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

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

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

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

To date, South Africa has mined approximately 3.2 billion tons of coal from a number of different coal reserves located in various parts of the country. A large number of the mines have reached the end of their productive life, resulting in numerous mine closures. With closures, groundwater levels have rebounded, resulting in decant of mine water into the environment. This paper describes a case study of a closed underground coal mine, the rebound of water levels, the evolution of the groundwater quality and the impact it has had on the management of the potential decant.

On closure of the Ermelo Mines in 1992, initial water quality monitoring indicated that a water treatment plant would be required to treat the mine decant. However, as the groundwater levels in the mine rebounded, the water quality in the mine void evolved from sulphate type water to sodium type water. The evolution of the water quality can be attributed to sulphate reducing bacteria, vertical recharge from the hanging aquifer and stratification. Water level and quality monitoring have shown that the water in the old mine void will not decant to surface due to the depth of the mine void, hydrogeological conditions, a "hanging aquifer"  and the recharge mechanisms. As a result, no water treatment will be required and the mine will not impact on the surface water. The main applications from this paper are:

•  Design  of  a  correct  monitoring  procedure  to  allow  for  monitoring  of  water  quality stratification in rebounding mines.
•  Identifying the role of sulphate reducing bacteria in the evolution of groundwater quality in a methane rich coal mine void.
•  The role of a hanging aquifer in recharging of a coal mine void and resultant stratification. 
• Designing of a mine taking into consideration mine closure.

The main contribution of this paper is the use of hydrogeological information in design of a coal mine so as not to decant on closure.

Abstract

Inadequate characterisation of petroleum release sites often leads to the design and implementation of inappropriate remedial systems, which do not achieve the required remedial objectives or are inefficient in addressing the identified risk drivers, running for lengthy periods of time with little benefit. It has been recognised that high resolution site characterisation can provide the necessary level of information to allow for appropriate solutions to be implemented. Although the initial cost of characterisation is higher, the long-term costs can be substantially reduced and the remedial benefits far greater. The authors will discuss a case study site in the Karoo, South Africa, where ERM has utilised their fractured rock toolbox approach to conduct high resolution characterisation of a petroleum release incident to inform the most practical and appropriate remedial approach. The incident occurred when a leak from a subsurface petrol line caused the release of approximately 9 000 litres of fuel into the fractured sedimentary bedrock formation beneath the site. Methods of characterisation included: 

Surface  geological  mapping  of  regionally  observed  geological  outcrops  to  determine  the structural orientation of the underlying bedding planes and jointing systems. 

A surface electrical resistivity geophysics assessment for interpretation of underlying geological and hydrogeological structures. 

Installation of groundwater monitoring wells to delineate the extent of contamination. 

Diamond core drilling to obtain rock cores from the formation for assessment of structural characteristics and the presence of hydrocarbons by means of black light fluorescence screening and hydrocarbon detection dyes. 

Down-borehole geophysical profiling to determine fracture location, fracture density, fracture dip and joint orientation. 

Down-borehole deployment of Flexible Underground Technologies (FLUTe®) liners to determine the precise vertical location of light non-aqueous phase liquid (LNAPL) bearing joint systems and fracture zones, and to assist in determining the vertical extent of transmissive fractures zones.

ERM used the information obtained from the characterisation to compile a remedial action plan to identify suitable remedial strategies for mitigating the effects of the contamination and to target optimal areas of the site for pilot testing of the selected remedial methods. Following successful trials of a variety of methods for LNAPL removal, ERM selected the most appropriate and efficient technique for full-scale implementation.

Abstract

Open pit mining operations are located in various, usually complex, geological settings and equally variable climatic regions from arid to extremely high rainfall. Many Southern African open pit mines occur in competent and un-weathered rock masses, and groundwater flow is therefore structurally controlled. Assessing and reducing pit slope pore pressure should be incorporated into pit slope design. Site hydrogeological investigations followed by numerical groundwater modelling is completed to produce predicted pore pressure distributions over the life of a mine and to assess the potential effect of dewatering actions on slope stability. Investigations were completed for two Southern African pits and simulated pore pressure distributions were used in slope stability analysis. In the first case, the simulated slopes are shown to be free draining, and the designed pit slopes are predicted to remain safe and remain so even with the built-up of pore pressure. In the second instance, pore pressure reduction through an aggressive horizontal drill holes programme is demonstrated to improve probability of failure. This has demonstrated the need for collaboration between geotechnical and hydrogeological investigations to improve slope design, reduce likelihood of pit wall failures and reduce mining cost through excavating steeper depressurised slopes.

