Conference Abstracts
Title | Presenter Name | Presenter Surname | Area | Conference year Sort descending | Keywords | ||||||
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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. |
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Baseline concentrations of radionuclides in groundwater of the Namibian Uranium Province, Namib Desert, western Namibia | E | 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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Development of United Nations Framework Classification for Resources (UNFC) for Groundwater Resources Management | P | van der Keur | SDGs, UNFC, common pool resources, subsurface geo-resources, sustainable groundwater resources management | ||||||||
AbstractThere is an urgent need to support the sustainable development of groundwater resources, which are under increasing pressure from competing uses of subsurface geo-resources, compounded by land use and climate change impacts. Management of groundwater resources is crucial for enabling the green transition and attaining the Sustainable Development Goals. The United Nations Framework Classification for Resources (UNFC) is a project-based classification system for defining the environmental-socio-economic viability and technical feasibility of projects to develop resources and recently extended for groundwater. UNFC provides a consistent framework to describe the level of confidence in groundwater resources by the project and is designed to meet the needs of applications pertaining to (i) Policy formulation based on geo-resource studies, (ii) Geo-resource management functions, (iii) Business processes; and (iv) Financial capital allocation. To extend use in groundwater resources management, supplemental specifications have been developed for the UNFC that provide technical guidance to the community of groundwater professionals to enhance sustainable resource management based on improved decision-making. This includes addressing barriers to sustainably exploiting groundwater resources, avoiding lack of access to water and also related to ‘common pool resources’ in which multiple allocations are competing with domestic water supply (e.g. geo-energy, minerals, agriculture and ecosystems, and transboundary allocation of natural resources). UNFC for groundwater resources is designed to enhance governance to protect the environment and traditional users while ensuring socio-economic benefits to society. Consequently, it is a valid and promising tool for assessing both the sustainability and feasibility of groundwater management at local, national and international levels. |
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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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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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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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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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Southern African Pre-Cretaceous Deep Groundwater Flow Regimes: Evidence And Drivers | Eddie | Van Wyk | South Africa, Botswana, Namibia | 2013 | groundwater flow, deep drilling | ||||||
AbstractAfter drilling technology improvements in South Africa in the early 1900s, several deep (>300 m) exploratory drilling programmes were conducted to explore for pressurised groundwater resources. The results were not significant, except for the Cretaceous Uitenhage Artesian Basin and recent investigations in folded Table Mountain Group Aquifer systems. Large sedimentary units in Southern Africa do have the structural geometry to drive regional artesian systems; however, diverse climate and aquifer hydraulic limitations counteract these conditions to such a level that sustainable basin- like deep flow mechanisms are probably non-existing, except where enhanced by deep mining activities. On the contrary, several deep drilling projects in South Africa, Botswana and Namibia have undoubtedly proven the existence of pressurised groundwater strikes below 300 m (northern Kalahari) to as deep as 3 000 m (western Karoo Basin). Given the regional hydrogeological characteristics of these systems, the availability of sufficient recharge zones required to drive sustainable artesian flow or semiartesian conditions becomes a challenge. The existence of isolated pressurised compartments as a result of the lithostatic pressurisation in the deeper sections of many of the sedimentary successions may prove to be a more realistic explanation for these pressurised water strikes observed during deep drilling operations in Southern Africa. |
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Characterisation Of Hydrochemical Facies And Water Quality Of The Coastal Plain-Sand Aquifers Of Parts Of Eastern Niger Delta, Nigeria | AN | Amadi | Nigeria | 2013 | hydrochemical, Water quality, coastal aquifers | ||||||
AbstractSoil and water pollution are major environmental problem facing many coastal regions of the world due to high population, urbanisation and industrialisation. The hydrofacies and water quality of the coastal plain-sand of part of Eastern Niger-Delta, Nigeria, was investigated in this study. Hydrogeological investigations show that the aquifers in the area are largely unconfined sands with intercalations of gravels, clay and shale which are discontinuous and, however, form semi-confined aquifers in some locations. Pumping test results show that the transmissivity ranged between 152.0 m2/day and 2 835.0 m2/day with an average value of 1 026.0 m2/day, while the specific capacity varied between 828.0 m3/day and 15 314.0 m3/day with a mean value of 6 258.0 m3/day. Well-discharge ranged between 1 624.0 m3/day and 7 216.0 m3/day with an average value of 3 218.0 m3/day, while hydraulic conductivity varied between 3.2 m/day and 478.4 m/d with a mean