Conference Abstracts

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

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

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

Only 40% of all the available groundwater resources are developed in South Africa and the development of surface water are becoming more costly and challenging. The Minister of Water and Environmental Affairs acknowledge this and identified the need to increase the use of groundwater as one of the interventions to address the increasing water requirement of towns and communities. Over the last seven years the Department of Water Affairs developed many reconciliation strategies for the area of water management, the big metro municipalities and for the smaller towns and villages in South Africa. The reconciliation strategies entails, among other things, sustainable ways to source additional water supplies for the selected towns/metro’s or villages. 

Groundwater played a major role in the recommended interventions. The challenges are now the implementation of the groundwater schemes and sustainable management of the groundwater resources. Or differently put: the balancing act between selling of groundwater and the prevention of over-abstraction. The bankability of regional schemes, the credibility of groundwater as a bulk scheme source, poor management of boreholes/well-fields, institutional responsibility, acceptable quality and treatment of groundwater, still challenge the use of groundwater development. Groundwater need to play its role in addressing the future water needs of South Africa, or can it?

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

The concept of the ‘Groundwater Reserve’ is enshrined in the National Water Act that stipulates that a classification of all significant water resources must be undertaken and the Reserve requirements be determined and gazetted. The Reserve covers two different aspects, the Ecological Reserve to protect the water dependent ecosystems and the Basic Human Needs (BHN) Reserve to ensure that all people who depend on that water resource have sufficient water for their livelihood. The approach for determining and implementing the Reserve that was developed for surface water resources was adopted for groundwater resources as provided for in the Groundwater Resource Directed  Measures  (GRDM)  Manual,  inter  alia.  However,  there  is  no  separate  ‘Groundwater Reserve’, but rather a groundwater component of, or contribution to, the ecological Reserve and BHN. Hence, the implementation of this methodology often results in undesirable outcomes and is one of the inhibiting factors for sustainable groundwater development, as some of the aspects and methods are not applicable to groundwater and not appropriate for implementation. The current separation of the ‘Groundwater Reserve’ determination process from the ecological Reserve determination emphasises this pitfall of the process and methodology. This paper provides a critical review of the current concept of the ‘Groundwater Reserve’ and its implementation based on several case studies. It concludes  with recommended changes to the standard methodology and a possible way forward for developing an appropriate methodology for addressing and protecting the groundwater contribution to both the ecological and BHN Reserve.

Abstract

The article presents the application of a water balance model as a preliminary tool for investigating groundwater–surface water (GW–SW) interactions along an alluvial channel aquifer located in a semi-arid climate in the central province of South Africa. The model is developed based on the conservation of mass; solute and stable isotopic mixing of the model components. Discharge measurements were made for the river segment inflow and outflow components using stream velocity-area technique. The Darcy equation was used to calculate the groundwater discharge from the alluvial channel aquifer into the river segment. Electrical conductivity (EC) and δ2H isotope were measured for the inflow and outflow components of the model as indicators of solute and stable isotopic ratios. Measurements were conducted during a low river flow once-off period in October 2011, thus offering a great opportunity to assess GW–SW exchanges when other potential contributors can be regarded as negligible. The model net balance shows that the river interval is effectively losing water. The mass and solute balance approach provided close to a unique solution of the rate of water loss from the model. The model outcome provides a platform from which to develop appropriate plans for detailed field GW–SW interaction investigations to identify the mechanism through which the river is losing water.

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

Edible vegetable oil (EVO) substrates have been successfully used to stimulate the in situ anaerobic biodegradation of groundwater contaminated with chlorinated solvents, as well as numerous other anaerobically biodegradable contaminants like nitrates and perchlorates at many commercial, industrial and military sites throughout the world. EVO substrates are classified as a slow release fluid substrate, and comprise of food-grade vegetable oil such as canola or soya bean oil. The EVO substrate serves as an easily biodegradable source of carbon (energy) used to create a geochemically favourable environment for the anaerobic microbial communities to degrade specific contaminants of concern. EVO substrate’s can either be introduced into the subsurface environment as pure oil, in the form of light non-aqueous phase or as an oil/water emulsion. The emulsified vegetable oil substrates has several benefits over non-emulsified vegetable oil as the fine oil droplet size of the commercially manufactured emulsified oils can more easily penetrate the heterogeneous pore and fracture spaces of the aquifer matrix. The use of this technology to stimulate in situ biodegradation of groundwater contaminants is still relatively unknown in South Africa. This paper gives an overview of  the  EVO  technology  and  its  application,  specifically  looking  at  the  advantages  of  using  this relatively inexpensive, environmentally-friendly based technology to remediate contaminated groundwater within fractured rock environments commonly encountered in South Africa.

