Conference Abstracts
Title | Presenter Name | Presenter Surname | Area | Conference year | Keywords | ||||||
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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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Groundwater Resource Assessment For Water Supply To The Heuningvlei Socio-Economic Development Area | Collen | Monokofala | Northern Cape | 2013 | groundwater recharge, flow regime analysis, socio-economic development | ||||||
AbstractThe Heuningvlei pipeline scheme was built in the 1980s to supply water to rural communities in a low rainfall area (<300 mm/annum) – Northern Cape Province. In 2008, the Joe Morolong Local Municipality identified the need to refurbish and upgrade the pipeline scheme for socio-economic reasons. The safe yield and water quality information of existing sources supplying the scheme was unreliable. This was investigated by borehole test pumping and water quality sampling, which indicated reduced yields and deteriorating water quality since 1989. Water demands, which includes supply to communities for domestic use, schools, clinics and stock watering in the Heuningvlei area, was estimated at 2 380 m3/day or 868 700 m3/annum. The potable groundwater supply recommended from 11 existing boreholes is 316 937 m3/annum, leaving a deficit of 551 763 m3. The aquifers utilised for the existing water supply comprise fractured banded iron formations (BIF) and dolomite bedrock. Kalahari sedimentary and dolomite aquifers to the east of the pipeline scheme contain high saline water not suitable for domestic use. No surface water sources exist in the area and the feasibility of the socio-economic development project depends on establishing local groundwater resources that would not impact on existing sources. A target area was identified which is approximately 10 km south from the pipeline. This area is covered by the thick Kalahari sediments (up to 130 m) underlain by dolomite bedrock with a potable groundwater balance of 2.3 million m3/a. Both the associated primary (Kalahari) and secondary (Dolomite) aquifers contain potable water. The target area was not investigated in the past due to perceived poor water quality (elevated salinity) conditions, very low (<10 %) borehole exploitability prospect and difficult drilling conditions. The paper will discuss the importance of recharge estimate and understanding of flow regime at sub-catchment and local scale, use of an airborne magnetic survey in conjunction with ground geophysics, mapping of Kalahari sediment thickness, and successful drilling of exploration boreholes to exploit the deeper Kalahari sedimentary and dolomite bedrock aquifers. The successful development of localised potable water in a low rainfall area made it feasible to implement the Heuningvlei socio-economic development project. |
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Aquifer Vulnerability Assessment Of The Molototsi And Middle Letaba Quaternary Catchments, Limpopo Province, South Africa | OT | Makonto | Limpopo | 2013 | aquifer, vadose zone | ||||||
AbstractThe aquifer vulnerability of the Molototsi (B81G) and Middle Letaba (B82D) quaternary catchments was assessed to determine the influence of the vadose zone on the groundwater regime. The aquifer vulnerability was assessed by developing a new method, which evaluates the vadose zone as a pathway for pollutants by using the following four parameters: Recharge, Depth to water table, Soil type (saturated vertical hydraulic conductivity) and Slope (RDSS). Recharge was estimated using the Chloride-mass balance method and the depth to the water table was measured in the field using dipmeter. The seepage behaviour (soil type) was determined as hydraulic conductivity from in situ infiltration and percolation testing (SABS 0252-2:1993 and double ring infiltrometer). The slopes were determined with the digital elevation method using ArcGIS software. The four parameters were overlaid using Weighted Sum, Weighted Overlay and Raster Calculator to produce the vulnerability map. Different weightings were attributed in the methods and the best selected. The results obtained indicated high vulnerability on the lower and upper parts of both catchments. Aquifers in areas which showed high vulnerability are at high risk of contamination. The benefits of the method described are (a) the easy quantification of the parameters through fairly simple methods and (b) the exclusion of arbitrary index values. |
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Towards The Effective Management Of Groundwater Resources During Unconventional Gas Mining | Surina | Esterhuyse | National | 2013 | Unconventional gas | ||||||
AbstractUnconventional gas mining is a new and unprecedented activity in South Africa that may pose various risks to groundwater resources. According to legal experts, South Africa does not currently have the capacity to manage this activity effectively due to various lacunae that exist in the South African legislation. The possible impacts of unconventional gas mining on groundwater, as well as governance strategies that are used in countries where unconventional gas mining is performed; have been analysed and will be discussed. Based on possible impacts and strategies to manage and protect groundwater internationally, possible governance options for the management of South Africa’s groundwater resources are proposed |
