactions between adjacent boreholes within the wellfield. Should this not be achieved, a step-wise start to production with the ability to optimize flow rates is strongly recommended.

Abstract

South Africa has committed to achieving the United Nations Sustainable Development Goals (SDG's) by 2030. But what does this mean and how does groundwater fit in to this? SDG 6 in particular focuses on ensuring universal access to safe and affordable drinking water for all by 2030. SDG 6 requires that the country protects and restores water-related ecosystems such as forests, mountains, wetlands, aquifers and rivers which are essential if we are to mitigate water scarcity. To accomplish this, South Africa has proceeded to align various plans, strategies, and policies to encompass the targets of the SDG's. This paper will focus on SDG sub-goal 6.3 which incorporates improvement of water quality and sub-goal 6.6 which involves protection and restoration of ecosystems. The methodology given by the UN for the groundwater in indicator 6.3.2 stipulates that countries are required to report on "proportion of water with good ambient water quality", in South Africa however we had to domesticate the indicator i.e. render it suitable for South African conditions so we changed the methodology to "proportion of water the conforms to the Water Quality Objectives (WQO's)" but there are virtually no WQO's developed for groundwater. Four core groundwater quality parameters (Electrical Conductivity, pH, Nitrate and Sulphate) are available through ZQM stations categorized through 65 hydrogeological (Vegter) regions. Groundwater water quality baseline is calculated as a reference period/range per hydrogeological region. For SDG 6.6, the indicator required for groundwater is "Quantity of groundwater within aquifers" The methodology received by the UN for "Quantity of groundwater within aquifers" required a baseline (average reference period of five years) in meters per hydrogeological region. This indicator is again domesticated for South Africa and based on the 40-60 percentiles of groundwater levels per hydrogeological region. There are a number of future indicators that can be included for aquifers under SDG 6.6, but the groundwater sector needs to come together and decide what is important to report on. These SDG targets reporting has given the Water and Sanitation sector a new look at data. It has forced us to critically think of concepts such as baseline and performance monitoring. We now know where our data gaps and targets are, and we have to provide an action plan to address these.

Abstract

The uncertainties associated with both the sampling process and laboratory analysis can contribute to the variability of the results. In most cases, it does appear that if the water samples have been analysed by an accredited laboratory, the results are acceptable. While the accreditation of analytical laboratory and therefore its credibility is very important to uphold quality and integrity, the same should be said about the sampling process. The quality and credibility of a sampling process is typically left to the responsibility of the appointed groundwater practitioner without any criteria to evaluate the quality and integrity of the sampling process. Perhaps the quality and integrity of the sampling process is evaluated based on trust or experience of the practitioner. However without any form of scientific criteria to evaluate the quality and integrity of the sampling process, it is difficult for the sampling process to be scrutinized. The quality and integrity of both the sampling process and laboratory analysis must be scientifically evaluated based on the uncertainty of measurements in line with the monitoring goals/requirements. This presentation discusses the aspects of evaluation of measurement uncertainties associated with groundwater sampling as an important component of quality assessment of groundwater sampling processes. The potential implications of the uncertainties on the final results and their use in decision making is also discussed. The credibility of the decisions made also depends on the knowledge about the uncertainties of the final results

Abstract

For years hydrogeologists have bemoaned the fact the groundwater is often pushed aside in favour of surface water resources being developed for water supply purposes. This is despite the advantages of groundwater being less vulnerable to the impact of drought, generally significantly cheaper to develop and being ubiquitous in character. The intangible character of groundwater was thought to be a major factor in water resources engineers favouring surface water resource development, as well their limited appreciation of the character, exploration, development and management of the resource. But is this really the case? Recent experiences in developing groundwater as an alternative source of water across the Western Cape Province in the face of failing municipal water supplies has highlighted poor communication being a central issue. It was observed that the hydrogeologists had little appreciation of the controls and constraints that govern getting groundwater to the user. Further, their recommendations around the use of groundwater were at times confusing to the uninitiated. Engineers, on the other hand, were found to not adhere to recommended pumping regimes nor appreciate groundwater management requirements. The treatment of groundwater emerged as a constraint that added greatly to the complexity of developing these supplies and requiring ongoing operation and maintenance efforts.

Abstract

The demand on fresh water has increased to such an extend that supply cannot keep up with demand, especially in areas where desalination of seawater is not an option. There is a large gap between the water user, the water supplier and the capacity of the resource/s. The water user sees it as his/her right to be provided with clean water in sufficient volumes to sustain their most basic needs.At the same time people want higher levels of service, especially where sanitation is concerned. The recent droughts in Cape Town and in Port Elizabeth have put significant focus on groundwater and we've seen uncontrolled drilling for groundwater reaching new heights, which is a problem on its own. We can no longer afford not to bring the groundwater user into the water planning cycle, so that the users, on all levels of society, can be educated to understand that the quantity and quality of fresh water (ground -and surface water) is limited and dependent on recharge from rainfall, size of the catchment, topography and all that takes place on the surface. This education must be specific to a target audience and must take into account the existing knowledge and understanding of the user profile. As an example, a case study will be discussed where there are large groundwater users operating within the upper parts of a catchment, followed by municipal abstractions and private abstractions within the central parts of the same catchment. Four profiles of users are therefore present: (1) large-scale irrigation by farmers, (2) large-scale municipal abstractions, (3) private residents and (4) formal / informal settlements, with the latter probably competing for top pot in terms of water use, with the irrigation. They key deliverable of the presentation / paper will be to (1) make people aware of the problem/challenge, and (2) suggest ways to bridge gaps and get all users and service providers to work together to save water and to understand that there are limits to the quantities available.

Abstract

Water scarcity is a global challenge, particular in South Africa, which is a semi-arid country. Due to the continuing drought, appropriate groundwater management is of great importance. The use of groundwater has increased significantly over the years and has become a much more prominent augmentation component to the supply chain especially in rural communities. However, the approach used to develop groundwater resources, specifically in rural areas, can be improved in numinous ways to ensure drilling of successful boreholes that could meet water demands. A recent study done in the Thaba Nchu area focused on an adapted approach, which resulted in drilling successful boreholes that would be able to sustain their augmentation role in the long term. The adapted approach involves (i) a hydro-census that includes local knowledge and focused field observations, (ii) study of aerial photographs and geological maps on a regional scale, rather than on a village scale area, (iii) an optimised geophysical investigation to identify and map geological structures to drill production boreholes, (iv) conducting aquifer pump test to determine an optimum sustainable yield, (v) collecting water samples to determine if water quality is suitable for its specific use (vi) providing a monitoring program and abstraction schedule for each borehole. The adapted approach highlights the following improvements: (i) drilling of new production boreholes during times of bounty to allow for better time management on the project; (ii) including an experienced geohydrologist during planning phases, (iii) including a social component focussing on educating local communities on the importance of groundwater and introducing them to the concept of citizen's science, (iv) establishing a communication channel through which villagers can report any mechanical, electrical, quantity or quality issues for timeous intervention. Through applying these small changes to established components of development of groundwater resources, budgets and time management were optimised and additional communities could be added to the project without additional costs. This approach not only emphasised ways to improve the awareness and potential of groundwater resources, but also affects the economical-, social- and environmental welfare in rural communities.