value of 98.6 m/day. These findings indicate that the aquifer in the area is porous, permeable and prolific. The observed wide ranges and high standard deviations and mean in the geochemical data are evidence that there are substantial differences in the quality/composition of the groundwater within the study area. The plot of the major cations and anions on Piper, Durov, and Scholler diagrams indicated six hydrochemical facies in the area: Na-Cl, Ca-Mg-HCO3, Na-Ca-SO4, Ca-Mg-Cl, Na-Fe-Cl and Na-Fe-Cl-NO3. Heavy metal enrichment index revealed 12 elements in the decreasing order of: Fe > Ni > Cu > Zn > Mn > Cd > V > Co > Pb > Cr > As > Hg. The study identified salt intrusion, high iron content, acid-rain, hydrocarbon pollution, use of agrochemicals, industrial effluents and poor sanitation as contributors to the soil and water deterioration in the area. Saltwater–freshwater interface occurs between 5 m to 185 m, while iron-rich water is found between 20 m to 175 m. The first two factors are natural phenomenon due to the proximity of the aquifer to the ocean and probably downward leaching of marcasite contained in the overlying lithology into the shallow water table, while the last four factors are results of various anthropogenic activities domiciled in the area. The DRASTICA model, a modification of the DRASTIC model, was developed and used in the construction of the aquifer vulnerability map of the area. Modern sanitary landfill that ensures adequate protection for the soil and groundwater was designed and recommended to replace the existing open-dumpsites. Owing to the monumental and devastating effects of hydrocarbon pollution in the area, the need to eradicate gas-flaring and minimise oil spills in the area was advocated. Bioremediation and phytoremediation techniques were recommended to be applied in the clean-up of soils and water contaminated with hydrocarbon in the area.
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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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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 | AA | 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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Hydraulic Tests Of Strong Artesian Boreholes: Well-Head Construction And Test Design | Kornelius | Riemann | National | 2013 | hydraulic tests, artesian conditions, aquifer | ||||||
AbstractArtesian boreholes are a common feature worldwide in confined aquifers. However, the hydraulic testing of these boreholes and estimation of aquifer properties from such tests still pose a challenge for hydrogeologists. Common hydraulic tests, such as step-drawdown or constant discharge rate tests require a static water level at the start of the test, and the measurement of drawdown (increasing over time) and abstraction rate (fixed for a period of time). Usually, when undertaking a pumping test in an artesian borehole, the drawdown is measured from ground level, and the drop in hydraulic head between static pressure and ground level is often ignored. This also implies that the starting time of the test is not at the static water level. A constant head test, set at ground level, is the other option. However, the decrease in flow rate is not only dependent on the hydraulic properties of the aquifer, but also masked by pipe hydraulic effects within the well. This kind of test would also limit the available drawdown to be utilised for the test. Hence, it was required to develop a method for undertaking hydraulic tests in strong artesian boreholes allowing for the drawdown to fluctuate between above and below ground and avoiding the pitfalls described above. The solution is a specially designed and constructed well-head for the installation of the pump and monitoring equipment prior to the hydraulic test. The standard tests are slightly modified and will only be carried out after sealing the well-head and reaching static hydraulic pressure. The recommended well-head construction and subsequent hydraulic tests were carried out at a strong artesian borehole in the Blossoms Well-field, south of Oudtshoorn in the Western Cape of South Africa. |
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Effects Of Dolerite Intrusions On The Geohydrology Of Upper Karoo Sediments In The Elundini Area, South Africa | J | Prinsloo | The Elundini Area, South Africa | 2013 | Dolerite Intrusions, Geohydrology, Groundwater | ||||||
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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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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Setting Water Quality Compliance Limits For Contaminated Groundwater In Fractured Rock Aquifers | Morne | Burger | National | 2013 | Water quality, fractured rock (504, aquifer, contamination | ||||||
AbstractIndustrial facilities and mining activities represent a potential contamination hazard to down gradient surface water and groundwater environments. The assessment of the risks posed by such contaminant sources should facilitate regulators to determine set compliance limits. These limits should, however, take in consideration the heterogeneous nature of fractured rock aquifers. This paper will focus on the limitations or technical feasibility of applying single groundwater quality compliance limits for fractured rock aquifers. It will also aim to describe how groundwater contamination limits could be determined in a more feasible manner. |
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Natural methane in the Karoo: Its occurrence and isotope clues to its origin | Siep | Talma | Karoo | 2013 | Methane concentration | ||||||
