Conference Abstracts
Title | Presenter Name | Presenter Surname | Area | Conference year Sort ascending | Keywords | ||||||
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Arsenic In The West-African Water Reserves: Investigation Into Sources Of The Contaminant Through Case Studies In The Region | André | van Coller | West African region | 2013 | Contaminant, case study | ||||||
AbstractThe mineral-rich basin of the West African region has vast reserves of gold, diamond as well as iron ore deposits. Throughout the regional geological setting characterised by structural variations and intrusive belts with metamorphic mineral-rich sequences covered by saprolite soils, one common chemical constituent remains a constant in the water reserves. Arsenic is in high concentrations throughout the region with chemical ranges commonly above the various country guidelines as well as international IFC and WHO standards. The aqueous chemical species is associated with arsenopyrite-rich mineralogy of the regional greenstone belts and highly weathered soils. This conference presentation investigates the natural source of the arsenic through baseline data, as well as the effect of mining on the already high concentrations of arsenic in both the groundwater and surface water. Natural levels of various chemical species in the regional area are already high at baseline level. One of the main research questions is thus whether mining and other anthropogenic activities will have an impact on the environment or will the changes to concentrations be so insignificant to allow the ecosystems and water users to continue in their current ways without any effect. Various case studies in Burkina Faso, Liberia, Sierra Leone and other countries have been combined to investigate the arsenic-rich resources of the West African region through groundwater specialist investigative methods with emphasis on geochemical modelling of the fluid–rock and fluid–fluid interactions leading to the aqueous chemical conditions in the region. |
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The Challenges Facing Delineation Of Integrated Units Of Analysis Within Context Of The Groundwater Resources Directed Measures | Sagadevan | Kisten | National | 2013 | groundwater resource directed measures | ||||||
AbstractThe Department of Water Affairs (DWA), Chief Directorate: Resource Directed Measures has developed guidelines over the past decade in order to facilitate proper implementation of the Groundwater Resource Directed Measures (GRDM) (also known as determination of the groundwater component of the Reserve). An intrinsic component of the GRDM is delineation of Integrated Units of Analysis (IUAs) from which the allocatable groundwater and surface water components are calculated, which essentially drives the allocation of water use licenses. Delineation typically follows a three-tiered approach, namely primary, secondary and tertiary level. Primary delineation is based on quaternary boundaries (considered to be the basic building block of the IUA); secondary follows geological, hydrogeological and hydrological boundaries, groundwater abstraction zones and baseflow contribution; and tertiary is dependent on management criteria. How then, do we undertake this challenging task of delineating IUAs to a level where it can be better managed and monitored? Complexities arise when hydrogeological data are scarce, hydrological and hydrogeological systems are not in sync, aquifers extend across a quaternary, water management area, provincial and administrative boundaries, surface water and groundwater interactions are not well understood, and legislation on protection of water resources differs greatly from one country to the next. Having undertaken delineation of IUAs in the Waterval Catchment (Upper Vaal WMA), Olifants WMA and Mvoti to Umzimkhulu WMA with the available datasets, the key criteria for the respective WMAs have ultimately been management class, significant aquifers, groundwater– surface water interaction and groundwater stressed areas, and secondary catchment boundaries, followed by other hydrogeological, geological and management considerations. |
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In Situ Iron Removal: Innovative Option For Preventing Production Borehole Clogging | Kate | Robey | International | 2013 | Borehole clogging, prevention strategies, Iron Removal | ||||||
AbstractMany aquifer systems worldwide are subject to hydrochemical and biogeochemical reactions involving iron, which limit the sustainability of groundwater schemes. This mainly manifests itself in clogging of the screen and immediate aquifer with iron oxyhydroxides resulting in loss of production capacity. Clogging is caused by chemical precipitation and biofouling processes which also manifests in South African well-fields such as in Atlantis and the Klein Karoo. Both well-fields have the potential to provide a sufficient, good quality water supply to rural communities; however, clogging of the production boreholes has threatened the sustainability of the schemes as quality and quantity of water is affected. Rehabilitation of the affected boreholes using techniques such as the Blended Chemical Heat Treatment method does not provide a long-term solution. Such treatments are costly with varying restoration of original yields achieved and clogging recurs with time. Currently the research, management and treatment options in South Africa have focused on the clogging processes which are complex and site-specific, making it extremely difficult to treat and rectify. This project attempts to eliminate elevated concentrations of dissolved iron, the cause of the clogging. High iron concentrations in groundwater are associated with reducing conditions in the aquifer allowing for the dissolution of iron from the aquifer matrix. These conditions can be natural or human-induced. Attempts to circumvent iron clogging of boreholes have focussed on increasing the redox potential in the aquifer, by injection of oxygen-rich water into the system, to prevent dissolution and to facilitate fixation of iron in the aquifer matrix. Various in situ treatment systems have been implemented successfully overseas for some time. In South Africa thus far in situ treatment of iron has only been proposed as a solution for production borehole clogging. Based on experience from abroad the most viable option to research the elimination of ferrous iron in South African aquifer systems would be through the in situ iron removal treatment. Different techniques of increasing the dissolved oxygen concentration in the injected water to intensifying the redox change in the aquifer can be applied; however, the use of ozone as the oxidant is a new approach. Its effectiveness is evaluated by the results in iron removal in surface water treatment for drinking water supply. |
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Hydrogeology Of Cedarville Flat Primary Aquifer | Nwabisa | Ndlovu | Cedarville, Eastern Cape | 2013 | Hydrogeology, aquifer, Groundwater, development, hydrogeological conceptual model | ||||||
AbstractPOSTER The study focuses on the primary aquifer in the Cedarville flats. Groundwater extracted from the aquifer is the primary source for domestic and agricultural purposes for farmers and the community in the Cedarville area. The aim of the study is to develop a conceptual hydrogeological model of the primary aquifer in Cedarville flats which may be used as an input to a groundwater flow model that will predict the behaviour of the aquifer. The main objectives of the research are: Characterise the aquifer based on borehole log information, depth to water, hydraulic properties of the aquifer and recharge. Examine the hydrochemistry and environmental isotope composition of groundwater. Develop a conceptual hydrogeological model for the Cedarville primary aquifer. The study area boundary covers a large area including towns like New Amalfi and it goes to Lehlohonolo, but the main focus is in the primary aquifer in the Cedarville flats. The topography varies from predominantly hilly around the escarpment with numerous rivers draining deep valleys to a less mountainous undulating central area like Cedarville flats. Cedarville flats found in the midst of extremely broken ground forming the only considerable extent of plane country in the Eastern Cape territories. They cover about roughly 90 square miles and are hemmed in by ranges of mountains on the south and east and by small hills on the west and north. The aquifer is recharged by Mzimvubu River, which is the largest river in the Mzimvubu river basin; it extends from the Lesotho highlands to the Indian Ocean. It has four main tributaries: the Tsitsa, Tina, Kinira and Mzintlava, all having their headwater in the Drakensberg Mountains. The study area only shows the Tswerika, Riet, Mvenyane, Droewing and non-perennial streams. These streams all flow into the Mzimvubu River and their headwater is from the smaller mountains around the area. The local geology of the area is formed by the Beaufort Group rocks and alluvium rocks which are quaternary in age. The geology that is specifically found in the Cedarville flats aquifer is made of alluvial deposits consisting of clay, sand and gravel. Surrounding the aquifer are Tarkastad subgroup rocks which are predominantly argillaceous rocks, including shale, carbonaceous shale, clay stone, mudstone and siltstone. The primary aquifer in the Cedarville flats is capable of sustaining long-term, large-scale production, and these kinds of aquifers are rarely found in the southern Karoo Basin. Existing boreholes will be used to examine the bore log information, like lithology and thickness of the rocks that form the aquifer. Groundwater hydrographs will be drawn to determine the groundwater level variation. Pumping tests will be conducted to help with hydraulic conductivity, storativity and transmissivity of the aquifer. Water samples will be collected to test the water chemistry and environmental isotopes of the groundwater. Secondary data will be requested from National Groundwater Archives (NGA), Weather SA and the Department of Water Affairs. When all the data is collected, then a conceptual hydrogeological model will be produced.