Abstract

Large parts of the City of Cape Town overlie a significant aquifer. Urban development proceeded without acknowledgement of the importance of this aquifer causing contamination in some areas and a lack of protection of recharge areas. Use of the aquifer for private domestic and industrial purposes has also largely continued unchecked. With the recent drought in Cape Town use of the aquifer dramatically increased, as did the City's understanding that the aquifer is a strategic resource to them. This paper presents the pros and cons of decentralised groundwater use. The current status quo of decentralised groundwater use in Cape Town, from basements to garden irrigation boreholes and to large-scale industrial users is presented, along with an assessment of the impact of the drought on groundwater availability. Recommendations are provided for how best to manage the challenges of decentralised groundwater use.

Abstract

The Two-Streams catchment located in the KwaZulu-Natal Midlands, South Africa has been used as an experimental catchment over the past decade to investigate the impacts of Acacia mearnsii stands on hydrological processes. As part of the ongoing study, the hydrogeology of the catchment was investigated and characterized to understand the impacts of Acacia Mearnsii plantations on groundwater. The hydrological, hydrogeological, hydrochemical and environmental isotope methods were employed in characterizing the hydrogeology of the catchment. The study area is underlain by three geological units: top weathering profile, mainly of clay, which is underlain by weathered shale. Shale is in turn underlain by granite rock. Two hydrostratigraphic units were identified: an unconfined aquifer occurring along the weathered shale and the underlying regional semi-confined aquifer. The regional aquifer is characterised by transmissivity range of 0.15 to 0.48 m2/day, hydraulic conductivity of 0.04 m/day and annual recharge of 31.9 mm. The catchment receives a mean annual rainfall of 778 mm, mean annual evapotranspiration of 802 mm and mean annual stream discharge of 20387 m3. The groundwater and stream samples are characterised by mean specific electrical conductivity of 28.5 mS/m and Ca-HCO3 and Ca-Cl dominant hydrochemical facies. Isotopic values indicate recharge from rainfall with insignificant evaporation during or prior to recharge. Seasonal stream isotope data analysis indicates groundwater as the main contributor of streamflow during dry season. Furthermore, the impacts of Acacia mearnsii trees on groundwater were investigated. Results show that direct groundwater uptake by tree roots from the saturated zone at Two-Streams would not be possible due to limiting root depth. Thus, in instances where the regional groundwater table is not available for direct abstraction by tree roots, trees can have large impact on groundwater by extracting water from the unsaturated zone, reducing recharge to aquifers and baseflow, without having direct access to groundwater

Abstract

The advent of the 'Big Data' age has fast tracked advances in automated data analytics, with significant breakthroughs in the application of artificial intelligence (AI). Machine learning (ML), a branch of AI, brings together statistics and computer science, enabling computers to learn how to complete given tasks without the need for explicit programming. ML algorithms learn to recognize and describe complex patterns and relationships in data - making them useful tools for prediction and data-driven discovery. The fields of environmental sciences, water resources and geosciences have seen a proliferation of the use of AI and ML techniques. Yet, despite practical and commercial successes, ML remains a niche field with many under-explored research opportunities in the hydrogeological sciences. Currently physical-process based models are widely applied for groundwater research and management, being the dominant tool for describing and understanding processes governing groundwater flow and transport. However, they are limited in terms of the high data requirements, costly development and run time. By comparison, ML algorithms are data-driven models that establish relationships between an input (e.g. climate data) and an output (e.g. groundwater level) without the need to understand the underlying physical process, making them most suitable for cases in which data is plentiful but the underlying processes are poorly understood. Combining data-driven and process-based models can provide opportunities to compensate for the limitations of each of these methodologies. We present applications of ML algorithms as knowledge discovery tools and explore the potential and limitations of ML to fill in data gaps and forecast groundwater levels based on climate data and predictions. Results represent the first step in on-going work applying ML as an additional tool in the study and management of groundwater resources, alongside and enhancing conventional techniques such as numerical modelling.

Abstract

The hydrogeological setting of a proposed mine site can significantly influence the viability of the mining venture. The management of groundwater inflows, costs of the dewatering technology, construction and maintenance of storage facilities, discharge strategies and anticipated environmental impacts are vital factors for consideration. It is fundamental to assess the hydrogeological setting at an early stage of the mine life cycle and should involve the collection of sufficient hydrogeological data, conceptualisation of the hydrogeological setting and an assessment of planned mine operations and anticipated impacts. Ambient hydrogeological conditions at the deposit area may be identified by conducting a hydrocensus and utilising existing ore exploration drilling data. Information from the hydrocensus and ore exploration drilling can provide valuable preliminary data on groundwater risks, dewatering and available groundwater resources. Potential groundwater/surface water interactions and receptors sensitive to environmental impacts can be identified during a hydrocensus. Similarly, water strikes and fracture density recorded during exploration drilling provide valuable insight to the subterranean environment. It is also possible to obtain aquifer hydraulic properties through packer testing of exploration boreholes. Geochemical test work on exploration borehole-cores could provide valuable information regarding contamination risks from ore deposit and waste material storage. The installation of piezometers within available and accessible exploration holes that extend below the regional groundwater level can pioneer the collection of monitoring data crucial for consideration during the mine life cycle and provide an understanding of the interaction between hydrogeological units and recharge characteristics. Ultimately, mine operations and associated potential impacts on the surrounding groundwater environment can be simulated with the application of numerical hydrogeological flow and contaminant transport models. The numerical models can simulate the regional groundwater flow system and complexities of the mine environment, the accuracy of which is influenced by the type, spatial and temporal distribution of the data collected. It is accordingly suggested that the collection of hydrogeological data and information during the exploration phase would facilitate the timely conceptualisation of potential groundwater risks and effective planning of hydrogeological investigations required during upcoming phases while assisting in the budget optimisation of these future studies.

Abstract

In South Africa, the use of stochastic inputs in surface water resources assessments has become the norm while this is rarely done for groundwater resources. Studies that have applied multi-site and multi-variate methods that incorporate stochastic generation of groundwater levels are limited. Stochastic based inputs account for uncertainties attributed to inherent temporal and spatial variability of hydrologic variables and climatic conditions. This study applied variable length block (VLB) stochastic generator for simultaneous generation of multi-site stochastic time series of rainfall, evaporation and groundwater levels. In the study, 100 stochastic sequences with record length of 34 years (1980-2013), similar to the historic one were generated. Performance of VLB was assessed by comparing single statistics of historic time series located within box plots of the 100 annual and monthly stochastically generated time series. The statistics used include mean, median, 25th and 75th percentiles, lowest and highest values, standard deviation, skewness, and serial and cross correlation coefficients. Majority (9 out of 10) of the historical statistics were mostly well preserved by VLB, except for skewness. Historic highest groundwater levels were mostly underestimated. Historic statistics below interquartile range (overestimation) is a common problem of weather generators which can be reduced by including additional covariates that influence atmospheric circulation. The generation of multi-site stochastic sequences support realistic assessment of groundwater resources and generation of groundwater operating rules.

