Masters Degrees (Institute for Groundwater Studies (IGS))

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Open Access
Acid-base potential characterisation in the Southern highveld coalfield of Mpumalanga
(University of the Free State, 2017-07) Ntwaeaborwa, Gaonkile Molly; Deysel, Lore-Mari
Pyrite, iron disulphide is the most common mineral in the metal sulphite and coal deposit. The oxidation of Pyrite and other metal-sulphide minerals by oxygen has a large environmental impact and plays a key role in Acid Mine Drainage (AMD). Environmental impact shows that soil acidity, toxic metal concentrations and vegetation damage are the predominant negative impact of AMD. AMD is a major concern for the mining industry because mining activities tend to increase the amount of rock surface exposed to air and water. Mining companies are increasingly required to evaluate the AMD potential at future mine sites and provide detailed plans to prevent or minimise AMD at all phases of mine operation as part of the environmental Impact assessment (EIA) process. An investigation was conducted in two mine (Mine 1 and Mine 2) areas in the Southern Highveld Coalfield of Mpumalanga. Mine 1 is an underground coal mine and is situated 10 km outside Trichardt on the road to Bethel. It was established in May 2012 and its shaft supply coal to Sasol Synfuels. Mine 2 is an open-cast coal mine and is situated between 2 towns, amely Trichardt and Kriel. Construction activities started in 1990 and the mine reached full production in September 1992. Both Mines fall in the Karoo Supergroup which comprises of Ecca group formation and consist dominantly of sandstone, siltstone, shale and coal. The aim of this study was to investigate the acid-base potential of these two Mines. 118 samples were collected from Mine 1 borehole core and 71 samples were collected from Mine 2 borehole core to conduct mineralogical and Acid Base Accounting (ABA) analysis. Acid- base potential leachate were further analysed for major and trace elements using Inductively Coupled Plasma-Optical Emission Spectrometer (ICP-OES). Most of the samples analysed for Mine 1 have been found to have High AMD risk at the interburden and these samples have low NNP values, all these samples consisted of coal and they contained pyrite mineral as indicated in the mineralogical analysis. These samples must be taken into consideration to minimise oxidation. Samples (Mine 1) that contained layers of sandstone, siltstone and shale have the highest NNP values and these layers can be used as a buffer to neutralise the AMD. Therefore Mine 1 will produce an AMD at the coal seam once exposed during mining. Mine 2 shows that 3 samples have High AMD risk at the interburden while 2 boreholes show the risk between 20m and 60m, and these samples were coal samples and others were sandstone samples and they contained pyrite. These samples that have coal showed low NNP. Therefore most of the acid generation would be mainly found at the coal seams. Layers that show high NNP values consisted of sandstone, siltstone and shale. They showed no indication of acid generation, therefore they will work as buffers to neutralise the any AMD that will be produced. Mine 2 also indicate that AMD will be produced at the interburden at layers that contains coal, therefore more consideration is needed when these layers are exposed during mining. With such condition it is possible for the mines to predict the types of situations that might arise concerning groundwater quality, and implement proper prevention or remediation programs.
Open Access
Analysis of dissolution trapping mechanisms on CO₂ plume: Carbon capture and storage
(University of the Free State, 2022) Kholotsa, Mathapelo Emely; Atangana, A.
The practice of carbon capture and storage effectively lowers greenhouse gas emissions and mitigates climate change and global warming. To determine whether long-term geological CO₂ sequestration is safe and practical, scientists have increasingly relied on model-based predictions of CO₂ behavior beneath the earth's surface in recent years. This investigation aims to get a firm grasp of the CO₂ dissolution trapping process and mathematical models depicting the behavior of the CO₂ convective dissolution process (Fingering) in saline aquifers. This comprehension will eventually help to ensure that the CO₂ plume stays inside the designated locations of CO₂ storage. The approach involved employing the concept of fractional differentiation by replacing the classical time derivative with the Caputo, Caputo Fabrizio, and Atangana Baleanu fractional derivative. To analyze the finger development process using three non-local operators: Power law, exponential law, and Mittag-Leffler function. Equally important, through performing linear stability analysis, we considered the stability evolution equation for the perturbation, which incorporated the exponential law and thus resulted in a memoryless function. We then replaced the exponential kernel with the Mittag-Leffler kernel to the perturbation equation to modify it into a process that has memory. By incorporating the Mittag-Leffler kernel into the perturbation equation, we suggest a new approach that provides a more accurate, robust, and efficient solution algorithm to capture finger development. In conclusion, we demonstrated some numerical simulations obtained using MATLAB.
Open Access
Application of artificial neural networks in the field of geohydrology
(University of the Free State, 2009-03) Steyl, Gideon; Dennis, S. R.
