Conference Abstracts

Abstract

The 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.

Abstract

For 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.

Abstract

This 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.

Abstract

Lake  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.

Abstract

Variability in both rainfall and raw water demands at South African mines and lack of accurate predictive planning tools often leads to water shortages or spillages of excess dirty water. The demand varies due to changing production rates, scheduled and unscheduled maintenance, while available water resources are greatly influenced by droughts and untimely storm events. Using averages in static water balances or planning for “worst case scenarios” by increasing storm water capacity or securing larger volumes from external sources “for in case”, is expensive and could still be inadequate.

A dynamic simulation model can integrate all the variables above with available ground- and surface water resources. Groundwater is  often underestimated as  a  source.  A  simulation model can  test  strategies to optimise its role before expensive dams or pipelines are considered.

In the case studies presented, Arena simulation software (from Rockwell) are used with hourly time steps to dynamically simulate water flows/levels, evaporation, seepage and rainfall runoff. All flows and dam levels are recorded to Excel for statistical analysis after simulation runs. To calculate the significance of overflow events and maximum demands the model runs multiple iterations which render specific confidence intervals for results, for example a 95% confidence level that a specific dam will not overflow more than once during the life of mine. Models may span several shafts, concentrator plants and smelter complexes. One model integrated over 1 000 flows and 75 dams with respective flow logic on the backdrop of a Google map of operations. Highlights of recent case studies include: 

• Groundwater from shallow anthropogenic aquifers greatly reduced external raw water requirements.
• This also prevented the clean water from overflowing into the underground workings where it is then pumped from depth as dirty water. 
• Artificial recharge of an aquifer with sporadic excess surface water increased the groundwater in storage that was used as a buffer for drought periods. 
• Optimised models proved that external raw water requirements and overflows into the environment could be significantly reduced and in some cases eliminated.

A dynamic water balance simulation model integrates business components with all related flows and storages and is the best tool available to accurately predict water resource demands and overflows to the environment. It enables the testing and optimization of water management strategies long before capital is spent and enhances the understanding, buy-in and decision support for all affected parties.

A picture is worth a thousand words... A (good) simulation is worth a thousand pictures!

Abstract

The key towards modern groundwater management lies in a profound strategy from monitoring data collection over data processing and information management to clear reporting on the development of groundwater resources. Only thus planners are enabled to take informed decisions towards sustainable use and well-keeping of available groundwater. A core in this strategy is the digital database in which all relevant data and information is stored, handled and displayed. It is thus that the Namibian Ministry of Agriculture, Water and Forestry (MAWF) decided to replace within the activities of the Namibian–German cooperation project “Groundwater for the north of Namibia”, the existing national groundwater database GROWAS with the completely new development of the GROWAS II  version.  Through  the  experience  of  the  project  partner  BGR  (Federal  Institute  for Geosciences and Natural Resources) the focus was put on the critical issue of data quality control. As the analysis of the old system indicated unclear data operation procedures as a major source of errors, improved user-friendliness was high on the agenda for the new database. Developed closely to  the  needs  of  Namibian  Water  Authorities,  GROWAS II  features  a  GIS-based  graphical  user interface (GUI) with a vast range of query functions, a modular system including time series tools, hydrochemistry, licenses for abstraction application and groundwater status reporting functions, among others. Quality control is secured through different measures like the “fosterage” option which allows the input of data into a temporary status with restricted access until released by senior experts, the quick and direct interaction with Google Earth to verify locations and the extensive use of look-up tables and descriptive keys in alignment with other regional geo-databases. Furthermore, data entries can be marked according to their estimated reliability with traffic light coding. These measures should ensure that only good quality data will be added in the future. Upcoming development steps are the practical tests of the single modules in day-to-day use, the integration into or exchange with other information systems and the improvement of older existing data as far as possible. Namibia will thus be better prepared for future groundwater challenges.

Abstract

The possibility of large reserves of shale gas underlying the Karoo and their exploitation has focused attention on the groundwater resources and aquifers of this region. Much is known about the relatively shallow aquifers (<300 m) which supply many local municipalities and farmers with water for domestic, stock and irrigation use (mostly from boreholes <150 m in depth). Conversely, little is known about the deeper formations (>500 m) and associated groundwater occurrences and their possible interconnection to the shallow aquifer systems. This paper covers a desk study of the southern Karoo, mostly above the Great Escarpment, carried out by a group of hydrogeologists/geochemists with a cumulative experience of about 250 years. The main consideration at this stage has been the collation and analysis of existing information, using GIS, conceptualisations, and identification of knowledge gaps.