Abstract

PMWIN5.3 has been one of the most commonly used software for groundwater modelling because of its free source and the adoption of the popular core program MODFLOW. However, the fixed formats required for data input and lack of GIS data support have posted big challenges for groundwater modellers who are dealing with large areas with complicated hydrogeological conditions. In South Africa, most geological and hydrogeological data have been captured and stored in GIS format during various national research projects such as WR2005, NGA, etc. Therefore, a proper linkage between PMWIN and ArcGIS is expected to do the pre-processing for modelling in PMWIN. Visual Basic for Application (VBA) embedded in ArcGIS 9.3 was used to develop the linkage. Based on the conceptualisation of the study area, the model dimension, discretisation and many value-setting processes can be easily carried out in ArcGIS other than directly in PMWIN. Then the grid specification file and other input files can be exported as the PMWIN-compatible files. The functions on the modification of model geometrics have also been integrated with the toolbar. The linkage can be used with a higher version of PMWIN or ArcGIS. It has been applied to several gold fields in the Witwatersrand gold basin to simulate the groundwater flow and mass transportation for various conditions and scenarios. One of the applications will be presented in this paper. It has been proven that the linkage is efficient and easy to use.

Abstract

The pollution of water resources has become a growing concern worldwide. Industrial, agricultural and domestic activities play a pivotal role in water resources pollution. The challenge faced by pollution   monitoring   networks   is   to   understand   the   spatial   and   temporal   distribution   of contaminants. In hydrology, tracers have become a critical research tool to investigate surface water and groundwater transport dynamics. Synthetic DNA (deoxyribonucleic acid) tracers are being used in hydrological research to determine source areas, where uniquely labelled DNA from each source area  is  identified.  The main  objective  of the  study  was to  determine  the mass  balance of  the synthetic DNA tracer in surface water streams. Furthermore, to gain knowledge on DNA adsorption and decay and determine whether DNA behaves as conservative tracer in the surface water streams. Understanding the adsorption and decay characteristics of synthetic DNA tracers may promote its robustness in hydrological research. In this study, field injection experiments using synthetic DNA were  carried  out,  the  DNA  tracer  was  injected  together  with  sodium  chloride  (salt)  and deuterium as conservative reference tracers. The purpose was to compute DNA mass balance calculations with reference to the two conservative tracers. In this study two different DNA markers were used, namely T22 and T23. Additionally, with each injection experiment a field batch experiment was carried out to determine DNA loss characteristics on the field. From our study, the DNA loss between the injection point and the first measurement was greater than 90%. Therefore, it was important to conduct additional laboratory batch experiments to explain DNA loss characteristics. However, the issue of the initial DNA loss remained unresolved. Laboratory batch experiments results allow us to conclude the following: the type of material used, filtering, ion concentration and water composition reduced DNA concentration. Moreover, initial DNA losses occurred and not DNA decay. From our experiments we concluded that DNA can be used for long-term tracer experiments, subsequently, limiting synthetic DNA mass balance determination of synthetic DNA as it is a reactive. Overall, we can conclude that DNA does not behave as a conservative tracer.

Abstract

The aim of this project was to establish a detailed geohydrological database and monitoring network for  the  karst  aquifer  within  the  boundaries  of  the  Vanrhynsdorp  Water  User  Association.  An adequate monitoring network is necessary for the Vanrhynsdorp Water User Association to implement sustainable water use management as well as for the Department Water Affairs to ensure its mandate as trustee of all water resources. Hydrocensus projects were conducted in phases as the project escalated from historic town supply during 1978 towards a catchment driven water user association after implementation of the new National Water Act in October 1998 (Act 36 of 1998). With the successive hydrocensuses conducted, the monitoring network also evolved in regard to area monitored, point locations, monitoring schedules and parameters measured. Hydrocensus data were captured on the National Groundwater Archive, time series data on the Hydstra database and chemical analysis on the Water Management System. Time series graphs were compiled to analyse the monitoring data and to create a conceptual model of the karst aquifer. The study showed a general decline in groundwater levels and quality in the study area. The conclusion is that the aquifer is over exploited. It is recommended that an extensive management plan is developed and implemented to ensure sustainable use of this sensitive water resource. The installation and monitoring of flow meters on all production boreholes should be seen as urgent and stipulated as such in licensing conditions. This will ensure the effective management and regulation of this valuable groundwater resource.