Abstract

The City of Cape Town (CoCT) commenced a study into the feasibility of the Table Mountain Group aquifers (TMGA) for augmenting the water supply to the city in 2002. It comprised drilling of exploration boreholes in several target areas and the establishment of a hydrogeological and ecological monitoring network. Due to the prolonged drought and associated water crisis, the CoCT decided to fast-track the TMGA development in 2017. The first wellfield is currently developed within the catchment area of the Steenbras Dam comprising production boreholes targeting the Skurweberg and the Peninsula aquifers of the TMGA. Since groundwater abstraction from the Peninsula and Skuweberg aquifers might have a short-term or long-term impact on aquatic ecosystems (i.e. streams and wetlands) that are linked to the TMGA. As a result, evaluation of the potential impact of groundwater abstraction from this aquifer system requires an understanding of the nature and extent of groundwater dependency of the ecosystems. A variety of data sets and parameters have been measured over the last decade at ecological monitoring sites across the study area, of which two sites are located within the Steenbras catchment that are probably connected to the Skurweberg Aquifer. Recently further boreholes and monitoring sites have been added. This paper describes the various methods used and results of the analysis towards a conceptual understanding and quantification of the groundwater dependency of the selected ecosystems. While groundwater contribution is only one factor in ecosystem functioning, sustainable and adaptive management of the groundwater use must be based on the conceptual model and ongoing monitoring of the ecosystem responses.

Abstract

Groundwater water levels and the ability of aquifers to sustain water have been reportedly on the decline in specific areas in the Northern Cape Province in South Africa. The study area is located in an arid regional with mean annual precipitation of less than 400 mm/a, which is drought prone. The hydrological balances indicated that the required groundwater recharge to balance is at least 20 times less than the expected minimum natural recharge. Further investigation indicated that evapo-transpiration forms +95% of the hydrological balance. The models were very sensitive to evapo-transpiration, which focused the study towards land use and land cover. Research on land cover provided evidence that bush encroachment of especially alien species (e.g. Prosopis and Acacia Millefelera) could be responsible for increasing evapo-transpiration if compared to natural grassy vegetation with infestation levels of 5% to 8% in the study area. The hydrological models indicated that infestation of 2.5 % is sufficient to capture all the rainfall reducing groundwater recharge to zero. The study shows that infestation in combination with a thick soil cover of Kalahari Sand or associated formations provide a buffer for groundwater recharge as the soils have a high soil moisture retention capacity which is ideal for use by plants, especially deep rooted woody species. More detailed investigations are under way to compare present and historical land cover and evapo-transpiration potential to qualify the findings of the initial study. Land management and mitigation of bush encroachment is recommended to ensure the sustainability of future soil moisture and groundwater recharge.

Abstract

Well-established engineered systems for depth-discrete monitoring in fractured rock boreholes (referred to as a Multilevel System or MLS) are commercially available and offer much diversity in design options, however, they are used infrequently in professional practice and have seen minimal use in groundwater research. MLSs provide information about hydraulic head and hydrochemistry from many different depths in a single borehole and, therefore, magnify greatly the knowledge value of each borehole. Conventional practice globally is devoted to standard monitoring wells, either alone as longer single screened wells or in clusters or nests with a few wells screened at different depth intervals. These are the mainstay of the groundwater science and engineering community and severely limit prospects for each borehole to provide the information needed to solve the complex problems typically posed by fractured rock. This paper outlines the nature and evolution of MLS technologies and points to recent literature showing how MLSs add important insights that cannot be obtained using conventional wells. Also, it reviews commercially available MLS technologies, which present a range of robust options with each system having different characteristics and niches depending on characterization and monitoring goals and site conditions. The paper also describes refined MLS criteria aimed at improving the cost effectiveness and expanding capabilities of MLSs, so as to improve their accessibility for high resolution data acquisition in the context of both groundwater system characterization and long-term monitoring.

Abstract

Synthetic flocculants are widely used in water treatment for their efficiency when it comes to flocculation but pose a risk to the environment and human health. The need for an alternative flocculant was investigated in this study. Bioflocculants which are produced by microorganisms have the potential to flocculate fine suspended particles. The bioflocculant production by Bacillus sp. isolated from Umlalazi Estuary in Mtunzini, KwaZulu-Natal Province was evaluated. Optimum flocculation conditions were obtained with an inoculum size of 1% v/v (89%), carbon source which was glucose with a flocculating activity of 88%, a multiple nitrogen source with a flocculating activity of 88%, an optimum temperature of 400C with 95% flocculating activity, shaking speed of 120 rpm with 95% flocculating activity, K+ for the cations was optimum at 95% flocculating activity and the pH of 7 had the flocculating activity of 94%. In the time course assay optimum conditions were reached after 84 hours with the flocculating activity of 92% at pH 5.29 using 0.4% (w/v) kaolin suspension. After extraction and purification, a bioflocculant yield of 2.1g/L was recovered from a 1L fermentation broth. Water treatment without the risk to human health is now a reality.

Abstract

Open pit mines often experience problems related to groundwater inflows. To perform mineral extractionin safe conditions with high productivity, it is essential to have dry working conditions. For this reason, the groundwater table is often lowered below the elevation of the floors of the pits by using various dewatering schemes. Numerical groundwater models are powerful tools that can be used to simulate the behaviour of aquifers during dewatering operations. However, these models typically require a lot of geohydrological data which are often expensive and time-consuming to collect. When geohydrological input data are limited, artificial neural networks (ANNs) provide an alternative approach of predicting the behaviour of the groundwater system during dewatering. This study investigated the possibility of predicting the impacts of pit dewatering on the aquifer system in the vicinity of open pit mines where geohydrological inputs are limited, using ANNs. First, the performance of the ANNs in predicting hydraulic head responses was evaluated by using synthetic data sets generated by a numerical groundwater model developed for a fictional mine. The synthetic data sets were then used to both train and evaluate the performance of the ANNs. The ANN found to give the best predictions of the hydraulic heads had an architecture of 2-6-1 (input-hidden-output layers) and was based on the hyperbolic tangent transfer function. This network was selected to predict the hydraulic heads at a number of piezometers installed at two open pit mines in the Democratic Republic of the Congo. The only input to the ANN was the recorded hydraulics heads and the time of recording. A portion of the real data set was used to train the ANN, while the remaining portion was used to evaluate the performance of the ANN in predicting the hydraulic heads. The results of the performance analyses indicated that the ANN successfully predicted the general behaviour of the aquifer system under dewatering conditions, using only limited input data. The results of this investigation therefore illustrate the great potential of using ANNs to predict aquifer responses during dewatering operations in the absence of comprehensive geohydrological data sets. Since these networks recognise patterns in the training data sets without considering the underlying physical principles that govern the processes, the responses of complex systems that are dependent on numerous parameters may be predicted.

