Acid mine drainage is by far the most significant long term groundwater quality impact associated with both opencast and underground coal mining, in both a local and international context. The modern day geohydrologist has access to numerous tools, which can be used to determine important decant issues â issues ranging from when decanting will begin to occur, and the volumes of water that are expected to decant. The continuous development and improvement of numerical groundwater flow models is steadily leading to an increasing dependence on them. The main aim of the thesis was to determine whether there exists any correlation between modern day numerical groundwater flow models and analytical calculations, and the presentation of a toolbox of tools that may be used for decant related issues. The following conclusions were drawn after numerous numerical and analytical scenarios and statistical correlations were performed: ⢠Given the amount of uncertainty regarding aquifer heterogeneity, there do exist a good correlation between the numerical and analytical groundwater decant volume estimations, ⢠An increase in the effective porosity of the backfilled opencast pits cause an increase in the time-to-decant, as more water is required to fill the pits to their decant elevations, ⢠An increase in the effective aquifer recharge cause an increase in the decant volumes and a decrease in the time-to-decant, because more water is available to fill the pits to their decant elevations, ⢠The effective aquifer recharge is a very sensitive parameter (more so than specific yield, storage coefficient, and transmissivity), as significant decreases in the time-to-decant were simulated with an increase in the aquifer recharge, as were significant increases in decant volumes simulated with an increase in recharge, ⢠The volumes of groundwater decant are more sensitive to variations in the transmissivity of the surrounding aquifer/s compared to the transmissivity of the backfilled opencast pits, ⢠During the numerous flow model scenarios it was found that the groundwater contribution to pit water is far less compared to the recharge component. The above conclusions prove that there are still applications for analytical calculations in modern day geohydrology, despite the continuous development of numerical groundwater flow models. Based on experience in similar coal mining operations within the Mpumalanga coal fields, the results of both the analytical decant volume and time-to-decant estimations correspond well with actual figures. One must however understand and master the various equations and keep in mind that an aquifer is a highly heterogeneous system. The results of both numerical groundwater flow model simulations and analytical calculations are only as good as the understanding of the geohydrological environment and the data they are based on.

Groundwater contamination as a result of Light Non Aqueous Phase Liquid (LNAPL) releases into the subsurface is a widespread occurrence across South Africa which threatens current and future water resources within the country. Groundwater contaminant fate and transport modelling are common elements of hydrogeological investigations and remedial design methodologies in many developed countries where the models are use as management and decision making tools. In South Africa this is not the case, with contaminant flow and transport modelling rarely being employed as part of LNAPL contamination investigations. Over the last 3 years the Beaufort West study area has had extensive investigative work carried with regards to the determination and delineation of LNAPL related groundwater contaminant plumes which are present underneath a significant portion of the town. As a result an extensive data set has been generated with regards to aquifer geometry, fracture network distribution, aquifer parameters and contaminant plume concentrations and extent. The dataset should in theory provide an opportunity to construct a groundwater contaminant fate and transport model for the area as a remedial management tool. By means of collating previously existing data through a comprehensive desktop study, and supplementing this data with a toolkit of field investigations techniques such as diamond barrel core drilling, percussion drilling, electrical conductivity profiling, fluid electrical conductivity profiling, aquifer pump testing, and low flow inorganic and organic groundwater sampling, the conceptual model of the study area was updated and refined to a point where feasibility of constructing a groundwater contaminant fate and transport model could be assessed. Based upon the conceptual understanding of the study area as defined in the conceptual model developed in the study, a groundwater contaminant fate and transport model is not considered feasible for the study area with body of data currently available. This is attributed mainly to the high level of complexity of the observed natural environment and the challenges in acquiring acceptable quality field data such as aquifer parameters given the uncontrolled pumping environment which is present due to the high number of private groundwater users. Potentially an even greater detractor to the construction of a model, is that considering the conceptual understanding of the study area, there are very few questions of significance whose answers could be provided by a model, and this would indicate that a model would not be an effective remedial management or decision making tool in the current scenario.

