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This study was aimed at studying bulkflow parameters in groundwater systems at littoral zone of the Modder River. In this thesis, all the aspects were synthesised and exemplified by incorporating a multidisciplinary perspective to develop a sound conceptual framework of the alluvial stream aquifer system. Hydraulic characterisation of the near aquifer system was achieved by acquiring data from a 6-spot pattern well network from which lithological, aquifer hydrogeology, and groundwater hydrogeochemistry characterisations were comprehensively undertaken. The aquifer overburden was estimated to have the permeability of 2.42m/d when its textural classification was found on average to consist of 22% clay+silt and 77% very fine sand. The geology of the study area is typical of the Karoo geology. This was affirmed by massive mudstone bedrock of the Ecca group underlying the study domain. The unconsolidated sediments of gravel, sand and silt, overlie this Karoo mudstone. Therefore, the aquifer is a three units and unconfined alluvial stream aquifer situated in the alluvial deposits along the course of the Modder River. The main units of the system are the upper unit, middle unit and lower aquitard made up of the overbank-fine sand deposits, gravel and mudstone respectively. Groundwater is a bicarbonate type water and falls along a mixing line from sulfatechloride type water to calcium-magnesium type water. This water was found to be both unpolluted sodium enriched and chloride enriched strongly be attributed to forestation of the site where evapotranspiration rates are widespread. Groundwater plots close and parallel to GMWL indicating that recharge is primarily derived from the direct infiltration of precipitation. The δ18O and δD composition of water from the sampled wells indicates that water from all wells drilled in the Riparian or Bank storage aquifer is isotopically lighter than water from wells located on the Terrestrial aquifer. Tritium ranges are indicative of modern water suggesting that the possible influx source might have been precipitation or precipitation derived water. In other words, the groundwater gets recharged with modern rainfalls and has short circulation time in the ground indicative of short travel time. The plot of pH-Tritium indicates that the majority of the samples fall within the rage 6 to 8.5 attributed to recharges with modern and highly neutralised rainfalls. This also suggests short groundwater circulation time in the ground. The groundwater samples with the lowest nitrate concentration were the ones with the lowest tritium level indicating that, although the groundwater source lies on agricultural land, it has not been contaminated by nitrate fertilizers. Groundwater head differences yield the hydraulic gradients from terrestrial aquifer towards riparian aquifer. On average the hydraulic gradient is 0.0083. Flow direction over the entire study domain generally trend SE, sub-perpendicular to the regional surface water flow direction. The EC-profiles show the gravel unit as a major groundwater conduit as shown by a jump in EC values at this unit and this unit is the same water source for all the wells that intercepted the gravel. The transmissivity of the siteâs aquifer ranges between 0.3m2/d and 164m2/d. Highest transmissivity estimated at a maximum level are observed in wells located in the riparian aquifer. The unconfined aquifer specific yield is in the order of 0.005- 0.023. Darcy velocity was estimated at 4.16m/d for CYS1BH4 and natural flow velocity for this well was ultimately estimated at 1.81 m/d. On the other hand, Darcy velocity for CYS1BH3 was estimated at 9.01 m/d with natural flow velocity ultimately estimated at 3.92 m/d. Last in the list is CYS1BH5 whose Darcy velocity was estimated at 11.24 m/d and natural flow velocity ultimately estimated at 22.4 m/d. The estimated velocities are relatively high and this observation holds true for transmissivities so high. Baseflow calculations gave a negative value signifying no base flow contribution of groundwater in to the river. This suggests that most groundwater is used up by the riparian vegetation.

