Department of Earth Science

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https://hdl.handle.net/10566/272

Research is organized in the broad fields of Environmental Water & Science and Applied Geology. The main research areas are in Petroleum Geology, Economic Geology/ Exploration Geochemistry, Tectonic Evolution, Integrated Water Resource Management and Groundwater studies under the leadership of the UNESCO Chair.

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Now showing 1 - 20 of 415

3D static modeling and CO2 static storage estimation of the hydrocarbon-depleted charis beservoir, Bredasdorp basin, South Africa
(Natural Resources Research, 2023) Afolayan, Blessing Ayotomiwa; Opuwari, Mimonitu; Mackay, Eric
An essential greenhouse gas effect mitigation technology is carbon capture, utilization and storage, with carbon dioxide (CO2) injection into underground geological formations as a core of carbon sequestration. Developing a robust 3D static model of the formation of interest for CO2 storage is paramount to deduce its facies changes and petrophysical properties. This study investigates a depleted oilfield reservoir within the Bredasdorp Basin, offshore South Africa. It is a sandstone reservoir with effective porosity mean of 13.92% and dominant permeability values of 100–560 mD (1 mD = 9.869233 × 10–16 m2). The petrophysical properties are facies controlled, as the southwestern area with siltstone and shale facies has reduced porosity and permeability. The volume of shale model shows that the reservoir is composed of clean sands, and water saturation is 10–90%, hence suitable for CO2 storage based on petrophysical characteristics. Static storage capacity of the reservoir as virgin aquifer and virgin oilfield estimates sequestration of 0.71 Mt (million tons) and 1.62 Mt of CO2, respectively. Sensitivity studies showed reservoir depletion at bubble point pressure increased storage capacity more than twice the depletion at initial reservoir pressure. Reservoir pressure below bubble point with the presence of gas cap also increased storage capacity markedly.
A comparative analysis of long-term variations of temperature and rainfall in rural and urban areas, and their effects on the estimation of design storms in Kenya
(University of the Western Cape, 2016) Gachahi, Lydiah Wangechi; Mazvimavi, Dominic
My Thesis aimed at expanding the current knowledge on how variations of temperature characteristics including the possible existence of urban heat islands (UHI) over urban areas of Kenya could be influencing rainfall characteristics, and to examine if the stationary extreme value distributionis still suitable for modeling urban storm designs in view of the global climate change. My hypothesis was that the floodingoccurring frequently in major urban areas of Kenya are due to increased rainfall caused by global climate change, and the urban heat island (UHI) effect. To put this perception into perspective, temperature and rainfall characteristics and their inter-relationships, of four of the major urban areas in Kenya namely, Nairobi, Mombasa, Kisumu, and Nakuru, were investigated. I obtained data from meteorological stations in and around each urban area, which had at least thirty (30) years of continuous monthly (or daily) temperatures and rainfall values, from the Kenya Meteorological Department. I checked the datasets for quality and missing values and adjusted where necessary before commencing with analysis. I sourced other supporting global dataset from various websites' data banks.I used various methods of data analysis which included; i) exploratory data analysis techniques such as the continuous wavelet transform (CWT), geographical information system (GIS) maps, and visual time series plots. In particular and unique in my Thesis was the use of the CWT method as a diagnostic tool to examine non-stationaritiesand variability of temperature and rainfall time series.
A comparison of Brine evaporation rates under controlled conditions in a laboratory
(University of the Western Cape, 2018) Bent, Denzil; Petrik, Leslie
There are growing concerns around the environmental issues related to processed water as the demand for potable water is on the increase in South Africa. Effluents discharged from various sectors such as water treatment facilities pose a constant threat to the environment and natural water resources, including rivers and groundwater due to their poor chemical and physical composition. As a result, the demand for predicting the elevated concentrations of salts in a spatial and temporal dimension is constantly growing. The effluent at the eMalahleni water reclamation plant in Mpumalanga, South Africa, is being processed through a triple reverse osmosis that improves the water quality of the mine water to potable standards. Two water quality streams emerge from this process, i.e. a potable standard and the other a brine concentrate which is stored in ponds. Brine ponds are used for inland brine disposal in the eMalahleni water reclamation plant. The large volumes and limited capacity to store brines has placed great emphasis on enhanced evaporation rates to increase the efficiency of the ponds. In order to improve the rate of brine evaporation in the pond, an understanding of the effect of brine salt content and other parameters affecting the rate of evaporation is required. This study aimed at establishing the physical and chemical behaviour of the brine from the eMalahleni plant in a controlled environment. The investigation incorporated actual brine from the eMalahleni plant as well as synthetic salts typical of the major components of the eMalahleni brine.