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Numerical groundwater flow model for the Palla Road wellfield, Botswana | Martin | Holland | Botswana | 2013 | numerical groundwater flow model | ||||||
AbstractThe Palla Road well-field is located in the Central District of Botswana approximately 160 km from Gaborone and 50 km from Mahalapye. The aim of this project was to review and update the existing groundwater model developed in the late 1990s of the Palla Road well-field in order to assess the viability of long-term groundwater abstraction due to the increasing water demands in the region. The main hydrogeological units recognised in the project area comprise of aquifer systems developed in the Ntane Sandstone Formation and formations of the Middle Ecca Group with minor aquifers developed in Mosolotsane Formation and the Stormberg Basalt. The finite-difference model boundary covers an area of 3 702 km2 and was set-up as a three-dimensional semi-uniform grid comprising of four layers. Eight recharge and 14 hydraulic conductivity zones in accordance with the geological model were distinguished. Steady state calibration was accomplished by varying the hydraulic conductivity values, while keeping the recharge rates constant in order to achieve a unique solution. Transient calibration of the model covered three larger stress periods namely: (1) initial condition (pre-1988), (2) abstraction period (1988 to 2012) and (3) predicted model simulations (2013 to 2036). The calibrated groundwater flow model was used to assess the impacts associated with the proposed abstraction scenarios for the Palla Road and Chepete well-fields with consideration of potential cumulative impacts due to the Kudumatse well-field. Three basic scenarios comprising certain sub-scenarios based on the future water demand for the Palla Road and Kudumatse region were considered. The model simulations show that the abstraction scenario 2a, namely simultaneous abstractions from the Chepete/Palla Road and Kudumatse well-fields, poses a risk to the sustainability of downstream water resources. The maximum simulated drawdown in the central and southern parts of the Palla Road well-field reach 14 m after six years of pumping. Although outflow diminishes after a six-year period, it is restored to approximately 80-90% after the simulated recovery period. The presented 3-D multi-layer model can be used as a tool to determine the optimal abstraction rates while giving cognisance to the sustainability of the resource. |
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Integrating Adaptive Groundwater Management To Mining Phases – Lessons Learnt From Modelling At Eia Stage At A Proposed Zinc Mine | Helen | Seyler | National | 2013 | groundwater management, EIA | ||||||
AbstractThe benefits of numerical groundwater modelling in resource management and scenario-testing are well known; it provides quantitative predictions of aquifer responses to stresses not yet experienced, albeit with uncertainties. Modelling is hence a widely used tool in Environmental Impact Assessment (EIA), in which prior to project commencing, the likely impacts must be assessed quantitatively to determine their significance. Based on these results mitigation measures can be proposed such that the residual impact is deemed acceptable. At the stage of an EIA there is often very little data on which to base a model. Generally one is required to predict timescales in the order of hundreds of years with only very short-term time series data, and required to predict the response to stresses far beyond those used in the calibration. The very nature of the problems posed at EIA stage therefore render the accuracy of most modelling conducted at EIA phase severely limited. Recognising this, an appropriate model for the problems at hand can still be constructed and provide useful results. The model results need to be seen as the first phase in an adaptive management cycle, rather than a standalone prediction which a mine can use for future operation. To strengthen the resulting predictions, the cycle in which monitoring results are used to update the model, and thus update predictions and update future requirements for monitoring repeating the cycle, needs to be entrenched into the mine phases by ensuring the recommendation as detailed in the Environmental Management Plan. Thus, what started as a useful demonstrative tool, but with large uncertainties, becomes an accurate quantitative prediction tool for operation, closure and post-closure planning. This paper outlines a case study of a proposed open-pit zinc mine on an inselberg in South Africa, within which these themes are explored. Limited initial data was sufficient to build a useful yet simplified model. The purpose and known limitations of the model approach dictated the spatial discretisation of the model, its dimensions, and the geometry of the aquifer units, yet the simplification of the aquifer systems into the numerical model was only feasible once the complexity of the aquifer systems had been recognised, else over- or unjustified simplification is a risk. The paper concludes with a framework for integrating the adaptive groundwater management into the mine life cycle through applying appropriate models at each phase, which would strengthen the use of groundwater models in mining. |
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The Complexity Of Baseline Monitoring In Unconventional Gas Projects | Richard | O'Brien | Karoo | 2013 | anthropogenic influence, groundwater monitoring | ||||||
AbstractThe monitoring of groundwater to detect changes resulting from anthropogenic activities requires an understanding of the particular aquifer system, release mechanisms and migration pathways which form the basis of a conceptual hydrogeological model. This conceptual hydrogeological model illustrates the connections between sources, pathways and receptors. The objective of a monitoring programme implemented in the context of shale gas exploration activities in the Karoo would be the detailed monitoring of groundwater quality for the protection of groundwater users. This objective requires a defensible baseline dataset so that changes in water quality can be investigated. In selecting parameters to monitor, cognisance must be taken of parameters which occur in multiple sources, those naturally present in the shallow potable aquifer, potential tracers representing the deeper groundwater and additives arising from the exploration activities. Sodium, potassium and chloride are all likely to be present in both deep and shallow groundwater and are potential additives. Given the expected higher salinity of deep connate groundwater, the use of aggregate parameters such as electrical conductivity might be of particular importance. Lithium, fluoride, strontium and uranium, while constituents of both the shallow and deep groundwater, are likely to be present at higher concentrations in the deeper groundwater, and could be indicators of deeper groundwater. Geochemical analysis of cores may provide initial clues as to such indicator parameters. Methane, which is known to occur in some existing Karoo boreholes, is potentially one of the more mobile tracers which could indicate migration from potential future production zones to shallow aquifers. The viability of using methane and other dissolved gasses (for example ethane) as indicators would require the use of stable isotope analyses to elucidate the origin of the gases.
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The Role Of High Resolution Site Characterisation In Informing Remediation Decisions At A Petroleum Release Site Overlying A Fractured Rock Aquifer In South Africa | Steve | McKeown | National | 2013 | remediation, petroleum, fractured rock, aquifer | ||||||
AbstractInadequate characterisation of petroleum release sites often leads to the design and implementation of inappropriate remedial systems, which do not achieve the required remedial objectives or are inefficient in addressing the identified risk drivers, running for lengthy periods of time with little benefit. It has been recognised that high resolution site characterisation can provide the necessary level of information to allow for appropriate solutions to be implemented. Although the initial cost of characterisation is higher, the long-term costs can be substantially reduced and the remedial benefits far greater. The authors will discuss a case study site in the Karoo, South Africa, where ERM has utilised their fractured rock toolbox approach to conduct high resolution characterisation of a petroleum release incident to inform the most practical and appropriate remedial approach. The incident occurred when a leak from a subsurface petrol line caused the release of approximately 9 000 litres of fuel into the fractured sedimentary bedrock formation beneath the site. Methods of characterisation included: Surface geological mapping of regionally observed geological outcrops to determine the structural orientation of the underlying bedding planes and jointing systems. A surface electrical resistivity geophysics assessment for interpretation of underlying geological and hydrogeological structures. Installation of groundwater monitoring wells to delineate the extent of contamination. Diamond core drilling to obtain rock cores from the formation for assessment of structural characteristics and the presence of hydrocarbons by means of black light fluorescence screening and hydrocarbon detection dyes. Down-borehole geophysical profiling to determine fracture location, fracture density, fracture dip and joint orientation. Down-borehole deployment of Flexible Underground Technologies (FLUTe®) liners to determine the precise vertical location of light non-aqueous phase liquid (LNAPL) bearing joint systems and fracture zones, and to assist in determining the vertical extent of transmissive fractures zones. ERM used the information obtained from the characterisation to compile a remedial action plan to identify suitable remedial strategies for mitigating the effects of the contamination and to target optimal areas of the site for pilot testing of the selected remedial methods. Following successful trials of a variety of methods for LNAPL removal, ERM selected the most appropriate and efficient technique for full-scale implementation. |
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How Good Is Your Consultant? A Laymens’ Guide To Critically Assessing Consultants | ME | Convery | National | 2013 | Consultant | ||||||
AbstractWith increasing focus on wasted expenditure within local government and recent media reports on the money spent on poor quality service, it is becoming progressively important for those in a position of engaging consultants, either for groundwater supply or environmental work, to have confidence in the company or person they have employed. This paper focuses on how to assess consultants before they walk through the door based on qualifications, CVs, professional registrations and previous work experience. It goes through the project lifestyle, explaining in a non- technical fashion the different processes involved in a groundwater supply or groundwater contamination assessment and provide simple indicators of good practice that should be evident in the consultant's work. Topics covered include assessing proposals, gathering background information, health and safety, appointing sub-contractors, data quality, the use of appropriate published procedural guidelines, the use of relevant quality guidelines and what deliverables should be provided. |