English: Groundwater has been identified as a viable alternative for future freshwater production in South Africa. The management thereof is steadily gaining more recognition from governmental institutions. A significant obstacle in the development of this resource is the conceptual understanding of surface water and groundwater interaction. The availability of reliable data for rainfall, flow volumes in rivers and water levels in boreholes have prompted an investigation into patching incomplete data sets. This study also focused on predicting the influence of rainfall and flow volumes in a river on the surrounding groundwater levels. Neural networks have been used to investigate both data patching and forward prediction of water levels in selected data sets.
Open Access
Application of the Mixing Cell Model to the quantification of groundwater – surface water interaction
(University of the Free State, 2013-07) Matthews, Amy Jane; Witthüser, K. T.; Van Tonder, G. J.
English: The significance of a reliable groundwater resource assessment is of growing importance as water resources are stretched to accommodate the growing population. An essential component of a groundwater resource assessment is the quantification of surface water – groundwater interaction. The insufficient amount of data in South Africa and the apparent lack of accuracy of current estimates of the groundwater component of baseflow lead to the investigation of a new 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 – 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 – 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.
Open Access
Appraisal of geophysical methods used for groundwater exploration in South Africa
(University of the Free State, 2023) Kolobe, Libuseng T.; Fourie, F. D.
Groundwater is a crucial resource that has been a means of survival for humans for many years, as seen in the tendency to settle near springs (Fitts, 2013). Interestingly, groundwater was extracted from dry mountain basins by Persians in what is now modern Iran (Fitts, 2013). Indeed, many methods have been developed over time to explore groundwater, as has been done with other resources of the Earth that are not readily visible. According to Arefayne 𝘦𝘵 𝘢𝘭. (2016), groundwater exploration is “the investigation of underground formations to understand the hydrologic cycle, know the groundwater quality, and identify the nature, number, and type of aquifers”. Numerous exploration methods are employed and are often used in conjunction with one another to ensure the most accurate estimation of groundwater potentiality in a given area. These exploration methods may be direct or indirect (Balasubramanian, 2017), with surface methods often indirect. These include esoteric techniques, which are the most ancient, also known as water witching or dowsing. Here, operators using a forked stick or an egg (Balasubramanian, 2017) claim to be able to detect water underground, the accuracy of which is fairly unproven (Arefayne and Abdi, 2016). Geomorphological methods study the landforms in the area of interest to show where the groundwater is likely to occur (Balasubramanian, 2017). Features such as pediplains or valley flats often show good groundwater potential (Sedhuraman et al., 2014). The slope and drainage density are also particularly important features as there is more infiltration in gently sloping areas, and a higher drainage density indicates more runoff and, hence, less potential for recharge (Sedhuraman et al., 2014). Other surface exploration methods may be geological in nature (Balasubramanian, 2017). Such methods first collect and analyse topographic maps, aerial photographs, geological maps, and core logs. This is then supplemented by geological field reconnaissance and evaluation of hydrological data on stream flows, springs, well yields, groundwater recharge levels, and water quality (Balasubramanian, 2017). Faults, joints, and lineaments are also noted, as these may form preferential flow paths for groundwater (Van Tonder 𝘦𝘵 𝘢𝘭., 2001). The structure of the water-bearing strata can also give indications for groundwater occurrence (Balasubramanian, 2017). Contacts between permeable rock overlying impermeable strata along the sides of valleys are suitable locations for groundwater (Balasubramanian, 2017). Quartz veins and dykes can be linear and form ridges (Nel, 2017). There, erosion-prone rock types may form depressions and are connected with structures ideal for water storage (Nel, 2017). Geobotany, which is the study of how plants are related to the subsurface, can also be used in the exploration of groundwater (Odhiambo, 2016). This means observing any anomaly in the growth of vegetation or trees growing in a straight line can be an indicator of subsurface moisture changes (Nel, 2017). The presence of phreatophytes can also allude to the presence of groundwater (Nel, 2017). Halophytes and white efflorescence of salt on the ground may also be an indication of shallow brackish or saline groundwater (Balasubramanian, 2017). Playas and precipitation of salt are also good indicators of possible groundwater occurrence (Balasubramanian, 2017). Photogeology, which is the use of aerial photography to study geology, can also provide valuable information for targets of a groundwater exploration exercise (Mekel, 1988). Another manner through which groundwater exploration can be conducted is through the use of geophysical methods. There are a variety of geophysical methods used in groundwater exploration employed for several reasons. However, the main objective of geophysical surveys in hydrogeology is to provide parameters for the creation of models essential for decision-making in groundwater exploration and protection (Mpofu 𝘦𝘵 𝘢𝘭., 2020). Geophysical survey methods can be airborne, conducted on the surface, or even conducted down boreholes (Balasubramanian, 2017). These methods operate primarily by detecting anomalies or contrasts in the physical properties of the Earth (Balasubramanian, 2017). These properties include but are not limited to density, elasticity, magnetism, and electrical resistivity. Such anomalies indicate the potential zones which can be exploited for groundwater. The use of geophysics in groundwater exploration is very important as it removes the need to drill many boreholes before the target is reached (Mpofu 𝘦𝘵 𝘢𝘭., 2020). Geophysical tools are invaluable in groundwater exploration; therefore, this study will be primarily based on the use of geophysics for groundwater exploration in South Africa.