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The Geohydrological Status Of The Vanrhynsdorp Karst Aquifer | Jana | Brits | Vanrhynsdorp | 2013 | Geohydrological, Aquafer | ||||||
AbstractThe aim of this study was to determine the geohydrological status of the aquifer within the boundaries of the Vanrhynsdorp Water User Association with emphasis on the central catchment, E33F. This will assist the Department of Water Affairs with the introduction of compulsory groundwater-use licensing and empowerment of the Vanrhynsdorp Water User Association to manage the resource. In this study emphasis was given to the determination of the water balance and groundwater reserve of the central catchment and the designing of a representative groundwater monitoring network. A literature study of five projects conducted since 1978 was done. Comparisons were made between the data and results of these studies. All the historical data from these studies, as well as the data from the current monitoring programme up until December 2012, were put together and analysed. A conceptual model and groundwater reserve determination, as well as a representative monitoring network, were produced. The study showed a general decline in groundwater levels over a 34-year period. It also showed an increase in rainfall over the last 20 years. Based on the reserve determination and the declining groundwater level in spite of increased rainfall and thus recharge, it was concluded that over-abstraction of groundwater in the study area is taking place. It is recommended that compulsory licensing should be put in place as soon as possible and that no additional groundwater-use licences should be granted in the study area. The installation of flow meters on all production boreholes should be stipulated in the licensing condition. This will assist the monitoring and regulation of groundwater abstraction volumes. |
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Sampling Protocol Optimisation Using Fluid Electrical Conductivity Logging | Candice | Lasher | National | 2013 | Electrical conductivity, Sampling Protocol | ||||||
AbstractCharacterisation of fracture positions is important when dealing with groundwater monitoring, protection and management. Fractures are often good conduits for water and contaminants, leading to high flow velocities and the fast spread of contaminants in these conduits. Best practice guidelines related to groundwater sampling suggest that specific depth sampling with specialised bailers or low flow purging are the preferred methodologies to characterise a pollution source. These methods require knowledge about the fracture positions and, more importantly, flow zones in the boreholes. Down-the-hole geophysical and flow logging are expensive, complicated and time consuming. Not all fracture zones identified with geophysical logging seem to contribute to flow through the borehole. An efficient and cost-effective methodology is required for the characterisation of position and flow in individual fractures. This research reviewed the use of Fluid Electrical Conductivity (FEC) logging to assist with the development of a monitoring protocol. FEC logging proved to be beneficial as it provided individual fracture positions, fracture yields and vertical groundwater flow directions. FEC logging proved to be fast, cost-effective and practical in deep boreholes. The technique allows the development of a site-specific sampling protocol. The information so obtained assists with the identification of the appropriate sampling depths during monitoring. |
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Quenching A Thirsty Country | Fanus | Fourie | National | 2013 | Groundwater, strategy, Boreholes | ||||||
AbstractOnly 40% of all the available groundwater resources are developed in South Africa and the development of surface water are becoming more costly and challenging. The Minister of Water and Environmental Affairs acknowledge this and identified the need to increase the use of groundwater as one of the interventions to address the increasing water requirement of towns and communities. Over the last seven years the Department of Water Affairs developed many reconciliation strategies for the area of water management, the big metro municipalities and for the smaller towns and villages in South Africa. The reconciliation strategies entails, among other things, sustainable ways to source additional water supplies for the selected towns/metro’s or villages. Groundwater played a major role in the recommended interventions. The challenges are now the implementation of the groundwater schemes and sustainable management of the groundwater resources. Or differently put: the balancing act between selling of groundwater and the prevention of over-abstraction. The bankability of regional schemes, the credibility of groundwater as a bulk scheme source, poor management of boreholes/well-fields, institutional responsibility, acceptable quality and treatment of groundwater, still challenge the use of groundwater development. Groundwater need to play its role in addressing the future water needs of South Africa, or can it? |