AbstractThe possible future exploitation of methane in the Karoo has stimulated work from various disciplines to examine its occurrence, exploitability and exploitation risks. Groundwater issues are vital in this context because of its possible use during exploration and exploitation, and more important, to understand the risks of its pollution during and after all these activities. This paper presents the experiences of the authors to document the presence of methane in the Karoo based on data from boreholes, springs, tunneling and deep drilling. There have been frequent anecdotal reports of explosive gas in boreholes, both dry and wet, in the Karoo. In some cases the gas is identified as methane. Thermal spring waters in the Karoo invariably contain some amounts of methane. Methane pockets have been found in the Karoo during tunneling projects and in some deep Soekor boreholes. A groundwater study in the vicinity of the Gariep Dam indicated substantial quantities of methane in warm groundwater and an association with helium. The isotope concentrations of carbon and hydrogen in methane characterise the methane-forming processes. Such analyses in samples from the central Karoo basin are consistent with that of thermogenic gas found elsewhere in the world. Towards the edges of the basin, lower 13C-values indicate that methane there is produced by microbial processes at shallower depths. The presence of thermogenic methane together with helium on the surface is likely to give clues to pathways from depth. |
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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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Comparison Of Analytic And Numerical Estimations Of Groundwater Drawdown Evolution For Open Pit Dewatering | Jaco | Nel | Kolwezi, Democratic Republic of the Congo | 2013 | dewatering, Drawdown | ||||||
AbstractA new mining site situated near Kolwezi in the Democratic Republic of the Congo plans to develop a pit in phases over a period of six years. The mine requires dewatering volume estimates of the pit as well as a constant water supply to the plant. Hydrogeologic data available at the site during the scoping phase was limited to a few water level measurements and blowout yields from only five hydrological boreholes. Hydraulic properties from reports at neighbouring sites were extrapolated to the geological units at the site. The depth to water level at the site is about 20 m, with a planned final pit depth of approximately 180 m below surface. Based on the limited data available an analytical approach to estimate the inflow into the mine was adopted. Analytical calculations proposed by Marinelli and Niccoli (2000) were used to estimate the inflow into the Pumpi mine pits. The analytical calculations consider recharge, depth of mining vertical and horizontal hydraulic conductivities. Drawdown evolution of pit dewatering are obtained by using different mining depths at different mine stages. The output results from the analytical calculations are the maximum extent of influence of the pit as well as the volume of water inflow into the pit. Limitations of the analytical equations are that they, amongst others, cannot consider complex boundaries. Drilling and pump testing to obtain local hydraulic properties and boundary conditions are planned during the first quarter of 2013. The numerical model will be set up after the drilling and pumping tests, using the new data for calibration. The numerical model will contain as much of the physical layer definitions and potential internal boundaries as possible with model boundaries incorporated along far field fault zones and hydraulic boundaries. The numerical model should improve the reliability of estimates of pit inflow and water supply to the plant. The results between the analytical and numerical approaches can then be compared to improve future dewatering estimates with limited data. It is expected that the reliability of the analytical predictions will reduce after year 4, where the role of boundaries are expected to influence the drawdowns and related flow towards the pit. |
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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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Delineation Of Zones At Risk From Groundwater Inflows At An Underground Platinum Mine In South Africa | A | Stoll | National | 2013 | groundwater inflow | ||||||
AbstractThe subject mine has a policy of avoiding groundwater inflow into the underground workings due to the impact on the mine operations. It has already implemented a significant mitigation measure by excluding shallow mining and a large pillar under the river that is present in the mining area. To assess the potential for groundwater inflows into the underground mine workings as a result of a planned expansion project, Environmental Resources Management (ERM) undertook numerical groundwater modelling based on a detailed geological investigation to define the proposed mining area into high, medium and low mining risk areas with respect to potential groundwater inflow. The conceptual definitions of the mining risk areas are: High Risk – general groundwater seepage and inflow expected in the face and roof of the mining unit from numerous joints and fractures which is regarded as serious enough to permanently halt mining operations. Medium Risk – possibility of limited point source groundwater inflow in the face and roof of the mining unit from sporadic selective joints and fractures. Not expected to halt mining operations. Low Risk – no significant groundwater risk to mining operations expected. The areas identified as being potentially at risk from groundwater inflow were determined using a combination of geological mapping, ground geophysics and percussion drilling that was incorporated into a numerical hydrogeological model. The study undertaken by ERM enabled the mine to incorporate the identified mining risk zones into the early stages of the mine planning, and allowed for a significant reduction in the size of the safety pillar under the river. |