A Karoo Groundwater Atlas was published in 2012 and Volume 2 has been released at this conference, which present a summary of the main analyses. Borehole yield, recharge and quality in the shallow aquifer tend to improve, and water levels become shallower, from west to east, associated with higher rainfall and increased percentage of dolerite and sandstone. Aquifer yield, quality, lithology and presence of dolerites constitute 60% of a groundwater attributes ratings classification; 54% of the study area has a high rating. Twenty four percent of the study area has a high vulnerability rating. Knowledge of the characteristics of groundwater associated with the deeper formations is restricted to a few thermal springs and sparse data from some deep hydrocarbon exploration wells. Weak artesian flows were recorded from two such wells in the Dwyka Group below the Great Escarpment, with Total Dissolved Solids of up to 10 000 mg/L and temperatures of up to 77 oC, from depths of 2 347 to 3 100 m. Further work and cooperation with other researchers/institutions is on-going and planned to fill in knowledge gaps and assess the risks to groundwater of shale gas exploration.

Abstract

The National Environmental Management Waste Act, 59 of 2008 (NEMWA) clearly identifies the status and risk of contaminated sites and provides a legislative mechanism for remediation activities to be implemented and controlled. The Draft National Framework for the Management of Contaminated Land (henceforth Framework) provides national norms and standards for the practical implementation of remediation activities in compliance with NEMWA. A soil-screening value (SSV) for the protection of water resources is based on a two-phase equilibrium partitioning and dilution model which includes a dilution factor (DF) and partitioning coefficient (Kd) which converts the water quality guideline to a total soil-screening value. This paper presents a methodology to use soil-specific Kd  values to improve the accuracy of the new South African guideline for contaminated land.

Appropriate Phase 1 screening assessments are important due to the potential consequence it holds. Some uncertainty exists in the Phase 1 screening values due to variability in Kd values for different soil. This study shows that the Kd  values selected for the Framework is not representative of typical South African soils. Cu Kd values exceed the value provided by the Framework in all soils, but are lower that the Framework V Kd value in all soils. For Pb, low clay content weathered soils have lower Kd, but higher clay content soils are up to four orders of magnitude higher that the Kd in the Framework. Furthermore, due to the large variability (three to four orders of magnitude for Cu and Pb) point estimates of a single Kd value cannot be used for all soil types. However, for V only one order of magnitude variation is found. 

A way of addressing the uncertainty would be to determine the water soluble portion during the assessment. This would dramatically increase the certainty with which screening is conducted and could prevent significant inappropriate screening. Additional cost incurred be offset by saving as a result of unnecessary Phase 2 assessments or the reduction of undetected risks that later could impact the environment. 

Phase 1 screening could also be improved by including soil classification and some basic soil properties in the site assessment and adjusting Kd values, accordingly. Soil properties that can be used are typically clay content, pH and organic matter content. From these properties more appropriate Kds can be estimated for use in setting screening values.

Abstract

Groundwater is the water that is found beneath the surface of the ground in a saturated zone (Bear 1979). Groundwater contamination refers to the groundwater that has been polluted commonly by human activities to the extent that it has higher concentrations of dissolved or suspended constituents. The scale of the potential supply of groundwater from the Cape Flats Aquifer Unit (CFAU) is very significant due to the increase of the population in Cape Town that leads to limited water resources (Maclear 1995). Groundwater contamination is a threat in the Cape Flats. This is because sand is more susceptible to pollution as a result of urbanisation, industrialisation, intense land use area for waste disposal and agricultural activities (Adelana 2010). The aim of this paper is to evaluate groundwater contamination and assess possible prevention and treatment measures in the CFAU. Pumping tests were done in UWC site in Borehole 5 (pumping borehole) and Borehole 4 (observation borehole) for six hours; three hours was for the pumping and the other three hours for recovery. This was done in order to see how the aquifer recovers after pumping. Water samples were also taken and analysed in the lab. This was done to find the type of contamination, whether it is degradable or non-degradable. The Borehole 5 drawdown plot is showing a straight line. This suggests a linear flow and that there is no confining bed beneath. This is because straight lines are showing the Cooper-Jacob type curve, which is for unconfined aquifers. The curve of Borehole 4 can be fitted to a Theis-type curve. This suggests a radial flow pattern indicating homogeneous characteristics in the deeply weathered zone and that there is a confining bed beneath. This is because aquifers responding in the same manner as the Theis-type curve, are confined aquifers (Hiscock 2005).The groundwater samples are showing a TDS range of 260 to 1 600 mg/l. This could be the result of the waste water treatment plant that is near UWC and the industries that are near the airport and at Bellville South. In conclusion, the geology of the CFAU is very susceptible to groundwater contamination, which is due to agricultural, industrial and human activities.