A MeerKAT polarization survey of southern calibration sources
(2024) Taylor, A.R; Legodi, L.S
We report on full-Stokes L-band observations of 98 MeerKAT calibration sources. Linear polarization is detected in 71 objects above a fractional level of 0.2%. We identify ten sources with strong fractional linear polarization and low Faraday rotation measure that could be suitable for wide-band absolute polarization calibration. We detect significant circular polarization from 24% of the sample down to a detection level of 0.07%. Circularly polarized emission is seen only for flat spectrum sources α>−0.5. We compare our polarized intensities and Faraday synthesis results to data from the NVSS at 1400 MHz and the ATCA SPASS survey at 2300 MHz. NVSS data exist for 54 of our sources and SPASS data for 20 sources. The percent polarization and rotation measures from both surveys agree well with our results. The residual instrumental linear polarization for these observations is measured at 0.16%, and the residual instrumental circular polarization is measured at 0.05%. These levels may reflect either instabilities in the relative bandpass between the two polarization channels with either time or antenna orientation, or atmospheric/ionospheric variations with pointing direction. Tracking of the hourly gain solutions on J0408-6545 after transfer of the primary gain solutions suggests a deterioration of the gain stability by a factor of several starting about 2 hr after sunrise. This suggests that observing during the nighttime could dramatically improve the precision of polarization calibration.
Acid mine drainage prediction techniques and geochemical modelling: case study on gold tailing dams, West Rand, Witwatersrand basin area, South Africa
(University of the Western Cape, 2021) Wu, Changhong; Khotseng, Lindiwe
Acid Mine Drainage (AMD) is identified as one of the contributors to environmental hazard in the gold mining region of South Africa, as caused by the mining operational activities performed by mining industries in South Africa. This effect motivates the development of AMD prediction techniques application and geochemistry modelling using gold tailing dams located in West Rand area, Witwatersrand Basin as a case study. Control strategies are devised to assess, understand and measure the acidic potential generation of waste materials in ensuring the right method required to analyse risks caused by AMD to environment. The method encompasses mineralogical and geochemical analysis of 93 samples collected, AMD prediction, test modification and geochemical modelling. This method was appropriately applied to understand the basic mechanisms involved in controlling acid generation, assessing prediction procedure and selecting the right prediction tools. Study objectives are attained by performing a series of experimental lab tests on the samples collected from the two major tailing dams (Mogale and Gold One_1 tailings). Results derived from the lab experiments (XRD and SEM-EDS) show presence of mineral phases characterised with the surface feature of samples, and unknown substances of samples were identified. Geochemical characterisation was performed by XRF and ICP-MS to determine the major oxides elements and trace elements, respectively. Leco test generate total sulphur and total carbon. Multistatistical analysis is used to interpret the data derived from geochemical characterisation process to explicate the metal and trace elements distribution and occurrence. Initial samples were screened and categorised based on paste pH and EC using kinetic tests to determine acid-forming and neutralising minerals in samples and static tests to determine acid generation potential in samples. Net Acid Producing (NAPP) was mathematically calculated from Acid Neutralising Capacity (ANC), Maximum Potential Acidity (MPA) and total Sulphur. Results obtained from the Paste pH demonstrate that samples collected from 1 meter downward the holes to 10 meters, with a few meters samples in hole T003 at Gold One_1 are non-acidic while the remaining tailing samples are acidic. ANC/MPA ratio was applied to assess the risk of acid generation from mine waste materials. Graphical illustrations of the Acid Base Account (ABA) are plotted to demonstrate the net acidic generation potential trends of samples, which were classified into non-acid forming, potential acid forming and uncertain categories. Results integration between ANC, Single Addition Net Acid Generation (NAG) test and NAPP were used to classify acid generation potential of the samples. Leachate collected from leaching column test were analysed for pH, EC and chemical element by ICP-MS. The leaching column test used to analyse samples (T004) and (T001) collected from the two major tailings was set up for a 4-month experiment. Study findings present environmental assessment report on the two investigated gold tailing dams in Witwatersrand Basin area. Other findings are improved understanding of the application and limitations of various existing AMD prediction methods for assessment of gold mine waste and conceptual geochemical modelling developed to test appropriate methodology for AMD potential at a given gold mine site.