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Flowing Fluid Electrical Conductivity Profiling – An Inventive And Cost-Effective Alternative To Conventional Downhole Hydraulic Profiling Techniques | Samuel D | Möhr | National | 2013 | Electrical conductivity, Hydraulic profiling | ||||||
AbstractFlowing fluid electrical conductivity (FFEC) profiling provides a simple and inexpensive way to characterise a borehole with regards to the vertical location of transmissive zones, the hydraulic properties of the various transmissive zones and the intra-well flow conditions which may be present in the well under ambient conditions. The method essentially involves analysing the time evolution of fluid electrical conductivities in a borehole under pumped and ambient conditions using a down-hole conductivity/temperature data logger. The premise of the method is that the borehole column of water has its electrical conductivity altered by adding saline water into the borehole. This results in a contrast in electrical conductivity (EC) between the water in the borehole and the water in the adjacent formation. At depths where transmissive zones are present, decreases in EC values in the FFEC profile will be observed where formation water with a lower EC (relative to the borehole water column) enters into the well, whilst pumping at low abstraction rates (between 500 ml and 1 liter per minute). By altering the EC of the well-borewater and maintaining a constant pumping rate, the sequence of FFEC profiles depicts the dynamic flow and transport response which is dependent upon the hydraulic properties of the formation. In this paper the authors present several examples where FFEC profiling has been used to identify transmissive zones in boreholes where no information existed with regards to the vertical distribution of transmissive zones. Furthermore, the authors present case studies where FFEC profiling has been employed as an alternative technology to more conventional hydraulic profiling techniques. This includes a comparative technology case study where down-hole impeller flow meter technology was employed in addition to FFEC profiling and a multi-rate FFEC profile test which was used to determine discrete fracture transmissivity values in a borehole where packer testing equipment could not be installed. Within the context of groundwater contamination investigations, the method holds several attractions as it generates minimal waste water to be managed and disposed of, is inexpensive and can be completed within a relatively short time period. |
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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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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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Potential Impacts Of Fracking On Groundwater In The Karoo Basin Of South Africa | Gerrit | Van Tonder | Karoo | 2013 | potential impact | ||||||
AbstractDetermining impacts associated with the production of shale gas in the semi-arid Karoo on groundwater is vital to people living in the Karoo. On the one hand shale gas can be a game-changer for energy supply, but on the other it may have a devastating effect on the environment. Knowing the potential impacts of shale gas mining beforehand, the government can set appropriate regulatory protocols and tools in place to mitigate potential risks. This paper describes research done on the potential impact that hydraulic fracturing could have on groundwater in the Karoo. A wild card that only exists in the Karoo Basin of South Africa is the numerous dolerite intrusions. These dolerite structures are associated with relative high-yielding boreholes because of the fractured contact aureole that exist between solid dolerite and the adjacent Karoo sediments. Compromised cement annuli of gas wells are the major preferential flow paths along which methane and fracking fluid can escape into shallow, freshwater aquifers. This study focused solely on the impact of compromised cement annuli of gas wells. The Karoo Basin is under artesian conditions which imply that any pollutant will always try to migrate upwards in the Karoo. The hot-water springs in the Karoo indicate that upward velocities of water are relatively high (the spring water take only days to travel from deep down to the surface). The cubic law was used to estimate potential upward leakage rates from gas wells (during production, but after cessation thereof as well, when pressures will rebuild because of artesian behaviour of the Karoo formations). Potential leakage rates along faulty annuli of a well can vary between a value close to zero to two liters per second in the case of an aperture of 0,5 mm. These leakage rates were used as input to a 2D numerical groundwater flow and mass transport model. The 2D model was run for 30 years and the movement of pollution from the gas wells on the pad simulated. The model indicates that an area of 300 ha could be contaminated over a period of 30 years in a downstream groundwater flow direction. If an abstraction borehole drilled along a fault zone or a dyke, intersecting the fracked reservoir, is introduced into the model, results predict that the pollutant will reach the borehole in less than two months if the borehole is situated six kilometres from the well-pad. The total impact that fracking will have on the groundwater in the Karoo, is a function of the total area that will be fracked. The outcomes of this research clearly show that fracking in South Africa cannot be done in the same way than it is currently done worldwide. A rule that will force gas companies to disclose fracking fluid contents is non-negotiable. Companies should also be required to measure pressures in the fracked gas reservoir after closure. An additional requirement to enforce sealing of the entire fracked reservoir with a very dense material like bentonite or a mud with a very high density to capture the fracking fluids deep down in the gas reservoir should not be negotiable. |