Abstract

Determining   impacts   associated   with   the   production   of   shale   gas   in   the   semi-arid   Karoo   on groundwater is vital to people living in the Karoo. On the one hand shale gas can be a game-changer for energy supply, but on the other it may have a devastating effect on the environment. Knowing the potential  impacts  of  shale  gas  mining  beforehand,  the  government  can  set  appropriate  regulatory protocols  and  tools  in  place  to mitigate  potential  risks.  This paper  describes research  done  on  the potential impact that hydraulic fracturing could have on groundwater in the Karoo. A wild card that only exists in the Karoo Basin of South Africa is the numerous dolerite intrusions. These dolerite structures are associated with relative high-yielding boreholes because of the fractured contact aureole that exist between solid dolerite and the adjacent Karoo sediments. Compromised cement annuli of gas wells are the  major  preferential  flow  paths along which  methane  and fracking fluid  can escape  into shallow, freshwater aquifers. This study focused solely on the impact of compromised cement annuli of gas wells. The Karoo Basin is under artesian conditions which imply that any pollutant will always try to migrate upwards in the Karoo. The hot-water springs in the Karoo indicate that upward velocities of water are relatively high (the spring water take only days to travel from deep down to the surface). The cubic law was  used  to  estimate  potential  upward  leakage  rates  from  gas  wells  (during  production,  but  after cessation thereof as well, when pressures will rebuild  because  of  artesian  behaviour  of  the  Karoo formations).  Potential  leakage  rates  along  faulty annuli of a well can vary between a value close to zero to two liters per second in the case of an aperture of 0,5 mm. These leakage rates were used as input to a 2D numerical groundwater flow and mass transport model. The 2D model was run for 30 years and the movement of pollution from the gas wells on the pad simulated. The model indicates that an area of 300 ha could be contaminated over a period of 30 years in a downstream groundwater flow direction.  If  an  abstraction  borehole  drilled  along  a  fault  zone  or  a  dyke,  intersecting  the  fracked reservoir, is introduced into the model, results predict that the pollutant will reach the borehole in less than two months if the borehole is situated six kilometres from the well-pad. The total impact that fracking will have on the groundwater in the Karoo, is a function of the total area that will be fracked.

The outcomes of this research clearly show that fracking in South Africa cannot be done in the same way than  it  is  currently  done  worldwide.  A  rule  that  will  force  gas  companies  to  disclose  fracking  fluid contents is non-negotiable. Companies should also be required to measure pressures in the fracked gas reservoir after closure. An additional requirement to enforce sealing of the entire fracked reservoir with a very dense material like bentonite or a mud with a very high density to capture the fracking fluids deep down in the gas reservoir should not be negotiable.

Abstract

Quantification of hydrological processes is required for many projects related to potential groundwater recharge. Thus, investigation on various hydrogeologic conditions is paramount. Changes of climate can affect the hydrological cycle by altering groundwater recharge. As a result, an understanding of the hydrological conditions is essential to make sensible predictions of the possible groundwater recharge. Thus WetSpass, which yields spatially varying groundwater recharge using hydrological inputs, can be used together with a geographical information system to quantify the environmentally acceptable flow regime of the catchment area. This paper presents an overview on the use of WetSpass in combination with GIS on quantification of groundwater potential which will assist to sustainable groundwater development in the catchment area. Previous applications are presented.

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

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

Gold mining  activities over  the  past 60 years  in the Klerksdorp  goldfield produced  saline mine drainage that polluted water. Oxidation of sulphide material in tailings storage facilities, waste rock dumps and extraction plants is mobilised to produce saline mine drainage with sulphate, minor salts and  metals  that  seep  to  the  groundwater  and  ultimately  into  surface  water  resources.  Water regulation requires mines to prevent, minimise/reduce or eliminate pollution of water resources. The waste philosophy has matured from tolerate and transfer to treat and termination of pollution sources.  The  impact  of  the  pollution  was  determined  and  possible  technologies  to  treat  the impact   were   evaluated.   Source   controls   with   proper  water  management  by  storm  water management,  clean  dirty  water  separation,  lined  water  conveyance  structures  and  reduced deposition of water on waste facilities are crucial. The aquifer character determines the possible remediation technology. From the possible technologies phytoremediation, physical interception and  re-use  of  this  water  was  selected.  In  future  possible  treatment  of  the  water  would  be considered. This paper explain the strategy and report on the phased implementation of these plans and the expected results. The establishment of 500 ha of woodlands as phytoremediation, interception trenches of 1 000 m, 38 interception boreholes and infrastructure to re-use this water is planned. The total volume of 15 Ml/day would be abstracted for re-use from the boreholes and trenches. The woodlands can potentially attenuate and treat 5 Ml/day. The established woodlands of 150 ha prove to be successful to intercept diffused seepage over the area of establishment and reduce  the  water  level  and  base  flow.  The  two  production  interception  well- fields  that  are abstracting  50  and  30 l/s,  respectively  , indicate  a  water  level decline of between 2 to 14 m, with regional cones of depression of a few hundred meters to intercept groundwater flow up to a 20 m depth. Predictions from groundwater modelling indicate that these schemes can minimise pollution during the operational phase and protect downstream water resources. Predictions from modelling indicate that the pollution sources need to be removed to ensure long-term clean-up to return the land to safe use. The gold and uranium prize is securing the removal of the sources through  re-processing  of  the  tailings  and  waste  rock  dumps.  After  removal  of  the  sources  of pollution,  the  remediation  schemes  would  have  to  be  operated  for  20  years  to  return  the groundwater to an acceptable standard  of  stock  watering  and  industrial  water  use.  The  water quality is observed by a monitoring network of approximately 100 observation boreholes.