Open Access
Aquaponics as a productive rehabilitation alternative in Mpumalanga Highveld coalfields
(University of the Free State, 2016-03-11) Botha, Ilse; Weaver, Alex.
The Mpumalanga Highveld Region is commonly known for its coal mining activities, especially surface mines. South Africa is still reliant on coal as its main energy source. A dilemma identified is that most of the coal reserves in Mpumalanga are (or were) located below highly productive arable land formerly used for food production such as maize. With a growing energy demand, these valuable areas of land are being impacted negatively. The post-mining land is predominantly rehabilitated to a grazing land capability instead of the pre-mining arable land capability, hindering the production of crops on those areas when mining ceases. This adds to the food security threat which South Africa is currently facing. The National Development Plan 2030 indicated the intentions to diversify the national economy. It was identified that agricultural activities should be expanded to relieve the high levels of poverty in rural areas, and that sustainable agriculture should be the main focus. With the prevailing trends of surface coal mines expanding on available arable land, the realization of this goal might not be possible. This study looked at aquaponics as a possible environmental management alternative that will enhance the agricultural productivity of rehabilitated mine land. An experimental site located close to Middelburg and Emalahleni was used as the base for this study to determine the financial feasibility of such a venture. Five chosen mines within a 20km radius were investigated to understand their rehabilitation practices and to prove that the sites are rehabilitated to a grazing land standard. These sites were all identified as favourable for the initiation of aquaponics. The two post-mining land use alternatives were compared with one another to understand what the benefits and constraints are. The economic driver was a main focus, followed with a brief overview of environmental and social aspects that can be kept in mind when these land uses are established.
Open Access
Assessing the feasibility of constructing a groundwater contaminant fate and transport model for an LNAPL affected fractured rock aquifer
(University of the Free State, 2011-05) Möhr, Samuel; Dennis, Ingrid
English: 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.
Open Access
Assessment of groundwater ingress into mine workings from the deep-seated fractured rock aquifer in the Bushveld Igneous Complex at Dishaba mine
(University of the Free State, 2023) Dumakude, Sbusiso Kwanda; Fourie, Francois D.
Dishaba Mine is reported to experience approximately 16 ML of groundwater ingress daily. The water ingresses occur across the mine, from off-reef haulages to mostly Merensky reef stopes. The water enters the mine workings through fractures, boreholes, and open mining excavations, and poses a risk in terms of mine safety. However, the water entering the mine also presents an opportunity for the mine to reduce its reliance on potable water and potentially use groundwater to meet day to day water requirements for mining and ore processing.
Open Access
Assessment of groundwater resource in the Tsineng area, Northern Cape: a geophysical survey perspective
(University of the Free State, 2016-07) Mokgatle, Tumelo; Fourie, F.
English: In this study the groundwater resource the in Tsineng area, Northern Cape was assessed in terms of the volumes of water that may be sustainably abstracted from the aquifer system, and the quality of the available groundwater. A strong emphasis was placed on the use of airborne and ground geophysical techniques to gain a better understanding of the geological and geohydrological conditions in the study area. The airborne geophysical technique employed during the current investigation was the time-domain electromagnetic method (using the SkyTEM system), while ground geophysical surveys employed the gravity, magnetic, frequency-domain electromagnetic and electrical resistivity tomography methods. The geophysical techniques were used to provide information on physical changes in the subsurface conditions that may be related to the presence of geological structures associated with potential groundwater resources. The results of all the geophysical methods used were collated and correlated to the local geology to make an informed decision during the selection of drilling targets for the installation of production boreholes. From the TDEM data, information on the subsurface distribution of resistivities was obtained. Well-defined resistivity anomalies correlated well with the known presence of two prominent fault zones. Furthermore, resistivity anomalies were also identified at the locations of mapped dolerite dykes known to intersect the study area. The ground geophysical investigations were conducted across