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Hydrogeology Of The Kosi Bay Lakes System, South Africa | Mbali | Ndlovu | The Kosi Bay Lakes, KwaZulu-Natal, South Africa | 2013 | Hydrogeology, Groundwater | ||||||
AbstractPOSTER Lake Kosi Bay is an estuary-linked lake system composed of four interconnected lakes, namely Makhawulani , Mpungwini , Nhlange , Amanzamnyama and interconnecting channels, which drains via a sandy opening to the Indian ocean and three extensive areas of swamps (Wright 2002 ). The Kosi Bay lake system is considered as the most pristine lake system on the South African coast and has been used as a recreational fishing destination since 1950 (James et al. 2001). The lakes are separated from the ocean by a strip of forested sand dunes (South African Wetlands Conservation Programme 1999; Wright 2002). Groundwater utilisation in the area ranges from extraction of seasonal groundwater from shallow, hand-dug wells to drilling of boreholes for family or communal use and development of groundwater well-fields for agricultural projects (Botha et al. 2012). The exact amount of abstraction of the groundwater is unknown. The Kosi Bay system is situated on the northern KwaZulu-Natal coast, 2.9 km south of the Mozambique international boarder. According to a Statistics South Africa survey (2007), the approximate population is 163 694. The Kosi system falls under the UMkhanyakude District Municipality, which covers more than 128 818 km2. The travelling distance from north of Durban is 470 km and coordinates of the Kosi Bay system are 2650S-2711S, 3238E- 3253 (Write et al. 1997). The catchment has an area of about 304 km2. The Kosi Bay system is principally clean, white sands, particularly in the northern most reaches where tidal influences are most marked and the system experiences a seasonal inflow of fresh water into its heard (Andeas Holbach 2012). |
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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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Investigation Of Possible Contaminant Plumes Emanating From Residual Mine Deposits In The Mpumalanga Province Of South Africa, Results From Geophysical Surveys | Emmanuel | Sakala | Mpumalanga | 2013 | contamination, plumes, geophysical methods | ||||||
AbstractAcid-mine drainage (AMD) has received considerable media coverage in South Africa as of late. This have caused a considerable increase in researches, most of them with emphasis on decanting of contaminated water from the old gold mines in Witwatersrand basins and fewer on mine residue contamination from coal and gold mines in the Mpumalanga Province. The paper outlines results of ground geophysical surveys that were carried out along the perimeter of two mine residual deposits (dumps) in the Barberton Greenstone Belt, Mpumalanga Province. The aim of the study was to generate a 3D geoelectric model of the subsurface showing possible acid-mine drainage contaminant pathways. Two geophysical methods, namely Frequency Domain Electromagnetic Profiling (FDEM) and Electrical Resistivity Tomography (ERT) were applied in order to investigate the variation of electrical conductivity in the subsurface. The ERT method was done over frequency domain electromagnetics anomalies. FDEM electrical conductivity values ranging between 40 mS/m to 60 mS/m were considered as anomalous in that geological terrain. These areas were then surveyed by the ERT method to check the depth extent of these FDEM anomalies. On the resistivity section, between station 40 m and 80 m of Dump 1 – ERT1, a discontinuity in the bedrock was identified. The area could act as a pathway for contaminants to flow from the dump to groundwater. The FDEM survey identified an area with high conductivity values to the north of Dump 1. The ERT results also showed a shallow plume at 30 m depth which is consistent on two parallel sections on Dump 1. The area could be a possible AMD pathway of a mine dump residue to a Komati tributary on the north. The bedrock is generally characterised by high resistivity values; a break in the bedrock exists on this high resistivity zone on ERT 6. This break could be a fault zone which can act as possible pathway of (AMD) from a mine dump residue to a shallow aquifer. Potential contaminant recharge pathways were delineated using geophysical, electrical and electromagnetic methods. Potential groundwater recharge pathways and sub-vertical low resistivity zones with values <100Ohm.m were delineated using the ERT method. Investigation of contaminant plume migration is recommended over the anomalies that were generated from geophysics data in the Barberton areas. New technologies (artificial neural networks (ANN), fuzzy logic, etc.) combined with laboratory studies is recommended for development of a software platform that accepts 3D geoelectric data (present study), constrained with geology, geochemistry (soil and water), hydrology and hydrogeology data. |
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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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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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Gis-Pmwin, A Preprocessor In Arcgis For Groundwater Modelling With Pmwin | Haili | Lin | National | 2013 | Groundwater, Groundwater Modelling, Hydrogeological | ||||||