Abstract

Water is integral to our economy, the health of our environment, and our survival as a species. Much of this water is accessed from surface sources, mostly rivers, which are now under increased threat due to over use and the resulting hydro-political forces. Yet, groundwater exists as a viable option in many countries facing these mounting challenges. Knowledge of our deeper groundwater systems, although increasing, is still quite limited due to our propensity to focus efforts in the lower cost, lower risk, near- surface environment. However, accessibility to shallower groundwater is tightening due to increasing use, changing regulatory requirements, and climate change.

The use of classical geophysics to explore for groundwater resources, such as seismic, gravity, magnetics, and resistivity, has been the industry standard for many decades. These technologies have proven quite effective both in the shallow and medium depth environments. However, newer remote sensing and ground-based technologies are now emerging with the ability to significantly reduce costs and time, and increase success for groundwater exploration and development programs. Quantum Direct Matter Indicator (QDMI) technologies, or applied methods of Quantum Geoelectrophysics (QGEP), are poised to enhance the hydrogeophysical industry, much like electro-magnetic (EM) and electrical resistivity tomography (ERT) did years ago. QDMI utilizes resonant frequency remote and direct sensing technologies that detect perturbations in the earth’s natural electric, magnetic and electromagnetic fields. Controlled source electromagnetic pulse methods with electromagnetic spectrum spectroscopy are used to identify aquifers, including thickness, water quality (fresh or saline) and temperature, to depths of 1000 m or more accurately. With multiple successes around the world, the deployment of this inventive and effective approach to groundwater exploration is poised to advance exploration geophysics globally.

Abstract

The Verlorenvlei estuarine lake is one of only two freshwater estuarine systems in South Africa. Whilst being important ecologically it is also a critical agricultural region, supporting a significant proportion of South African potato crops as well as a number of other diverse crops. The vlei itself is fed by the Verloren River which is thought to be fed by surface water inflows and baseflow throughout the year along several tributaries, namely the Krom Antonies, Hol, Berg Vallei and Kruismans. Each of these tributaries has a distinct hydrochemical character defined by cation and anion concentrations, as well as O, H and Sr isotopes. Simulated discharge from each tributary suggests that all tributaries contribute to the chemistry of the Verloren River. The Krom Antonies which has the freshest water has the highest discharge at around 50% of surface water inflows, whilst the Hol with the highest EC values contributes around 35% of surface water inflows. In spite of this, the surface water hydrochemistry in the Verloren River, is remarkedly fresh and very similar in character to the surface water of the Krom Antonies. Sr isotopes in each of the tributaries are distinct and support mixing of different components of each tributary above the confluence. However, below the confluence, they drop significantly which indicates mixing with another unidentified Sr-source. This source was thought to be baseflow from the deeper groundwater system, but the Sr isotope composition of deeper groundwater indicates that it is not the contributing component. Recent years have seen dramatic reductions in precipitation, while increases in pumping for agricultural purposes potentially exceeds the long-term sustainable yield of the aquifer system. Identification of this unknown component has therefore become a priority for groundwater management in the area as it is unclear how vulnerable this component will be to climate change and hence what impact climate change will have on the vlei.

Abstract

Water plays a significant role in the economies of the agricultural, business and industrial sectors. Expanding populations, economies and climate change have put pressure on the quality and availability of water resources in South Africa, therefore water resource protection becomes increasingly important for sustainable water supply management. Hence, a review of the state-of-the-art of water resource protection in South Africa has been undertaken on behalf of the WRC, applying the water resource governance framework. Gaps in scientific understanding and implementation with regards to water resource protection have been identified through literature review and discussions with stakeholders and experts. Aiming to improve the water resource protection in South Africa, a research strategy has been developed to tackle the most relevant of the identified gaps. The legislation in South Africa with respect to water resource protection is state-of-the-art and one of the best in the world. However, there is still space for improvement in that the different acts need to be aligned better to facilitate cooperative governance and improve the implementation of the legislation. Regulations and guidelines are plentiful covering most of the relevant activities and various water resources. The main challenge for implementing the intent of the National Water Act with respect to groundwater resource protection is that the standard methodology for determining Resource Directed Measures (RDM) was developed for surface water resources and is not applicable to groundwater or wetlands. Furthermore, classification and Reserve determination are mostly carried out at a scale that is insufficient for effective groundwater resource protection. The methodology requires update to incorporate potential impacts of climate change, changing land use and changing demographics. The different elements of the RDM methodology need to be aligned. There is also often an insufficient spatial and temporal distribution of monitoring networks to effectively manage groundwater resources. Integrated catchment management can provide a solution to the current state of water resource protection. However, this must be based on a scientific understanding of the complex natural system. The different challenges, research needs and possible solutions are demonstrated on a case study of Stanford Aquifer.

Abstract

The Elandsfontein Phosphate Mine is situated midway between the Langebaan Lagoon and the town of Hopefield. It is located on the Cape West Coast, within the Saldanha Bay Municipality. The mine is positioned within the Elandsfontein Aquifer Unit – which comprises an upper and lower aquifer separated by an aquitard. The economic phosphate layer is situated within the saturated zone of the Upper Aquifer Unit. There are fresh water inflows into the Langebaan Lagoon and all measures must be taken to ensure the natural geohydrological flows are not impacted. Numerous groundwater studies and numerical modelling was carried out to optimize the best way of minimizing the impact on the geohydrology of the area. The dewatering system that has been designed includes re-injection of the groundwater approximately 2 km down-gradient of the open pit. This paper reviews the geological and geohydrological setting of the area and the outcomes of the dewatering and injection systems in place.

Abstract

The Western Cape of South Africa is rich in small stream sized rivers forming part of its water resources. The Lourens river and Eerste river, both situated in this region are the base for this study. Rivers are affected by their surrounding environments and the continuous development around these rivers could affect their health adversely. Diverse land-use patterns contribute to a wide range of pollutants with different characteristics. Indeed, some of the pollution levels in the Eerste and Lourens rivers were linked directly to specific land-use practices surrounding the rivers. However, the large change in weather during a seasonal cycle causes a significant difference in pollution levels too, because the transport of pollutants from the source to the rivers is primarily based on surface run-off, which in turn is predominantly dependent on the precipitation of the region.