Not available

The fertilizer production facility had a negative impact on the soil, groundwater and surface water environment due to the handling / storage and production activities at the site. Observations and numerical modelling found the fertilizer product loadings areas as the main source area of contaminants viz. Ca, Mg, NO3, Cl, SO4, EC and TDS. Uncontrolled run-off emanating from the site is a major contributing factor to contaminating the groundwater and surface water resources. A distinct difference could be observed between the geochemical signature of the potential contaminated seepage and that of the groundwater. This geochemical characterisation of the contaminant plume identified an interaction of the leachate and the soil with a high clay (montmorillonite) content, with various cation exchange and sorption processes occurring. Potassium is largely exchanged (for sodium), while phosphates are likely to sorbed on the clay particles. Nitrate is likely to be retarded to a limited extent, especially when redox conditions are conducive to the conservation of the nitrate specie. The elevated contaminant concentrations pose a health risk to potential users and livestock which may ingest the water, especially nitrate concentrations. Numerical modelling was used to validate and develop the site conceptual model. Iterative modelling improved the initial correlation R2 of modelled and observed nitrate concentrations, the correlation improved from 0.29 to 0.64. The model was validated by assuming that horizontal and bedding plan fractures are likely to play a role in contaminant transport (which was not modelled). Artificial recharge (seepage and leachate infiltration) was present at the plant area. Groundwater abstraction from farmers boreholes downstream had an influence on the development of the nitrate plume. Surface water contamination contributed to the current plume geometry and therefore partly responsible for the current plume extent. A secondary groundwater contaminant source was found in the south western part of the study area. Predictive modelling found abstraction of groundwater from site to be the most effective containment measure when compared to a cut-off trench. The groundwater contamination is likely to pose a low current and future risk to groundwater users, as no current groundwater users are found in proximity to the site and the contaminant plume. However a potential surface contaminant risk does occur to down stream surface water bodies during a flood event.

The Waterberg coalfields represent the last area in South Africa, which contain large quantities of coal resources. According to Dreyer (pers. comm. 2009) the Waterberg coalfields contain nearly 50% of the remaining coal resources of South Africa. Given the great demand for coal both local and abroad, primarily to be used as a fuel source for the power generation, the Waterberg coalfields have been targeted for large scale developments in order to exploit the coal. The primary method for exploiting coal is through mining. Mining, in any setting and any location has a diverse and often very serious impact on the environment. A scoping level study was under taken in order to determine the effect the mines will have on the groundwater resources and the pre-mining conditions of the aquifers and the quality of the groundwater. At present there is one operational colliery in the study area, the Grootegeluk mine. This mine has been in operation since the 1980âs and has had a well planned and operated monitoring system in place since the beginning of mining operations. This mine was used as a model to determine the impact new mines will have on the area. From the investigations it became apparent that the coalfield is situated in the Karoo Supergroup geology with the Mokolian Supergroup being represented in the study area by the Waterberg group quartzites. The coalfield is delineated by three major geological structures, the Daarby-, Eezaamheid- and the Zoetfontein faults. With the Daarby- and Eenzaamheid faults being impermeable according to Dreyer (pers. comm. 2009), The Daary fault serves to divide the study area into an area west of the fault with shallow coal and an area east of the fault with deeper coal. Only the shallow coal will be mined. According to Dreyer (pers. comm. 2009), all of the planned infrastructure for the new mines will be located on the Waterberg group rocks south of the Eenzaamheid fault or on the Karoo rocks east of the Daarby fault. To determine the impact the mines would have on the groundwater of the study area, aquifer parameter testing (pumping test and slug tests), water quality determinations (inductively coupled spectrometry), acid-base accounting and numerical modelling were conducted. The results of the aquifer testing indicated low yielding aquifers with the harmonic mean of the transmissivities indicating a low transmissivity of 0.4 m2/d. In addition the recharge for the study area was calculated by means of the Cl and E.A.R.T.H. methods, resulting a value of 1.5% for the area. The average water level for the area was found to be approximately 28 m. The water quality determinations for areas that had not been affected by mining, indicated waters that had high EC values, near neautral pH value and medium to high Cl and sulphate values. The areas that have been affected by activities such as power generation and mining, displayed higher EC, Cl, and sulphate values than the unaffected areas. To more accurately determine the impact the mines would have on the area, numerical modelling was done. Three scenarios were simulated using similar parameters to determine the expected inflow into the mines and whether the mines would ever decant. The results indicated that the worst possible scenario there was an influx varying between 755 m3/d and 1283 m3/d depending on the location of the pits. For the decant models, 50 years after mining had stopped there was a rise of 3 m in the pits themselves. With the pits being simulated being 110 m deep it is concluded that the mines in the area will never decant. The results of the project indicate that the addition of new mines to the area will have an effect on the groundwater quality and quantity and steps should be taken to minimise this as much as possible.