Abstract

Groundwater in South Africa is an essential source of potable water for rural communities, farms and towns. Semi-arid conditions of South Africa, a growing population and surface water resources almost entirely being exploited to their limits, increase  the demand for groundwater resources. Therefore,  the  relation  between  the  geology  and  geohydrology  of  South  Africa  becomes  an important tool in locating groundwater resources that can provide sustainable quantities of water for South Africans. A document was therefore compiled, providing valuable geohydrological information  on  the  geological  formations  of  the  whole  of  South  Africa.  The  information  was gathered by means of interviews with experienced South African geohydrologists and reviewing of reports and articles of geohydrological studies. The geohydrological characteristics discussed include rock/aquifer parameters and behaviour, aquifer types (primary of secondary), groundwater quality, borehole yields and expected striking depths, and geological target features and the geophysical method  used  to  locate  these  targets.  Due  to  the  fact  that  90%  of  South  Africa’s  aquifers  are classified as secondary aquifer systems, groundwater occurrence within the rocks of South Africa is mainly controlled by secondary fractured systems; therefore, understanding the geology and geological processes (faulting, folding, intrusive dyke/sills and weathering) responsible for their development and how they relate, is important. However, the primary aquifers of South Africa (Coastal Cenozoic Deposits) should not be neglected as these aquifers can produce significant amounts of groundwater. Drilling success rates and possibility of striking higher yielding boreholes can be improved dramatically when an evaluation of the structural geology and geohydrological conditions of an area together with a suitable geophysical method is applied. The ability to locate groundwater has been originally considered (even today) a heavenly gift and can be dated back to the Biblical story of Moses striking the rock to get water: “behold, I will stand there before thee there upon the rocks thou shalt smite the rock and there shall come water out of it” (Exodus 17:6).

Abstract

When the South African Government in 1998 re-demarcated its 283 municipalities in such a manner that they now completely cover the country in a “wall-to-wall” manner (Section 21), their main focus was on facilitation of effective and sustainable developmental municipal management; in other words, the improvement of basic municipal services such as formalised municipal basic services (for example, safe potable water, effective refuse removal and environmental health) to all the residents of the new geographical areas consisting of millions of citizens who previously might have been neglected. Unfortunately, it seems like topographical, physical and environmental characteristics of all the resulting municipal areas have been negated in this important demarcation process. Fuggle and Rabie (2005:315) are of the opinion that this can lead to ineffective, inefficient and non- economical municipal management of basic services.

By means of a literature review as well as the use and study of geographical tools such as maps, ortho-photos and information data bases, and field visits, the bare essential geographical and geo- hydrological aspects of importance for the municipal service providers and managers in the Lindley area have been identified. From this research and various other obvious reasons (for example, deteriorating physical environment due to pollution, sub-standard storm water and sewage management, and migration [informal settlements] and increasing sophisticated needs of municipal residents), the presenters of this paper want to state  that the quest for improved cooperative governance in the developing South Africa, and especially in the case of the Lindley town’s geographical area of responsibility, must be facilitated according to the DWA identified surface water catchment regions.

In conclusion, the presenters will recommend adherence to the following requirements as essential:

•  An  environmental,  holistical  and  integrated  management  (IWRM)  approach  by  all  the involved and committed role-players, researchers and stakeholders must be adopted in the whole Vals River catchment.
• Effective co-operative governance must be facilitated and maintained.
• Basic hydrological, geo-hydrological and engineering geology knowledge and skills must be identified,  obtained,  modified  into  layman  language  and  incorporated  in  the  afore- mentioned approaches.