A six months long monitoring in 2016 showed that processes like surface run- off, together with first flush events and dilution control the pollution concentrations in the Lourens river and Eerste river. Physicochemical parameters, major agricultural nutrients and industrially produced heavy metals all reacted differently to these processes, thus, providing an insight into the effects continuous development and climate change have on surface water as a national resource. Interestingly, both rivers included sections with substantial retention and/or reduction of pollutants. The natural riparian vegetation, hyporheic zone and microbial community present in these rivers are proposed to be the main drivers behind both rivers’ ability to reduce or retain pollutants. These drivers are sensitive to their environment and react differently depending on the weather, available nutrients, and physicochemical environment. With the effects of climate change becoming more apparent, it is important to study the impact of warmer temperatures, longer droughts, and heavier rain events, for instance, on the pollutant retaining capabilities of these streams.

Abstract

In a town where 98% of the population relies on groundwater-dominated resources, Atlantis is also plagued by varied abstraction rates that promoted iron and manganese borehole clogging. Conventional treatment methods, such as pump-and-treat technology, can be costly and inefficient. In-Situ Iron Removal (ISIR) technologies addresses issues such crucial skilled operators, handling and storage of chemicals, expert management, and the disposal of generated sludge. ISIR has been successfully practised worldwide especially in Europe, for well over a 100 years. In South Africa however this methodology has not filtered through, although our groundwater systems have clogging problems related to iron and manganese precipitation. Atlantis in the Western Cape has benefitted from a pilot study that looked into ISIR and the unique idea of utilizing ozonation. The pilot project was successful, although applied on a small scale. This called for a further study that is now looking into extending the range of treatment, applying the principles of the Vyredox method, and lengthening the treatment period to 3 months of continuous injection. The study also aims to develop the engineering design criteria for full scale application. The success of this project and the technology to be developed goes a long way towards achieving Sustainable Development Goal 6 and improving South Africa’s groundwater systems.

Abstract

This paper studies and reports the water usage behavior of a primary school. Three interventions were implemented to change this behavior to support water conservation. The aim of the study was to quantify the effects of the technological interventions on behavioral change. The school’s water usage pattern was found to be predictive and regular except for daily losses, which were measured and extrapolated from midnight to early morning volumes. The water usage distribution was Gaussian with the mean being centered around break time. The interventions were able to reduce water consumption of the school by 44% when compared to the use of a school across the road where the interventions were not implemented.

Abstract

Water stress is frequently experienced in many parts of South Africa. To ensure the longevity of the country’s water resources, particularly groundwater, accurate quantification of the resource and prediction of the responses of each water resource unit to natural and anthropogenic stresses are necessary. To this endeavour, Simbithi Eco-Estate, located at Shaka’s Rock, KwaZulu-Natal requires the implementation of a Water Management Plan that includes a hydrogeological investigation. A hydrogeological conceptual model was developed for the eco-estate, based on which a numerical groundwater flow model was calibrated to simulate the impacts of different rates of groundwater abstraction within the estate. Hydrometeorological information, subsurface geology, hydraulic head, hydraulic characteristics of the aquifer units and hydrochemical data were analysed to develop a two-layer hydrogeological conceptual model. The conceptual model was used as the main input to the numerical groundwater flow model. The calibrated steady-state numerical model, developed using the finite-difference groundwater modelling code, MODFLOW, was used to determine the sustainability of groundwater abstraction within the eco-estate. During calibration, the hydraulic conductivities of the hydrostratigraphic units, and recharge were varied. The Model calibrated recharge was 5.5 % of the mean annual precipitation (MAP). The five abstraction scenarios considered were: Scenario 1, which is the sustainable abstraction rate determined from the analysis of pumping test data, and Scenario 2 to 5 which are assigned progressively increasing abstraction rates of Scenario 1, by a factor of 20%, 50%, 100%, and 1000%, respectively. The numerical model simulations indicate that Scenario 1 is most sustainable in terms of groundwater level drawdown and saltwater intrusion. The simulated groundwater drawdown progressively increased throughout the succeeding four scenarios.

The simulation results of the 5th scenario indicate that part of the model domain within the vicinity of the northern boreholes becomes dry and subsequent application of forward particle tracking on the simulation results predicts saltwater intrusion from the Indian Ocean towards the south eastern boreholes. It is accordingly recommended that groundwater resource development should be limited to below the abstraction rates of Scenario 4. Additionally, continuous monitoring of all boreholes within the eco-estate is recommended to generate time-series groundwater level information, which would be used to improve the predictive capabilities of the current steady-state model through a transient numerical groundwater flow model. To that end, an immediate establishment of a groundwater level and specific electrical conductivity (EC) monitoring network, equipped with data loggers, is recommended.

Abstract

The Table Mountain Group is a major fractured rock aquifer system throughout the Western Cape, with many interconnected but semi-independent parts, each having its own recharge area, flow paths and discharge area. Groundwater is known to travel long distances and reach great depths, including through the Olifants River syncline, such as at The Baths hot spring near Citrusdal. Stable isotope compositions of rain and groundwater in the Cederberg and Olifants River Mountains were measured over a period of 2-3 years. Rainfall in the Cederberg averaged -22‰ and -4.7‰ for D and  18O respectively, whereas rainfall in the Olifants River Mountains averaged -11‰ and -3.0‰ similarly. Groundwater used by farmers in the Olifants River Mountains averaged -13‰ and -2.9‰ similarly. The similarity between groundwater and rainfall isotope compositions in the Olifants River Mountains suggests local groundwater movement. It was concluded that the source of groundwater abstracted by farmers in the Olifants River Mountains is from the peaks west of the Olifants River with little to no contribution from the Cederberg, east of the Olifants River syncline. Geological evidence (thinning of the Olifants River syncline and increased faulting northwards) supports this conclusion.

Abstract

Groundwater recharge assessment was undertaken in the crystalline aquifer of the Upper Crocodile River Basin, Johannesburg South Africa. The basin is characterised by the complex hydrogeological setting represented by weathered and fractured granitic gneisses overlain by quartzite, shale and dolostone. A number of recharge estimation methods including the Stable Isotope Enrichment Shift method, were tested. The measurement of δ 18O and δD in springsrevealed the presence of high elevation recharge or cold weather recharge that occurs prior to extreme evaporation, undergoing deep circulation and discharging at the contact between the Witwatersrand quartzite and the underlying shale. In the dolostones, recharge occurs after evaporation at higher elevation undergoing deeper circulation through the dissolution cavities.

The Water Table Fluctuation method in the dolostone resulted in the mean annual recharge of 99 mm/year, representing 14% of mean annual precipitation. The Reservoir Water Balance method revealed that the Pretoria Group shale aquifer contributes 16% of dam water outflow per year (groundwater discharge) which equates to 3 429 662 m3 on average, while 7% of dam inflow is lost to groundwater constituting groundwater recharge of average 2 084 131 m3 per annum. Baseflow Separation method applied gave an average recharge value of 9.4% for the entire catchment. The estimated average recharge for the entire catchment was found to be 13% corresponding to 91 mm, which equates to 374 Mm3 . The Stable Isotope Enrichment Shift Method resulted an average annual recharge of 26.1% in the aquifers composed of quartzites and 3% in the dolostones. The method is found to be promising for application in spring regimen however, a further development is recommended since small shifts exaggerate recharge while large shifts undermine it.