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Establishing An Aquifer Protection Policy For Co2 Geological Storage Utilising Hydrogeological Numerical Modelling, Bela-Bela (South Africa). | Tshegofatso | Mophatlane | Bela-Bela, Limpopo | 2013 | aquifer protection, Hydrogeological, geological storage | ||||||
AbstractSouthern Africa hosts over 93% of the continent's energy, which has been conserved in coal seams deposited in various Karoo age sedimentary basins. Carbon dioxide geological storage (CGS) is proving to be an emerging greenhouse gas technology (GHGT), that global governments have elected to mitigate the projected coal use in Southern Africa. One of the major challenges of successfully introducing CGS to the public and world leaders is the significant risk the technology poses to groundwater resources. Lack of public confidence is further coupled by the poor knowledge of the subsurface behaviour of injected media, such as CO2, in South African potential lithological reservoirs. The study has utilised data from a current MSc research, in which the Springbok Flats Coal Basin (SFCB) has been used as the problem set-up. The aim of this study is to determine which FELOW™ mesh geometry would be the most suitable to simulate a CO2 ingress plume within a regional aquifer. The study has utilised principals of dense vegetation zones (DVZ) and density- variable fluid flow (DVFF) when simulating the ingression. The specific objective is to utilise the simulation results to guide amendments of water legislature, towards accommodating CO2 geological injection and storage operations. Results indicate that a combination of high-quality triangular meshes of various geometries, created with the FEFLOW compatible mesh generator, TRIANGLE, produced the best 3D model and simulation results. The basic matrice unit for the DTZ was defined as a quad mesh composed of two right-angled triangles and one equi-angualar triangle (five nodes), while the unit for modelling springs was defined as a quad mesh with four-equi-angular triangles, both used in various scales. The results were used to amend the Stream Flow Reduction Activities (SFRA) policy and thus the aquifer licensing procedure of the National Water Act, in order to accommodate the allocation of aquifer use licenses for CO2 geological storage operations. The amendments illustrate the significance of finite element simulation codes for integrated water resources management policy. |
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Groundwater Asset Management In The Mining Industry | Mike | Deed | National | 2013 | groundwater management, Mining , Boreholes | ||||||
AbstractGroundwater boreholes are a key element of many mining projects, as part of dewatering and water supply systems, and must achieve high levels of operational efficiency and service availability. Outside of the mining industry, planned borefield maintenance programmes have become a key part of professional well-field management, with proven benefits in terms of operational cost savings and continuity of pumping. However, the benefits of proactive planned maintenance of groundwater boreholes on mine sites have only recently been widely recognised. Potential operational problems are described, including water quality issues which can result in mineral contamination leading to deposits and scale build-up which can clog screens and pumps, reduce water flow and yield, and eventually cause pump breakdowns and mine stoppages. Best practice methodologies to remove or minimise the contamination are described and the benefits of implementing a planned maintenance programme are discussed. Case studies are described from two significant mines in Australia, where boreholes suffered from mineral contamination, including calcium carbonate and iron bacteria contamination. Both mines suffered from increased pump breakdowns, groundwater yields consistently below target and serious cost overruns. Borehole rehabilitation treatment plans were implemented to resolve the immediate contamination problems followed by an ongoing maintenance programme to prevent or minimise their reoccurrence. Treatment programmes included a downhole camera survey, use of a bespoke software program to review the results of the survey and the available water quality data, and a purpose built rehabilitation rig that included the use of specialist chemical treatments to remove and control the existing encrustation and clogging deposits. |
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The Use Of Vegetable Oil Substrates In The Treatment Of Contaminated Groundwater | M | Pienaar | National | 2013 | prevention strategies, contamination, Water treatment | ||||||
AbstractEdible vegetable oil (EVO) substrates have been successfully used to stimulate the in situ anaerobic biodegradation of groundwater contaminated with chlorinated solvents, as well as numerous other anaerobically biodegradable contaminants like nitrates and perchlorates at many commercial, industrial and military sites throughout the world. EVO substrates are classified as a slow release fluid substrate, and comprise of food-grade vegetable oil such as canola or soya bean oil. The EVO substrate serves as an easily biodegradable source of carbon (energy) used to create a geochemically favourable environment for the anaerobic microbial communities to degrade specific contaminants of concern. EVO substrate’s can either be introduced into the subsurface environment as pure oil, in the form of light non-aqueous phase or as an oil/water emulsion. The emulsified vegetable oil substrates has several benefits over non-emulsified vegetable oil as the fine oil droplet size of the commercially manufactured emulsified oils can more easily penetrate the heterogeneous pore and fracture spaces of the aquifer matrix. The use of this technology to stimulate in situ biodegradation of groundwater contaminants is still relatively unknown in South Africa. This paper gives an overview of the EVO technology and its application, specifically looking at the advantages of using this relatively inexpensive, environmentally-friendly based technology to remediate contaminated groundwater within fractured rock environments commonly encountered in South Africa. |
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Ecosystems In Fractured Aquifer Groundwater Can Treat Contamination | Willem J | van Biljon | National | 2013 | Ecosystems, aquifer, contamination | ||||||
AbstractGroundwater is not often regarded as ecosystems and especially fractured aquifer systems are seen as organism free. Conventional tests show very little to no presence of micro-organisms in groundwater. However, these micro-organisms are ubiquitous and can be detected by using sophisticated methods. In this specific case study where petroleum hydrocarbon contamination exists in a fractured rock aquifer, the presence of micro-organisms has been for years inferred by means of monitoring for secondary lines of evidence that prove attenuation of the contaminants, not only by means of dilution, adsorption or diffusion into the matrix, but through metabolism. The sampling evidence is clear that the preferential sequence of metabolism is taking place whereby electron acceptors are reduced as predicted for such biodegradation. Specifically sulphate is consumed and mostly manganese is reduced, with some iron reduction also being observed. Monitoring has shown that groundwater recharge bringing in new nutrients effected increased biodegradation. In order to definitively identify the contribution made by micro-organisms, DNA testing was performed. The results support the secondary lines of evidence. Outside of the contaminated zone very low population numbers of organisms were detected in the groundwater. Inside the contaminated zone elevated population numbers were observed indicating that active biodegradation is taking place. Furthermore, the edges of the plume, where contaminant levels are mostly below detection, contained a more diverse population of micro-organisms than the central area. Conditions on the edge of the plume probably represent an ideal nutrient environment for the organisms as opposed to the high concentration source, which might be toxic to some organisms. Better understanding of the bio-dynamics of this fractured aquifer presents a unique opportunity to better manage and enhance the remediation of the contaminants. Possible strategies include the addition of nutrients when necessary and the cultivation of the naturally occurring organisms to augment the population. The data shows that aquifers are ecosystems even in fractured environments. |
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A Summary Of Wetland Legislation In South Africa Over The Past Fifty Years | Nelda | Breedt | National | 2013 | wetland legislation | ||||||
AbstractThe deterioration of wetlands due to human activity has been a problem for many years. Under the old Water Act 36 of 1956 no provision of water was made for managing the environment. This idea was only introduced in the 1970s and focussed mainly on maintaining the floodplains and estuaries in the Kruger National Park, with small amounts being allocated to drinking water for wildlife. This was followed by the Conservation of Agricultural Resources Act, 43 of 1983, the first legislation under which wetlands could be protected, and which today still provides an important legal platform for the protection of wetlands, through integrated conservation of the soil, water resource and vegetation. South Africa became a signatory to the Ramsar Convention in 1975, but until the late 1990s not much was done to enforce wetland conservation. With the introduction of the National Water Act, 36 of 1998, and the National Environmental Management Act, 107 of 1998, South African legislation became the first to balance human, environmental and economic interests, for the purpose of sustainable development. As part of this review I refer to case studies in Gauteng and discuss some of the challenges we still face. |
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Developing Groundwater Supplies To Supplement The Water Supply Of Ladismith, Western Cape Province | Roger | Parsons | Ladismith, Western Cape Province | 2013 | Water supply | ||||||
AbstractLadismith was established in 1851 where freshwater discharge from the Klein Swartberg Mountains. Growth of the town required building of the Goewerments Dam in 1920 and the Jan F le Grange Dam in 1978. However, water demand now matches supply, and water shortages are being experienced. Poor management and recent droughts exacerbated the situation. A project was initiated to address shortcomings with the existing supply and identify additional sources of water. Groundwater is an obvious option, with the regionally extensive Cango Fault located directly north of the town. The west-east trending fault juxtaposes highly productive Table Mountain Group Aquifers with less productive argillaceous rocks of the lower Witteberg Group. The Alluvial Aquifer is also a target, with a recently drilled DWA monitoring borehole reported to be high-yielding. Drilling and testing of three exploration boreholes drilled into the fault, returned lower than expected borehole yields, but still sufficient to contribute to the town’s water supply and merit further exploration. Boreholes drilled north of Ladismith could be used to increase the existing water supply by 50%. |
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‘Groundwater Reserve’ – A Critical Review | Kornelius | Riemann | National | 2013 | Groundwater reserve | ||||||