The Kombat Aquifer, as investigated in this study, comprises the dolomite of the upper and lower Otavi Group, encompassing a radius of about 10 km around Kombat Mine. Groundwater flow controls, structural influence, and hydraulic behavior of the groundwater flow system are investigated. The entire study area is initially conceptualized within a typical karst aquifer framework. Readily available data on climate, groundwater water levels, satellite geology, water chemistry, hydraulic tests, borehole hydrographs, borehole fracture logs, water strikes, geomorphology, supplemented with fracture field mapping and groundwater temperature logging, are used to delineate and study structures, structural controls, hydraulic response and to conceptualize the groundwater flow regime of the Kombat Aquifer. The results indicate that tectonic facies, layering, geomorphology, relief and relative position along the flow system largely influence the distribution of storage, permeability, hydraulic head stability, vertical and horizontal flow patterns, as well as the geometry of the Kombat Aquifer groundwater flow system. A comparison of groundwater temperature of the recharge and the discharge areas shows a temperature increase of about 5oC. An analysis of hydrograph recession curves enabled the understanding of the hydraulic response as well as the hydro_ dynamics of the flow system and confirmed the co-existence of two mutually inclusive groundwater flow components. The statistical examination of transport parameters reveals a very high tendency of dispersion, suggesting that extreme transport values could be more significant to groundwater flow parameterization than average values. A joint combination of blocky fracturing, flat relief and decreasing proximity to discharge zones enhance the long-term safe yield and hydraulic stability of production boreholes. Hence areas that are dominated by parallel fracturing, high elevation and long distances to discharge zones have the most unstable hydraulic head response and the lowest borehole yields. Results from hydraulic tests show that two permeability networks co-exist in different combinations and define the physical framework within which groundwater resides and moves. The connectivity between the two permeability networks characterise the hydraulic response of the Kombat Aquifer to groundwater withdrawal.

Site characterisation aims to obtain fundamental data needed to describe the subsurface flow pathways and distribution of contaminants. The study describes the application of various geohydrological techniques as complimentary tools to characterise an LNAPL contaminated fractured - rock aquifer on the Beaufort West study area in South Africa. Field investigations were designed to define and determine the properties of the fracture preferential flow paths responsible for LNAPL transportation in a typical Karoo fractured â rock aquifer system. The research places emphasis on the integration of results to maximise the subsurface geological understanding in particular location of fracture features chiefly responsible for facilitating LNAPL migration and distribution. The core and percussion drilling explorations, cross - correlated with borehole geophysics, were valuable for geological subsurface investigations in particular locations of bedding fractures, which are often associated with high hydraulic conductive flow zones. Tracer and pump tests were conducted to determine hydraulic and mass transport parameters respectively. Hydraulically conductive bedding plane fracture flow zones were identified by integrating results from the geological core logs, borehole geophysics and aquifer tests. The chemical characterisation of the study area was conducted by means of organic hydrocarbon, inorganic water analyses and volatile organic carbon measurements in the soil during air percussion drilling. Based on the findings, the hydrogeological structure of the formation was conceptualised as a fractured sandstone aquifer, characterised by bedding plane fracture preferential flow paths at contact areas, with shale and mudstone formations. The study findings demonstrate the merit and value in the application of various geohydrological tools to complement one another for optimised site understanding. The findings and recommendations of the case study are not necessarily confined to LNAPL contaminated fractured - rock aquifers, but may also be applicable to other types of contaminants in fractured - rock aquifer formations.