Abstract

The past few years hydraulic fracturing has been a hotly researched topic. Currently, most published documents are just speculation of what can happen if hydraulic fracturing is to take place in South Africa. There is very little work done to firstly establish a baseline on the current groundwater quality and secondly look at the current state of the groundwater around the Soekor wells. For these reasons a geochemical investigation was launched looking at the Soekor wells and the surrounding boreholes to determine a valid baseline.

Looking at the two Soekor wells; geochemical analyses was conducted on water, soil and rocks. The drill core of the wells; soils from the waste ponds and water at or nearby the wells were sampled and analysed. By making use of XRF; XRD, Stable Isotopes and water chemistry analyses, a better picture of these wells and groundwater can be developed to give better guidelines to what should happen during the monitoring of hydraulic fracturing wells.

Abstract

The City of Cape Town is a favourite tourist destination. With Table Mountain being one of the new seven natural wonders of the world, Cape Town is also uniquely positioned where the Benguela and Atlantic ocean currents meet. Proximate environs play home to some of the most unique biodiversity found in the world with the fynbos biome protected in numerous reserves such as the Cape Peninsula, Table Mountain and Kogelberg Nature Reserves. Cape Town is also South Africa’s cultural heartbeat where artists, film makers, designers and wine connoisseurs contribute to the tourism of the country.

The recent drought and increasing demands through urbanisation are raising concerns regarding water scarcity and supply. Will the city be able to supply this growing demand, notably with additional stress due to climate change?

The Hydrological Heritage Overview aims to address the important power water has over Mankind and how we can harness that to our benefit without compromising the environment. The selection of Cape Town (following completion of Pretoria and Johannesburg) supplies the opportunity to address the mechanical impacts of water: Table Mountain formed through the action of water, and was shaped into its characteristic landform due to subsequent erosion by water action. Additional emphasis on the power of water relates to aspects of hydropower, the impacts of floods and droughts, and additionally of the power of water as it is harnessed as a vital life supporting resource and as a means of recreation.

As the final deliverable of this project, a short 12-minute documentary film has been made for the information of the general public and interested parties. The film showcases the water history of the City of Cape Town, emphasising supply from springs, dams and, more recently, artificial groundwater recharge. Although not a technical presentation, showcasing of the film will advance citizen science and public appreciation for the value of water.

Abstract

The availability of freshwater is one of the major development challenges that South Africa faces. South Africa is a water-scarce (semi-arid) country with rainfall distributed unevenly and away from the centres of major developments. The rainfall is tied to seasonal cycles that drive us repeatedly between floods and droughts. This paper serves to study the groundwater chemistry in light of the uranium mining that precedes shale gas fracking in the Karoo Uranium Province. The aim is to have groundwater baseline chemistry assessment before mining commence in order to be able to track mining effect on groundwater in the future. A total of 128 samples are dealt with in this work, 112 collected from groundwater, 9 collected from springs and 7 extracted from a database. The samples were analysed for physical parameters, cations, anions and metals. Redox potential was also determined as it plays a pivotal role because it controls the availability and form of uranium in a solution. Uranium is a radioactive actinide naturally occurring in the area. Therefore, this assessment will be crucial in order to understand how changing redox and pH conditions affect uranium solubility and to estimate the extent of uranium transport by water during and after mining. The effects of the redox potential and pH on uranium mobility have been examined in this work by means of computer modelling by using the Geochemist’s Workbench (GWB) 11.0. The composition of the water used for modelling resembled that of a typical bedrock groundwater of Karoo Uranium Province. The simulations were carried out under different redox potentials at different pH levels in the presence of ferrihydrite, dissolved organic matter and carbonates/bicarbonates to include the effects of uranium adsorption. The results show that the redox potential at which the uranium mineral (uraninite) dissolves varies depending on the pH of the groundwater.

Analysis of the simulation results indicated that the dissolution of uraninite takes place at a lower Redox condition with increasing pH (alkaline pH condition). This means higher redox conditions are needed for the dissolution of uraninite at low pH. Moreover, it is further concluded that the adsorption of uranium to ferrihydrite and carbonates is important at pH 6-10 and pH 5-8 respectively, which therefore play an important role in controlling the mobility of uranium in the modelled groundwater.

Abstract

The natural CO2 springs at the Bongwana area emanates from a number of sites along an 80 km long N-S trending fault known as Bongwana fault. CO2 rich groundwater is observed at a shallow depth in a borehole drilled for water supply parallel to the main fault. The geology along the entire fault length is characterized mainly by Dwyka Group sediments. The objectives of this study are to characterize the CO2 springs and assess their impacts on groundwater and surface water quality. To that end, existing literature and data were reviewed followed by the collection of groundwater and surface water samples at both CO2 emission and CO2 free streams, springs and boreholes around the length of the Fault zone. Major ions, trace elements and environmental isotopes analyses were carried out on the samples collected. EC, TDS, pH, Temperature, DO, Eh, ORP, total alkalinity, CO3 2- , HCO3 - ) were measured onsite. Acidic pH conditions, elevated TDS, EC and trace metals concentration were detected in all CO2 emission sites compared to CO2 free streams, springs and boreholes. These results clearly show the impacts of CO2 on groundwater and surface water quality within the vicinity of emission points. All the travertine cone springs located near Umtamvuna River are characterized by Na-Ca-Mg-HCO3 water types, while boreholes from shallow groundwater and river samples show Ca-Na-Mg-HCO3 types. The correlation among the deep CO2 rich groundwater parameters indicates that the major geochemical processes that could be responsible for the observed chemical composition are the precipitation of calcite and dolomite where their saturation indices (SI) range from 0.74 to 0.82 and from 0.24 to 1.35, respectively and the weathering of feldspars. Stable isotope (δ18O and δ2H) composition of the travertine cone springs shows a major negative shift from the meteoric water lines with δ18O and δ2H values ranging from -7.78 to -6.52 ‰ and -21.5 to -17.9 ‰, respectively. The stable isotopic composition of shallow groundwater reflects local and modern meteoric recharge. These observations indicate that the reservoir and source of recharge for the deep circulating groundwater are different from the shallow groundwater. It appears that natural CO2 emission along the Bongwana fault have impacted the ambient groundwater and surface water quality at the emission sites rendering it unfit for human consumption due to elevated concentration of dissolved constituents above safe drinking standards. The implication of this to CCS in South Africa is the fact that any unintended CO2 leakage into fresh groundwater and surface water resources from subsurface storage site can impact this already scarce resource. Therefore, strict scientific site selection protocols and CO2 leakage detections through properly designed monitoring systems are required to minimise the risk.