Abstract

In  South  Africa  salinisation  of  water  resources  by  dissolved  sulphates  resulting  from  acid  rock drainage (ARD) and metal leaching (ML) from surface coal mine spoils has a significant effect on water supply in the Gauteng Province. Predictions of mine water quality is required to select cost- effective rehabilitation and remediation measures to reduce future ARD and ML risks and to limit long-term  impacts.  A  load  balance  model  was  developed  in  Microsoft  Excel  to  simulated contaminant loads in a completely backfilled opencast mine in the Karoo Basin of South Africa after closure. The model calculated the balance between contaminant load into the pit water system from mainly pyrite oxidation processes in the spoils and load removed through decanting. Groundwater flow modelling data and simulated spoils seepage qualities for the mine site were used as input in the contaminant load calculations. The model predicted that the amount of contaminants added to the pit from spoils decrease considerably from the time of closure over a period of approximately 100 years. Thereafter the contaminant load decrease is gradual. This is due to a decrease in the volume of unsaturated spoils, as spoils at the bottom become permanently inundated as the pit fills up, thus limiting oxygen diffusion and oxidation. Cumulatively, the contaminant load gradually increases  in  the  backfilled  pit  until  the  onset  of  subsurface  and  surface  decant,  when  the contaminant load declines. This is due to removal of contaminants from the mine water system via decanting. Approximately 200 years after mine closure, 86% of the spoils are inundated. The model predicted that the quality of decanting water improves with time due to a decrease in load from spoils, removal of contaminants through decanting water and dilution effects of relatively clean groundwater inflows. Mass loads were used as input into the numerical groundwater model for the contaminant mass transport simulations to predict the migration of contaminant plumes with time. The geochemical model results assisted in developing conceptual water and waste management strategies for the opencast mine during operational and closure phase.

Abstract

After a period of heavy rainfall in 2006, pit water from a rehabilitated opencast coal mine in the Mpumalanga Province started decanting, causing impacts on the adjacent agricultural land and river system. Various actions have since been taken to manage the pit water, including construction of contour berms to prevent clean water entering the ramps, construction of levees and dam walls to increase the decant level, irrigation of mine water on the rehabilitated areas of the pits, disposal of pit water in nearby pans, recirculation of pit water by means of pumping between the various voids, controlled release of pit water to the river system, and construction of a pipeline to pump pit water to a nearby colliery where there is a demand for process water. For the purpose of mine closure, a water management plan was required for which an estimate of the water make of the colliery was needed. The water make was estimated by using measured quantities (rainfall data, pumping rates, dam water levels) and estimated quantities (evaporation from open water bodies), while making a number of simplifying assumptions. This approach revealed that the conventional method of estimating the water make as a percentage of rainfall recharged through the spoils, significantly underestimates the volumes of water that need to be dealt with at the colliery. Large volumes of groundwater appear to be entering the pits along preferential pathways connected to recharge zones at higher elevations, contributing to the water make of the colliery.