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Witwatersrand Mine Voids – Their Hydrochemistry And Hydrodynamic Characteristics | Eddie | van Wyk | Witwatersrand | 2013 | Hydrochemistry, hydrodynamics | ||||||
AbstractGold mining on the Witwatersrand has started in the late nineteenth century as sporadic open cast mining and ceased in the late twentieth century, leaving a complex network of haulages, tunnels and ultra-deep vertical shafts/sub-vertical shafts. At least three ore bodies (conglomeritic horizons) were mined down to a depth in excess of 3 000 m from surface. Three large mining basins resulted from the mining methodology applied, namely the Western, Central and Eastern (Rand) Basins. In the early days of mining on the Witwatersrand reefs, gold mine companies realised that dewatering of their mine workings is required to secure mining operations at deeper levels and decades of pumping and treatment of pumped mine water followed. As the majority of deep gold mines on the Witwatersrand ceased operations since 1970, the deeper portions of the mine voids became flooded and led to a new era in the mining history in the Witwatersrand. Rewatering of the mine voids is a combination between excessive surface water ingress generated by surface runoff, and to lesser degree recharge from an overlying fractured and weathered aquifer system (where developed). The flow regime in the mine voids from a scattering of ingress/direct recharge points and single discharge points are complex and is driven by shallow (<100 m) and probably deep (>1 000 m) man-made preferential pathways. The high concentrations of iron sulphide minerals (pyrite. for example FeS2) content, three percent (by weight), of the mined reefs/backfilled stopes and surrounding waste rock piles/tailings dams mobilised significant levels of sulphates (SO4) and ferrous iron (Fe2+) producing an acidic mine-void water (<3 pH). Monitoring of the rewatering mine void hydrological regime became necessary following the first acid-mine water decant from a borehole in the West Rand Basin, and the Department initiated a mine-void water table elevation trend and water quality monitoring programme. Results from this monitoring programme will be illustrated and discussed in this paper with some views on the future water quality and discharge scenarios. |
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Arsenic In The West-African Water Reserves: Investigation Into Sources Of The Contaminant Through Case Studies In The Region | Andre | van Coller | Western Africa | 2013 | Contaminant, investigations, Groundwater reserve | ||||||
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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Hydrogeological Characterisation Of The Fountains East And Fountains West Karst Aquifer Compartments | Vevanya | Naidoo | Gauteng | 2013 | fountains | ||||||
AbstractThe Fountains East and Fountains West groundwater compartments (by means of the Upper and Lower Fountain springs) have been supplying the City of Pretoria with water since its founding in 1855. These adjacent compartments which are underlain by the Malmani dolomites of the Chuniespoort Group are separated by the Pretoria syenite dyke and are bounded to the north by the rocks of the Pretoria Group (Timeball Hill Formation). Inorganic chemistry data (2007-2012), as well as spring discharge volumes (2011-2012) for the Upper and Lower Fountain springs, supplied by the City of Tshwane Municipality, is being used to characterise the two compartments. This is done by means of piper diagrams, bar graphs and temporal plots. Interpretation of the combined chemical and discharge volume data as well as geotechnical and isotope data (in progress) will aid in understanding the karst aquifer and the controls on groundwater system within and possibly between these compartments. |
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Petroleum Hydrocarbon Contamination In Soil And Groundwater: Case Study On The Coastal Tank Farm, Southern Africa | Pieter | Badenhorst | The Coastal Tank Farm, Southern Africa | 2013 | petroleum, Hydrocarbon, contamination, Groundwater, case study | ||||||
AbstractIn this study, a petroleum hydrocarbon contamination assessment was conducted at a cluster of petroleum products storage and handling facilities located on the Southern African Indian Ocean coastal zone. The Port Development Company identified the need for the assessment of the soil and groundwater pollution status at the tank farms in order to develop a remediation and management plan to address hydrocarbon related soil and groundwater contamination. Previous work conducted at the site consisted of the drilling and sampling of a limited number of boreholes. The current investigation was triggered by the presence of a free-phase product in the coal-grading tippler pit located ~350 m down gradient and south-east and east of the tank farms, rendering the operation thereof unsafe. The assessment intended identifying the source of product, distribution and mobility, the extent of the contamination, and the human health