Although the countryâs legislation emphasizes the importance of waste prevention, recovery and re-use, waste disposal currently forms the basis of waste management within South Africa. Due to the lack of facilities as well as the high cost of waste disposal by incineration, the most common form of organic and inorganic waste disposal in South Africa is by landfill. Waste disposal by landfill may be cost effective and is environmentally acceptable if carried out correctly and appropriately. The prime environmental media that are affected by waste disposal by landfill are typically water and air, of which ground water forms one of the major migration pathways for contaminants. Ground water is one of South Africaâs major water resources and it is thus of utmost importance that the countries ground water resource be protected. The greatest threat posed by modern landfills to the ground water environment is the leachate that is generated at the base of the landfill disposal facility. This leachate consists essentially of water-soluble compounds that accumulate in association with infiltrating water as it percolates through the waste. The quality of this leachate is variable and due to the processes by which certain wastes are generated, may contain elements that could potentially have an adverse impact on the environment if the waste is not disposed of correctly. All waste is required to be assessed and appropriately disposed of, as currently formalized in the Department of Water Affairs and Forestryâs, Waste Management Series, Second Edition 1998 - Minimum Requirement Documents. These documents classify waste into two classes, namely general waste and hazardous waste, according to the toxological risk that the waste poses on contaminating the environment. The Minimum Requirement Documents have proposed 10 different landfill liner designs which are required to be installed at landfill disposal facilities according to the classification of the waste. The two landfill liner designs that are suitable for hazardous waste disposal are required to entail significant leachate interception and removal systems, irrespective of the site water balance or site specific conditions and are thus often unrepresentative for the specific disposal facility. Use was made of site specific parameters, such as the required site water balance, geochemical composition and analyses of the slag, physical properties of the slag material as well as the efficiency of the layers within the liner design, to determine the most optimal liner design for the slag disposal facility investigated. Slag in an inorganic metallurgical waste that is generically produced at ferrochrome producing plants in South Africa. Slag is disposed of by means of landfill as a dry aggregate material with an average grain size of 20 mm. The risk that the slag disposal facility posed on contaminating the environment was assessed in accordance with the current environmental legislation and the optimized liner design was determined. The optimized liner design for the 50 ha slag disposal facility investigated consists of 4 layers and is capable of capturing the required volume of leachate in order to optimally protect the environment from any adverse effects caused by the leachate. The liner has thus been designed according to the Best Practicable Environmental Option norm and at the most optimal cost.

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.

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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 used 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 three years, the Beaufort West study area has had extensive investigative work carried out 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 investigation 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 the 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

Eight of the 21 Ramsar-designated wetlands in South Africa are located in similar geohydrological settings as Groenvlei, a 359 ha lacustrine wetland found east of Sedgefield in the southern Cape. Groenvlei is unique as it is isolated from the sea and neither fed nor drained by rivers. Consequently, the lake is fed only by rainfall and groundwater inflow. Losses comprise evaporation and groundwater outflow. These characteristics result in a relatively uncomplicated hydrological system that allows for the geohydrological component to be quantified and understood. Using climatic and lake data monitored by the Department of Water Affairs and geohydrological data collected over a period of a decade, research was conducted to quantify the groundwater contribution to the system and develop an improved understanding of the hydrology of Groenvlei. A daily water balance based on rainfall, adjusted S pan evaporation data and lake levels was used to compute that the nett groundwater contribution to Groenvlei amounted to about 0.3 mm/d. It was shown that S pan evaporation data adjusted by coefficients prescribed by Midgley et al. (1994) should be used to quantify lake evaporation, and that the reed collar transpired 10% to 30% more during summer than evaporated from open water. No water is transpired by the reed collar in winter as the vegetation is dormant. Integrating the water balance results with steady-state Darcian flow calculations and a chemical mass balance indicated direct rainfall (71.6%) and groundwater inflow along the western and northern boundaries of the lake (28.4%) constituted inflow into the system. This is balanced by evaporation from open water (61.7%), transpiration from the reed collar in summer (21.4%) and groundwater outflow along the southern boundary (16.9%). This latter component invalidates claims that Groenvlei is endorheic in character. Recharge to the Eden Primary aquifer was estimated to be in the order of 20% MAP. It was calculated only 5.7% of rainfall in the lake catchment discharges into the lake. The balance of rain entering the subsurface is lost through terrestrial evaporation or discharges into the sea via the deeper part of the aquifer. It was interpreted that the deceptively thick vadose zone plays a buffering role in the hydrology of the area and that evapotranspiration losses are appreciable. The importance of the reed collar was further exemplified by the retention of salts in the vegetative fringe. Salts are assimilated by the vegetation and retained in the hyporheic zone until re-entrained into the main water body through wind and wave action. This results in only part of the salt load leaving the lake along the southern boundary and affecting groundwater quality between the lake and the sea. Further research is required to confirm this. The results of the research allowed for tools to be developed to assess the impact of groundwater abstraction from the lakeâs catchment on lake levels and water quality. These tools could also be used to demonstrate Groenvlei has long since lost its connection to the marine or estuarine environments, with a new equilibrium being reached within 120 years of disconnect. The young lake is dynamic in character and rapidly responds to hydrological change. In its short history, Groenvlei has adapted and responded to changes in both sea level and climate, collectively resulting in the present-day system. In addition to highlighting the importance of sound conceptualisation, data quality and a convergence of evidence, the outcomes of this study challenged the findings of Roetsâ (2008) PhD research and found no scientific evidence to support his contention that Groenvlei is sustained by underlying Table Mountain Group aquifers. It was also found that the permeability south of Groenvlei is not low and the extent of the lake catchment is 25 km2. Past research of Groenvlei has resulted in a number of misconceptions and it was argued a need exists to link hydrologists and ecologists to better understand wetlands, with each contributing specific skills and knowledge. An important contribution of the research documented in this thesis is that the approach used can be applied to similar wetlands where the role of groundwater might be less obvious because of river flows and tidal exchange. The importance of sound conceptualization and direct rainfall onto wetlands, quantification of evaporative losses using S pan data and coefficients prescribed by Midgley et al. (1994), and the relationship between open water losses and transpiration losses are three aspects that could improve the understanding and quantification of lake â groundwater interaction elsewhere. A limitation to understanding the geohydrology of Groenvlei is the lack of information pertaining to aquifer thickness. It is therefore recommended four boreholes be drilled to either bedrock or at least 100 m in depth (whichever is reached first) to quantify the thickness of the aquifer. Other limitations that require attention include: ï· Uneven spatial distribution of the geohydrological data; ï· Lack of information of losses from open water and the reed collar; and ï· Absence of monitored groundwater data needed to address temporal relationships between groundwater and the lake.