Abstract

This paper outlines the core factors related to the economic assessment of groundwater resources. Included in the discussion is a delineation of the factors that determine the economic value of groundwater as well as a thorough description of the range of ecosystem services that are derived from groundwater resources.

Several factors affect the economic value of aquifers, but these factors can split into two categories, natural asset values and ecosystem services values.

Ecosystem services are the benefits that humans receive from ecosystems, and are officially defined by the Millennium Ecosystems Assessment. Ecosystems produce these ecosystem services on an annual basis, and the value of these services accrue on a country’s national income statement, and should ideally be measured through indicators that relate to Gross Domestic Product (GDP).

Aquifer themselves are natural assets. They form part of the ecological infrastructure of a country and the values of these assets theoretically appear on a country’s natural resources balance sheet. The asset value can be determined by calculating the Net Present Value (NPV) of the perpetual stream of aquifer ecosystem services delivered.

By understanding the full range of factors that underlie the natural asset values of aquifers, along with their ecosystem service values and the full range of inter-temporal and inter-ecosystem service characteristics, we can begin to adequately assess the economic value of groundwater resources.

Abstract

The 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.

Abstract

Abstract

The assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin, South Africa. The cessation of dewatering lead to large volumes of contaminated surface discharges in the western parts of the basin. Towards the eastern extremity of the Witwatersrand basin the detached Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2 000 m below ground, while overlain by shallower coal mining operations. The hydrogeology of the Evander basin can be categorised by a shallow weathered-fractured rock aquifer comprising of the glacial and deltaic sediments of the Karoo Supergroup, while the deeper historically confined fractured bedrock aquifer consist predominantly of quartzite with subordinate lava, shale and conglomerate of the Witwatersrand Supergroup. The deep Witwatersrand aquifer has been actively dewatered for the last 60 years, with a peak rate of 60 Ml per day in the mid late 1960s. Modelling the impacts of mine dewatering and flooding on a regional scale as for the Evander basin, entails challenges like the appropriate discretisation of mine voids  and  the  accurate  modelling  of  layered  aquifer  systems  with  different  free  groundwater surfaces on a regional scale. To predict the environmental impacts of both the historic and future deep mining operations at Shaft 6, the detailed conceptual model of the aquifer systems and three- dimensional model of the mine voids were incorporated into a numerical groundwater model to simulate the dewatering and post-closure rebound of the water tables for the basin. The presented model could serve as an example for the successful modelling of mine dewatering and flooding scenarios for other parts of the Witwatersrand basin.

Abstract

The determination of a sustainable groundwater yield is a complex and challenging task. There is a high degree of uncertainty associated with most aquifer parameters such as recharge from rainfall and aquifer storativity, especially in  fractured aquifers. This leads  to  analysts often taking a  very  conservative and  risk  adverse approach  in  determining  the  “sustainable” yield  for  boreholes.  The  problem  with  this  approach  is  that groundwater can be considered as impractical or not an option, due to the low and conservative yields. Potential well-fields also become too expensive to develop. The concept of sustainability does not only cater for the environment, but also for people (social) and the economy (business). A popular method to determine groundwater sustainability is the groundwater balance (also known as the groundwater budget) method. This method has come under scrutiny as it is proposed that capture zone method is a more conservative and technically correct approach. Two of the most important parameters in determining long-term borehole yield, namely recharge and storativity, are unknown and unknowable at the time of well-field development. At best, qualified guesses can be made with regard to these two parameters. This makes the capture method impractical as boreholes have to be drilled and tested first and capital spent before any planning can be done. 

In this paper, it was shown that the risk adverse approach in determining borehole yield will result in the most expensive groundwater development option. The principle of sustainability requires that environmental, social and economic considerations be taken into account. By following a risk adverse approach, which would be the most expensive, the principle of sustainability is violated and it cannot be claimed that the borehole yield is “sustainable”. Due  to  the  exponential relationship between  risk  and  cost,  a  no-risk  approach  would  be infinitely expensive. It was shown that due to the uncertainties, it is actually impossible to determine the sustainable yield of a borehole. The objective should rather be to develop a sustainable groundwater management plan. This can be achieved by following a systems management approach based on the minimum groundwater balance. The minimum groundwater balance approach makes use of, for example, hydro census data to determine a minimum groundwater balance for a system of aquifers based on recharge at a minimum level of assurance, for example lower 95th percentile, rather than making use of the mean annual precipitation (MAP). The potential effects of storativity are neglected at this stage. The systems management approach was applied on a case study to demonstrate the application where some risk was taken for a limited period of time while monitoring takes place. Proactive warning systems would alert decision-makers when to develop new aquifers which are predefined, based on the minimum groundwater balance method. The difference is that in the case of the risk adverse approach, should it come to light that the recommended abstraction rates were wrong in the sense that it is too low, the capital is spent and cannot be recovered. In the case of the systems approach, where slightly risky abstraction rates are recommended for a limited period of time, additional well- fields can be developed well in advance, before any negative environmental impacts can occur.