risks associated with the contamination. To achieve these, the investigation comprised site walkover and interviews, drilling of 76 hand auger and 101 direct push holes to facilitate vertical soil profile VOC screening and sampling (soil and groundwater), as well as granulomeric analysis to understand grain size distribution within the soil profile. The highest concentrations were associated with the coarse sand layers with the highest permeability. Free-phase hydrocarbons product was found in holes adjacent to the pipeline responsible for the distribution of the product from the jetty to the different tanks farms. Of the 57 soil samples, 21 had high values of GRO and DRO, with 22 below Detection Limit and 14 can be described having traces of hydrocarbon. Both TAME and MTBE were detected in most of the water samples, including from wells located far down gradient. The groundwater sink, adjacent to the pipeline running from west to east, resulted in the limited lateral spread of MBTE in this area, with limited movement towards the sea. The depth of the soil contamination varies over the sites. Based on the site assessment results it was concluded that most of the groundwater contamination, which is a mixture of different product types, is associated with the pipeline responsible for transporting product from the jetty to the different petroleum companies. |
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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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The Thermal Springs Of Swaziland – A Review | Nicholas | Robins | Swaziland | 2013 | thermal springs, hydrochemical | ||||||
AbstractThe thermal springs of Swaziland and adjacent KwaZulu-Natal have, over the years, attracted attention from hydrogeologists, hydrochemists and structural geologists. While some of the springs in Swaziland are well known amenities, others are less well-visited and some difficult to access. There are eleven warm springs in Swaziland, discharging between 1 and 10 l/s from Precambrian age rocks; all are situated at or near valley bottoms. The springs have surface discharge temperatures of between 25 and 52 oC and total dissolved solids concentrations of less than 400 mg/l. In all cases the water is meteoric in origin. Geothermometry indicates that maximum temperatures up to 100 oC are achieved during circulation. If the average geothermal gradient is about 20 oC/km as recorded in a deep mine at Barberton, then this would require circulation up to a depth of several kilometres. However, it is likely that circulation bottoms at about 1 km, as pressure of overburden inhibits dilation of fractures at such depths, and the excess temperature may derive from a locally enhanced geothermal gradient. The discharge water is young, with 14C ages of between 4 000 and 5 000 years. |
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An Evaluation Of The Physical Parameters That Affect Evaporation Rates On Multi-Component Hyper-Saline Effluents In A Controlled Environment | D | Bent | National | 2013 | Evaporation rates, Hyper-Saline Effluents, Controlled environment | ||||||
AbstractThe effluent at the eMalahleni water reclamation plant is being processed through reverse osmosis which improves the quality of the mine water to potable standards. Brine ponds are generally used for inland brine disposal and this option has been selected for the eMalahleni plant. Limited capacity to store the brines requires enhanced evaporation rates and increased efficiency of the ponds. This study aims to establish the physical behaviour of the brine from the eMalahleni plant in an artificial evaporation environment. This includes the actual brine and synthetic salts based on the major components. An experimental unit was designed to accommodate and manipulate the parameters that affect the evaporation rate of brines and distilled water under certain scenarios. Two containers, the one filled with 0.5M of NaCl and the other with distilled water were subjected to the same environmental conditions in each experimental cycle. Each container had an area of a 0.25 m² and was fitted with identical sensors and datalogger to record the parameter changes. The energy input was provided by infra-red lights and wind-aided electrical fans. This equipment used in these experiments was to simulate actual physical environmental conditions. The rate of evaporation was expected to be a function of humidity, wind, radiation, salinity and temperature. The experiments showed the type of salt and thermo-stratification of the pond to be significant contributors to the evaporation rate. The results also showed that the NaCl solution absorbed more heat than the water system. The difference in evaporation observed was ascribed to a difference in the heat transfer rate, which resulted in a higher temperature overall in the brine container than in the water container under similar applied conditions. This effect remained despite the introduction of 2 m/s wind flow over the tanks as an additional parameter. The wind factor seemed to delay evaporation due to its chilling effect upon the upper layers of the ponds, initially hindering the effective transfer of radiative heat into the ponds.