AbstractPMWIN5.3 has been one of the most commonly used software for groundwater modelling because of its free source and the adoption of the popular core program MODFLOW. However, the fixed formats required for data input and lack of GIS data support have posted big challenges for groundwater modellers who are dealing with large areas with complicated hydrogeological conditions. In South Africa, most geological and hydrogeological data have been captured and stored in GIS format during various national research projects such as WR2005, NGA, etc. Therefore, a proper linkage between PMWIN and ArcGIS is expected to do the pre-processing for modelling in PMWIN. Visual Basic for Application (VBA) embedded in ArcGIS 9.3 was used to develop the linkage. Based on the conceptualisation of the study area, the model dimension, discretisation and many value-setting processes can be easily carried out in ArcGIS other than directly in PMWIN. Then the grid specification file and other input files can be exported as the PMWIN-compatible files. The functions on the modification of model geometrics have also been integrated with the toolbar. The linkage can be used with a higher version of PMWIN or ArcGIS. It has been applied to several gold fields in the Witwatersrand gold basin to simulate the groundwater flow and mass transportation for various conditions and scenarios. One of the applications will be presented in this paper. It has been proven that the linkage is efficient and easy to use. |
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Simulated Pore Pressure In Highwalls Of Open Pit Mines | Ismail | Mahomed | National | 2013 | Open pit mines | ||||||
AbstractOpen pit mining operations are located in various, usually complex, geological settings and equally variable climatic regions from arid to extremely high rainfall. Many Southern African open pit mines occur in competent and un-weathered rock masses, and groundwater flow is therefore structurally controlled. Assessing and reducing pit slope pore pressure should be incorporated into pit slope design. Site hydrogeological investigations followed by numerical groundwater modelling is completed to produce predicted pore pressure distributions over the life of a mine and to assess the potential effect of dewatering actions on slope stability. Investigations were completed for two Southern African pits and simulated pore pressure distributions were used in slope stability analysis. In the first case, the simulated slopes are shown to be free draining, and the designed pit slopes are predicted to remain safe and remain so even with the built-up of pore pressure. In the second instance, pore pressure reduction through an aggressive horizontal drill holes programme is demonstrated to improve probability of failure. This has demonstrated the need for collaboration between geotechnical and hydrogeological investigations to improve slope design, reduce likelihood of pit wall failures and reduce mining cost through excavating steeper depressurised slopes. |
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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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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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A Methodology To Assess The Movement Of Hydrocarbons And Associated Remediation Thereof | Sascha | Roopa | National | 2013 | Methodology, Hydrocarbon, remediation, contamination | ||||||
AbstractPOSTER Water is an invaluable resource without which life would cease to exist. Supply in South Africa has become limited due to increases in demand brought upon by population growth, urbanisation and industrialisation. In Southern Africa, water systems are considerably degraded by mining, industry, urbanisation and agricultural activity and a large amount of the fresh surface water has already been utilised. The stresses on this resource will unlikely make the current usage sustainable in years to come. In order to provide for basic needs for the future, groundwater as a resource will have to play a major role. It is for this reason that groundwater integrity needs to be preserved. Hydrocarbon contamination is a huge threat to groundwater as it contains toxic substances that are insoluble in water. These toxins are carcinogenic and mutagenic, and have a major impact on human health and ecosystem stability. When spilled, hydrocarbons will move downward through the unsaturated zone under the influence of gravity and capillary forces, trapping small amounts in the pore spaces. Accumulation will result in added weight along the water table, forcing the entire surface to be displaced downward. Some of the components can dissolve in the groundwater and move as a plume of contaminated water by diffusion and advection within the saturated zone. The transport of contaminants from petroleum hydrocarbon spills needs to be described in terms of a multiphase flow system in the unsaturated zone, taking into account contaminant movement in each of the three phases: air, water and free light non-aqueous phase liquid. Petroleum hydrocarbon behaviour in the subsurface is additionally complicated by the presence of multiple compounds, each with different properties. The net result is that some hydrocarbon fractions are transported faster than others and a contamination plume of varying intensity may spread over a large area. The aim of this study is to develop a methodology to map and simulate the movement of groundwater that has been contaminated by hydrocarbons and to determine the fate of the water quality through decomposition. Associated remediation options will be determined thereafter. |
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Contaminant Source-Term Model Development For A Backfilled Opencast Coal Mine In The Karoo Basin | K | Lupankwa | Northern Cape | 2013 | Contaminant, opencast coal, Karoo | ||||||