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

This paper has been based on a study conducted at the Nyalazi plantation in KwaZulu-Natal, South Africa. The study was conducted in order to determine the impacts of the different timber species planted on the groundwater levels associated with the site area. Commercial timber plantations are widespread  throughout  the  country  and  form  an  essential  component  of  the  South  African economy. The site is located 200 km north of the port of Durban and approximately 20 km north of the town of St Lucia in the KwaZulu-Natal Province. The study area, the Nyalazi plantation, is located on the western shores of Lake St Lucia, situated on a peninsula between the Nyalazi River, west of the site and Lake St Lucia to the east. The two main tree species which are located in the Nyalazi plantation are Pinus elliottii and Eucalyptus grandis Camaldulensis. The geological units which influence the hydrogeological regime of the site area include the recent deposits of cover sands and the Port Durnford Formation. These geological successions are the most influential on the groundwater environment as these are the units closest to the surface. The study area is located on the Maputuland coastal plain, also referred to as the Zululand coastal plain, which is classified as a primary aquifer and is the largest of its kind in South Africa. High recharge is experienced within the upper formations of the coastal plain which are unconfined aquifers (Mkhwanazi, 2010). This aquifer consists of unconsolidated clays and sands, which may be defined as an alluvial or primary aquifer (Rawlins & Kelbe, 1991). The monitoring network was initiated by SAFCOL (South African Forest Company, Ltd) in 1995, now known as SiyaQubeka. In total 21 monitoring points were installed, which  includes  piezometers  and  deeper  boreholes.  The  trends  of  the  groundwater  level  data collected over the 17-year period was analysed. Limited historical information was available for the Pinus elliottii plantation; however, based on the data it was evident that the mature pine plantations had minor effects on the groundwater environment of the study area. Conversely, the Eucalyptus species indicated a significant impact with the lowering of the groundwater table between 10 and 16 m over a period of 13 years within the plantation area, which equates to an average decline of one metre per year.

Abstract

Vapour intrusion (VI) is the term used to define the encroachment of vapour phase contaminants from subsurface sources into structures such as buildings and basements. It is widely recognised that VI often forms the principal risk of exposure to receptors at petroleum release sites. Petroleum VI (PVI) generally occurs where a release of petroleum hydrocarbon product migrates from its source (for example, from a leaking underground storage tank) to the groundwater table at which point, given favourable conditions, the hydrocarbon plume may migrate laterally beneath an adjacent building or structure. Subsequent volatilisation of the petroleum product results in the upward diffusion of vapours towards the surface where the vapours may enter into the building or structure at concentrations which may be harmful to human health. The subject of PVI with regards to its fate and transport mechanisms, as well as associated mitigation measures, is rapidly gaining attention on a global scale, although to date this exposure pathway remains largely unassessed in South Africa, with no regulatory guidance currently available. In the late 1990s and early 2000s focus was placed on the development of VI screening criteria by which sites could be screened with respect to their hydrogeological conditions and contamination status so as to determine whether VI may be a potential exposure pathway of concern, with much of the early work being completed by the United States Environmental Protection Agency. For the past decade the majority of the available screening criteria  and  guidance  has  not,  or  has  only  partially  accounted  for  biodegradation  processes associated with VI, which has led to doubt over the application of such screening criteria in many cases. Furthermore, recent research conducted abroad has highlighted the importance of the role of oxygen in the vadose zone in the natural attenuation of petroleum hydrocarbon vapours as they diffuse through the soil profile. This research is pointing towards the notion that currently applied screening criteria may be overly conservative when applied to petroleum impacted sites, leading to many  unnecessary  PVI  investigations  being  conducted  to  the  disruption  of  occupants  of  the buildings, and at great cost. Over the last two years ERM has compiled a dataset of PVI results from numerous investigations it has conducted throughout Southern Africa and in this paper the authors present data that supports the growing global trend towards recognising the role that oxygen plays in attenuating petroleum hydrocarbon vapours in the vadose zone. The data also support the notion that confirmed cases of PVI into buildings have generally been found to be the exception to the rule and not the norm.

Abstract

POSTER The Evander Goldfield basin has been mined since the early 1950s at depths between 400 and 2 000 m below ground and is detached from the larger Witwatersrand basin. The assessment and prediction of mine water rebound has become increasingly important for the gold mining industry in the Witwatersrand basin as more mine shafts mothballs and dewatering ceases. The development of a  3-D  mine  void  model  is  crucial  in  predicting  the  rate  of  flooding  as  the  prediction  of  the groundwater rebound is primarily driven by the volumes of mine voids along with the amount of recharge. All available mine plan data for the Evander Gold Mine (EGM) were obtained digitally from Harmony Gold. However, the majority of the old mine workings (e.g. Leslie and Winkelhaak) were available  as  2-D  data  and  elevations  of  the  mine  developments  (stopes  and  drives)  had  to  be captured from hardcopy plans. Data from the more recent mining operations (e.g. Shaft 6), including updated survey and mine plan data, were directly used for the development of the 3-D void model. The calculated mine void volume, based on the EGM operations mine plan data, is approximately 80 518 045 m3. The mine void calculations were checked against the total tons of rock milled by the EGM operations since the late 1950s and was considered valid estimations of the EGM mine void volume. The validated EGM 3-D mine workings plan was subsequently used to determine the stage- volume relationships. The 3-D mine void model established, will then be incorporated into a regional numerical groundwater flow model to be calibrated against observed abstractions and water levels and utilised to predict future dewatering rates.