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Hydrogeochemical Footprint As A Result Of Mining Activities In The Johannesburg Area | Tamiru | Abiye | Johannesburg | 2013 | hydrochemical | ||||||
AbstractThe water quality in the crystalline rocks of the Johannesburg and its environs has been severely altered by the mining activity. Due to freshwater scarcity and dependency of the people on the groundwater, it is important to understand the extent of hydrogeochemical footprint in the area. The water quality characteristic has been thoroughly assessed in the crystalline aquifers based on the input from hydrogeochemical characteristics and environmental isotopes. The results show that the calculated dilution factor for acid-mine decant is in the range of 68% as a result of interaction with surrounding fresh water. The SO4/Cl ratio has a wide range of values that falls between 0 and 306.37, while that of Fe/Ca ratio falls between 0 and 5.59. High SO4/Cl values potentially indicate the interference of acid-mine decant with the groundwater system traced through sulphate concentration. Similarly, a high Fe/Ca ratio also indicates the impact of acid-mine decant on the groundwater system where iron is traced with respect to calcium concentration. In this regard the ratios above 0,25 (with the assumption of 1 to 4 natural abundance for Fe:Ca in water in the area) could potentially represent acid-mine decant source.The results confirm that most of the water- supply wells have heterogeneous chemistry with distinctive hydrogeochemical footprint represented by abnormally high Fe, SO4 and Si as a result of acid-mine decant. |
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Conceptual Modelling Of Lake–Groundwater Interactions For The Lake Sibayi Catchment, North-Eastern South Africa | Jannie | Weitz | Lake Sibayi Catchment, North-Eastern South Africa | 2013 | conceptual model, hydrochemical | ||||||
AbstractLake Sibayi (a topographically closed freshwater lake) and coastal aquifers around the Lake in eastern South Africa are important water resources and are used extensively for domestic water supplies. Both the Lake and groundwater support an important and ecologically sensitive wetland system in the area. Surface and subsurface geological information, groundwater head, hydrochemical and environmental isotope data were analysed to develop a conceptual model of aquifer–lake interaction for further three-dimensional numerical modelling. These local geologic, groundwater head distribution, lake level, hydrochemistry and environmental isotope data confirm a direct hydraulic link between groundwater and the Lake. In the western section of the catchment, groundwater flows to the lake where groundwater head is above Lake stage, whereas along the eastern section, the presence of mixing between Lake and groundwater isotopic compositions indicated that the Lake recharges the aquifer. Stable isotope signals further revealed the movement of lake water through and below the coastal dune cordon and eventually discharges into the Indian Ocean. Quantification of the 14-year monthly water balance for the Lake shows strong seasonal variations of the water balance components. Recent increase in rate of water abstraction from the lake combined with decreasing rainfall and rapidly increasing pine plantations may result in a decrease in lake level which would have dramatic negative effects on the neighboring ecosystem and a potential seawater invasion of the coastal aquifer. |
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Groundwater Stratification And Impact On Coal Mine Closure | Andrew | Johnstone | National | 2013 | Groundwater, coal mine | ||||||
AbstractTo date, South Africa has mined approximately 3.2 billion tons of coal from a number of different coal reserves located in various parts of the country. A large number of the mines have reached the end of their productive life, resulting in numerous mine closures. With closures, groundwater levels have rebounded, resulting in decant of mine water into the environment. This paper describes a case study of a closed underground coal mine, the rebound of water levels, the evolution of the groundwater quality and the impact it has had on the management of the potential decant. On closure of the Ermelo Mines in 1992, initial water quality monitoring indicated that a water treatment plant would be required to treat the mine decant. However, as the groundwater levels in the mine rebounded, the water quality in the mine void evolved from sulphate type water to sodium type water. The evolution of the water quality can be attributed to sulphate reducing bacteria, vertical recharge from the hanging aquifer and stratification. Water level and quality monitoring have shown that the water in the old mine void will not decant to surface due to the depth of the mine void, hydrogeological conditions, a "hanging aquifer" and the recharge mechanisms. As a result, no water treatment will be required and the mine will not impact on the surface water. The main applications from this paper are:
The main contribution of this paper is the use of hydrogeological information in design of a coal mine so as not to decant on closure. |
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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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Towards The Effective Management Of Groundwater Resources During Unconventional Gas Mining | Surina | Esterhuyse | South Africa | 2013 | Unconventional gas | ||||||
AbstractUnconventional gas mining is a new and unprecedented activity in South Africa that may pose various risks to groundwater resources. According to legal experts, South Africa does not currently have the capacity to manage this activity effectively due to various lacunae that exist in the South African legislation. The possible impacts of unconventional gas mining on groundwater, as well as governance strategies that are used in countries where unconventional gas mining is performed; have been analysed and will be discussed. Based on possible impacts and strategies to manage and protect groundwater internationally, possible governance options for the management of South Africa’s groundwater resources are proposed. |
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Numerical modelling of mine dewatering and flooding in the Evander Gold Basin, South Africa | Kai T | Witthueser | Witwatersrand | 2013 | gold mining, mine water rebound | ||||||