Advancements in satellite remote sensing for mapping and monitoring ofalien invasive plant species (AIPs)
(Elsevier, 2019) Royimani, Lwando; Mutanga, Onisimo; Dube, Timothy
Detecting and mapping the occurrence, spatial distribution and abundance of Alien Invasive Plants (AIPs) have recently gained substantial attention, globally. This work, therefore, provides an overview of advancements in satellite remote sensing for mapping and monitoring of AIPs and associated challenges and opportunities. Satellite remote sensing techniques have been successful in detecting and mapping the spatial and temporal distribution of AIPs in rangeland ecosystems. Also, the launch of high spatial resolution and hyperspectral remote sensing sensors marked a major breakthrough to precise characterization of earth surface feature as well as optimal resource monitoring. Although essential, the improvements in spatial and spectral properties of remote sensing sensors presented a number of challenges including the excessive acquisition and limited temporal resolution. Therefore, the use of high spatial and hyperspectral datasets is not a plausible alternative to continued and operational scale earth observation, especially in financially constrained countries. On the other hand, literature shows that image classification algorithms have been instrumental in compensating the poor spatial and spectral resolution of remote sensing sensors. Furthermore, the emergence of robust and advanced non-parametric image classification algorithms have been a major development in image classification algorithms.
Advancements in the satellite sensing of the impacts of climate and variability on bush encroachment in savannah rangelands
(Elsevier, 2022) Maphanga, Thabang; Dube, Timothy; Shoko, Cletah
An increase in shrubs or woody species is likely, directly or indirectly, to significantly affect rural livelihoods, wildlife/livestock productivity and conservation efforts. Poor and inappropriate land use management practices have resulted in rangeland degradation, particularly in semi-arid regions, and this has amplified the bush encroachment rate in many African countries, particularly in key savannah rangelands. The rate of encroachment is also perceived to be connected to other environmental factors, such as climate change, fire and rainfall variability, which may influence the structure and density of the shrubs (woody plants), when compared to uncontrolled grazing. Remote sensing has provided robust data for global studies on both bush encroachment and climate variability over multiple decades, and these data have complemented the local and regional evidence and process studies. This paper thus provides a detailed review of the advancements in the use of remote sensing for the monitoring of bush encroachment on the African continent, which is fuelled by climate variability in the rangeland areas.
Advances in satellite remote sensing of the wetland ecosystems in Sub-Saharan Africa
(Taylor and Francis Group, 2022) Thamaga, Kgabo Humphrey; Dube, Timothy; Shoko, Cletah
Wetlands are highly productive systems that act as habitats for avariety of fauna andflora. Despite their ecohydrological signifi-cance, wetland ecosystems are severely under threat from globalenvironmental changes as well as pressure from anthropogenicactivities. Such changes results in severe disturbances of plantspecies composition, spatial distribution, productivity, diversity,and their ability to offer critical ecosystem goods and services .However, wetland degradation varies considerably from place toplace with severe degradation in developing countries, especiallyin sub-Saharan Africa due to poor management practices thatleads to underutilization and over reliance on them for liveli-hoods. The lack of monitoring and assessment in this region hastherefore led to the lack of consolidated detailed understandingon the rate of wetland loss.
An analysis of sustainability of communally-managed rural water supply systems in Zimbabwe
(University of the Western Cape, 2016) Kativhu, Tendai; Mazvimavi, Dominic
Sustainability of rural water supply systems is a major development challenge in most developing countries including Zimbabwe. This thesis aimed to analyse the sustainability of communally managed rural water supply systems in Zimbabwe. Specifically, it determined the factors influencing sustainability of water supply systems; investigated how the implementation of Community Based Management (CBM) is contributing to the sustainability of water supply systems; explored how multiple uses of water influence sustainability of water supply systems under CBM and determined how the principal factors influencing sustainability and the CBM implementation practices, can be incorporated at the different stages of the development of a water supply system. The study was done in Nyanga, Chivi and Gwanda districts. A total of 399 communally- managed water points were studied and 300 households participated in the study. Questionnaires were used to collect data from households and Water Point Committees (WPCs). Data was also collected using Key Informant Interviews (KIIs) with a total of 33 key informants being drawn from the national, district and community levels.