The purpose of the study is to trace the development of risk-based audit approaches, in order to understand the complexities and difficulties of these approaches, as well as to evaluate these risk-based audit approaches, with the objective of assisting in the process of improving the risk-based audit approach followed by the audit profession. The only defence auditors have against the anger (or frustration) of stakeholders in instances of corporate failures is sufficient, appropriate audit evidence that proves their innocence. This audit evidence will be the result of a well-planned and performed audit. An audit approach, currently a risk-based audit approach, is therefore a crucial component in the performance of an audit. Changing the risk-based audit approach is a normal consequence of the striving for the improvement and development of the services that the auditing profession provides. In developing the risk-based audit approach, there are certain complexities surrounding an audit that should be considered. The major complexities in the performance of an audit are: first, the expectation gap; second, the uncertainties surrounding the responsibilities of the auditor; third, the provision of reasonable assurance, and fourth, the practical implementation of audit standards. The auditing profession should, during this continuous process of changing the auditing standards and guidance, consider and evaluate changes against the theoretical foundations of auditing to support the credibility of the audit process. The theoretical framework that formed the background of this study is discussed in the second chapter, including the meaning of ârisk-based audit approachesâ. Audit approaches are discussed that developed before the acceptance of the risk-based audit approach, together with audit approaches that were never followed or accepted by practitioners, and which influenced the development of risk-based audit approaches. The development of the first risk-based audit approach, the statistical audit risk approach (audit risk model) that originated from the Elliott and Rogers model is discussed in the third chapter. The critique on the statistical audit risk approach is summarised and consists mainly of the following: that the audit risk modelâs event structure is ill-defined and that the risk components lack independence, which is a basic assumption for the use of the multiplicative formula. The risk components are complex and interdependent and are difficult to assess therefore, practitioners prefer to assess these risk components in linguistic terms e.g. low, medium and high. The multiplicative rule does not provide protection against an understatement of audit risk if the audit outcome space is not completely specified and when a revision of the audit plan is needed. The aggregation of the individual risks is problematic and therefore the audit risk model should be used only for planning purposes. The development of the inherent risk audit approach (audit risk model from a conceptual perspective) is discussed in the fourth chapter. The critique against the inherent risk audit approach includes the unsuccessful decomposition structure of audit risk, due to the interdependency of inherent risk and control risk. The concept of âinherent riskâ is also too broad and vague. The business risk audit approach is also discussed in the fourth chapter. This approach was developed by audit firms as an intended improvement on the inherent risk audit approach and is still widely used. The main critique against the business risk audit approach is the lack of a clear link between business risks and possible risks of material misstatement. The ârisk-process audit approachâ is addressed in the fifth chapter. For the purposes of this study, the name of the current risk-based audit approach is the risk-process audit approach. The reason for this formulation is the emphasis in the audit risk standards on the risk management tasks. The concept of âriskâ in the performance of the task of identification of risks is, in essence, a choice in which the auditor has the freedom to choose an approach, and is referred to as ârisk of material misstatementâ. The concept of ârisk of material misstatementâ is much broader and different from the suggested definition in the auditing standards, and includes the consideration of potential misstatements according to the assertions on the assertion level (assertion-focus), and lacks conceptual clarity. The criteria for the task of âassessment of identified risksâ are as follows: the different types of assertions are used as the criteria for assessing risks of material misstatements through the identification of possible misstatements. The concept of âmisstatementsâ is the criterion used to consider the likelihood of misstatement(s), and the concept of âplanning materialityâ is used to consider the magnitude of misstatement(s). In the sixth and final chapter of this study, the development of risk-based audit approaches is summarised through a comparison of the risk-based audit approaches. In the future development of the current risk-process audit approach it is suggested that a fourth aspect, the significance of audit procedures, additional to the current nature, timing and extent of audit procedures maybe considered in respect of aspects that influence the response to risks of material misstatement included in the audit plan. Furthermore, the definition of the concept of ârisk of material misstatementâ could include the assertionfocus. The importance and possibilities of the division of audit planning in the financial statement level and the assertion level is also not yet fully considered. In conclusion, the author believes that the history of risk-based audit approaches has repeated itself and that the development of the risk-based audit approach and changes thereto were not considered against, and based on a sound foundation of auditing theory.