AbstractThe concept of the ‘Groundwater Reserve’ is enshrined in the National Water Act that stipulates that a classification of all significant water resources must be undertaken and the Reserve requirements be determined and gazetted. The Reserve covers two different aspects, the Ecological Reserve to protect the water dependent ecosystems and the Basic Human Needs (BHN) Reserve to ensure that all people who depend on that water resource have sufficient water for their livelihood. The approach for determining and implementing the Reserve that was developed for surface water resources was adopted for groundwater resources as provided for in the Groundwater Resource Directed Measures (GRDM) Manual, inter alia. However, there is no separate ‘Groundwater Reserve’, but rather a groundwater component of, or contribution to, the ecological Reserve and BHN. Hence, the implementation of this methodology often results in undesirable outcomes and is one of the inhibiting factors for sustainable groundwater development, as some of the aspects and methods are not applicable to groundwater and not appropriate for implementation. The current separation of the ‘Groundwater Reserve’ determination process from the ecological Reserve determination emphasises this pitfall of the process and methodology. This paper provides a critical review of the current concept of the ‘Groundwater Reserve’ and its implementation based on several case studies. It concludes with recommended changes to the standard methodology and a possible way forward for developing an appropriate methodology for addressing and protecting the groundwater contribution to both the ecological and BHN Reserve. |
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Multi-Data Integration Approach In Groundwater Resource Potential Mapping: A Case Study From The North West Province, South Africa | A | Tessema | Naledi Local Municipality, North West Province | 2013 | case study, Groundwater | ||||||
AbstractA multi-data integration approach was used to assess groundwater potential in the Naledi Local Municipality located in the North West Province of South Africa. The geology comprised Archaean crystalline basement, carbonate rocks (dolomite and limestone) and windblown sand deposits of the Kalahari Group. The main objective of the study is to evaluate the groundwater resource potential using multi-data integration and environmental isotope approaches. Prior to data integration, weighting coefficients were computed using principal component analysis. The results of integration of six layers revealed a number of groundwater potential zones. The most significant zone covers ~14% of the study area and is located within carbonate rocks in the southern part of the study area. The localisation of high groundwater potential within carbonate rocks is consistent with the results of principal component analysis that suggests that lithology significantly contributed to the total data variance corresponding to principal component 1. In other words, carbonate rocks consisting of dolomite and limestone largely account for groundwater occurrence in the southern part of the area. In addition, the relatively elevated isotopic signature of tritium (≥1.0 TU) in groundwater samples located in the southern part of the area suggests a groundwater recharge zone. Furthermore, moderate-to-good groundwater potential zones within the Ventersdorp lava coincide with maximum concentration of fractures, which is consistent with the results of statistical correlation between borehole yield and lineament density. The multi-data integration approach and statistical correlation used in the context of evaluating groundwater resource potential of the area provided a conceptual understanding of hydrogeological parameters that control the development of groundwater in crystalline and carbonate rocks. Such approach is crucial in light of the increasing demand for groundwater arising from municipal water supply and agricultural use. The two approaches are very effective and can be used as a sound scientific basis for understanding groundwater occurrence elsewhere in similar hydrogeological environments. |
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Acid-Mine Drainage And Its Potential Impact On The Water Resources In The Waterberg Coalfield | Vanessa | Aphane | Limpopo | 2013 | Water resource | ||||||
AbstractSouth Africa currently ranks number nine in the world of the proved coal reserves that has been estimated to last for over 200 years. Coal constitutes about 77% of the primary energy needs in the country, with the Waterberg Coalfield estimated to host about 40% of the remaining South African coal resources. Coal deposits in the study area largely consist of shales, mudstones, siltstones and sandstones which host coal-containing clay minerals; quartz, carbonates, sulphides and the most abundant sulphide mineral is pyrite. Once mining begins, the sulphide minerals are exposed to surface which allows contact with atmospheric oxygen and water causes oxidation to take place, therefore causing acid-mine drainage (AMD). Acid-base accounting (ABA) was used to determine the balance between the acid-producing potential (AP) and acid-neutralising potential (NP). From the analysis the Net Neutralising Potential (NP-AP) was determined, which is one of the measurements used to classify a sample as potentially acid or non-acid-producing. Mineralogical analyses will be done by x-ray defraction (XRD) to define and quantify the mineralogy of the geological samples which can help in the management plan to minimise generation of acid. AMD does not only result in the generation of acid, but as well as in decreased pH values and increased values of specific conductance, metals, acidity, sulphate, and dissolved and suspended solids. Inductively coupled plasma analysis was done to determine the release of the heavy metals which can be detrimental to the environment. Sample analysis was done on the interburden, overburden as well as the coal samples. From results obtained, over 35% to 50% of the samples have an excess of acid potential which classifies the samples as having a higher risk for acid generation. About 30% to 40% of the samples have a higher neutralising potential; the rest of the samples have a medium acid risk generation. The water demand will increase as developments continue in the area, with inter- catchment transfers identified as the answer to fill the gap of water scarcity. Acid mine drainage poses a big threat on water resources, both groundwater and surface water nationally, which might be less of a problem in the Waterberg because of the cycle of low rainfall in the area, but the potential of AMD cannot be neglected. |
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Characterisation Of Groundwater Potential In The Northern Parts Of The Limpopo Province, South Africa: Results From Integrated Geophysical Studies Across The Sagole Hot Spring | PK | Nyabeze | Sagole Hot Spring, Limpopo Province | 2013 | groundwater potential, Geophysics, investigations | ||||||
AbstractThe Sagole hot spring is located in the northern Limpopo Province of South Africa. Investigations were carried out in order to investigate the groundwater aquifer and water chemistry. Results were envisaged to the understanding of the geothermal potential of the area. Regional scale airborne magnetic data and geology were used for identifying structures and lithological boundaries that are associated with thermal groundwater aquifers. Detailed ground follow-up and verification surveys were carried out across the target, using magnetic, electrical resistivity tomography (ERT), frequency-domain electromagnetic (FDEM) and radiometric methods. Water samples were collected from the spring eye and archival groundwater data was analysed. The interpretation of the airborne magnetic data revealed the presence of west to east, northwest and intersecting lineaments at the hot spring. From magnetic data, the groundwater aquifer was found to be capped by basalt with heat rising to the surface along possible geological contacts, faults or fractures. The FDEM profile data across the aquifer zone had peak values above 100 mS/m. The inversion of ERT data defined a highly electrical conductive, low resistivity with thickness of about 60 m. Chemical analysis of the ground water revealed that the water does not have any indication of pollution. The thermal water was found to be of meteoric origin. The drilling of artesian thermal boreholes through the capping basalt should be explored. The hot-water boreholes will be utilised by the community for domestic, irrigation and possible development of micro-geothermal systems. |
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A Numerical Simulation Of Solute Transport In The Unsaturated Zone Of Dry Coal Ash Dumps With A Case Study In South Africa | Innocent | Muchingami | Mpumalanga | 2013 | unsaturated zone, Simulations, waste disposal | ||||||
AbstractAn understanding of the movement of moisture fluxes in the unsaturated zone of waste disposal sites play a critical role in terms of potential groundwater contamination. Increasing attention is being given to the unsaturated or vadose zone where much of the subsurface contamination originates, passes through, or can be eliminated before it contaminates surface and subsurface water resources. As the transport of contaminants is closely linked with the water flux through the unsaturated zone, any quantitative analysis of contaminant transport must first evaluate water fluxes into and through this region. Mathematical models have often been used as critical tools for the optimal quantification of site-specific subsurface water flow and solute transport processes so as to enable the implementation of management practices that minimize both surface water and groundwater pollution. For instance, numerical models have been used in the simulation of water and solute movement in the subsurface for a variety of applications, including the characterisation of unsaturated zone solute transport in waste disposal sites and landfills. In this study, HYDRUS 2D numerical simulation was used to simulate water and salt movement in the unsaturated zone at a dry coal ash disposal site in Mpumalanga, South Africa. The main objective of this work was to determine the flux dynamics within the unsaturated zone of the coal ash medium, so as to develop a conceptual model that explains solute transport through the unsaturated zone of the coal ash medium for a period of approximately 10 year intervals. Field experiments were carried out to determine the model input parameters and the initial conditions, through the determination of average moisture content, average bulk density and the saturated hydraulic conductivity of the medium. A two-dimensional finite-element mesh of 100 m × 45 m model was used to represent cross section of the ash dump. Two-dimensional time lapse models showing the migration of moisture fluxes and salt plumes were produced for the coal ash medium. An explanation on the variation of moisture content and cumulative fluxes in the ash dump was done with reference to pre-existing ash dump data, as well as the soil physical characteristics of the ash medium. |
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Groundwater Remediation In The Klerksdorp Goldfields | Gawie | van Dyk | Klerksdorp | 2013 | Groundwater | ||||||