An assessment of the contribution of surface and subsurface flows to river flows of the Sandspruit in the Berg River Catchment, South Africa.
(University of the Western Cape, 2018) Damons, Matthew; Mazvimavi, D
Studies have shown that the primary origin of salinity in river flows of the Sandspruit in the Berg Catchment located in the Western Cape Province of South Africa was mainly a result of atmospheric deposition of salts. The salts are transported to rivers through surface runoff and subsurface flow (i.e. through flow and groundwater flow). The purpose of this study was to determine the contributions of subsurface and surface flows to the total flows in the Sandspruit, Berg Catchment. Three rain events were studied. Water samples for two rain events were analysed for environmental tracers ?18O, Silica or Silicon dioxide (SiO2), Calcium (Ca2+) and Magnesium (Mg2+). Tracers used for two component hydrograph separation were ?18O and SiO2. The tracers, Ca2+ and Mg2+, revealed inconsistent contributions of both subsurface flow and surface flow. Two component hydrograph separations indicated is that groundwater is the dominant contributor to flow, while surface runoff mainly contributes during the onset of the storm event. Groundwater response to precipitation input indicated that boreholes near the river have a quicker response than boreholes further away from the river. Boreholes nearer to the river also indicate higher water levels in response to precipitation, in comparison to boreholes further from the river.
An assessment of wetland vulnerability to artisanal mining in Zimbabwe
(Universty of the Western Cape, 2024) Dube, Thandekile; Dube, Timothy
The preservation of wetlands and pristine riverine eco-hydrological systems in sub-Saharan Africa, is crucial for biodiversity, ecosystem stability, and water availability. These face escalating threats from factors such as rapid population growth, agricultural expansion, and, more importantly, emerging illegal artisanal mining. To address these challenges, this study comprehensively evaluates the impact of artisanal mining on wetland ecosystems in Zimbabwe and proposes possible management strategies for mitigating environmental degradation. To achieve this goal, the research begins with a comprehensive literature review focused on the impact of artisanal mining on wetlands in semi-arid environments of sub-Saharan Africa. The findings underscore the detrimental effects of artisanal mining on wetland ecosystems, including habitat loss, biodiversity decline, riverbed sedimentation, and heavy metal pollution. Subsequently, the study investigated in the Umzingwane Catchment, located in southern Zimbabwe as a case study, to analyse variations in water nutrient and metal concentrations in wetlands affected by illegal mining activities along riparian zones (wetland-dominated areas).
An integrated approach to understanding the geological controls on gas escape and migration pathways in offshore northern Orange Basin, South Africa.
(University of the Western Cape, 2017) Samakinde, Chris Adesola; Van bever Donker, Jan
The use of an integrated approach in science has gained more prominence recently because it is thorough and provides a dynamic perspective from which scientific problems can be investigated and solutions proffered. Here, an integrated approach (Litho and seismic stratigraphy, structural modelling, Seismic attributes analyses and 3D numerical simulation of hydrocarbon generation and migration) were used to investigate geological controls (faults and stratigraphic features) on hydrocarbon migration pathways and suggest prospective areas within the Block 1 of Orange Basin, South Africa.
Analysis of monthly MOD16 evapotranspiration rates at sites with different climatic characteristics; Heuningnes and Letaba catchments in South Africa
(University of the Western Cape, 2017) Ndara, Nolusindiso; Mazvimavi D.; Jovanovic, N.