Abstract

Most of the Northern Cape has been hit with a drought for the past 4-7years. The western part of the Northern Cape have been dry for at least 7 years now with no rainfall or very little rainfall, while the more central part have been dry for the past 4 years with very little rainfall. It is only the past 2 years that this has been seen as a problem, but for the past 7years the Department with local municipalities have tried their utmost to manage the problem of water scarcity.

During the past 7years the DWS has learned many lessons on how to manage the groundwater in these areas to ensure sustainable future use but must also look at new initiatives to deal with this problem as drought is going to be the new norm in the western parts of South Africa.

Abstract

This keynote paper addresses several issues central to the conference theme of “Change, Challenge and Opportunity”. For hydrogeologists to exert greater influence on groundwater management globally, proper education and training is essential. Universities play a key role in educating hydrogeologists in the fundamental principles of groundwater science through taught Masters and other degree programmes. Scientific associations such as the International Association of Hydrogeologists (IAH) also have an important part to play in education and training through short courses, conferences and mentoring schemes, and in enhancing groundwater science through journal and book publications and scientific commissions. IAH’s mission is to promote the wise use and protection of groundwater and, in this respect, a series of Strategic Overview papers have been prepared to inform professionals in other sectors of the interactions between groundwater and these sectors. Two of the Strategic Overview papers focus on the SDGs and global change, and some of the groundwater challenges in these areas are described. Whilst these challenges will provide hydrogeologists with opportunities to influence global water issues in the 21st century, hydrogeologists will need to be able to communicate effectively with all of the stakeholders, using traditional and more modern forms of communication, including social media.

Abstract

Hydrogeologists have moved past merely investigating for water supply and quantification of sustainable yields. In the 21st century, and with rapid urbanisation and climate change, hydrogeologists are expected to work in cross-disciplinary fields of geochemistry, aquatic biodiversity, surface water – groundwater interaction, groundwater economics, law and management. In addressing important hydrological parameters such as recharge, recharge rates, advection of contaminants and interflow, the role of the vadose zone becomes increasingly important. A series of case studies and physical models were used to evaluate the movement of water at variable saturation through media with primary, secondary and tertiary porosity. Scales of models varied based on different volumes of observation and relevance from discreet fractures to regional hillslopes.

Centrifugal acceleration was employed in some of the models to scale predetermined variables. Models included consolidation of heterogeneous soil successions, discreet fractures and their intersections, flow from soil into discreet rock fractures, and column testing of dolomite residuum. Advances are made in the qualitative and often quantitative assessment of interflow, soil-to-rock percolation, discrete fracture flow, and flow through dolomite residuum. Further to this, insight is gained into empirical quantification of hydraulic parameters through, for instance, the cubic law; the relevance of flow regimes (turbulent versus laminar) at various Reynolds numbers; and breaching of interfaces to promote vertical percolation of water stored in partially saturated geological media. Applications include improved understanding of pore water pressure distributions in media, induced seepage under consolidation, ingress water eroding soil into bedrock cavities resulting in sinkholes or surface subsidence, drainage of slopes and cuttings, water influencing infrastructure, indirect and localised recharge rates, aquifer susceptibility to contamination from surface, and urban hydrology in general.

The paper addresses some key findings and examples within the context of an extensive series of publications and research reports.

Abstract

Denmark is a small country in the northern part of Europe. The water supply in Denmark is solely reliant on groundwater. In the past 40 years Danish groundwater management has undergone a major development. A key aspect of this, which could be of relevance in South Africa, is The Danish Groundwater Vulnerability Mapping. During a 15 year period, Denmark has spent 2.7 billion DKK (App. 385 million USD) on mapping 40 % of Denmark, in order to conduct a thorough vulnerability mapping and proper delineation of catchment areas and groundwater protection zones. The mapping has been developed intensively through the years.

The approach includes development of key components as practice oriented guidance documents on all the professional areas of groundwater mapping, geophysical methods, groundwater modelling etc. As an example the airborne geophysical method of Sky-TEM which is a spin-off from the mapping can be mentioned. Other key tools in the groundwater mapping is geological modelling in GeoScene3D and groundwater modelling in GMS/MODFLOW and MIKE SHE. The foundation for Danish Groundwater Mapping is access to data. In Denmark almost all subsurface data is made available in publicly accessible databases. There are dedicated databases for; boreholes (JUPITER), geophysical data (GERDA), geological and groundwater models (Model database) and groundwater reports (Report database). In recent years Denmark has increased its focus on sharing this knowledge with other countries, including South Africa, China and the United States. Through the Strategic Water Sector Cooperation Program (SSC) on Water between the South African Department of Water and Sanitation and the Danish Ministry for Environment and Food, the Danish method of Groundwater Mapping is being tested on two case studies, in South Africa. One is of an alluvial aquifer in Western Cape, which has similarities to the Danish geological setting. The other is in a fractured rock setting which is widespread in South Africa, but seldom seen in Denmark.

Abstract

Using citizen science approach to influence implementation of science-policy interface concept leads to optimal use and protection of groundwater resources that ensures sustained research for practical policy dialogue. Mere determination of water resource classes, the reserve and resource quality objectives within the resource directed measures (RDM) concept for protection of groundwater water resources without considering implementation aspects, propels for defiance in policy implementation at local scale. Although water resource classes and resource quality objectives have not yet been implemented at any catchment at this stage, however findings indicate that in some areas challenges have been experienced with preliminary Reserve implementation at local level, especially in water use license applications. There is a need for an orthodox link between RDM and Source Directed Controls (SDC) to complement current methods used and processes followed in GRDM projects for uncontested RDM implementation to ensure sustainable groundwater resource protection especially at local site where the resource reside. The argument in this paper is that a feasible implementation for GRDM at local level provides science-policy interface platform for the sustained operation of the science-citizen approach. The objective of study was to design a field-tested conceptual model of science-policy interaction that monitors and evaluates GRDM intervention. How policy implementation and evaluation utilizes scientific research outputs at local level were examined using ecological model. Key findings  indicated that (i) systems analysis approach was lacking at local level (ii) practical assessments of GRDM at local specific quaternary catchment scale was not adequate (iii) optimal reserve determination methodology for uncontested water utilisation was not clear to provide proper guidance for water use license application (iv) Reflective operational plan (GRDM monitoring) to enhance science-policy interaction was not available at quaternary catchment scale (v) Best practices of adaptive management principle to sustain groundwater resource protection were limited at local level. From these results, it can be said that the up scaling of the current approach for RDM especially GRDM requires refinement for practical uptake of scientific results. The study recommended that a feasible implementation plan for GRDM at local level that provides science-policy interface platform for the sustained operation of the science-citizen approach need to be designed, implemented, monitored and evaluated with citizens to inform reflective policy implementation. Although, the results of this study are not conclusive, the insights as a starting point for proactive buy in approach is provided to ensure that science-policy interaction remain practical and relevant to scientists and policy makers as well as society.