Abstract

The colliery is situated in the Vereeniging–Sasolburg Coalfield, immediately southwest of Sasolburg in the Republic of South Africa. The stratigraphy of this coal field is typical of the coal-bearing strata of the Karoo Sequence. The succession consists of pre-Karoo rocks (dolomites of the Chuniespoort Group of the Transvaal Sequence) overlain by the Dwyka Formation, followed by the Ecca Group sediments, of which the Vryheid Formation is the coal-bearing horizon. Mainly the lava of the Ventersdorp and Hekpoort Groups underlie the coal. The Karoo Formation is present over the whole area and consists mainly of sandstone, shale and coal of varying thickness.

The underground mine was flooded after mining was ceased at the colliery in 2004. The colliery is in the fortunate position that it has a very complete and concise monitoring programme in place and over 200 boreholes were drilled in and around the mine throughout the life of the mine. To stabilise mine workings located beneath main roads in the area, an ashfilling project was undertaken by the colliery since 1999. A key issue is if the mine will eventually decant, and what the quality of the water will be. This is important for the future planning of the company, as this will determine if a water treatment plant is necessary, and what the specifications for such a plant will be, if needed. Therefore it was decided to do a down-the-hole chemical profile of each available and accessible borehole with a multi- parameter probe with the aim of observing any visible stratification. Ninety-four boreholes were accessible and chemical profiles were created of them.

From the data collected a three-dimensional image was created from the electrical conductivity values at different depths to see if any stratification was visible in the shallow aquifer.  The ash-filling operations disturbed the normal aquifer conditions, and this created different pressures than normally expected at a deeper underground  colliery.  From  the  three-dimensional  image  created  it  was  observed  that  no stratification was visible in the shallow aquifer, which lead to the conclusion that in the event that if decant should occur, the water quality of the decanting water will still be of very good quality unless external factors such as ash-filling activities are introduced. It is not often that it is possible to create chemical profiles of such a large number of boreholes for a single colliery and as a result a very complete and informative three-dimensional electrical conductivity image was created. This image is very helpful in aiding the decision-making process in the future management of the colliery and eventually obtaining a closure certificate, and also to determine whether ash-filling is a viable option in discarding the ash.

Abstract

This study, near Thyspunt between St. Francis and Oyster Bay in the Eastern Cape Province of South Africa, focused on identification and quantification of surface water–groundwater links between the mobile Oyster Bay dune field and the coast. The specific objective was to establish the extent to which important wetlands such as the Langefonteinvlei and the numerous coastal seeps along the coast are directly or indirectly dependent on groundwater as their main water source. A further objective was to establish the extent to which any of the coastal seeps derive their water from the Langefonteinvlei, and are thus interdependent on the integrity of this system. The study also investigated the contribution of the Algoa and Table Mountain Group aquifers to these wetlands. The   monitoring   network   established   as   part   of   this   study   focused   on   unpacking   the interrelationships between surface and groundwater flows, aquifer hydrochemistry and wetland function, as related to the Langefonteinvlei and the coastal seeps in particular. Results indicate that the Langefonteinvlei is fed by groundwater flowing from the mobile Oyster Bay dune field in the north and the water divide in the northeast, which emerges at the foot of the high dune in the north and northeast of the wetland. However, the majority of the vlei area is ‘perched’ above the local water table on a layer of organic-rich sediment. The coastal springs located southwest and west of the Langefonteinvlei are not fed by water from the Langefonteinvlei. They emerge near the coast, where the bedrock lies close to the surface, and are fed by groundwater draining directly from the Algoa and Table Mountain Group aquifers to the Indian Ocean.

Abstract

Historically groundwater exploration consisted of reconnaissance geophysical surveys followed by detail ground surveys. Where no potentially water-bearing geological structures are shown on geological maps and aerial photos, the project area would be divided into a grid on which the ground geophysical survey would be done. This type of exploration is time-consuming and expensive. In some cases the terrain or cultural noise prohibits the use of conventional geophysical methods, with only more expensive and time-consuming methods being left as an option. This is where the high resolution airborne magnetic survey excels. The results obtained from this type of survey are of such a nature that ground geophysical surveys are only performed where potential drilling targets were identified  from  the  aerial  survey.  Not  only  can  there  be  cost-  and  time-savings  on  ground geophysical surveys, but drilling of dry boreholes can be limited, which makes up the largest cost component of a groundwater exploration project. This paper will discuss successes achieved using high resolution aeromagnetic surveys as the basis for groundwater exploration in traditionally low- yielding igneous geology.