AbstractGold mining activities over the past 60 years in the Klerksdorp goldfield produced saline mine drainage that polluted water. Oxidation of sulphide material in tailings storage facilities, waste rock dumps and extraction plants is mobilised to produce saline mine drainage with sulphate, minor salts and metals that seep to the groundwater and ultimately into surface water resources. Water regulation requires mines to prevent, minimise/reduce or eliminate pollution of water resources. The waste philosophy has matured from tolerate and transfer to treat and termination of pollution sources. The impact of the pollution was determined and possible technologies to treat the impact were evaluated. Source controls with proper water management by storm water management, clean dirty water separation, lined water conveyance structures and reduced deposition of water on waste facilities are crucial. The aquifer character determines the possible remediation technology. From the possible technologies phytoremediation, physical interception and re-use of this water was selected. In future possible treatment of the water would be considered. This paper explain the strategy and report on the phased implementation of these plans and the expected results. The establishment of 500 ha of woodlands as phytoremediation, interception trenches of 1 000 m, 38 interception boreholes and infrastructure to re-use this water is planned. The total volume of 15 Ml/day would be abstracted for re-use from the boreholes and trenches. The woodlands can potentially attenuate and treat 5 Ml/day. The established woodlands of 150 ha prove to be successful to intercept diffused seepage over the area of establishment and reduce the water level and base flow. The two production interception well- fields that are abstracting 50 and 30 l/s, respectively , indicate a water level decline of between 2 to 14 m, with regional cones of depression of a few hundred meters to intercept groundwater flow up to a 20 m depth. Predictions from groundwater modelling indicate that these schemes can minimise pollution during the operational phase and protect downstream water resources. Predictions from modelling indicate that the pollution sources need to be removed to ensure long-term clean-up to return the land to safe use. The gold and uranium prize is securing the removal of the sources through re-processing of the tailings and waste rock dumps. After removal of the sources of pollution, the remediation schemes would have to be operated for 20 years to return the groundwater to an acceptable standard of stock watering and industrial water use. The water quality is observed by a monitoring network of approximately 100 observation boreholes. |
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The Structural Hydrogeology Of A Gold Mine In Mali | Stephen | Fonkem | Mali | 2013 | Hydrogeology, gold mining | ||||||
AbstractThe occurrence of groundwater around a mined-out open pit, connected to an active underground working is not completely understood, but it is fascinating. It has been established that gold mineralisation in study area was structurally controlled. The geomorphology of the local drainage system is highly controlled by the fold or fault architecture. Surface water flowed through, and eroded open fractures in exposed damaged zones (zone of subsidiary structures surrounding a fault). Previous conceptual hydrogeological models of groundwater system suggested is a two-aquifer system, consisting of a fractured aquifer overlain by a weathered aquifer, where groundwater flow mimics surface topography. Based on recent drilling and reassessment of historic geological and hydrogeological data, the groundwater system around the mine could not only be described in terms of an elevation or stratigraphic units, as traditional aquifers are. The weight of the study was placed on accurately understanding the groundwater system in the deposit area by using structural hydrogeology as a best tool in the hydrogeological tool box. From a hydraulic head point of view, in addition to the weathered groundwater system, there are as many bedrock aquifers and aquitards as there are major structures in the pit area. |
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Characterisation Of A Large Light Non-Aqueous Phase Liquid (Lnapl) Plume Over A Fractured Gneiss Aquifer In Limpopo Province, South Africa; With Reference To An Ongoing Pump-And- Treat Remediation Technology | M | Phahlamohlaka | Limpopo | 2013 | plumes, remediation | ||||||
AbstractWork is being conducted in Limpopo province following a large volume release of petroleum hydrocarbons that took place from a leaking underground pipeline, resulting in significant groundwater contamination. This is considered to be the largest petroleum hydrocarbon release recorded to date in South Africa. The leak took place for 15 years before it was discovered 13 years ago in 2000. From the pressure tests that were performed, 10-15 ML of A-1 Jet fuel is considered to have been released to the subsurface. Product bailing was the first method employed for the recovery of the free product, and was later replaced with a P&T system which was considered to be more effective. The village located about 6 km to the north of the spillage depends mostly on groundwater. This paper presents a progress update of works that have been conducted in support of developing a conceptual model which aims to determine the areal extent of the plume. |
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Linking Geology And Wildlife Water Supply In The Hwange National Park, Kalahari Basin | David | Love | The Hwange National Park, Kalahari Basin, Zimbabwe | 2013 | Water supply, Geology | ||||||
AbstractMost of the 14 651 km2 Hwange National Park in Zimbabwe is on monotonous Aeolian sands of the Kalahari Basin, with endorheic drainage. The large game populations of the park are sustained by seasonal accumulations of water in grassy pan depressions and year-round supply of groundwater to pans (except in the northwest where there are rivers and dams). Some of this is from natural seeps, such as at the Shakwanki, Nehimba and Ngweshla Pans, but most are supplied from boreholes. Game animals show clear preferences for some pans over others and it has long been speculated by wildlife managers that there is a nutritional or taste basis for this discrimination. In this preliminary study, the location, host geology and sub-Kalahari lithologies of the pans are compared with the frequency of use by game animals. Results show that the pans that are most frequented by game are hosted in fossil drainage channels, with limestone horizons (calcrete) developed within the Kalahari Sands. Many popular pans are also found on Kalahari Sand overlying the granitic rocks and the meta- sedimentary Malaputese Formation of the Kamativi–Dete Inlier. This can be related to sodium and potassium enrichment. |
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Application Of A Water Balance Model To Investigate Groundwater–Surface Water Interactions | Modreck | Gomo | National | 2013 | Groundwater, water balance | ||||||
AbstractThe article presents the application of a water balance model as a preliminary tool for investigating groundwater–surface water (GW–SW) interactions along an alluvial channel aquifer located in a semi-arid climate in the central province of South Africa. The model is developed based on the conservation of mass; solute and stable isotopic mixing of the model components. Discharge measurements were made for the river segment inflow and outflow components using stream velocity-area technique. The Darcy equation was used to calculate the groundwater discharge from the alluvial channel aquifer into the river segment. Electrical conductivity (EC) and δ2H isotope were measured for the inflow and outflow components of the model as indicators of solute and stable isotopic ratios. Measurements were conducted during a low river flow once-off period in October 2011, thus offering a great opportunity to assess GW–SW exchanges when other potential contributors can be regarded as negligible. The model net balance shows that the river interval is effectively losing water. The mass and solute balance approach provided close to a unique solution of the rate of water loss from the model. The model outcome provides a platform from which to develop appropriate plans for detailed field GW–SW interaction investigations to identify the mechanism through which the river is losing water.
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The Relation Between South African Geology And Geohydrology | Paul JH | Lourens | National | 2013 | Geology, Geohydrology, Groundwater | ||||||
AbstractGroundwater in South Africa is an essential source of potable water for rural communities, farms and towns. Semi-arid conditions of South Africa, a growing population and surface water resources almost entirely being exploited to their limits, increase the demand for groundwater resources. Therefore, the relation between the geology and geohydrology of South Africa becomes an important tool in locating groundwater resources that can provide sustainable quantities of water for South Africans. A document was therefore compiled, providing valuable geohydrological information on the geological formations of the whole of South Africa. The information was gathered by means of interviews with experienced South African geohydrologists and reviewing of reports and articles of geohydrological studies. The geohydrological characteristics discussed include rock/aquifer parameters and behaviour, aquifer types (primary of secondary), groundwater quality, borehole yields and expected striking depths, and geological target features and the geophysical method used to locate these targets. Due to the fact that 90% of South Africa’s aquifers are classified as secondary aquifer systems, groundwater occurrence within the rocks of South Africa is mainly controlled by secondary fractured systems; therefore, understanding the geology and geological processes (faulting, folding, intrusive dyke/sills and weathering) responsible for their development and how they relate, is important. However, the primary aquifers of South Africa (Coastal Cenozoic Deposits) should not be neglected as these aquifers can produce significant amounts of groundwater. Drilling success rates and possibility of striking higher yielding boreholes can be improved dramatically when an evaluation of the structural geology and geohydrological conditions of an area together with a suitable geophysical method is applied. The ability to locate groundwater has been originally considered (even today) a heavenly gift and can be dated back to the Biblical story of Moses striking the rock to get water: “behold, I will stand there before thee there upon the rocks thou shalt smite the rock and there shall come water out of it” (Exodus 17:6). |
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Municipal Management And Geohydrological Aspects Of Importance In Municipal Potable Water Supply: The Case Of Lindley | Eric J | Nealer | Lindley | 2013 | Municipalities, Governance, potable water supply, skills development | ||||||