Abstract

With increasing focus on wasted expenditure within local government and recent media reports on the money spent on poor quality service, it is becoming progressively important for those in a position of engaging consultants, either for groundwater supply or environmental work, to have confidence in the company or person they have employed. This paper focuses on how to assess consultants  before   they   walk  through   the  door  based   on   qualifications,   CVs,   professional registrations and previous work experience. It goes through the project lifestyle, explaining in a non- technical fashion the different processes involved in a groundwater supply or groundwater contamination assessment and provide simple indicators of good practice that should be evident in the   consultant's   work.   Topics   covered   include   assessing   proposals,   gathering   background information, health and safety, appointing sub-contractors, data quality, the use of appropriate published procedural guidelines, the use of relevant quality guidelines and what deliverables should be provided. 

Abstract

The 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.

Abstract

Work 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.

Abstract

This study explores some of the principle issues associated with quantifying surface  water and groundwater interactions and the practical application of models in a data scarce region such as South Africa. The linkages between the various interdependent components of the water cycle are not well understood, especially in those regions that suffer problems of data scarcity, and there remain  urgent  requirements  for  regional  water  resource  assessments.  Hydrology  (both  surface water and groundwater hydrology) is a difficult science; it aims to represent highly variable and non- stationary processes which occur in catchment systems, many of which are unable to be measured at the scales of interest. The conceptual representations of these processes are translated into mathematical form in a model. Different process interpretations, together with different mathematical representations, result in the development of diverse model structures. These structural uncertainties are difficult to resolve due to the lack of relevant data. Further uncertainty is introduced  when  parameterising  a  model,  as  the  more  complex  the  model,  the  greater  the possibility that many different parameter sets within the model structure might give equally acceptable results when compared with observations. Incomplete and often flawed input data are then used to drive the models and generate quantitative information. Approximate implementations (model structures and parameter sets), driven by approximate input data, will necessarily produce approximate results. Most model developers aim to represent reality as far as possible, and as our understanding of hydrological processes has improved, models have tended to become more complex. Beven (2002) highlighted the need for a better philosophy toward modelling than just a more explicit representation of reality and argues that the true level of uncertainty in model predictions  is  not  widely  appreciated.  Model  testing  has  limited  power  as  it  is  difficult  to differentiate  between  the  uncertainties  within  different  model  structures,  different  sets  of alternative parameter values and in the input data used to run a model. A number of South African case studies are used to examine the types of data typically available and explore the extent to which a model is able to be validated considering the difficulty in differentiating between the various sources of uncertainty. While it is difficult to separate input data, parameter and structural uncertainty, the study found that it should be possible to at least partly identify the uncertainty by a careful examination of the evidence for specific processes compared with the conceptual structure of a specific model. While the lack of appropriate data means there will always be considerable uncertainty surrounding model validation, it can be argued that improved process understanding in an environment can be used to validate model outcomes to a degree, by assessing whether a model is getting the right results for the right reasons.

Abstract

The 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.

Abstract

Limestones  and  dolomites  form  an  important  aquifer  system  in  Zambia.  The  municipal  water supplies for Lusaka and several population centres on the Copperbelt all depend on the carbonates for a substantial proportion of their water supply. Currently 155,912 ha of land are irrigated in Zambia, which is about 30 percent of the economical irrigation potential. Development of large scale irrigation schemes from carbonate rock aquifers proves to be a viable groundwater resource in Zambia.

The Katanga carbonate rock aquifers are considered to have good groundwater potential, with high yielding anomalies of up to 60l/s common in certain areas of the country. A phased approach was adopted  to   characterise   the   Katanga   Carbonates   by  means  of  quantifying   the  volume  of groundwater available for abstraction within the geological boundaries. The first phases included geophysical surveys (mainly electrical resistivity and magnetic methods), exploration drilling and aquifer   testing.   Later   phases   included   the   drilling   of   production   boreholes   and   wellfield development. 