Abstract

National legislation is the outcome of processes, locally, provincial and nationally. Certain aspects of water management have first been the product of legal initiatives of the South African government, seeking  to  address  local  problems.  As  a  result,  the  National  Water  Act,  36  of  1998,  was promulgated. The Act is in line with the Constitution of the Republic of South Africa, 108 of 1996, which embrace human rights. The Water Services Act, 108 of 1997, regulates the accessibility of water and sanitation by domestic users. Groundwater, in many parts of South Africa, provides the sole  and/or  partial  water  supply  for  meeting  basic  human  needs.  With  an  increase  in  the dependency on groundwater usage, the need to properly and effectively protect, use, develop, conserve,  manage  and  control  groundwater  resources  has  become  a  national  priority  by  the custodian of all water resources: the National Department of Water Affairs. The question arises whether  or  not  the  current  groundwater  allocation  decision-making tools  are  enough  to  make informed  decisions  regarding  the  final  approval,  or  not,  of  groundwater  use  licenses,  and whether  a  proper  framework  that  includes  guidelines  together  with  licensing  conditions  are available  for  decision- making   in   complex  groundwater   scenario   situations   as   part   of   the groundwater license decision process. The current research contributes to answering this question and finding solutions in order to improve and make the groundwater use authorisation process more  effective.  The  groundwater  situation  will  be  discussed  on  a  comparative  basis  from international case studies regarding water legislation and groundwater resource management tools. A full evaluation and analysis of groundwater use authorisation process and decision-making tools on  regional and  national level  in  South  Africa will be done  and a Framework and tool for the evaluation, decision-making and determination of authorisation conditions of groundwater use authorisations, which includes existing lawful water use, general authorisations, and groundwater use licensing, will be developed. Scenarios and case studies are currently implemented.

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

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

The benefits of numerical groundwater modelling in resource management and scenario-testing are well known; it provides quantitative predictions of aquifer responses to stresses not yet experienced, albeit with uncertainties. Modelling is hence a widely used tool in Environmental Impact Assessment (EIA), in which prior to project commencing, the likely impacts must be assessed quantitatively to determine their significance. Based on these results mitigation measures can be proposed such that the residual impact is deemed acceptable.

At the stage of an EIA there is often very little data on which to base a model. Generally one is required to predict timescales in the order of hundreds of years with only very short-term time series data, and required to predict the response to stresses far beyond those used in the calibration. The very nature of the problems posed at EIA stage therefore render the accuracy of most modelling conducted at EIA phase severely limited. Recognising this, an appropriate model for the problems at hand can still be constructed and provide useful results.

The model results need to  be seen  as  the first phase  in  an  adaptive management cycle, rather than  a standalone prediction which a mine can use for future operation. To strengthen the resulting predictions, the cycle in which monitoring results are used to update the model, and thus update predictions and update future requirements for monitoring repeating the cycle, needs to be entrenched into the mine phases by ensuring the recommendation as detailed in the Environmental Management Plan. Thus, what started as a useful demonstrative tool, but with large uncertainties, becomes an accurate quantitative prediction tool for operation, closure and post-closure planning.

This paper outlines a case study of a proposed open-pit zinc mine on an inselberg in South Africa, within which these themes are explored. Limited initial data was sufficient to build a useful yet simplified model. The purpose and known limitations of the model approach dictated the spatial discretisation of the model, its dimensions, and the geometry of the aquifer units, yet the simplification of the aquifer systems into the numerical model was only feasible once the complexity of the aquifer systems had been recognised, else over- or unjustified simplification is a risk.

The paper concludes with a framework for integrating the adaptive groundwater management into the mine life cycle through applying appropriate models at each phase, which would strengthen the use of groundwater models in mining.