AbstractIn South Africa salinisation of water resources by dissolved sulphates resulting from acid rock drainage (ARD) and metal leaching (ML) from surface coal mine spoils has a significant effect on water supply in the Gauteng Province. Predictions of mine water quality is required to select cost- effective rehabilitation and remediation measures to reduce future ARD and ML risks and to limit long-term impacts. A load balance model was developed in Microsoft Excel to simulated contaminant loads in a completely backfilled opencast mine in the Karoo Basin of South Africa after closure. The model calculated the balance between contaminant load into the pit water system from mainly pyrite oxidation processes in the spoils and load removed through decanting. Groundwater flow modelling data and simulated spoils seepage qualities for the mine site were used as input in the contaminant load calculations. The model predicted that the amount of contaminants added to the pit from spoils decrease considerably from the time of closure over a period of approximately 100 years. Thereafter the contaminant load decrease is gradual. This is due to a decrease in the volume of unsaturated spoils, as spoils at the bottom become permanently inundated as the pit fills up, thus limiting oxygen diffusion and oxidation. Cumulatively, the contaminant load gradually increases in the backfilled pit until the onset of subsurface and surface decant, when the contaminant load declines. This is due to removal of contaminants from the mine water system via decanting. Approximately 200 years after mine closure, 86% of the spoils are inundated. The model predicted that the quality of decanting water improves with time due to a decrease in load from spoils, removal of contaminants through decanting water and dilution effects of relatively clean groundwater inflows. Mass loads were used as input into the numerical groundwater model for the contaminant mass transport simulations to predict the migration of contaminant plumes with time. The geochemical model results assisted in developing conceptual water and waste management strategies for the opencast mine during operational and closure phase. |
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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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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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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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An Innovative Application Of The Mixing Cell Model To Quantify Surface Water–Groundwater Interaction | Amy | Allwright | National | 2013 | Innovation, groundwater resource management, baseflow | ||||||
AbstractThe significance of a reliable groundwater resource assessment is of growing importance as water resources are stretched to accommodate the growing population. An essential component of a groundwater resource assessment is the quantification of surface water–groundwater interaction. The insufficient amount of data in South Africa and the apparent lack of accuracy of current estimates of the groundwater component of baseflow lead to the investigation of a new method. This applicability of this new approach, the Mixing Cell Model (MCM), to quantify the groundwater contribution to baseflow is examined to assess whether the method would be of use in further groundwater resource assessments. The MCM simultaneously solves water and solute mass balance equations to determine unknown inflows to a system, in this application the groundwater component of baseflow. The incorporation of water quality data into the estimation of the surface water–groundwater interaction increases the use of available data, and thus has the ability to increase the confidence in the estimation process. The mixing cell model is applied to datasets from the surface water–groundwater interaction test site developed by the University of the Free State, in addition to data collected along the middle Modder River during a fieldwork survey. The MCM is subsequently applied to a set of quaternary catchments in the Limpopo Province for which there are available calibrated estimates of the groundwater component of baseflow for the Sami and Hughes models. The MCM is further applied to the semi-arid quaternary catchment D73F to assess the applicability of the mathematically-based MCM in a flow system within a regionally-defined zero groundwater baseflow zone. The results indicate that the MCM can reliably estimate the groundwater component of baseflow to a river when sufficient data are available. Use of the MCM has the potential to evaluate as well as increase the confidence of currently determined groundwater baseflow volumes in South Africa, which will in turn ensure the responsible and sustainable use of the countries water resources. |
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Estimating The Water Make Of A Rehabilitated Opencast Coal Mine In Mpumalanga | Francois D | Fourie | Mpumalanga | 2013 | opencast coal, decanting | ||||||
AbstractAfter a period of heavy rainfall in 2006, pit water from a rehabilitated opencast coal mine in the Mpumalanga Province started decanting, causing impacts on the adjacent agricultural land and river system. Various actions have since been taken to manage the pit water, including construction of contour berms to prevent clean water entering the ramps, construction of levees and dam walls to increase the decant level, irrigation of mine water on the rehabilitated areas of the pits, disposal of pit water in nearby pans, recirculation of pit water by means of pumping between the various voids, controlled release of pit water to the river system, and construction of a pipeline to pump pit water to a nearby colliery where there is a demand for process water. For the purpose of mine closure, a water management plan was required for which an estimate of the water make of the colliery was needed. The water make was estimated by using measured quantities (rainfall data, pumping rates, dam water levels) and estimated quantities (evaporation from open water bodies), while making a number of simplifying assumptions. This approach revealed that the conventional method of estimating the water make as a percentage of rainfall recharged through the spoils, significantly underestimates the volumes of water that need to be dealt with at the colliery. Large volumes of groundwater appear to be entering the pits along preferential pathways connected to recharge zones at higher elevations, contributing to the water make of the colliery. |