preliminary targets defined from the airborne TDEM data. The ground geophysical investigations confirmed the presence of the structures identified from the TDEM data. Based on the results of the geophysical investigations and the known local geological conditions, drilling targets were selected at positions deemed promising for the installation of successful production boreholes. A total of 78 exploration boreholes were drilled during the current investigations. Sixty of these boreholes had water strikes and were thus considered successful. A combined total blow-yield of 409 l/s was measured in the successful boreholes. Forty of the drilled boreholes had blow-yields in excess of 2 l/s. These boreholes were selected for aquifer hydraulic tests to assess the hydraulic parameters of the intersected aquifer systems. From the estimated hydraulic parameters, sustainable yields were determined for the tested boreholes. The total estimated sustainable yield from the boreholes was more than 7 500 m3/day. Water samples from the 40 high-yielding boreholes were submitted for chemical analyses. The results of the analyses showed that the water in the study area is generally of very good quality, suitable for human consumption. It is therefore concluded that groundwater may be successfully used to augment the municipal water supply in the Tsineng area. The results of the current research demonstrate that the use of geophysical techniques could greatly contribute to an understanding of the geological and geohydrological conditions in a study area, which could in turn lead to a higher success rate during groundwater exploration programmes. Keywords: Geophysical Afrikaans: In hierdiestudie is die grondwaterbronne in die Tsineng-area in die Noord-Kaap Provinsiegeëvalueer in terme van die volumes water wat volhoubaaronttrekkan word vanuit die akwifeersisteem, asook die kwalitiet van die beskikbaregrondwater. ‘nSterkklem is geplaas op die gebruik van geofisiesetegnieke om ‘n beterinsig in die geologieseengeohidrologiesetoestande van die studie-area teverkry. Die lug-geofisiesetegniek wat gebruik is gedurende die huidigeondersoek was die tyd-domeinelektromagnetiesemetode (die SkyTEM-sisteem is gebruik), terwyl die grondgeofisieseopnames die gravitasie-, magnetiese-, frekwensie-domeinelektromagnetiese-enelektrieseweerstandtomografie-metodesgebruik het. Die geofisiesetegnieke is gebruik om inligtingtebekomoor die fisieseveranderingeondergronds wat verband mag hou met die teenwoordigheid van geologiesestrukturegeassosieer met potensiëlegrondwaterbronne. Die resultate van al die geofisiesemetodes is gesamentlikbeskouengekorreleer met die plaaslikegeologieomingeligtebesluitete neem tydens die seleksie van boorteikensvir die installering van produksieboorgate. Vanaf die TDEM data is inligtingoor die ondergrondseverspreiding van soortlikeweerstandeverkry. Goed-gedefinieerdeweerstands-anomalië het goedooreengestem met die bekendeteenwoordigheid van twee prominenteverskuiwingsones. Verder is weerstands-anomaliëookgeïdentifiseer by die posisiesvan bekendedolerietgange wat die studie-area deurkruis.Die grondgeofisieseondersoeke is gedoenoorvoorlopigeteikens, soosgedefinieervanaf die TDEM-data.Die grondgeofisieseondersoekehet die teenwoordigheidbevestig van die strukture wat vanaf die TDEM-data geïdentifiseer is. Vanaf die resultate van die geofisieseondersoeke, asook die bekendeplaaslike geologiesetoestande, is boorteikensgekies op plekke wat as belowendbeskou is vir die installering van suksesvolle produksie boorgate. ‘n Totaal van 78 eksplorasie boorgate is geboortydens die huidigeondersoeke.Sestig van hierdieboorgate het water getrefen is gevolglik as suksesvolbeskou.‘n Gekombineerde total eblaaslewering van 409 l/sis gemeet in die suksesvolleboorgate.Veertig van die boorgate het blaaslewerings van meer as 2 l/s gehad. Hierdieboorgate is gekiesvirhidrouliesetoetsing van die akwifeerom die hidrouliese parameters van die akwifeer-sisteemtebepaal. Vanaf die geskattehidrouliese parameters, is volhoubareleweringsvir die getoetsteboorgatebepaal. Die total egeskattevolhoubarelewering van die boorgate was meer as 7 500 m3/day. Watermonsters van die 40 hoë-leweringboorgate is ingedienvirchemieseanalises. Die resultate van die chemieseanalises het getoondat die water in die studie-area oor de algemeen van baiegoeiekwaliteit is, geskikvirmenslikegebruik. Die water kandussuksesvolgebruik word om die munisipalewatertoevoer in die Tsineng-area aantevul. Die resultate van die huidigeondersoek toon dat die gebruik van geofisiesetegniekegrootlikskanbydra tot die begrip van die geologieseengeohidrologiesetoestande in ‘n studie-area, wat weerkan lei tot ‘n hoërsukseskoersgedurendegrondwatereksplorasieprogramme
Open Access
Assessment of the groundwater potential of the Middel Kop/Appleby aquifer, Stella District, Northwest Region
(University of the Free State, 2001-08) Nel, Jacobus Marthinus; Botha, J. F.