Abstract

Most of the 14 651 km2 Hwange National Park in Zimbabwe is on monotonous Aeolian sands of the Kalahari Basin, with endorheic drainage. The large game populations of the park are sustained by seasonal accumulations of water in grassy pan depressions and year-round supply of groundwater to pans (except in the northwest where there are rivers and dams). Some of this is from natural seeps, such as at the Shakwanki, Nehimba and Ngweshla Pans, but most are supplied from boreholes. Game animals show clear preferences for some pans over others and it has long been speculated by wildlife managers that there is a nutritional or taste basis for this discrimination. In this preliminary study, the location, host geology and sub-Kalahari lithologies of the pans are compared with the frequency of use by game animals. Results show that the pans that are most frequented by game are hosted in fossil drainage channels, with limestone horizons (calcrete) developed within the Kalahari Sands. Many popular pans are also found on Kalahari Sand overlying the granitic rocks and the meta- sedimentary Malaputese Formation of the Kamativi–Dete Inlier. This can be related to sodium and potassium enrichment.

Abstract

The Department of Water Affairs (DWA), Chief Directorate: Resource Directed Measures has developed guidelines over the past decade  in order  to  facilitate  proper implementation of the Groundwater   Resource   Directed   Measures   (GRDM)   (also   known   as   determination   of   the groundwater component of the Reserve). An intrinsic component of the GRDM is delineation of Integrated Units of Analysis (IUAs) from which the allocatable groundwater and surface water components are calculated, which essentially drives the allocation of water use licenses. Delineation typically follows a three-tiered approach, namely primary, secondary and tertiary level. Primary delineation is based on quaternary boundaries (considered to be the basic building block of the IUA); secondary follows geological, hydrogeological and hydrological boundaries, groundwater abstraction zones and baseflow contribution; and tertiary is dependent on management criteria. How then, do we undertake this challenging task of delineating IUAs to a level where it can be better managed and monitored? Complexities arise when hydrogeological data are scarce, hydrological and hydrogeological systems are not in sync, aquifers extend across a quaternary, water management area, provincial and administrative boundaries, surface water and groundwater interactions are not well understood, and legislation on protection of water resources differs greatly from one country to the next. Having undertaken delineation of IUAs in the Waterval Catchment (Upper Vaal WMA), Olifants WMA and Mvoti to Umzimkhulu WMA with the available datasets, the key criteria for the respective  WMAs  have  ultimately  been  management  class,  significant  aquifers,  groundwater– surface water interaction and groundwater stressed areas, and secondary catchment boundaries, followed by other hydrogeological, geological and management considerations.

Abstract

Evidence suggests that physical availability of groundwater may be only one of many factors in determining whether groundwater-based rural water supply schemes in South Africa are reliable or "sustainable". Other factors include budgetary constraints, community preferences, policy decisions, operation and maintenance procedures, and the availability of skilled staff. These factors and others combine to create "complex problems" around the issue of rural water supplies that require a multidisciplinary approach if they are to be effectively resolved. This work is an on-going part of Water Research Commission Project K5/2158, “Favourable Zone Identification for Groundwater Development: Options Analysis for Local Municipalities”, due to be completed in March 2014.

Abstract

The 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.

Abstract

Zimbabwe occupies a tectonically stable plateau underlain by ancient Precambrian crystalline basement rocks. These  form a central craton bounded by east-west trending mobile belts; the Zambezi mobile belt to the north and the Limpopo mobile belt to the south. Zimbabwe receives generally low and variable quantities of seasonal rainfall within a semi-arid to savannah type climate characterised by moderate to high temperatures. Evaporation commonly exceeds rainfall so that recharge to the thin near surface aquifers is generally low and in some years non-existent. The groundwater resources of the weathered and fractured basement aquifers that underlie more than 60% of the country are of limited potential, typically sufficient to supply the needs of small villages and cattle ranches. However, within the central plateau area of the African to Post-African erosion surfaces, the weathered and fractured basement may exceed 60 m in thickness. The thickness of this zone diminishes towards the main valley systems where subsequent cycles of erosion have stripped the weathered zone away, leaving only a shallow surface fractured zone that may only be 20-30 m thick. Groundwater resources have been developed extensively in Zimbabwe since the 1920s. During 1991/92 drought abstraction from urban boreholes within the southern Harare area caused yield decline and ultimate failure of numerous boreholes. It is now time to question the long-term viability of groundwater development within the basement aquifers in Zimbabwe given the uncertainty in groundwater resources, the complexities of the climate–groundwater interactions and the projected demands of a growing rural population.