AbstractWhen the South African Government in 1998 re-demarcated its 283 municipalities in such a manner that they now completely cover the country in a “wall-to-wall” manner (Section 21), their main focus was on facilitation of effective and sustainable developmental municipal management; in other words, the improvement of basic municipal services such as formalised municipal basic services (for example, safe potable water, effective refuse removal and environmental health) to all the residents of the new geographical areas consisting of millions of citizens who previously might have been neglected. Unfortunately, it seems like topographical, physical and environmental characteristics of all the resulting municipal areas have been negated in this important demarcation process. Fuggle and Rabie (2005:315) are of the opinion that this can lead to ineffective, inefficient and non- economical municipal management of basic services. By means of a literature review as well as the use and study of geographical tools such as maps, ortho-photos and information data bases, and field visits, the bare essential geographical and geo- hydrological aspects of importance for the municipal service providers and managers in the Lindley area have been identified. From this research and various other obvious reasons (for example, deteriorating physical environment due to pollution, sub-standard storm water and sewage management, and migration [informal settlements] and increasing sophisticated needs of municipal residents), the presenters of this paper want to state that the quest for improved cooperative governance in the developing South Africa, and especially in the case of the Lindley town’s geographical area of responsibility, must be facilitated according to the DWA identified surface water catchment regions. In conclusion, the presenters will recommend adherence to the following requirements as essential:
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3-D Electrical Conductivity Image as a Decision-Aiding Tool in the Post-Closure Management of a South African Colliery | Danie | Vermeulen | Free State | 2013 | Electrical conductivity, closure management | ||||||
AbstractThe colliery is situated in the Vereeniging–Sasolburg Coalfield, immediately southwest of Sasolburg in the Republic of South Africa. The stratigraphy of this coal field is typical of the coal-bearing strata of the Karoo Sequence. The succession consists of pre-Karoo rocks (dolomites of the Chuniespoort Group of the Transvaal Sequence) overlain by the Dwyka Formation, followed by the Ecca Group sediments, of which the Vryheid Formation is the coal-bearing horizon. Mainly the lava of the Ventersdorp and Hekpoort Groups underlie the coal. The Karoo Formation is present over the whole area and consists mainly of sandstone, shale and coal of varying thickness. The underground mine was flooded after mining was ceased at the colliery in 2004. The colliery is in the fortunate position that it has a very complete and concise monitoring programme in place and over 200 boreholes were drilled in and around the mine throughout the life of the mine. To stabilise mine workings located beneath main roads in the area, an ashfilling project was undertaken by the colliery since 1999. A key issue is if the mine will eventually decant, and what the quality of the water will be. This is important for the future planning of the company, as this will determine if a water treatment plant is necessary, and what the specifications for such a plant will be, if needed. Therefore it was decided to do a down-the-hole chemical profile of each available and accessible borehole with a multi- parameter probe with the aim of observing any visible stratification. Ninety-four boreholes were accessible and chemical profiles were created of them. From the data collected a three-dimensional image was created from the electrical conductivity values at different depths to see if any stratification was visible in the shallow aquifer. The ash-filling operations disturbed the normal aquifer conditions, and this created different pressures than normally expected at a deeper underground colliery. From the three-dimensional image created it was observed that no stratification was visible in the shallow aquifer, which lead to the conclusion that in the event that if decant should occur, the water quality of the decanting water will still be of very good quality unless external factors such as ash-filling activities are introduced. It is not often that it is possible to create chemical profiles of such a large number of boreholes for a single colliery and as a result a very complete and informative three-dimensional electrical conductivity image was created. This image is very helpful in aiding the decision-making process in the future management of the colliery and eventually obtaining a closure certificate, and also to determine whether ash-filling is a viable option in discarding the ash. |
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Groundwater/Wetland Interactions In A Coastal Aquifer In The Eastern Cape Province Of South Africa. | Desmond | Visser | Eastern Cape | 2013 | Groundwater, coastal wetland, coastal aquifers, aquifer, surface water | ||||||
AbstractThis study, near Thyspunt between St. Francis and Oyster Bay in the Eastern Cape Province of South Africa, focused on identification and quantification of surface water–groundwater links between the mobile Oyster Bay dune field and the coast. The specific objective was to establish the extent to which important wetlands such as the Langefonteinvlei and the numerous coastal seeps along the coast are directly or indirectly dependent on groundwater as their main water source. A further objective was to establish the extent to which any of the coastal seeps derive their water from the Langefonteinvlei, and are thus interdependent on the integrity of this system. The study also investigated the contribution of the Algoa and Table Mountain Group aquifers to these wetlands. The monitoring network established as part of this study focused on unpacking the interrelationships between surface and groundwater flows, aquifer hydrochemistry and wetland function, as related to the Langefonteinvlei and the coastal seeps in particular. Results indicate that the Langefonteinvlei is fed by groundwater flowing from the mobile Oyster Bay dune field in the north and the water divide in the northeast, which emerges at the foot of the high dune in the north and northeast of the wetland. However, the majority of the vlei area is ‘perched’ above the local water table on a layer of organic-rich sediment. The coastal springs located southwest and west of the Langefonteinvlei are not fed by water from the Langefonteinvlei. They emerge near the coast, where the bedrock lies close to the surface, and are fed by groundwater draining directly from the Algoa and Table Mountain Group aquifers to the Indian Ocean. |
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Effects Of Dolerite Intrusions On The Geohydrology Of Upper Karoo Sediments In The Elundini Area, South Africa | Jakobus | Prinsloo | The Elundini Area, South Africa | 2013 | Geohydrology | ||||||
AbstractThe Karoo Supergroup has a hydrogeological regime which is largely controlled by Jurassic dolerite dyke and sill complexes. The study area is located in the north-eastern interior of the Eastern Cape Province, close to the Lesotho border. The sedimentary rocks of the upper Karoo constitute fractured and intergranular aquifers, due to relatively hydro-conductive lithologies. The main groundwater production targets within the upper-Karoo are related to dolerite intrusions that have a number of characteristics that influence groundwater storage and dynamics. Magnetic, electromagnetic and electrical resistivity geophysical techniques are used to determine the different physical characteristics of the dolerite intrusions, such as size, orientation and the level of weathering. Trends in the data collected from a large-scale development programme can provide evidence that intrusion characteristics also play a role in determining the hydrogeological characteristics of the area. Interpreted geophysical borehole drilling, aquifer testing and water chemistry data can be used to indicate hydrogeological differences between dolerite intrusion types. Observed trends could be used for more accurate future well-field target areas and development. |
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A Groundwater Vulnerability Assessment Of The Greater Pietermaritzburg Region Using DRASTIC In A GIS Environment | Andy | Zwiers | Pietermaritzburg, KwaZulu-Natal | 2013 | Groundwater, Groundwater Vulnerability, GIS | ||||||
AbstractPOSTER All groundwater is vulnerable to contamination, and natural in homogeneity in the physical environment results in certain areas being more vulnerable to contamination than others. Inherent in the agricultural, domestic and industrial sectors of Pietermaritzburg, is the generation of contaminants which, upon reaching the aquifer, result in the deterioration of the quality of groundwater, thus resulting in the water no longer being fit for its intended use. The DRASTIC method is used to calculate the groundwater vulnerability of a 670 km2 region, including the city of Pietermaritzburg. The suggested ratings of each parameter are scrutinised and adapted, according to their relevance to the region and according to known geological occurrences. The use of this method enables the user to generate a regional scale vulnerability map of the groundwater in Pietermaritzburg. The vulnerability map generated has the ability to effectively highlight vulnerable areas to groundwater contamination, which is of critical importance in correct land-use planning, as well as in indicating areas of particular concern, where further detailed investigations are needed. The results of such an assessment are used as an input, together with a contamination inventory to assess the potential risk of groundwater pollution in a groundwater risk map. Furthermore, the result informs local decision-makers and enables proactive prevention of groundwater pollution, in accordance with section 13 of the 1998 National Water Act. The intrinsic vulnerability of the Pietermaritzburg region was found to range from low to very high. The area found to be highly vulnerable is the region northeast of Springbank which requires investigation at a local scale. |
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Groundwater Use Authorisations As Part Of Groundwater Resource Management In Water Scares Areas Within South Africa | Yolanda | Kotze | National | 2013 | groundwater resource management | ||||||
AbstractNational legislation is the outcome of processes, locally, provincial and nationally. Certain aspects of water management have first been the product of legal initiatives of the South African government, seeking to address local problems. As a result, the National Water Act, 36 of 1998, was promulgated. The Act is in line with the Constitution of the Republic of South Africa, 108 of 1996, which embrace human rights. The Water Services Act, 108 of 1997, regulates the accessibility of water and sanitation by domestic users. Groundwater, in many parts of South Africa, provides the sole and/or partial water supply for meeting basic human needs. With an increase in the dependency on groundwater usage, the need to properly and effectively protect, use, develop, conserve, manage and control groundwater resources has become a national priority by the custodian of all water resources: the National Department of Water Affairs. The question arises whether or not the current groundwater allocation decision-making tools are enough to make informed decisions regarding the final approval, or not, of groundwater use licenses, and whether a proper framework that includes guidelines together with licensing conditions are available for decision- making in complex groundwater scenario situations as part of the groundwater license decision process. The current research contributes to answering this question and finding solutions in order to improve and make the groundwater use authorisation process more effective. The groundwater situation will be discussed on a comparative basis from international case studies regarding water legislation and groundwater resource management tools. A full evaluation and analysis of groundwater use authorisation process and decision-making tools on regional and national level in South Africa will be done and a Framework and tool for the evaluation, decision-making and determination of authorisation conditions of groundwater use authorisations, which includes existing lawful water use, general authorisations, and groundwater use licensing, will be developed. Scenarios and case studies are currently implemented. |