Abstract

South Africa has an energy crisis. The country requires 53 Gigawatt of new capacity by 2030. The exploitation  of  unconventional  gas  is  a  potential  game-changer  to  meet  South  Africa’s  current energy deficit to fuel economic growth and development. Water management, both in terms of abstraction and disposal, has emerged as a critical issue in the development of unconventional gas reservoirs. This presentation focuses on a high-level, qualitative analysis of the groundwater-related institutional and governance challenges associated with unconventional gas exploration and production. The findings represent a synthesis of information sourced from regulatory and legislative documents as well as international experience. The analysis maps the current groundwater institutional and governance landscape in South Africa and lessons learned from other regimes such as the United Kingdom and United States of America. Good governance entails ensuring that there is compliance with policy and legislation, effective decision-making, appropriately allocated accountability, transparency and that stakeholder interests are considered and balanced. This forms the basis of a preliminary gap analysis.

Abstract

POSTER One of the critical elements of water resource management is the dynamic exchange between groundwater and surface water. Quantifying this exchange strongly relies on an adequate characterisation of the lithological architecture of the involved aquifer system. In the past, this characterisation often relied on lithological data obtained through invasive methods. However, given the spatial heterogeneity of the subsurface, these methods do not provide the density of sampling required for an accurate ‘‘image’’ of the large‐scale architecture of the aquifer system, leading to large uncertainties in the variations and continuities of subsurface structure. These uncertainties inevitably lead to inaccuracies in the conceptual geohydrological model, thereby diminishing the prospects of an accurate assessment of the groundwater–surface water interaction. In order to limit the uncertainties, the results of electrical resistivity tomography (ERT) surveys conducted on a  site  near  the  Krugersdrift  Dam in the Free State Province of South Africa  were used to make inferences   regarding  the   prevailing  geohydrological  conditions.  The   resistivity  models   were compared to borehole logs from existing boreholes to produce a refined model of the subsurface architecture related to groundwater–surface water interactions.

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

The Paleozoicage Natal Group Sandstone (NGS) that outcrops from Hlabisa (in the north) to Port Shepstone (in the south) and Greytown (west) to Stanger (east) in the Province of KwaZulu-Natal, South Africa, is investigated in terms of its hydrogeological characteristics. This sandstone group, which comprises a lower Durban and an upper Marrianhill Formations, is a secondary/fractured aquifer system that has variable but good productivity across its members. It is characterised by variable borehole blow yields ranging from 0.2 l/s to as high as 20 l/s, with more than 50% of the boreholes having blow yield > 3 l/s. Preliminary analysis of these boreholes yields indicates that higher yielding boreholes are associated with a network of intersecting fractures and faults, and are recommended targets for future water well-siting in the area. Groundwater in the NGS is of good quality in terms of major and trace element composition and it has a total dissolved solids (TDS) composition of <450 mg/l. It was observed that the specific electrical conductivity (EC), TDS and major ions composition of groundwater within the sandstone decrease from north to south, which appears to be controlled by the geochemical composition of the aquifer material and an increase in the rate of recharge. Depth to groundwater is also found to decrease southwards because of an increase in the rate of recharge. Groundwater hydrochemical facies are generally either Na-HCO3 or Na-HCO3–Cl, and environmental isotope data (2H, 18O, Tritium) indicates that the groundwater gets recharge from modern precipitation. Furthermore, the EC increases from inland to the coastal zone, indicating maritime influences and the general direction of groundwater flow is eastwards, to the Indian Ocean.

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

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

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).