Abstract

 Seyler, H; Vahrmeijer, JT; Wiegmans FE

The Steenkoppies dolomite aquifer/compartment is situated 15 km north-west of Krugersdorp and has received great attention in March 2007 when the naturally discharging spring (known as “Maloney’s Eye”) reached the lowest flow on record, which was an incident that has drawn much attention. This incident caused major concern to the downstream users as the spring forms part of the Magalies River’s flow. At the time of this incident the flow measured at a record low of 1.58 Mm3 /a compared to an average flow rate since 1908 of 13.8 Mm3 /a. Coincidently in March 2016 exactly nine years after this time the record low flow of 1.58 Mm3 /a was again measured at the Eye. Continued drought conditions in 2016 resulted in the lowest flow recorded for five consecutive months. The flow rate of less than 2.2 Mm3 /a is a mere 38 % of the average flows of (5.7 Mm3 /a) recorded for the last 10 years. While the interest in exploiting groundwater from the Steenkoppies compartment dates back to the late 1890s it is only since the 1980s to 1990s when abstraction for irrigation became substantial. The volume of groundwater abstracted for irrigation increased more than 7.5 times since 1980. The crop area increased 2.6 fold since 1997, while the volume of water abstracted increased 1.6 fold.

Unfortunately, despite numerous conceptual reports, scientific papers, lawful water use verification studies and crop water use investigations, the Steenkoppies water users are still without a managing body and groundwater management/use plan. The lack of (adaptive) management has led to uncontrolled abstraction and issuing of new Water Use Licenses without the proper knowledge of the impact of additional water use on the system. The failed establishment of a water user association according to the National Water Act in 2013 dampened the hopes for any collaborated groundwater abstraction, -monitoring and -management plan.

The groundwater model developed for the Steenkoppies compartment should be seen as a prospective evaluation tool to determine the potential behaviour of the system with time, given a set of changing parameters. Numerical groundwater models are considered the best tools available to quantify/estimate groundwater, and the results can be used in management decisions.

Estimated groundwater abstraction per annum from the Steenkoppies compartment amount to between 25 Mm3 and 30 Mm3 , with a likely current rate of 28.5 Mm3 /a. Based on the modelled fluxes with average groundwater recharge (rainfall) conditions and induced recharge from irrigation return flows, it appears that 25 Mm3 is an optimal abstraction rate while maintaining a flow of around 5 Mm3 from the Maloney’s Eye. However, the Maloney’s Eye is sensitive to below average rainfall events leading to below average recharge conditions and resulting in lower volumes available for abstraction. Neglecting this fact for the past 30 years has resulted in the ‘unsustainable’ use of groundwater in the compartment

Abstract

Monitored natural attenuation (MNA) is becoming a commonly employed sustainable site remediation strategy for sites with petroleum hydrocarbon groundwater impacts. Natural attenuation is essentially the reduction in contaminant concentration, mass or mobility due to naturally occurring processes within the environment. Aromatic compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX) are common compounds of concern in the context of petroleum hydrocarbon related investigations because of their relative mobility and toxicity characteristics. Despite this, these compounds have historically displayed a strong affinity towards attenuating temporally and spatially away from the source areas. Evaluating plume stability is an important element of evaluating the overall attenuation of groundwater plumes and numerous methods have been developed in order to assess plume stability including graphical and statistical methods. It is often the case however that these analyses focus on single wells in isolation and do not take an integrated approach to evaluate the attenuation of contaminant mass over the entire plume. The authors present a case study where historical trends in plume characteristics have been used to assess overall plume stability. Trends in parameters such as average plume concentration, total plume contaminant mass, plume area and plume centre of mass were statistically assessed to determine whether the groundwater plume was expanding, stable, or shrinking. The methods employed in the plume stability analysis were found to be effective tools in demonstrating the occurrence of natural attenuation of contaminant plumes. It is important to note that a good quality dataset is required, in terms of a spatially representative monitoring well network and adequate time series data, in order to conduct analyses that will yield meaningful conclusions.

Abstract

Anticipated Shale Gas Development could intensify possible natural hydraulic connectivity between deep groundwater reservoirs and shallow aquifers in the Karoo. This project attempts to test geochemical evidence of natural mixing between old groundwater from deep aquifers and young groundwater from shallow aquifers using selected isotopic signatures in conjunction with borehole yields. Borehole yields were determined using slug tests. All isotopes (δ18O, δ2H, δ13C, 3H and 14C) were analysed in the laboratory of Environmental Isotope Group of iThemba Laboratories in Gauteng. To date, results from four water samples collected in Jansenville reveal these average isotope signatures: δ18O = -3.02 ‰, δ 2H = -21.17 ‰, δ 13C = 12.46 ‰ 3H = 0.45 TU and 14C = 65.38 pMC. The δ18O-δ 2H relationship for the groundwater has a gradient of 4.48. This demonstrates that the groundwater has experienced evaporation before or during recharge. The unevaporated isotopic signature of the water is -5.86 ‰ and -33.89 ‰ for δ18O and δ2H, respectively. The enriched δ13CDIC signature suggests that methanogenesis has influenced the groundwater. The unstable isotopes (3H and 14C) suggest that there is groundwater mixing in Jansenville between younger water from shallow aquifers and older water likely from deeper aquifers. Borehole yields increase with decreasing radioactive isotope concentrations. This suggests that high yielding boreholes are areas of potential contamination because they are associated with mixed groundwater.

Abstract

This study assessed the chemical and microbial quality of groundwater and potential risks to human health in Siloam Village, South Africa. Due to lack of access to potable water, residents in rural areas drill private boreholes within their homesteads without considering the potential sources of groundwater pollution. This exposes them to health risks associated with groundwater pollution. Water samples from 11 boreholes were collected from August 2013 to January 2014. pH and EC were measured using a multimeter and turbidity was measured using a turbidity meter. Non-metals and metals were analysed using Ion Chromatography and Atomic Absorption Spectroscopy, respectively. Colilert quanti-tray method was used to determine total coliforms and Escherichia coli. Descriptive statistics were used to determine the overall water quality status. Potential risks to human health were inferred based on Department of Water and Sanitation guidelines for domestic use. Water quality parameters found to have serious potential health effects on human beings were correlated with selected water quality parameters at a significance level (α) of 0.05 to understand the nature of correlation and possible sources of contamination. The study determined that nitrates and fluorides were the only parameters with excessively high concentrations in groundwater which are associated with health effects on human beings. Correlation of fluoride with calcium and pH indicated that further investigations are required to identify the local sources and fluoride control mechanisms in the study area. Correlation of nitrate with chloride and potassium indicated that faecal contamination and fertilisers are sources of nitrate pollution in the study area, though faecal contamination was the dominant source. Faecal contamination was confirmed from total coliforms and E.coli in most boreholes. The study identified the need to educate borehole owners in such villages of possible strategies to minimise groundwater pollution.