AbstractThe assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin, South Africa. The cessation of dewatering lead to large volumes of contaminated surface discharges in the western parts of the basin. Towards the eastern extremity of the Witwatersrand basin the detached Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2000 metres below ground, while overlain by shallower coal mining operations. The hydrogeology of the Evander basin can be categorised by a shallow weathered-fractured rock aquifer comprising of the glacial and deltaic sediments of the Karoo Supergroup, while the deeper historically confined fractured bedrock aquifer consist predominantly of quartzite with subordinate lava, shale and conglomerate of the Witwatersrand Supergroup. The deep Witwatersrand aquifer has been actively been dewatered for the last 60 years with a peak rate of 60 Ml per day in the mid late 1960s. Modelling the impacts of mine dewatering and flooding on a regional scale as for the Evander basin entails challenges like the appropriate discretisation of mine voids and the accurate modelling of layered aquifer systems with different free groundwater surfaces on a regional scale. To predict the environmental impacts of both the historic and future deep mining operations, the detailed conceptual model of the aquifers systems and a 3-dimensional model of the mine voids were incorporated into a numerical groundwater model to simulate the dewatering and post-closure rebound of the water tables for the basin. The presented model could serve as an example for the successful modelling of mine dewatering and flooding scenarios for other parts of the Witwatersrand basin. |
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Determining The Mass Balance Of Synthetic Dna Tracer In Headwater Streams | Judith | Seopa | National | 2013 | Headwater Streams, hillslopes | ||||||
AbstractThe pollution of water resources has become a growing concern worldwide. Industrial, agricultural and domestic activities play a pivotal role in water resources pollution. The challenge faced by pollution monitoring networks is to understand the spatial and temporal distribution of contaminants. In hydrology, tracers have become a critical research tool to investigate surface water and groundwater transport dynamics. Synthetic DNA (deoxyribonucleic acid) tracers are being used in hydrological research to determine source areas, where uniquely labelled DNA from each source area is identified. The main objective of the study was to determine the mass balance of the synthetic DNA tracer in surface water streams. Furthermore, to gain knowledge on DNA adsorption and decay and determine whether DNA behaves as conservative tracer in the surface water streams. Understanding the adsorption and decay characteristics of synthetic DNA tracers may promote its robustness in hydrological research. In this study, field injection experiments using synthetic DNA were carried out, the DNA tracer was injected together with sodium chloride (salt) and deuterium as conservative reference tracers. The purpose was to compute DNA mass balance calculations with reference to the two conservative tracers. In this study two different DNA markers were used, namely T22 and T23. Additionally, with each injection experiment a field batch experiment was carried out to determine DNA loss characteristics on the field. From our study, the DNA loss between the injection point and the first measurement was greater than 90%. Therefore, it was important to conduct additional laboratory batch experiments to explain DNA loss characteristics. However, the issue of the initial DNA loss remained unresolved. Laboratory batch experiments results allow us to conclude the following: the type of material used, filtering, ion concentration and water composition reduced DNA concentration. Moreover, initial DNA losses occurred and not DNA decay. From our experiments we concluded that DNA can be used for long-term tracer experiments, subsequently, limiting synthetic DNA mass balance determination of synthetic DNA as it is a reactive. Overall, we can conclude that DNA does not behave as a conservative tracer. |
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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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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 | Mahlogonolo | Phahlamohlaka | Limpopo | 2013 | LNAPLS | ||||||
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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Establishment Of A Database And A Representative Groundwater Monitoring Network For The Vanrhynsdorp Water User Association | Brian | Dyason | Vanrhynsdorp, Western Cape | 2013 | groundwater monitoring, Geohydrological | ||||||
AbstractThe aim of this project was to establish a detailed geohydrological database and monitoring network for the karst aquifer within the boundaries of the Vanrhynsdorp Water User Association. An adequate monitoring network is necessary for the Vanrhynsdorp Water User Association to implement sustainable water use management as well as for the Department Water Affairs to ensure its mandate as trustee of all water resources. Hydrocensus projects were conducted in phases as the project escalated from historic town supply during 1978 towards a catchment driven water user association after implementation of the new National Water Act in October 1998 (Act 36 of 1998). With the successive hydrocensuses conducted, the monitoring network also evolved in regard to area monitored, point locations, monitoring schedules and parameters measured. Hydrocensus data were captured on the National Groundwater Archive, time series data on the Hydstra database and chemical analysis on the Water Management System. Time series graphs were compiled to analyse the monitoring data and to create a conceptual model of the karst aquifer. The study showed a general decline in groundwater levels and quality in the study area. The conclusion is that the aquifer is over exploited. It is recommended that an extensive management plan is developed and implemented to ensure sustainable use of this sensitive water resource. The installation and monitoring of flow meters on all production boreholes should be seen as urgent and stipulated as such in licensing conditions. This will ensure the effective management and regulation of this valuable groundwater resource. |