Abstract

Groundwater boreholes are a key element of many mining projects, as part of dewatering and water supply  systems,  and  must  achieve  high  levels  of  operational  efficiency  and  service  availability. Outside of the mining industry, planned borefield maintenance programmes have become a key part of professional well-field management, with proven benefits in terms of operational cost savings and continuity of pumping. However, the benefits of proactive planned maintenance of groundwater boreholes on mine sites have only recently been widely recognised. Potential operational problems are described, including water quality issues which can result in mineral contamination leading to deposits and scale build-up which can clog screens and pumps, reduce water flow and yield, and eventually cause pump breakdowns and mine stoppages. Best practice methodologies to remove or minimise the contamination are described and the benefits of implementing a planned maintenance programme are discussed. Case studies are described from two significant mines in Australia, where boreholes suffered from mineral contamination, including calcium carbonate and iron bacteria contamination. Both mines suffered  from  increased  pump  breakdowns,  groundwater  yields  consistently  below  target  and serious cost overruns. Borehole rehabilitation treatment plans were implemented to resolve the immediate contamination problems followed by an ongoing maintenance programme to prevent or minimise their reoccurrence. Treatment programmes included a downhole camera survey, use of a bespoke software program to review the results of the survey and the available water quality data, and a purpose built rehabilitation rig that included the use of specialist chemical treatments to remove and control the existing encrustation and clogging deposits.

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 is not often regarded as ecosystems and especially fractured aquifer systems are seen as organism free. Conventional tests show very little to no presence of micro-organisms in groundwater. However, these micro-organisms are ubiquitous and can be detected by using sophisticated methods. In this specific case study where petroleum hydrocarbon  contamination exists in a fractured rock aquifer, the presence of micro-organisms has been for years inferred by means of monitoring for secondary lines of evidence that prove attenuation of the contaminants, not only by means of dilution, adsorption or diffusion into the matrix, but through metabolism. The sampling evidence is clear that the preferential sequence of metabolism is taking place whereby electron acceptors are reduced as predicted for such biodegradation. Specifically sulphate is consumed and mostly manganese is reduced, with some iron reduction also being observed. Monitoring has shown that  groundwater recharge bringing in  new  nutrients effected increased biodegradation. In order to definitively identify the contribution made by micro-organisms, DNA testing was performed. The results support the secondary lines of evidence. Outside of the contaminated zone very low population numbers of organisms were detected in the groundwater. Inside the contaminated zone elevated population numbers were observed indicating that active biodegradation is taking place. Furthermore, the edges of the plume, where contaminant levels are mostly below detection, contained a more diverse population of micro-organisms than the central area. Conditions on the edge of the plume probably represent an ideal nutrient environment for the organisms as opposed to the high concentration source, which might be toxic to some organisms. Better understanding of the bio-dynamics of this fractured aquifer presents a unique opportunity to better manage and enhance the remediation of the contaminants. Possible strategies include the addition of nutrients when necessary and the cultivation of the naturally occurring organisms to augment the population. The data shows that aquifers are ecosystems even in fractured environments.

Abstract

The deterioration of wetlands due to human activity has been a problem for many years. Under the old Water Act 36 of 1956 no provision of water was made for managing the environment. This idea was only introduced in the 1970s and focussed mainly on maintaining the floodplains and estuaries in the Kruger National Park, with small amounts being allocated to drinking water for wildlife. This was followed by the Conservation of Agricultural Resources Act, 43 of 1983, the first legislation under which wetlands could be protected, and which today still provides an important legal platform for the protection of wetlands, through integrated conservation of the soil, water resource and vegetation. South Africa became a signatory to the Ramsar Convention in 1975, but until the late 1990s not much was done to enforce wetland conservation. With the introduction of the National Water Act, 36 of 1998, and the National Environmental Management Act, 107 of 1998, South African legislation  became  the  first  to  balance  human,  environmental  and  economic  interests,  for  the purpose of sustainable development. As part of this review I refer to case studies in Gauteng and discuss some of the challenges we still face.

Abstract

A multi-data integration approach was used to assess groundwater potential in the Naledi Local Municipality located in the North West Province of South Africa. The geology comprised Archaean crystalline basement, carbonate rocks (dolomite and limestone) and windblown sand deposits of the Kalahari Group. The main objective of the study is to evaluate the groundwater resource potential using multi-data integration and environmental isotope approaches. Prior to data integration, weighting coefficients were computed using principal component analysis.