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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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The Environmental Impacts Of Groundwater On The St Lucia Wetland | Claudia | Brites | Myalazi Plantation, KwaZulu-Natal | 2013 | Environment, Groundwater | ||||||
AbstractThis paper has been based on a study conducted at the Nyalazi plantation in KwaZulu-Natal, South Africa. The study was conducted in order to determine the impacts of the different timber species planted on the groundwater levels associated with the site area. Commercial timber plantations are widespread throughout the country and form an essential component of the South African economy. The site is located 200 km north of the port of Durban and approximately 20 km north of the town of St Lucia in the KwaZulu-Natal Province. The study area, the Nyalazi plantation, is located on the western shores of Lake St Lucia, situated on a peninsula between the Nyalazi River, west of the site and Lake St Lucia to the east. The two main tree species which are located in the Nyalazi plantation are Pinus elliottii and Eucalyptus grandis Camaldulensis. The geological units which influence the hydrogeological regime of the site area include the recent deposits of cover sands and the Port Durnford Formation. These geological successions are the most influential on the groundwater environment as these are the units closest to the surface. The study area is located on the Maputuland coastal plain, also referred to as the Zululand coastal plain, which is classified as a primary aquifer and is the largest of its kind in South Africa. High recharge is experienced within the upper formations of the coastal plain which are unconfined aquifers (Mkhwanazi, 2010). This aquifer consists of unconsolidated clays and sands, which may be defined as an alluvial or primary aquifer (Rawlins & Kelbe, 1991). The monitoring network was initiated by SAFCOL (South African Forest Company, Ltd) in 1995, now known as SiyaQubeka. In total 21 monitoring points were installed, which includes piezometers and deeper boreholes. The trends of the groundwater level data collected over the 17-year period was analysed. Limited historical information was available for the Pinus elliottii plantation; however, based on the data it was evident that the mature pine plantations had minor effects on the groundwater environment of the study area. Conversely, the Eucalyptus species indicated a significant impact with the lowering of the groundwater table between 10 and 16 m over a period of 13 years within the plantation area, which equates to an average decline of one metre per year. |
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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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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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Groundwater Governance Requirements for the Exploration and Production of Unconventional Gas Sources | Kevin C | Pietersen | Karoo | 2013 | groundwater governance | ||||||
AbstractSouth Africa has an energy crisis. The country requires 53 Gigawatt of new capacity by 2030. The exploitation of unconventional gas is a potential game-changer to meet South Africa’s current energy deficit to fuel economic growth and development. Water management, both in terms of abstraction and disposal, has emerged as a critical issue in the development of unconventional gas reservoirs. This presentation focuses on a high-level, qualitative analysis of the groundwater-related institutional and governance challenges associated with unconventional gas exploration and production. The findings represent a synthesis of information sourced from regulatory and legislative documents as well as international experience. The analysis maps the current groundwater institutional and governance landscape in South Africa and lessons learned from other regimes such as the United Kingdom and United States of America. Good governance entails ensuring that there is compliance with policy and legislation, effective decision-making, appropriately allocated accountability, transparency and that stakeholder interests are considered and balanced. This forms the basis of a preliminary gap analysis. |
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Using Electrical Resistivity Tomography To Describe The Aquifer Architecture Linked To Groundwater And Surface Water Interaction | Teboho | Shakhane | Krugerdrift Dam, Free State | 2013 | Electrical Resistivity Tomography, aquifer, Groundwater, surface water | ||||||
AbstractPOSTER One of the critical elements of water resource management is the dynamic exchange between groundwater and surface water. Quantifying this exchange strongly relies on an adequate characterisation of the lithological architecture of the involved aquifer system. In the past, this characterisation often relied on lithological data obtained through invasive methods. However, given the spatial heterogeneity of the subsurface, these methods do not provide the density of sampling required for an accurate ‘‘image’’ of the large‐scale architecture of the aquifer system, leading to large uncertainties in the variations and continuities of subsurface structure. These uncertainties inevitably lead to inaccuracies in the conceptual geohydrological model, thereby diminishing the prospects of an accurate assessment of the groundwater–surface water interaction. In order to limit the uncertainties, the results of electrical resistivity tomography (ERT) surveys conducted on a site near the Krugersdrift Dam in the Free State Province of South Africa were used to make inferences regarding the prevailing geohydrological conditions. The resistivity models were compared to borehole logs from existing boreholes to produce a refined model of the subsurface architecture related to groundwater–surface water interactions. |
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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. |