English: The importance of groundwater is strongly reflected in the new South African water policy and legislation. All water resources, including groundwater, are now seen as an indivisible asset, with the National Government as its custodian to ensure that the resources are protected, developed and managed properly. Groundwater is the sole source of potable water for the town of Stella in the Lower Vaal Water Management Area of the Northwest Province, but the existing well-field is barely able to supply the present demand. Previous attempts to supply the town with water from groundwater resources have failed, because of the low potential of the aquifers and the poor quality of the groundwater. The proposed resettlement of 2 000 people therefore has to be postponed until sufficient additional water resources can be found for the town. One possible source, not included in previous groundwater explorations of the area, is the granitic aquifer on the farm Middel Kop situated approximately 5 km south-east of Stella. Farmers have used this aquifer extensively since 1990 to irrigate 171 ha of agricultural land. It was consequently decided to investigate this aquifer as a possible additional source of water for Stella. However, farmers have already noticed a continuous decline in the water levels over the years. This meant that the focus of the investigation had to be changed from merely an exploration exercise to an evaluation of the aquifer and the development of a suitable management scheme for the aquifer, as described in this thesis. There are not enough data available to perform a detailed assessment of the aquifer at the moment, a deficiency that should be addressed in future investigations and management of the aquifer. The existing data, however, indicate that the aquifer may be able to sustain a yield of approximately 4 227 m3 d-I in the near future. This volume of water will be able to supply in the needs of the present population and the additional 2 000 resettled people, while allowing 73% of the current irrigated area approximately 8 000 m3 ha-I annually for irrigation. The latter figure can only be achieved if the farmers are allowed to produce one crop per year instead of the two, which is in some cases the practice. This reduction in the water allocated for irrigation may seem harsh, but the decline in the water levels over the last couple of years clearly indicate that the farmers cannot continue with the present practices for much longer. The groundwater quality of the Middel Kop aquifer can be rated as marginal for human consumption. This applies in particular to the relatively high concentrations of fluoride and nitrate in the water, which could affect the health of the population adversely if used untreated for long periods. The conclusion reached in the thesis is that the Middel Kop aquifer can only be used as a source of water for Stella on condition that a detailed monitoring scheme is introduced from the beginning and used to develop a suitable management scheme for the aquifer. This approach will ensure that any impacts on the resource can be properly evaluated and that the quality and quantity of the water can be preserved for future generations.
Open Access
Baseline study of Kendal Power Station
(University of the Free State, 2011-05) Moolman, Dirk; Vermeulen, P. D.
Abstract not available
Open Access
Characterisation and management of a LNAPL pollution site along the coastal regions of South Africa
(University of the Free State, 2009-11) Vermaak, Kevin Harry; Van Tonder, G. J.; Steyl, G.
English: 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.
Open Access
Characterisation of the deep aquifers of South Africa - the Karoo Supergroup and Table Mountain Group
(University of the Free State, 2019-06) Makiwane, Nwabisa; Fourie, F. D.; Allwright, A.
Abstract not available
Open Access
Characterisation of the dolomitic aquifer in the Copperbelt Province, Northern Zambia
(University of the Free State, 2005-02) Prinsloo, Martiens; Vermeulen, P. D.
English: External factors that influence the aquifer characteristics of, and sustainable yield from, the dolomitic aquifer include topography, rainfall, surface drainage, evapotranspiration, plant growth, geology, and soils. The topography is gently undulating with a gradient of between 1:400 and 1:800. The low topographical gradients inhibit surface run-off and promote high recharge rates. The annual rainfall will provide the volume of water present in the catchment area that is available for potential recharge to the aquifer. The average rainfall is 1 115mm/annum. Water that leaves the hydrological system of the study area as surface run-off impacts on the volume of water available for recharge to the aquifer in the area. Despite the high rainfall volume and high rainfall intensity only one perennial surface run-off structure exists in the study area. The Kafue River is on average 10 to 20m wide and 3m deep. Only one non-perennial surface run-off feature exists. This feature feeds into the Ipumbu Dam. The volume of water that evaporates from the soil and vegetation before it can reach the underlying aquifer will impact on the volume of water that can be abstracted from the aquifer without negatively impacting on the volume of water in storage in the aquifer. Very little evaporation data is available for the study area. Comparing the calculated potential total evaporation volume with the measured net evaporation and annual rainfall indicates a discrepancy between the evaporation and rainfall data. The rainfall data is considered to be accurate, and based on perceived inaccuracy of the evaporation data, it is recommended that the evaporation data not be used in water balance calculations. The natural plant growth influences the evapotranspiration and in some cases the surface run-off characteristics. Brachystegia Miombo woodlands cover the study area with areas of widespread grass cover between the trees. The main aquifer consists of Upper Roan Formation limestone and dolomite. The main joint set (160º strike direction) controls the strike direction of the solution cavities in the area. Schist and quartzite of the Lower Roan Formation border the limestone and dolomite. Extensive fracturing in the dolomite is found in the geological logs of the high yielding boreholes drilled in the area. The soil in the study area displays infiltration rates higher than the observed rainfall intensity. Combined with the low topographical gradients that retard run-off the high infiltration rate leads to high recharge percentages. The aquifer hydraulic characteristics were determined during the investigation. It is considered that Lake Nampamba forms part of an extensive, well-connected solution cavity network. No compartmentalisation of the dolomite is