Vaalharts Irrigation Scheme is not only the largest in the country it is known as âThe Food Basketâ. In 1875, Mr Ford, a Government Surveyor got the idea that the Vaalharts area has irrigation scheme possibilities due to the topography of the area. The proposal was approved by government in 1833. Planning, soil tests and more surveys to investigate the possibility were done. A weir was constructed, in the Vaal River, 8.5 km upstream from Warrenton, to deviate water to the Jan Kempdorp/ Hartswater area. In 1938 the first farmers received plots. Today there are almost 1200 plots vary in size from 25 â 75 ha it cover a total area of 35 302 ha. At the start of the irrigation project the water table was 24 mbgl by 1971 it has risen to 1.5 mbgl and waterlogging was experienced. Streutker studied what the cause of the watertable rising were. The feeder canals were ground canals and it leached to the water table causing the rise, the canals were lined. The water table remained high, in 1976 Gombar & Erasmus investigated the possibility to drain the area with boreholes. It was a solution but to expensive, The water in the Spitskop dam in the Harts River, were all the drain water flow to do not show parallel deterioration and accumulation of salt as the groundwater in the irrigated areas. A research done by Haroldt & Bailey investigated where does the salts and water go. Findings was that there are a âsalt sink â present, mainly due to a perched water table and if at some stage the sink will be exhausted it would have severe effects. A 2004 research was done to find the âsalt sinkâ. Boreholes were drilled to study the groundwater characteristics, piezometers were installed, to check the possibility of two aquifers. The study concluded that water levels do not differ more than centimetres in the deep and shallow water systems. Water quality as profiled in piezometers indicated no major stratification of groundwater. The deep lying aquifer does not perform separately, thus no âsalt sinkâ. This study was done to conclude what is the effect of the irrigation on the groundwater and the following was done: ï§ Planning and Installation of piezometer network ï§ EC profiling of the piezometers ï§ Monitor groundwater levels and ECâs ï§ Determine Hydraulic Conductivity ï§ Sample collection and chemical analyses ï§ Monitor flow of drains in the K block ï§ Develop groundwater level contour maps ï§ Develop and run a model to estimate drainage needs ï§ Calculate salt and water balance A Piezometer network consisting of 246 piezometers were installed between Taung in the North and Jan Kempdorp in the south, 208 were surveyed for XYZ coordinates and used for monitoring. The water levels and EC values were measured four times over a period of a year to cover all seasons. The average water level was 1.63 mbgl and the EC average were 191.5 mS/m. Twenty five piezometer sites were selected to cover as much of the soil types present as possible, to determine the hydraulic conductivity. It was between 0.002 and 5.2 m/d. A map was generated to visualize it, and the values were used in the modeling of the drain zones. Water and salt Balance: The leaching requirement to ensure sustainable farming is 611.5 mm/a. According to the water balance it is 562 mm/a. Incoming salts through irrigation water = 4.65 t/ha/a. The TDS determined in 1976 averaged 1005 mg/l, in 2004 it was 1350 mg/l, an average increase of 13 mg/l/a. During the research period it were 1476 mg/l, an increase of 96 mg/l in 5 years an average increase of 19.25 mg/l/a. Irrigation salt not drained = 0.8 t/ha/a Upgrading of all infra structure is essential. Internal subsurface drainage should be cleaned and replaced and the spacing should be decreased to drain the area more effective. Effective drainage would minimize the salt loss prevent a salt build up and have a positive influence on farming and crop quality in the area. The drained water can be reticulated to a transpiration pond to recover the salt thus preventing it from influencing nature and activities downstream.

The project site experienced LNAPL spills in the recent past. In the characterisation of the site it was necessary to investigate the physical properties of the vadose and saturated zones. It was found that temperature, saturation, phase-distribution, the hydraulic properties and water levels contributed to the LNAPL being vaporised. The attributes of the soils substantiated the vaporisation model. The geology was found to be dominated by interbedded sandstones and mudstones, underlain by a dolerite sill. The pollution plume was delineated at the study area and an appropriate management plan was proposed for the site. MNA was shown to be an effective management option.