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

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

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 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

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

The 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.

Abstract

This 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.

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

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

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 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

POSTER All groundwater is vulnerable to contamination, and natural in homogeneity in the physical environment results in certain areas being more vulnerable to contamination than others. Inherent in the agricultural, domestic and industrial sectors of Pietermaritzburg, is the generation of contaminants which, upon reaching the aquifer, result in the deterioration of the quality of groundwater, thus resulting in the water no longer being fit for its intended use. The DRASTIC method is used to calculate the groundwater vulnerability of a 670 km2 region, including the city of Pietermaritzburg. The suggested ratings of each parameter are scrutinised and adapted, according to their relevance to the region and according to known geological occurrences. The use of this method enables the user to generate a regional scale vulnerability map of the groundwater in Pietermaritzburg. The vulnerability map generated has the ability to effectively highlight vulnerable areas to groundwater contamination, which is of critical importance in correct land-use planning, as well as in indicating areas of particular concern, where further detailed investigations are needed. The results of such an assessment are used as an input, together with a contamination inventory to assess the potential risk of groundwater pollution in a groundwater risk map. Furthermore, the result informs local decision-makers and enables proactive prevention of groundwater pollution, in accordance with section 13 of the 1998 National Water Act. The intrinsic vulnerability of the Pietermaritzburg region was found to range from low to very high. The area found to be highly vulnerable is the region northeast of Springbank which requires investigation at a local scale.

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

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

The study on estimation of groundwater recharge was done in Grasslands Catchment, about 70 km south-east of Harare, Zimbabwe. The catchment is underlain by Archean Granitic rocks intruded by dolerite  dykes/sheets  and  form  part  of  the  Basement  Complex.  The  catchment  is  a  stream headwater wetland, at the source of Manyame River. The catchment comprises an upland region or interfluves of area 2.12 km2 and a dambo area of 1.21 km2. The study focused on the assessment of temporal and spatial variability of moisture fluxes based on solute profiling, and groundwater recharge and investigations of moisture transport mechanisms. The methodology involved the use of  both  hydrometric  and  hydrochemical  techniques.  Groundwater  recharge  rates  and  moisture fluxes were calculated using a chloride mass balance technique in comparison to the hydrograph separation technique. Groundwater recharge was estimated to be 185 mm/year using the chloride mass  balance  and  215 mm/year  using  the  hydrograph  separation  technique.  Mechanisms  of recharge were investigated using the bimodal flow model that comprised of diffuse flow and preferential flow. The results revealed that preferential flow contributes up to 95% of the recharge in the interfluves, whilst diffuse flow contributes up to 5% of the total recharge. The results reveal that the groundwater hydrograph technique results are in agreement with the chloride mass balance method. The study illustrated how routine observations can improve process understanding on groundwater recharge mechanisms. The techniques are not expensive, are easy to use and can be replicated elsewhere depending on availability of data.

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

Industrial  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.

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

Zachariashoek  catchment  was  one  of  the  study  areas  looking  into  the  hydrological characteristics  of winter rainfall catchments in the Western Cape. Nearly thirty years of historical data are available for the Zachariashoek area. This data include rainfall, gauge plate readings for the weirs, and water levels for the boreholes in the area. Numerous articles and reports had been written  about  the  research  done  in  the  area,  concentrating  mostly  on  the  effects  of  fire  on streamflow and vegetation. This article will look at patterns that can be observed from the data record and correlate the different data sets for the Zachariashoek sub‐catchment. It will use the data from the two weirs, three rain gauges and at least three of the boreholes that was drilled in this sub‐catchment.  The information gained from this comparison can then be used to evaluate possible future hydrological patterns and the interaction between the various components of the hydrological system.

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

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.