evident. Three prominent karstic features (Lake Nampamba, Lake Kashiba and the “Chibili Pavement”) occur in the area. Both Lake Nampamba and Lake Kashiba are sinkholes in the dolomite. The author has no scientific evidence to conclude that the solution cavity network stretches as far as the Kafue River. However, analysis of the water level, abstraction and water level data does confirm that Lake Nampamba in the east and the dambo areas in the west that feed Ipumbu dam are interconnected. The groundwater displays a calcium-magnesium dominant character, as is expected from a dolomitic aquifer. Plotting the chemistry data on a trilinear (Piper) diagram indicates that the groundwater recently recharged. This corresponds to the theory of high recharge due to the relatively high rainfall, flat topography, and high soil infiltration rate. Depth to groundwater varies on a seasonal basis due to fluctuations in rainfall and thus recharge, and abstraction volumes. The groundwater level shows an immediate response to recharge, but does indicate a one to two month delay between maximum rainfall and peak groundwater level. A total of 65 boreholes were drilled in the study area between 1978 and 2004. Preliminary aquifer tests were performed on 38 boreholes, and 14 boreholes were identified as high yielding boreholes. Constant rate aquifer tests were performed on these boreholes. The aquifer test data was analysed to obtain the aquifer transmissivity. The aquifer transmissivity ranges between 1 and 6 900m2/day. This wide range is expected in karstic aquifers where the high transmissivity is associated with solution cavities and fractured areas. The low transmissivities are associated with the fine crystalline, competent, unweathered rock. Sustainable yields from the borehole calculated from the aquifer test data range between 5 and 100l/s (432 and 8 640m3/day). Recharge calculations were performed using the Chloride, SVF, Equal Volume and CRD methods. The chloride method is used only as an indication of the recharge percentage. The SVF, Equal Volume, and CRD methods calculated recharge as 25% of the annual rainfall. Aquifer storativity is calculated using the SVF and CRD methods at 0.02 (2%). The total volume of water that can be abstracted from the combined eastern and western aquifers is calculated to be 136Mm3/annum. The current and proposed future annual abstraction volumes are 25.3Mm3 and 44.42Mm3 respectively. This indicates that the combined eastern and western aquifers are capable of sustaining the abstraction volumes. A numerical model was constructed to evaluate the assumptions made, and correlates the calculated values of the manual calculations. The model was initially constructed in steady state without taking the abstraction from the aquifer into account. Once the model was successfully calibrated, the abstraction volumes were incorporated into the numerical model and the model was further calibrated against time series observed rainfall, groundwater levels and abstraction volumes by comparing the groundwater levels with time against those calculated using the numerical model. Once the model was calibrated, the model was applied to evaluate the sustainability of the current and proposed abstraction programs. The numerical model confirms that the combined eastern and western aquifers are capable of sustaining the abstraction programs.
Open Access
Comparing model calculated groundwater volumes with alternative methods in a mining enviroment
(University of the Free State, 2012-09) Boshoff, Elida; Van Tonder, Gerrit; Dennis, Ingrid
English: A new opencast coal mining operation is proposed in the Belfast region in Mpumalanga, South Africa. This proposed operation is the study site that was investigated in this thesis. The Belfast opencast operation is expected to be operational for 29 years and coal from mainly the number 2 and 3 seams will be mined. The inflow rate of the groundwater was determined by using both analytical and numerical groundwater methods. The rate at which groundwater flows into the mine voids are important to estimate before mining commence since this will determine at what rate groundwater needs to be pumped from the mining pits to ensure dry and safe working conditions. In order to obtain site specific data for the study area, several field investigations have been conducted. These investigations include a geophysical survey, drilling of monitoring boreholes and pump testing of the monitoring boreholes. These investigations are done to obtain a better overview of the aquifer conditions in the study area. For the study area a numerical groundwater flow model was constructed and the groundwater inflow was determined by making use of a water budget function. The analytical approach to determining the inflow included four different methods. A sensitivity analysis was done on the recharge with the numerical and analytical methods. The results from the numerical and analytical approaches were compared to determine whether the analytical approach is in fact a good way of obtaining values that relates with the numerically obtained results. If there is a good correspondence between the analytical and numerical results, the analytical approach can be regarded as a save and representative way to obtain groundwater related values. Especially during the early stages of mine planning analytical methods would be supportive to quickly determine mine related issues as this will assist in decision making and related cost estimates. From the results obtained in this thesis it can be concluded that the analytical approaches used during this study, although giving close to numerical answers, cannot be used in an effective manner in determining groundwater inflows during the early planning of mining. The fact that the analytical approaches did not reveal representative values for the groundwater inflows and also do not correlate with the numerical model results, does not mean that this will be the case at another site with different geohydrological characteristics. It is important to note that assumptions are always made in analytical methods. It is suggested that further research be conducted in relation with analytical and numerical modelling of opencast mines. Research should be performed at several mines to determine whether the relation between the numerical and analytical approaches display similar trends than was found during this study. These mines should preferably be on similar geological areas to compare with each other. The only way to determine whether the analytical methods can in fact be used to get a representative result is by repetition on several mining sites and also comparing these values with the numerical model results and also the actual inflow rates from the mine once mining has started.