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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 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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Preliminary Hydrogeological Investigation Of The Natal Group Sandstone, South Africa | Molla | Demlie | KwaZulu-Natal | 2013 | Hydrogeological, investigations, Boreholes | ||||||
AbstractThe Paleozoicage Natal Group Sandstone (NGS) that outcrops from Hlabisa (in the north) to Port Shepstone (in the south) and Greytown (west) to Stanger (east) in the Province of KwaZulu-Natal, South Africa, is investigated in terms of its hydrogeological characteristics. This sandstone group, which comprises a lower Durban and an upper Marrianhill Formations, is a secondary/fractured aquifer system that has variable but good productivity across its members. It is characterised by variable borehole blow yields ranging from 0.2 l/s to as high as 20 l/s, with more than 50% of the boreholes having blow yield > 3 l/s. Preliminary analysis of these boreholes yields indicates that higher yielding boreholes are associated with a network of intersecting fractures and faults, and are recommended targets for future water well-siting in the area. Groundwater in the NGS is of good quality in terms of major and trace element composition and it has a total dissolved solids (TDS) composition of <450 mg/l. It was observed that the specific electrical conductivity (EC), TDS and major ions composition of groundwater within the sandstone decrease from north to south, which appears to be controlled by the geochemical composition of the aquifer material and an increase in the rate of recharge. Depth to groundwater is also found to decrease southwards because of an increase in the rate of recharge. Groundwater hydrochemical facies are generally either Na-HCO3 or Na-HCO3–Cl, and environmental isotope data (2H, 18O, Tritium) indicates that the groundwater gets recharge from modern precipitation. Furthermore, the EC increases from inland to the coastal zone, indicating maritime influences and the general direction of groundwater flow is eastwards, to the Indian Ocean. |
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Groundwater Closure Cost Estimation For The Mining Industry | Pieter F | Labuschagne | National | 2013 | Mining | ||||||
AbstractThe increase in awareness of environmental issues and the desire for a cleaner environment by the public has caused mining companies to place greater emphasis on the continuous rehabilitation of harmful effects caused by mining operations. Ongoing rehabilitation is also a requirement of the government departments involved in mining in South Africa. The biggest concern for the relevant government departments is the possible uncontrolled pollution of water resources in the vicinity of mines, after they have closed. In the compilation of this paper, the unique nature of the South African situation has been considered – this refers to a legally acceptable approach towards current legislation and policies. This study leads to the construction of a logical approach towards mine closure, specifically to understand issues around costs and financial liability. The final product of this approach should ultimately give more clarity on: the principles followed to identify objectives for mine closure and groundwater assessment; key steps to follow when assessing site hydrogeology and to determine related impacts, risks, closure costs and liabilities; and an overview of methods that could be used for the mitigation of polluted aquifers and a brief site-specific application. |
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Assessing The Role Of Oxygen In The Attenuation Of Petroleum Hydrocarbon Vapours In The Vadose Zone | Samuel D | Möhr | National | 2013 | Hydrocarbon, petroleum | ||||||
AbstractVapour intrusion (VI) is the term used to define the encroachment of vapour phase contaminants from subsurface sources into structures such as buildings and basements. It is widely recognised that VI often forms the principal risk of exposure to receptors at petroleum release sites. Petroleum VI (PVI) generally occurs where a release of petroleum hydrocarbon product migrates from its source (for example, from a leaking underground storage tank) to the groundwater table at which point, given favourable conditions, the hydrocarbon plume may migrate laterally beneath an adjacent building or structure. Subsequent volatilisation of the petroleum product results in the upward diffusion of vapours towards the surface where the vapours may enter into the building or structure at concentrations which may be harmful to human health. The subject of PVI with regards to its fate and transport mechanisms, as well as associated mitigation measures, is rapidly gaining attention on a global scale, although to date this exposure pathway remains largely unassessed in South Africa, with no regulatory guidance currently available. In the late 1990s and early 2000s focus was placed on the development of VI screening criteria by which sites could be screened with respect to their hydrogeological conditions and contamination status so as to determine whether VI may be a potential exposure pathway of concern, with much of the early work being completed by the United States Environmental Protection Agency. For the past decade the majority of the available screening criteria and guidance has not, or has only partially accounted for biodegradation processes associated with VI, which has led to doubt over the application of such screening criteria in many cases. Furthermore, recent research conducted abroad has highlighted the importance of the role of oxygen in the vadose zone in the natural attenuation of petroleum hydrocarbon vapours as they diffuse through the soil profile. This research is pointing towards the notion that currently applied screening criteria may be overly conservative when applied to petroleum impacted sites, leading to many unnecessary PVI investigations being conducted to the disruption of occupants of the buildings, and at great cost. Over the last two years ERM has compiled a dataset of PVI results from numerous investigations it has conducted throughout Southern Africa and in this paper the authors present data that supports the growing global trend towards recognising the role that oxygen plays in attenuating petroleum hydrocarbon vapours in the vadose zone. The data also support the notion that confirmed cases of PVI into buildings have generally been found to be the exception to the rule and not the norm. |