The significance of a reliable groundwater resource assessment is of growing importance as water resources are stretched to accommodate the growing population. An essential component of a groundwater resource assessment is the quantification of surface water â groundwater interaction. The insufficient amount of data in South Africa and the apparent lack of accuracy of current estimates of the groundwater component of baseflow lead to the investigation of a new methodology. The applicability of the Mixing Cell Model (MCM) to quantify the groundwater contribution to baseflow is examined to determine whether the method would be of use in groundwater resource assessments. The MCM simultaneously solves water and solute mass balances to determine unknown inflows to a system, in this application the groundwater component of baseflow. The incorporation of water quality data into the estimation of the surface water â groundwater interaction increases the use of available data, and thus has the ability to decrease the uncertainty of the estimation process. The balance equations are equated to an error term which is used in the quadratic programming solution of minimizing the square error sums in order to determine the unknown inflows. The mixing cell model is applied to datasets from the surface water â groundwater interaction test site developed by the University of the Free State, in addition to data collected along the middle Modder River during a fieldwork survey. The MCM is subsequently applied to a set of quaternary catchments in the Limpopo Province for which there are available calibrated estimates of the groundwater component of baseflow for the Sami and Hughes models. The MCM is further applied to the quaternary catchment D73F, located in the semi-arid Northern Cape, to assess the applicability of the mathematically based MCM in terms of a flow system located within a regionally-defined zero groundwater baseflow zone. The MCM results for each study area are assessed in comparison to groundwater baseflow volumes determined by the Pitman, Sami and Hughes models. A chemical hydrograph separation method which also incorporates water quality data is additionally reported for the study areas to further validate the MCM. The results indicate that the mixing cell model can reliably estimate the groundwater component of baseflow to a river. This application of the mixing cell model could contribute to increase and evaluate the accuracy of current groundwater baseflow estimates in South Africa, which will in turn ensure the responsible and sustainable use of the countries water resources.