The results of integration of six layers revealed a number of groundwater potential zones. The most significant zone covers ~14% of the study area and is located within carbonate rocks in the southern part of the study area. The localisation of high groundwater potential within carbonate rocks is consistent with the results of principal component analysis that suggests that lithology significantly contributed to the total data variance corresponding to principal component 1. In other words, carbonate rocks consisting of dolomite and limestone largely account for groundwater occurrence in the southern part of the area. In addition, the relatively elevated isotopic signature of tritium (≥1.0 TU)  in  groundwater  samples  located  in  the  southern  part  of  the  area  suggests  a  groundwater recharge   zone.   Furthermore,   moderate-to-good   groundwater   potential   zones   within   the Ventersdorp lava coincide with maximum concentration of fractures, which is consistent with the results of statistical correlation between borehole yield and lineament density. The multi-data integration approach and statistical correlation used in the context of evaluating groundwater resource potential of the area provided a conceptual understanding of hydrogeological parameters that control the development of groundwater in crystalline and carbonate rocks. Such approach is crucial in light of the increasing demand for groundwater arising from municipal water supply and agricultural use. The two approaches are very effective and can be used as a sound scientific basis for understanding groundwater occurrence elsewhere in similar hydrogeological environments.

Abstract

South Africa currently ranks number nine in the world of the proved coal reserves that has been estimated to last for over 200 years. Coal constitutes about 77% of the primary energy needs in the country, with the Waterberg Coalfield estimated to host about 40% of the remaining South African coal resources. Coal deposits in the study area largely consist of shales, mudstones, siltstones and sandstones which host coal-containing clay minerals; quartz, carbonates, sulphides and the most abundant sulphide mineral is pyrite. Once mining begins, the sulphide minerals are exposed to surface which allows contact with atmospheric oxygen and water causes oxidation to take place, therefore causing acid-mine drainage (AMD). Acid-base accounting (ABA) was used to determine the balance between the acid-producing potential (AP) and acid-neutralising potential (NP). From the analysis the Net Neutralising Potential (NP-AP) was determined, which is one of the measurements used to classify a sample as potentially acid or non-acid-producing. Mineralogical analyses will be done by x-ray defraction (XRD) to define and quantify the mineralogy of the geological samples which can help in the management plan to minimise generation of acid. AMD does not only result in the  generation of acid, but as well as in decreased pH values and increased values of specific conductance, metals, acidity, sulphate, and dissolved and suspended solids. Inductively coupled plasma analysis was done to determine the release of the heavy metals which can be detrimental to the environment. Sample analysis was done on the interburden, overburden as well as the coal samples. From results obtained, over 35% to 50% of the samples have an excess of acid potential which classifies the samples as having a higher risk for acid generation. About 30% to 40% of the samples have a higher neutralising potential; the rest of the samples have a medium acid risk generation. The water demand will increase as developments continue in the  area, with inter- catchment transfers identified as the answer to fill the gap of water scarcity. Acid mine drainage poses a big threat on water resources, both groundwater and surface water nationally, which might be less of a problem in the Waterberg because of the cycle of low rainfall in the area, but the potential of AMD cannot be neglected.

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 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

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

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

Many aquifer systems worldwide are subject to hydrochemical and biogeochemical reactions involving iron, which limit the sustainability of groundwater schemes. This mainly manifests itself in clogging of the screen and immediate aquifer with iron oxyhydroxides resulting in loss of production capacity. Clogging is caused by chemical precipitation and biofouling processes which also manifests in South African well-fields such as in Atlantis and the Klein Karoo. Both well-fields have the potential to provide a sufficient, good quality water supply to rural communities; however, clogging of the production boreholes has threatened the sustainability of the schemes as quality and quantity of water is affected. Rehabilitation of the affected boreholes using techniques such as the Blended Chemical Heat Treatment method does not provide a long-term solution. Such treatments are costly with varying restoration of original yields achieved and clogging recurs with time. Currently the research,  management  and  treatment  options  in  South  Africa  have  focused  on  the  clogging processes which are complex and site-specific, making it extremely difficult to treat and rectify. This project attempts to eliminate elevated concentrations of dissolved iron, the cause of the clogging. High iron concentrations in groundwater are associated with reducing conditions in the aquifer allowing for the dissolution of iron from the aquifer matrix. These conditions can be natural or human-induced. Attempts to circumvent iron clogging of boreholes have focussed on increasing the redox potential in the aquifer, by injection of oxygen-rich water into the system, to prevent dissolution and to facilitate fixation of iron in the aquifer matrix. Various in situ treatment systems have  been  implemented  successfully  overseas  for  some  time.  In  South  Africa  thus  far  in  situ treatment of iron has only been proposed as a solution for production borehole clogging. Based on experience from abroad the most viable option to research the elimination of ferrous iron in South African aquifer systems would be through the in situ iron removal treatment. Different techniques of increasing the dissolved oxygen concentration in the injected water to intensifying the redox change in the aquifer can be applied; however, the use of ozone as the oxidant is a new approach. Its effectiveness is evaluated by the results in iron removal in surface water treatment for drinking water supply.

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

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

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

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.