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Characterisation And Development Of A Carbonate Rock Aquifer For Large Scale Irrigation In Zambia (A Case Study) | Kobus | Troskie | Zambia | 2013 | aquifer, case study, Groundwater | ||||||
AbstractLimestones and dolomites form an important aquifer system in Zambia. The municipal water supplies for Lusaka and several population centres on the Copperbelt all depend on the carbonates for a substantial proportion of their water supply. Currently 155,912 ha of land are irrigated in Zambia, which is about 30 percent of the economical irrigation potential. Development of large scale irrigation schemes from carbonate rock aquifers proves to be a viable groundwater resource in Zambia. The Katanga carbonate rock aquifers are considered to have good groundwater potential, with high yielding anomalies of up to 60l/s common in certain areas of the country. A phased approach was adopted to characterise the Katanga Carbonates by means of quantifying the volume of groundwater available for abstraction within the geological boundaries. The first phases included geophysical surveys (mainly electrical resistivity and magnetic methods), exploration drilling and aquifer testing. Later phases included the drilling of production boreholes and wellfield development. Lessons learned during the exploration included the identification of high yielding drilling targets and the role of anomaly frequency in target selection. Further development of the Katanga aquifers for production provided challenges regarding production borehole construction and design. The feasibility of the optimum design of production boreholes versus the initial capital cost of the development of these carbonates proved to be an important consideration in this regard. |
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Groundwater For Rural Water Supplies In South Africa | Jude E | Cobbing | National | 2013 | local municipality, groundwater development | ||||||
AbstractEvidence suggests that physical availability of groundwater may be only one of many factors in determining whether groundwater-based rural water supply schemes in South Africa are reliable or "sustainable". Other factors include budgetary constraints, community preferences, policy decisions, operation and maintenance procedures, and the availability of skilled staff. These factors and others combine to create "complex problems" around the issue of rural water supplies that require a multidisciplinary approach if they are to be effectively resolved. This work is an on-going part of Water Research Commission Project K5/2158, “Favourable Zone Identification for Groundwater Development: Options Analysis for Local Municipalities”, due to be completed in March 2014. |
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Modelling Of Impacts Of Fracking On The Karoo Groundwater Systems | Jennifer-lee | Pretorius | The Karoo | 2013 | Fracking | ||||||
AbstractPOSTER Hydraulic fracturing, also known as hydrofracking or fracking, is being engaged in the Karoo region of South Africa in order to enhance energy supplies and improve the economic sector. It will also lead to independence in terms of reduced amount of imports for fuel due to an estimated 13.7 trillion cubic metres of technically recoverable shale-gas reserves in South Africa. Fracking is an extraction technique used with the purpose of having access to alternative natural methane gas, which is interbedded in shale deposits deep under the surface of the earth. In this process boreholes are drilled horizontally into shale formations to cover a larger area in the shale and subsequently attain more natural gas. After these horizontal boreholes are drilled, large volumes of water, mixed with chemicals and sand, are pumped into these boreholes under a very high pressure, forcing the natural gas out. This water mixture is referred to as the fracking fluid. Water is the main component in the fracking fluid and the water used for the fluid reaches volumes up to 30 million litres per borehole. The aim of this study is to present a baseline study of the area and its water resources to ultimately facilitate in resolving the actual impact hydraulic fracturing will have in the area, using a simulation model which will predict the migration of the fracking fluid in the subsurface. In this model, the chemistry of the fracking fluid will be included to determine the impact it might have on the groundwater quality in the area |
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Can Groundwater Sustain The Future Development Of Rural Zimbabwe? | Jeffery | Davies | Zimbabwe | 2013 | Groundwater, development, Rural development | ||||||
AbstractZimbabwe occupies a tectonically stable plateau underlain by ancient Precambrian crystalline basement rocks. These form a central craton bounded by east-west trending mobile belts; the Zambezi mobile belt to the north and the Limpopo mobile belt to the south. Zimbabwe receives generally low and variable quantities of seasonal rainfall within a semi-arid to savannah type climate characterised by moderate to high temperatures. Evaporation commonly exceeds rainfall so that recharge to the thin near surface aquifers is generally low and in some years non-existent. The groundwater resources of the weathered and fractured basement aquifers that underlie more than 60% of the country are of limited potential, typically sufficient to supply the needs of small villages and cattle ranches. However, within the central plateau area of the African to Post-African erosion surfaces, the weathered and fractured basement may exceed 60 m in thickness. The thickness of this zone diminishes towards the main valley systems where subsequent cycles of erosion have stripped the weathered zone away, leaving only a shallow surface fractured zone that may only be 20-30 m thick. Groundwater resources have been developed extensively in Zimbabwe since the 1920s. During 1991/92 drought abstraction from urban boreholes within the southern Harare area caused yield decline and ultimate failure of numerous boreholes. It is now time to question the long-term viability of groundwater development within the basement aquifers in Zimbabwe given the uncertainty in groundwater resources, the complexities of the climate–groundwater interactions and the projected demands of a growing rural population.
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A Rapid Analysis Of Spring Water Quality In Some Neighbouring Villages Of Thohoyandou Town In Thulamela Local Municipality | Vusumzi | Mema | Thulamela Local Municipality, Limpopo | 2013 | springs, Water quality | ||||||
AbstractPOSTER A quick analysis of spring water quality was conducted in four neighbouring villages, namely Vondo, Matondoni, Maranzhe and Murangoni in Thohoyandou town under the Thulamela Local Municipality (TLM) of the Vhembe District Municipality (VDM). For the purposes of this study these villages will be termed VMMM villages. A study on the spring water quality of VMMM villages was conducted by the CSIR to determine whether the natural quality state of the spring water used by the surrounding communities was suitable for drinking purposes without pre-treatment. From the four springs that were identified in the VMMM villages, namely Tshali (S1), Ramufhufhi (S2), Tshinwela (S3) and Tshivhase (S4), water samples were taken for the quality analyses in the laboratory. The results indicated that S2 and S4 had a high coliform count of 35 and 600 per 100 ml, respectively), that is above 10 counts per 100 ml. In springs S2 and S4 the total coliform count also displayed the presence of E.coli (6 and 310 per millilitre, respectively) – E.coli should not be detected at all according to SANS standard limits (2011). While all other parameters were within standard limits (SANS 241, 2011), it was also interesting to note that both S3 and S4 had a problem of high turbidity (1, 6 and 105 NTU, respectively) compared to 1 NTU which is the standard limit (SANS 241, 2011). These results showed that although these communities relied on groundwater in the form of springs for drinking purposes, unmonitored use of these resources may be a health hazard that has a potential to result in disease outbreak and unprecedented deaths. While groundwater through springs is considered natural, increased activity around the source due to human activity and interference by domestic animals, these sources may be rendered unsafe for drinking purposes without prior treatment. Therefore, there is need for local authorities to put measures in place to monitor water resources considered indigenous and traditional to the communities, especially in areas where these resources have become the main source of water supply for drinking purposes. |
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Spoils Handling From Coal Mines In The Waterberg Coalfield Area, Limpopo | Nequita | MacDonald | Limpopo | 2013 | coal mine, Open pit mines | ||||||
AbstractThe 11 coal-bearing zones currently being mined at Exarro's Grootegeluk mine, discard intraburden onto discard dumps. During mining operations the open pit will be backfilled with plant discards, overburden and interburden on completion of mining. The plant waste will be covered with overburden and topsoil. Intraburden spoils consist of sandstone, mudstone and shale rich in minerals such as pyrite and siderite. These intraburden spoils thus have the capacity to generate acid when exposed to the appropriate conditions. The oxidation of iron sulphides (Pyrite (FeS2)), present within the discard dumps and stockpiles, can influence the hydrochemistry by generating acid-mine drainage, while siderite (FeCO3) can have a basic effect to the immediate surroundings. Acid-base- accounting done on samples gathered from different boreholes in the Waterberg coalfield helped to determine lithological units that can generate acid, with specific regard to the interburden removed and placed on the discard dumps, the interburden used in the pit as backfill, and the acid generation possibility from coal seams in stock piles. This indicated the zones that are more prone to acid- and base-producing potentials. Mineralogical investigations with X-ray diffraction and X-ray fluorescence gave a better record of minerals and elements present in trace amounts within interburden zones that could also have additional problems during storage and use. The areas that possess the highest risk regarding acid generation are the zones enriched in pyrite, as well as the coal seams from stock piles. The management plan for the acid generating spoils of the area has two possibilities: Firstly where acid producing potentials are higher, spoils should not be used where it will be exposed to oxygen and water for long periods of time, as the amount of acid generated cannot be controlled. A second option would entail the immediate compaction and flooding of the mined area so that the amount of acid produced would be controlled and limited. |
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Correlation Between Rainfall, Streamflow And Groundwater Levels For The Zachariashoek Sub‐Catchment Near Wemmershoek, Western Cape | Nicolette | Vermaak | Zachariashoek, Western Cape | 2013 | Rainfall, streamflow, Groundwater levels, Geohydrological | ||||||