Lessons learned during the exploration included the identification of high yielding drilling targets and the role of anomaly frequency in target selection. Further development of the Katanga aquifers for production provided challenges regarding production borehole construction and design. The feasibility of the optimum  design of  production  boreholes versus  the  initial capital  cost of the development of these carbonates proved to be an important consideration in this regard.

Abstract

A 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.

Abstract

The 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.

Abstract

In recent years there is an increased awareness of hydrocarbon contamination in South Africa, and the need for remediating sites affected by these contaminants. Hydrocarbon contamination of groundwater can be caused by a large variety of activities at industrial, mining or residential areas. Once these contaminants are discovered in groundwater where it poses risks to human health and/or the environment, remediation is often required. Remediation of groundwater has become a booming industry for groundwater practitioners and often there is an attitude of more sophisticated and expensive solutions are better. This paper will show that this attitude is not always the best solution, but rather recommend an approach where a combination of low cost/low maintenance system need to be investigated and applied to reach clean-up goals. Determination of natural attenuation potential and on-going monitoring forms an integral part of this type of solution.

Abstract

The 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.

Abstract

The 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.

Abstract

The aquifer vulnerability of the Molototsi (B81G) and Middle Letaba (B82D) quaternary catchments was assessed to determine the influence of the vadose zone on the groundwater regime. The aquifer vulnerability was assessed by developing a new method, which evaluates the vadose zone as a pathway for pollutants by using the following four parameters: Recharge, Depth to water table, Soil type (saturated vertical hydraulic conductivity) and Slope (RDSS). Recharge was estimated using the Chloride-mass balance method and the depth to the water table was measured in the field using dipmeter. The seepage behaviour (soil type) was determined as hydraulic conductivity from in situ infiltration and percolation testing (SABS 0252-2:1993 and double ring infiltrometer). The slopes were determined with the digital elevation method using ArcGIS software. The four parameters were overlaid using Weighted Sum, Weighted Overlay and Raster Calculator to produce the vulnerability map. Different weightings were attributed in the methods and the best selected. The results obtained indicated high vulnerability on the lower and upper parts of both catchments. Aquifers in areas which showed high vulnerability are at high risk of contamination. The benefits of the  method  described  are  (a) the  easy  quantification  of  the  parameters  through  fairly  simple methods and (b) the exclusion of arbitrary index values.

Abstract

Southern Africa hosts over 93% of the continent's energy, which has been conserved in coal seams deposited  in  various  Karoo  age  sedimentary  basins.  Carbon  dioxide  geological  storage  (CGS)  is proving  to  be  an  emerging  greenhouse  gas  technology  (GHGT),  that  global  governments  have elected to mitigate the projected coal use in Southern Africa. One of the major challenges of successfully introducing CGS to the public and world leaders is the significant risk the technology poses to groundwater resources. Lack of public confidence is further coupled by the poor knowledge of the subsurface behaviour of injected media, such as CO2, in South African potential lithological reservoirs. The study has utilised data from a current MSc research, in which the Springbok Flats Coal Basin (SFCB) has been used as the problem set-up. The aim of this study is to determine which FELOW™ mesh  geometry would  be  the most  suitable  to  simulate  a  CO2   ingress plume within  a regional aquifer. The study has utilised principals of dense vegetation zones (DVZ) and density- variable fluid flow (DVFF) when simulating the ingression. The specific objective is to utilise the simulation  results  to  guide  amendments  of  water  legislature,  towards  accommodating  CO2 geological  injection  and  storage operations.  Results indicate  that  a  combination  of  high-quality triangular meshes of various geometries, created with the FEFLOW compatible mesh generator, TRIANGLE, produced the best 3D model and simulation results. The basic matrice unit for the DTZ was defined as a quad mesh composed of two right-angled triangles and one equi-angualar triangle (five nodes), while the unit for modelling springs was defined as a quad mesh with four-equi-angular triangles, both used in various scales. The results were used to amend the Stream Flow Reduction Activities (SFRA) policy and thus the aquifer licensing procedure of the National Water Act, in order to accommodate the allocation of aquifer use licenses for CO2  geological storage operations. The amendments illustrate the significance of finite element simulation codes for integrated water resources management policy.

Abstract

Flowing 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.

Abstract

POSTER Electrical Resistivity Tomography (ERT) surveys were conducted in the Kruger National park (KNP) as part of a recent Water Research Commission project (titled: Surface water, groundwater and vadose zone interactions in selected pristine catchments in the Kruger National Park). The surveys were carried out in a pristine ephemeral third-order supersite catchment, namely the southern granite (Stevenson Hamilton). This supersite is representative of the southern granite region of KNP as it covers part of the dominant geology, rainfall gradient and dominant land system.