Open Access
Composition and performance of multi-layer liner systems to inhibit contaminant transport in a fly-ash dump
(University of the Free State, 2013-07) Mokhahlane, Lehlohonolo; Steyl, G.
English: The engineering properties of a South African class F fly ash were studied as a potential base liner for a dry coal ash dump. In order to increase the unconfined compression strength, lime and gypsum were added to the fly ash while also aiding in reducing the hydraulic conductivity. Lime was added in the range of 1 to 10% while the gypsum amounts were varied at 1% and 3% per specimen. The constant head method was used to determine the hydraulic conductivity of compacted specimens in the laboratory. Gypsum was observed to have more influence in reducing the hydraulic conductivity as specimens with 3% gypsum had a more reduced hydraulic conductivity that those with 1%. The variations in lime percentages did not appear to reduce the hydraulic conductivity but rather displayed higher values than fly ash specimens without additives when higher percentages of lime were used. A fly ash admixture of 3% lime and 3% gypsum was found to have the lowest hydraulic conductivity of 2.27 x10-9 m/s after 60 days of percolating with brine water. The unconfined compression strength also appeared to be more influenced by gypsum than lime percentages as specimens with 3% gypsum obtained higher strength values than those with 1% gypsum added. Unreacted lime was observed in specimens with higher percentages of lime added and these specimens also presented lower strength values. The addition of lime and gypsum was observed to have limited the release of some trace elements from fly ash. The secondary mineral ettringite was detected and could have possibly precipitated and captured out these toxic elements. An attempt was also made to increase the plasticity index of fly ash using lignosulphonate and values recommended by the South African legislative guidelines for liner materials were obtained. The plasticity was however not retained with subsequent leaching. Two multi-layer liner systems were loaded under different compaction rates in permeameter cells with fitted inflow and outflow points. The primary liners of both systems were able to contain over 95% of leachate that percolated through a waste layer. Compaction rate was found to affect the liners performance as primary liners with a higher compaction rate had less seepage than primary liner compacted at a lower rate. An addition of lime and gypsum improved the overall engineering properties of fly ash to levels accepted by the South African legislative guidelines for a liner material that is able to line hazardous waste. Even though concentrations of some trace elements in fly ash were reduced by addition of lime and gypsum the level of some of these trace elements remain above the threshold set by South African legislative guidelines and therefore remains a health and environmental concern.
Open Access
Coupled flow in groundwater systems : the study of bulkflow parameters
(University of the Free State, 2011-08) Shakhane, Teboho; Steyl, G.
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 site’s 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.
Open Access
Decant calculations and groundwater: surface water interaction in an opencast coal mining environment
(University of the Free State, 2010-11) Du Plessis, Johannes Lodewiekus; Dennis, I.
English: 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 – 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.
Open Access
Decant of sigma colliery
(University of the Free State, 2013-06) Wessels, Lize; Vermeulen, P. D.