This dissertation describes the results of field based investigations on groundwater flow at Ruashi Mine located in Katanga Province of Democratic Republic of Congo (DRC). The core objectives of the study were to simulate groundwater flow, estimate flow into the pits and ultimately design a dewatering strategy for the mine. In order to understand how groundwater flows into and through the mine, a detailed conceptual hydrogeological model was constructed as framework for numerical groundwater flow modelling. The numerical model was used simulate groundwater flow and predict pit inflow volumes. At the time of this research, mining at Ruashi was being carried out in three pits that are expected to reach terminal depth of 180 metres below ground level (mbgl) in 16 years of continued mining. The mine is located along a faulted overturned syncline composed of composed of Siltstones, Argillites, Sandstones and Shales and covered by Laterite. Based on aquifer hydraulic testing results, the transmissivity of the shallow aquifer was estimated to be 10 m2/d. The specific yield for the deep aquifer was estimated to be 1 x 10-5. The Chloride Mass Balance Method was used to estimate recharge to the groundwater system as 280 mm per annum (14% of Mean Annual Precipitation). Water levels vary from 1.02 to 62.5 mbgl. The general groundwater type was analysed to be calcium-magnesium-bicarbonate (Ca-Mg- HCO3), typical of young groundwater. The numerical groundwater flow model area is 15.7 km2 and comprises 5 layers, 17 240 elements and 10 614 nodes. The model results indicated that groundwater flow to the pits is unlikely to exceed 42 000 m3/d. Using the pumping capacity (15 000 m3/d) for year 2012, a maximum water level drawdown of 55 m was estimated. However, the numerical model demonstrated that the existing pumping boreholes can be augmented by an additional set of 16 boreholes pumping 2 000 m3/d per borehole. This pumping rate can lower the groundwater level to about 1 188 mamsl which is about two meters below pit terminal elevation. This study made significant contribution to understanding the hydrogeological properties of aquifers at the mine. The aquifer hydraulic testing data was used to estimate aquifer hydraulic parameters. However based on the field evidence, it is suggested that Packer testing could improve the estimates of aquifer hydraulic parameters for each aquifer. The numerical model demonstrated the typical aquifer response to different pumping scenarios. The different pumping scenarios were run in order to determine the optimum pumping rates to dewater the mine.

The vital role of water within the mining industry, both as an asset which generates value as well as a shared natural resource requiring responsible stewardship, have long been recognised. Due to extreme climate changes, an increasing population density and poor water management, securing of water has become a global challenge and water scarcity will continue to be one of the greatest challenges facing mine water management. There is no simple recipe for mine water management and regulations by environmental authorities, along with past polluting practices, are forcing mining operations to improve and prioritise their water consumption. Accordingly, this sector is expected to be increasingly required to demonstrate leadership through innovative water use management. A mine water balance is considered to be one of the most important and fundamental tools available for mining operations as management begins with a basic understanding of where water is sourced from, and where it is utilised. With this kept in mind, a mine water balance should be based on a holistic systems model approach with an appropriate relationship between the required level of complexity in the model structure and purpose. Excessive detail can cause the model to become clumsy and tend not to focus on strategic water management principles. Emphasis should be put on a system approach, taking into consideration the main interactions, feedbacks and functional relationships between the various parts of the whole system. An overall mine water balance that superimposes different water systems can be divided into a process water system and a natural water system. The natural water system is associated with the intrinsic hydrological cycle and is often disregarded due to uncertainties. It can however significantly impact on mine water usage and losses as indicated in this case study. Consequently, decision making and management options should be based on the evaluation of the system as a whole and inclusion of the natural system as a component of the mine water balance is imperative for accurate quantification. The natural system includes a surface water environmental circuit as well as a groundwater environmental circuit. Surface and groundwater resources have historically been managed separately, but more than ever before, interaction between these two systems are required to facilitate effective resource management. Mining activities have a major effect on the modification of the hydrological regime and the influence of increased hydraulic conductivity along with mining induced recharge, should be evaluated as part of the adapted mine water balance. Furthermore, mine dewatering predictions and climatic scenarios must be incorporated to reflect site conditions more accurately. As poor water management poses an operational risk to mining operations, this sector has developed novel ways to respond to water issues in differing circumstances and has illustrated the ability to turn risk into opportunity. Now, more than ever, special measures are needed to identify options for life-of-mine strategies and initiatives for water conservation and management. Future focus should be to continue investigation and implementation of the water use strategies in order to improve performance across operations and encourage engagement with other water users. Moreover, to share experiences, learn from others and contribute to water discussions and debate at local, national and international levels.