AbstractZachariashoek catchment was one of the study areas looking into the hydrological characteristics of winter rainfall catchments in the Western Cape. Nearly thirty years of historical data are available for the Zachariashoek area. This data include rainfall, gauge plate readings for the weirs, and water levels for the boreholes in the area. Numerous articles and reports had been written about the research done in the area, concentrating mostly on the effects of fire on streamflow and vegetation. This article will look at patterns that can be observed from the data record and correlate the different data sets for the Zachariashoek sub‐catchment. It will use the data from the two weirs, three rain gauges and at least three of the boreholes that was drilled in this sub‐catchment. The information gained from this comparison can then be used to evaluate possible future hydrological patterns and the interaction between the various components of the hydrological system. |
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Revision Of The Groundwater Quality Reserve | Ndivhuwo | Netshiendeulu | National | 2013 | Groundwater Quality | ||||||
AbstractThe groundwater quality component of the Reserve serves as guidance for groundwater quality requirements when assessing water use license applications. The Reserve is the quantity and quality of water required to satisfy the basic human needs and protect the aquatic ecosystem in order to ensure ecologically sustainable development and use of water resources. This component provides guidance when assessing the suitability of groundwater for drinking purposes. The current groundwater quality was based on the Quality of domestic water supplies, assessment guide (vol. 1,2nd ed., 1998). The parameters that were assessed in the current template include chemicals: sodium, magnesium, calcium, chloride, sulphate, nitrate and fluoride; and physical parameters: pH and electrical conductivity. The above-mentioned ions cater for most water uses applied for, whereas the revised template will also include microbiological (escherichia coli), toxics (zinc, manganese, iron, cadmium, cobalt and copper) for local government and mining commodity/by- product specific water use applications. The current water quality basic human needs values will also be replaced with SANS 241 (2011) guidelines. Inputs and suggestions are therefore requested from various end users/stakeholders. |
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Estimation Of Groundwater Recharge: The Case Of Grasslands Catchment, Marondera, Zimbabwe | Muchanyara | Jarawaza | Grasslands Catchment, Marondera, Zimbabwe | 2013 | groundwater recharge, hydrochemical | ||||||
AbstractThe study on estimation of groundwater recharge was done in Grasslands Catchment, about 70 km south-east of Harare, Zimbabwe. The catchment is underlain by Archean Granitic rocks intruded by dolerite dykes/sheets and form part of the Basement Complex. The catchment is a stream headwater wetland, at the source of Manyame River. The catchment comprises an upland region or interfluves of area 2.12 km2 and a dambo area of 1.21 km2. The study focused on the assessment of temporal and spatial variability of moisture fluxes based on solute profiling, and groundwater recharge and investigations of moisture transport mechanisms. The methodology involved the use of both hydrometric and hydrochemical techniques. Groundwater recharge rates and moisture fluxes were calculated using a chloride mass balance technique in comparison to the hydrograph separation technique. Groundwater recharge was estimated to be 185 mm/year using the chloride mass balance and 215 mm/year using the hydrograph separation technique. Mechanisms of recharge were investigated using the bimodal flow model that comprised of diffuse flow and preferential flow. The results revealed that preferential flow contributes up to 95% of the recharge in the interfluves, whilst diffuse flow contributes up to 5% of the total recharge. The results reveal that the groundwater hydrograph technique results are in agreement with the chloride mass balance method. The study illustrated how routine observations can improve process understanding on groundwater recharge mechanisms. The techniques are not expensive, are easy to use and can be replicated elsewhere depending on availability of data. |
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The Structural Hydrogeology Of A Gold Mine In Mali | Stephen | Fonkem | Mali | 2013 | Hydrogeology, gold mining | ||||||
AbstractThe occurrence of groundwater around a mined-out open pit, connected to an active underground working is not completely understood, but it is fascinating. It has been established that gold mineralisation in study area was structurally controlled. The geomorphology of the local drainage system is highly controlled by the fold or fault architecture. Surface water flowed through, and eroded open fractures in exposed damaged zones (zone of subsidiary structures surrounding a fault). Previous conceptual hydrogeological models of groundwater system suggested is a two-aquifer system, consisting of a fractured aquifer overlain by a weathered aquifer, where groundwater flow mimics surface topography. Based on recent drilling and reassessment of historic geological and hydrogeological data, the groundwater system around the mine could not only be described in terms of an elevation or stratigraphic units, as traditional aquifers are. The weight of the study was placed on accurately understanding the groundwater system in the deposit area by using structural hydrogeology as a best tool in the hydrogeological tool box. From a hydraulic head point of view, in addition to the weathered groundwater system, there are as many bedrock aquifers and aquitards as there are major structures in the pit area. |
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Complexity versus Simplicity: A comparative analysis of complex geology in hydrogeological modelling | Anton | Lukas | 2012 | modelling, FEFLOW | |||||||
AbstractThis paper was presented at the GWD Central Branch Symposium, Potchefstroom in 2012 Numerical modelling of hydrogeological systems has progressed significantly with the evolution of technology and the development of a greater understanding of hydrogeology and the underlying mathematical principles. Hydrogeological modelling software can now include complex geological layers and models as well as allow the pinching out of geological features and layers. The effects of a complex geology on the hydraulic parameters determined by numerical modelling is investigated by means of the DHI-WASY FEFLOW and Aranz Geo Leapfrog modelling software packages. The Campus Test Site (CTS) at the University of the Free State in Bloemfontein, South Africa was selected as the locale to be modelled. Being one of the most studied aquifers in the world, the CTS has had multiple research projects performed on it and as a result ample information is available to construct a hydrogeological model with a high complexity. The CTS consists primarily of stacked fluvial channel deposits of the Lower Beaufort Group, with the main waterstrike located on a bedding-plane fracture in the main sandstone aquifer. The investigation was performed by creating three distinct hydrogeological models of the CTS, the first consists entirely of simplified geological strata modelled in FEFLOW by means of average layer thicknessand does not include the pinching out of any geological layers. The second model was created to be acopy of the first, however the bedding-plane fracture can pinch out where it is known to not occur. The third and final model consisted of a complex geological model created in Leapfrog Geo which was subsequently exported to FEFLOW for hydrogeological modelling. |
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Baseline concentrations of radionuclides in groundwater of the Namibian Uranium Province, Namib Desert, western Namibia | Ester | Gustavo | Western Namibia | Namib Desert, baseline, Groundwater, radionuclides, uranium province | |||||||
AbstractThe Namibian uranium province, located in the Namib Desert, derives its name from the local presence of almost ten uranium tenements. The mines conduct monitoring of natural radionuclide concentrations of Ra226, Ra228, Pb210, U234, U238, Th232 and Po210 in local aquifers. This data is useful in mine rehabilitation and developing closure criteria, as only radiation doses additional to natural doses are usually considered ‘controllable’ for radiation protection purposes. An accredited laboratory analyzed the baseline data collected through quarterly groundwater sampling with submersible pumps. The uranium deposits are hosted in Damara age granites or as secondary mineralization in Tertiary calcareous paleochannels. The analysis of the long-term baseline data provides the background radionuclide concentrations of three aquifer types in the province, i.e., the Quaternary saturated alluvium of the Khan and Swakop ephemeral Rivers, the Tertiary paleochannel sediments, and Proterozoic basement aquifers. The ephemeral rivers are important because they supply groundwater downstream of the mines for agricultural use. The analysis demonstrated that the alluvial aquifers have the lowest natural radionuclide content, with the U234 concentrations ranging between 0.03 and 3.4 Bq/l, while paleochannel and basement aquifers show intermittent U234 concentrations ranging between 0.25 and 5.1 Bq/l. The groundwater in the immediate ore zones shows the highest U234 concentrations, ranging between 44.8 and 86.3 Bq/l, exceedingly higher than the WHO standards of 1 Bq/l. This study illuminates that radioactivity is a natural phenomenon and that groundwater baseline data is paramount to groundwater protection. |
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The National Integrated Water Information System (NIWIS) for geohydrology in South Africa | N | Nungu | Data, Decision Making, Groundwater, Information, Information System, Integration, South Africa | ||||||||
AbstractFor the Department of Water and Sanitation (DWS) to better leverage the wealth of information being collected by various “silo” operational source water information systems, a high-priority initiative was launched to establish a National Integrated Water Information System (NIWIS), which currently consists of over 40 web-accessible dashboards including groundwater related dashboards mostly accessible to the public. Dispersed and disintegrated data and information stored in different sources and formats would hinder decision support in the water sector and deter improvement in service delivery by the DWS. The DWS undertook an extensive and rigorous business requirements analysis exercise within the DWS to ensure that the proposed system does not become a white elephant and facilitate the prioritization of system deliverables. A prototype (waterfall) approach was adopted to develop the NIWIS to ensure the development was still within the suggested business requirements. NIWIS has enabled mostly DWS managers to establish one trusted source of decision-making information for timeous, effective and efficient responses to service delivery. The number of NIWIS dashboards continues to grow as improved data-related business processes are adopted. The unavailability of reliable data from DWS data sources and the exclusion of business requirements from organizations external to DWS were identified as the main challenges to NIWIS disseminating comprehensive, credible information. Therefore, this paper aims to provide some details of the geohydrological information that NIWIS provides and seek feedback from this International Hydrogeologists community for further development of NIWIS. |