Electrical   resistivity   profiling   provided   valuable   data   on   the   subsurface  geological   material distribution and results depended on soil/rock properties, water content and salinity. The purpose of electrical surveys was to characterise the hydrogeological components of weathering and depth to water level using the subsurface resistivity distribution. The ground resistivity is related to various geological parameters such as the mineral and fluid content, porosity and degree of water saturation in the rock.

Based on the initial ERT survey interpretations, boreholes were drilled providing actual subsurface results in the form of borehole drilling logs, water levels, hydraulic data and in situ groundwater quality  parameters.  Integrating  the  ERT  survey  data  with  the  results  from  the  intrusive  survey enabled an updated conceptualisation of groundwater flow characteristics and distribution across the southern granite supersite.

Abstract

The 11 coal-bearing zones currently being mined at Exarro's Grootegeluk mine, discard intraburden onto discard dumps. During mining operations the open pit will be backfilled with plant discards, overburden and interburden on completion of mining. The plant waste will be covered with overburden  and  topsoil.  Intraburden  spoils  consist  of  sandstone,  mudstone  and  shale  rich  in minerals such as pyrite and siderite. These intraburden spoils thus have the capacity to generate acid when exposed to the appropriate conditions. The oxidation of iron sulphides (Pyrite (FeS2)), present within the discard dumps and stockpiles, can influence the hydrochemistry by generating acid-mine drainage, while siderite (FeCO3) can have a basic effect to the immediate surroundings. Acid-base- accounting done on samples gathered from different boreholes in the Waterberg coalfield helped to determine lithological units that can generate acid, with specific regard to the interburden removed and placed on the discard dumps, the interburden used in the pit as backfill, and the acid generation possibility from coal seams in stock piles. This indicated the zones that are more prone to acid- and base-producing potentials. Mineralogical investigations with X-ray diffraction and X-ray fluorescence gave a better record of minerals and elements present in trace amounts within interburden zones that could also have additional problems during storage and use. The areas that possess the highest risk regarding acid generation are the zones enriched in pyrite, as well as the coal seams from stock piles. The management plan for the acid generating spoils of the area has two possibilities: Firstly where acid producing potentials are higher, spoils should not be used where it will be exposed to oxygen and water for long periods of time, as the amount of acid generated cannot be controlled. A second option would entail the immediate compaction and flooding of the mined area so that the amount of acid produced would be controlled and limited.

Abstract

In 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.

Abstract

The 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.

Abstract

Acid-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.

Abstract

The aim of this study was to determine the geohydrological status of the aquifer within the boundaries of the Vanrhynsdorp Water User Association with emphasis on the central catchment, E33F. This will assist the Department of Water Affairs with the introduction of compulsory groundwater-use licensing and empowerment of the Vanrhynsdorp Water User Association to manage the resource. In this study emphasis was given to the determination of the water balance and  groundwater  reserve  of  the  central  catchment  and  the  designing  of  a  representative groundwater monitoring network. A literature study of five projects conducted since 1978 was done. Comparisons were made between the data and results of these studies. All the historical data from these studies, as well as the data from the current monitoring programme up until December 2012, were put together and analysed. A conceptual model and groundwater reserve determination, as well as a representative monitoring network, were produced. The study showed a general decline in groundwater levels over a 34-year period. It also showed an increase in rainfall over the last 20 years. Based on the reserve determination and the declining groundwater level in spite of increased rainfall and thus recharge, it was concluded that over-abstraction of groundwater in the study area is taking place. It is recommended that compulsory licensing should be put in place as soon as possible and  that  no  additional  groundwater-use  licences  should  be  granted  in  the  study  area.  The installation  of  flow  meters  on  all  production  boreholes  should  be  stipulated  in  the  licensing condition. This will assist the monitoring and regulation of groundwater abstraction volumes.

Abstract

Ladismith was established in 1851 where freshwater discharge from the Klein Swartberg Mountains. Growth of the town required building of the Goewerments Dam in 1920 and the Jan F le Grange Dam in 1978. However, water demand now matches supply, and water shortages are being experienced. Poor management and recent droughts exacerbated the situation. A project was initiated to address shortcomings with the existing supply and identify additional sources of water. Groundwater is an obvious option, with the regionally extensive Cango Fault located directly north of  the  town.  The  west-east  trending  fault  juxtaposes  highly  productive  Table  Mountain  Group Aquifers with less productive argillaceous rocks of the lower Witteberg Group. The Alluvial Aquifer is also a target, with a recently drilled DWA monitoring borehole reported to be high-yielding. Drilling and testing of three exploration boreholes drilled into the fault, returned lower than expected borehole  yields,  but  still sufficient  to  contribute  to  the  town’s water  supply  and  merit  further exploration. Boreholes drilled north of Ladismith could be used to increase the existing water supply by 50%.