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Development Of The Evander Goldfields 3-D Mine Void Model | Martin | Holland | The Evander Goldfield, Mpumalanga | 2013 | development, gold mining | ||||||
AbstractPOSTER The Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2 000 m below ground and is detached from the larger Witwatersrand basin. The assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin as more mine shafts mothballs and dewatering ceases. The development of a 3-D mine void model is crucial in predicting the rate of flooding as the prediction of the groundwater rebound is primarily driven by the volumes of mine voids along with the amount of recharge. All available mine plan data for the Evander Gold Mine (EGM) were obtained digitally from Harmony Gold. However, the majority of the old mine workings (e.g. Leslie and Winkelhaak) were available as 2-D data and elevations of the mine developments (stopes and drives) had to be captured from hardcopy plans. Data from the more recent mining operations (e.g. Shaft 6), including updated survey and mine plan data, were directly used for the development of the 3-D void model. The calculated mine void volume, based on the EGM operations mine plan data, is approximately 80 518 045 m3. The mine void calculations were checked against the total tons of rock milled by the EGM operations since the late 1950s and was considered valid estimations of the EGM mine void volume. The validated EGM 3-D mine workings plan was subsequently used to determine the stage- volume relationships. The 3-D mine void model established, will then be incorporated into a regional numerical groundwater flow model to be calibrated against observed abstractions and water levels and utilised to predict future dewatering rates. |
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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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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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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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Using Hydrogeologic Conceptual Model To Implement A Successful Iwrm Approach In Limphasa River Catchment, Malawi | Thokozani | Kanyerere | Limphasa River Catchment, Malawi | 2013 | Hydrogeological, IWRM, conceptual model | ||||||
AbstractThis study examined the effective use of the hydrogeologic conceptual model (HCM) to implement the integrated water resource management (IWRM) approach. While research focuses on using hydrogeologic models in groundwater for planning, few studies show how to use HCM for a successful IWRM approach, especially in resource poor catchments. This is largely due to t he lack of adequate data to showcase such models. Despite the lack of numerical groundwater data, the HCM was used in this study and it provided the scientific and visual presentation of key issues for practical understanding by stakeholders. For the first time, HCM provided a practical understanding of t he groundwater system in the Limphasa River catchment. By using HCM and physical factors qualitatively, the study revealed that, apart from storage, abstraction mechanisms significantly contributes to regional initiatives of groundwater supply whose central objective is to utilise and manage such water sustainably. The model is based on the relationship between groundwater availability and its related hydrogeologic factors. Findings suggest improvement in quantifying the studied parameters through field experiments to provide a better estimation on storage and abstraction of groundwater in relation to impacts of a future changing climate. Since using HCM has shown practical usage, replicating it in catchments with similar physical and socioeconomic environments, would be desirable as refining the model progresses. |
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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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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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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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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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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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Case Study: Groundwater Exploration In The Basement Granites Of The Kraaipan Group Using Aeromagnetic Surveys | Marius | Terblanche | Kraaipan, North West Province | 2013 | groundwater exploration, case study, Granites | ||||||
AbstractHistorically groundwater exploration consisted of reconnaissance geophysical surveys followed by detail ground surveys. Where no potentially water-bearing geological structures are shown on geological maps and aerial photos, the project area would be divided into a grid on which the ground geophysical survey would be done. This type of exploration is time-consuming and expensive. In some cases the terrain or cultural noise prohibits the use of conventional geophysical methods, with only more expensive and time-consuming methods being left as an option. This is where the high resolution airborne magnetic survey excels. The results obtained from this type of survey are of such a nature that ground geophysical surveys are only performed where potential drilling targets were identified from the aerial survey. Not only can there be cost- and time-savings on ground geophysical surveys, but drilling of dry boreholes can be limited, which makes up the largest cost component of a groundwater exploration project. This paper will discuss successes achieved using high resolution aeromagnetic surveys as the basis for groundwater exploration in traditionally low- yielding igneous geology. |
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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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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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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. |