English: This study of Sigma Colliery was intended: • To determine the water quality of each aquifer associated with the mining area. • To determine the overall electrical conductivity profile of the mine to aid in the overall management of the mine. • To delineate possible decant positions with the help of water levels and to determine what the water quality of the possible decanting water will be. • To discuss the use of fly ash as a backfilling material in underground mines with the help of case studies. • To determine if ashfilling is a viable option for Sigma Colliery. From the study of Sigma Colliery, the following conclusions and recommendations could be made in this document: • A total of 12 samples were obtained from the shallow aquifer, classified according to the SANS 241:2006 drinking water standards and discussed in this document. Only sample WW024D was classed as above the maximum allowable limit and not suitable for human consumption. Four samples were classed within Class 2, suitable for human consumption for a limited duration use only. A total of seven samples were classed as Class 1, suitable for human consumption. • A total of 23 samples were obtained from the intermediate aquifer, classified according to the SANS 241:2006 drinking water standards and discussed in this document. Samples WW036, NW021, NW037 and UG001 were classed as above the maximum allowable limit and not suitable for human consumption. Three samples were classed as Class 2, suitable for human consumption for a limited duration use only while 16 samples were classed as Class 1, suitable for human consumption. • A total of 21 samples were obtained from the deep aquifer system, classified according to the SANS 241:2006 drinking water standards and discussed in this document. Samples NW006, NW036, NW040, NW041, NW042, NW044, NW046, NW051, UG027D, UG071, UG072D and UG072M were classed as above the maximum allowable limit and not suitable for human consumption. Two samples were classed within Class 2, suitable for human consumption for a limited duration use only and seven samples were classed as Class 1, suitable for human consumption. • A total of six samples were obtained from the disturbed aquifer system, classified according to the SANS 241:2006 drinking water standards and discussed in this document. Samples UG014 and UG023 were classed as above the maximum allowable limit and not suitable for human consumption. Two samples were classed within Class 2, suitable for human consumption for a limited duration use only and two samples were classed as Class 1, suitable for human consumption. • A total of 20 samples were obtained from the ashfill boreholes, classified according to the SANS 241:2006 drinking water standards and discussed in this document. Samples UG033, UG034, UG044, UG069, B12/179, B12/183D, B12/183M and B12/183S were classed as above the maximum allowable limit and not suitable for human consumption. Only one sample (sample C316/47) was classed within Class 2, suitable for human consumption for a limited duration use only and 11 samples were classed as Class 1, suitable for human consumption. • A total of 19 samples were obtained from the mine boreholes, classified according to the SANS 241:2006 drinking water standards and discussed in this document. Samples UG013D, UG024, UG037D, UG046, B12/53D and B12/53S were classed as above the maximum allowable limit and not suitable for human consumption. Five samples were classed within Class 2, suitable for human consumption for a limited duration use only and eight samples were classed as Class 1, suitable for human consumption. • All 94 boreholes were profiled and a three-dimensional image of the whole area was created with the use of the electrical conductivity profiles. From this image created, varies possible decant areas were identified and the water quality of these possible decant areas were discussed. • The ashfilling used turned out to be a viable option when there was still mine void space available before the mine was filled up with water from the flooding. • Since the mine voids were filled with water and the fine ash slurry was pumped into the mine voids, the conditions was disturbed in that the void space in the mine was decreased with some volume of water. • The storage of the strata above is not enough for the water that was pumped in with the ash and the water is therefore forced to decant. • The only place where decant and pollution of the shallow aquifer is evident is where ashfilling has been done. • The situation improves as soon as the ashfilling is ceased and this can be substantiated by the water level and water quality behaviour of borehole UG069. The water levels of borehole UG069 has been at decanting levels from September 2009 to March 2012 (Figure 15-3) after which the water level started to decrease again after the ashfilling was ceased. From the electrical conductivity profiling done of borehole UG069 (Figure 15-2) (after the ashfilling was ceased) the profile already indicates that the upper part of the water column is of a better quality than deeper down. • In this document it is therefore recommended that in the event that the company would like to continue with the ashfilling, they should pump water out of the mine to provide void space and prevent decant. • The ash slurry should simultaneously be injected into the mine with the water that is pumped out. This should be pumped in equal volumes, which will prevent other problems such as the collapsing of the mine roof.
Open Access
A decision support system to assess climate change impacts on rural communities
(University of the Free State, 2016-01) Luruli, Musiiwa Felicity; Fourie, Francois
English: Climate change is likely to affect the way in which people live. Natural resources such as groundwater, surface water and wood form a vital component of the livelihood in rural communities and are used extensively in rural areas where basic services have not yet been provided. The effect of climate change on all these natural resource may impact the lives of those in rural communities. Climate change is already starting to affect some of the poorest and most vulnerable communities around the world. The aim of the dissertation was to develop a framework to assess the vulnerability of rural communities to climate change. This framework used the Millennium Ecosystem Assessment Conceptual Framework as a guideline, but also incorporated the results of face-to-face interviews conducted with members of a selected community. The purpose of the interviews was to interrogate the communities’ level of awareness on climate change and to gain an understanding of the parameters influencing the community’s vulnerability to the effects of climate change. The developed framework allows the calculation of a numerical value which represents the vulnerability of a community to climate change. To illustrate its application, the framework was used to assess the vulnerability of a selected community. In the same way, the framework can be applied to other rural communities in South Africa to assess their vulnerabilities and to prioritise those communities where funds and resources should be allocated when combatting the impacts of climate change. Further work to improve the framework developed in this study is recommended. These recommendations include: 1) considering other existing frameworks to better understand climate change impacts on rural communities and to strengthen and improve the assessment of the vulnerabilities faced by rural communities, 2) expanding the study to include more rural villages in order to better understand how other rural communities are affected by climate change and to establish recommendations which could assist in finding solutions on a wider scale for rural communities that are affected by climate change, 3) including in the framework adaptation measures to protect biodiversity and ecological parameters that support the livelihood of the community, and, 4) including long-term projection of the changes brought on by climate change to refine and improve the framework.