Abstract

Unconventional 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

Abstract

Groundwater  is  a  reliable  freshwater  resource.  Its  location   underground  prevents  it  from evaporative  forces.  Thus  it  serves  as  storage  of  most  of  the  world’s  liquid  fresh  water.  Being enclosed in the ground it is not also easily contaminated. Since groundwater can be used wherever it exists without costly treatments, there is over-dependence on the resource. Though in the past it was mainly used by rural dwellers for domestic water supply, presently, due to effects of climate change on surface water resources, pressures of population growth leading to expansion of towns and cities, groundwater is also supplied for agriculture and industrial purposes. But, the resulting effect from these additional users is the vulnerability of groundwater resources to reduction and pollution. Its importance in sustaining livelihood and development has been highly credited and its management  is  looked  upon  as  a  prerogative.  To  enhance  groundwater  management  in  the Sandveld, a qualitative content analysis approach was used to evaluate six factors considered to be highly needed in groundwater management. This background was used to find out how institutional arrangement in South Africa facilitates or constraints groundwater management in the Sandveld, a highly groundwater dependent area in the West Coast of the Western Cape. The results showed that all  six  factors  are  present,  but  three  facilitate  groundwater  management  while  three  others constrain management. The community involvement which ranked first, is deficient. Thus, institutional weaknesses that need to be strengthened have been identified.

Abstract

Currently limited progress is made in South Africa (and Africa) on the protection of groundwater quality. To achieve the objective of water for growth and development and to provide socio- economic and environmental benefits of communities using groundwater, significant aquifers and well-fields must be adequately protected. Groundwater protection zoning is seen as an important step in this regard. Till today, only one case study of groundwater protection zoning exists in Africa. Protection zone delineation can be done using published reports and database data. However, due to the complexity of the fractured rock at the research site, more data are required. This data can be collected by conducting a hydro census and through aquifer tests. An inventory of the activities that can potentially impact water quality was done and aquifer characteristics such as transmissivity and hydraulic conductivity were determined through various types of aquifer testing. Fracture positions were identified using fluid-logging and fracture flow rates were also measured using fluid-logging data. A conceptual model and basic 3D numerical model were created to try to understand groundwater movement at the research site. The improved information will be used to build a more detailed numerical model and implement a trustworthy groundwater protection plan, using protection zoning. The expected results will have applicability to groundwater management in general. The protection plan developed during this project can be used as case study to update and improve policy implementation.

Abstract

Abstract

POSTER A quick analysis of spring water quality was conducted in four neighbouring villages, namely Vondo, Matondoni, Maranzhe and Murangoni in Thohoyandou town under the Thulamela Local Municipality (TLM) of the Vhembe District Municipality (VDM). For the purposes of this study these villages will be termed VMMM villages. A study on the spring water quality of VMMM villages was conducted by the CSIR to determine whether the natural quality state of the spring water used by the surrounding communities was suitable for drinking purposes without pre-treatment. From the four springs that were identified in the VMMM villages, namely Tshali (S1), Ramufhufhi (S2), Tshinwela (S3) and Tshivhase (S4), water samples were taken for the quality analyses in the laboratory. The results indicated that S2 and S4 had a high coliform count of 35 and 600 per 100 ml, respectively), that is above  10  counts  per  100 ml.  In  springs  S2  and  S4  the  total  coliform  count  also  displayed  the presence of E.coli (6 and 310 per millilitre, respectively)  – E.coli should not be detected at all according to SANS standard limits (2011). While all other parameters were within standard limits (SANS 241, 2011), it was also interesting to note that both S3 and S4 had a problem of high turbidity (1, 6 and 105 NTU, respectively) compared to 1 NTU which is the standard limit (SANS 241, 2011). These results showed that although these communities relied on groundwater in the form of springs for drinking purposes, unmonitored use of these resources may be a health hazard that has a potential to  result  in disease outbreak  and  unprecedented  deaths. While  groundwater through springs is considered natural, increased activity around the source due to human activity and interference by domestic animals, these sources may be rendered unsafe for drinking purposes without prior treatment. Therefore, there is need for local authorities to put measures in place to monitor water resources considered indigenous and traditional to the communities, especially in areas where these resources have become the main source of water supply for drinking purposes.

Abstract

Characterisation of fracture positions is important when dealing with groundwater monitoring, protection and management. Fractures are often good conduits for water and contaminants, leading to  high  flow  velocities  and  the  fast  spread  of  contaminants  in  these  conduits.  Best  practice guidelines related to groundwater sampling suggest that specific depth sampling with specialised bailers or low flow purging are the preferred methodologies to characterise a pollution source. These methods require knowledge about the fracture positions and, more importantly, flow zones in the boreholes. Down-the-hole geophysical and flow logging are expensive, complicated and time consuming. Not all fracture zones identified with geophysical logging seem to contribute to flow through   the   borehole.   An   efficient   and   cost-effective   methodology   is   required   for   the characterisation of position and flow in individual fractures. This research reviewed the use of Fluid Electrical Conductivity (FEC) logging to assist with the development of a monitoring protocol. FEC logging  proved  to  be  beneficial  as  it  provided  individual  fracture  positions,  fracture  yields  and vertical groundwater flow directions. FEC logging proved to be fast, cost-effective and practical in deep boreholes. The technique allows the development of a site-specific sampling protocol. The information so obtained assists with the identification of the appropriate sampling depths during monitoring.

Abstract

Accurate parameter estimation for fractured-rock aquifers is very challenging, due to the complexity of   fracture   connectivity,   particularly   when   it   comes   to   artesian   flow   systems   where   the potentiometric  is  above  the  ground  level,  such  as  semi-confined,  partially  confined  and  weak confined aquifers in Table Mountain Group (TMG) Aquifer. The parameter estimates of these types of aquifers are largely made through constant-head and recovery test methods. However, such tests are seldom carried out in the Table Mountain Group Aquifer in South Africa due to the lack of a proper testing unit made available for data capturing and an appropriate method for data interpretation. 

An artesian borehole of BH-1 drilled in TMG Peninsula Formation on the Gevonden farm in Western Cape Province was chosen as a case study. The potentiometric surface is above the ground level in the rainy season, while it drops to below ground level during the dry season. A special testing unit was designed and implemented in BH-1 to measure and record the flow rate during the free-flowing period, and the pressure changes during the recovery period. All the data were captured at a function of time for data interpretation at later stage. 

Curve-fitting software developed with VBA (Visual Basic Application) in Excel was adopted for parameter estimation based on the constant-head and recovery tests theories. The results indicate that a negative skin zone exists in the immediate vicinity of the artesian borehole in Rawsonville, and the  hydraulic  parameters  estimates  of  transmissivity  (T)  ranging  from  6.9  to  14.7 m2/d  and storativity  (S)  ranging  from  2.1×10-5   to  2.1×10-4   appear  to  be  reasonable  with  measured  data collected from early times. The effective radius is estimated to be 0.5 to 1.58 m. However, due to formation losses, the analytical method failed to interpret the data collected at later times. Consequently the analysed results by analytical solution with later stage data are less reliable for this case. Numerical modelling is proposed to address the issue in future.

Abstract

Gold 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.

Abstract

POSTER Hydraulic fracturing, also known as hydrofracking or fracking, is being engaged in the Karoo region of South Africa in order to enhance energy supplies and improve the economic sector. It will also lead to independence in terms of reduced amount of imports for fuel due to an estimated 13.7 trillion cubic metres of technically recoverable shale-gas reserves in South Africa. 

Fracking is an extraction technique used with the purpose of having access to alternative natural methane gas, which is interbedded in shale deposits deep under the surface of the earth. In this process boreholes are drilled horizontally into shale formations to cover a larger area in the shale and  subsequently  attain  more  natural  gas.  After  these  horizontal  boreholes  are  drilled,  large volumes of water, mixed with chemicals and sand, are pumped into these boreholes under a very high pressure, forcing the natural gas out. This water mixture is referred to as the fracking fluid. Water is the main component in the fracking fluid and the water used for the fluid reaches volumes up to 30 million litres per borehole.

The aim of this study is to present a baseline study of the area and its water resources to ultimately facilitate in resolving the actual impact hydraulic fracturing will have in the area, using a simulation model which will predict the migration of the fracking fluid in the subsurface. In this model, the chemistry of  the fracking fluid  will  be  included  to determine  the impact  it might  have  on the groundwater quality in the area

Abstract

The 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.

Abstract

Artesian 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.

Abstract

The 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.

Abstract

Abstract

The  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.

Abstract

POSTER 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).