Evapotranspiration (ET) is an important component of the water cycle that is estimated to return about 60% of precipitation back to the atmosphere. Actual ET can be estimated using remote sensing techniques and ground-based measurements. In recent years, a remote sensing product MOD 16 ET has been developed. The limited validation of this product done in South Africa showed that ET was underestimated at some sites. A comprehensive analysis of historic and seasonal trends in MOD 16 ET data in different climatic regions of South Africa has not been done. This study has the objective of evaluating if MOD 16 evapotranspiration estimates realistically represent the seasonal variations of ET on different land cover types in two different climatic regions; Mediterranean (Heuningnes catchment in Western Cape) and Sub-tropical (Letaba catchment in Limpopo) regions. Monthly MOD 16 ET maps for 2000-2012 for the Letaba catchment and Heuningnes catchment were created using ArcGIS. The results suggested that during the 2000 - 2012 period, ET was 438 - 753 mm/ year in the Letaba catchment and 432 - 458 mm/year in the Heuningnes catchment. The accuracy of MOD 16 ET was evaluated using estimates of actual ET from scintillometer data in Elandsberg (Western Cape) and flux tower data in Malopeni (Limpopo) and Skukuza (Limpopo). Monthly ET estimated using scintillometer and flux tower were calculated to coincide with the monthly MOD 16 ET data for a period of 1 year from Nov 2012- Oct 2013 in Elandsberg, 1 year 1 month from Mar 2009- Mar 2010 in Malopeni and 13 years from 2000- 2012 in Skukuza. In Elandsberg, the results showed that MOD 16 underestimated ET (R2 = 0.16, RMSE = 28.30 mm/month). In Malopeni, the results suggested that there is a strong relationship between ET estimated from flux tower data and MOD 16 ET (R2 = 0.77), but MOD 16 slightly overestimate ET (RMSE = 8.6 mm/month). MODIS ET estimates for Elandsberg had a poorer comparison with the results obtained at Malopeni and Skukuza.
Analysis of the fragmented legal regime pertaining to rehabilitation measures for wetlands: A South African perspective – part 1
(WIT Press, 2022) Lemine, Bramley Jemain; Kanyerere, Thokozani
Wetlands are disappearing and it is an international dilemma. Many efforts have been made to ensure its protection and conservation, including rehabilitation. Rehabilitation measures have been adopted in policies of various jurisdictions. In South Africa, the wetlands legislative framework is fragmented. It was submitted that a wetlands policy is in the pipeline for South Africa. As opposed to the research on the general protection of this resources, Part 1 of this research aimed, by way of a documentary analysis of the legislative wetland framework, journal articles, books and case law, to provide what the extent of the fragmentation, specifically, rehabilitation measures were, as well as the effect thereof. Part 2 of this research explicitly focused on rehabilitation measures taken by three other jurisdictions, as well as a design for such in South Africa’s envisaged policy.
Antimicrobial resistance screening and profiles: A glimpse from the South African perspective
(IWA Publishing, 2020) Genthe, Bettina; Ndlela, L.; Madlala, T.
According to the Centre for Disease Dynamics Economics and Policy, South Africa represents a paradox of antibiotic management similar to other developing countries, with both overuse and underuse (resulting from lack of access) of antibiotics. In addition, wastewater reuse may contribute towards antibiotic resistance through selective pressure that increases resistance in native bacteria and on clinically relevant bacteria, increasing resistance profiles of the common pathogens. Sediments of surface water bodies and wastewater sludge provide a place where antibiotic resistance genes are transferred to other bacteria. Crop irrigation is thought to be a potential source of exposure to antibiotic-resistant bacteria through the transfer from the water or sludge into crops. The objectives of this study were to examine the antibiotic-resistance profiles of Escherishia coli from three agricultural locations in the Western Cape, South Africa. Using a classical microbiology culture approach, the resistance profiles of E. coli species isolated from river water and sediments, farm dams and their sediments and a passive algal wastewater treatment ponds and sediment used for crop irrigation were assessed for resistance to 13 commonly used antibiotics. Randomly selected E. coli isolates from the sediment and water were tested for resistance.
Applicability of big data analytics to support groundwater management in Southern Africa
(University of the Western Cape, 2022) Gaffoor, Zaheed; Kanyerere, Thokozani
Groundwater is a vital resources for member states in the Southern African Development Community (SADC). However, sustainable managing groundwater resources in SADC is a challenge. Amongst the many issues facing groundwater managers in SADC, limited access to high fidelity data, as well as a poor understanding of the techniques needed to transform the data into information, has hampered the decision making process. Big data relates to large, voluminous and heterogenous datasets which are being generated through numerous activities, such as computer simulations, remote sensing, commercial transactions, internet activity, monitoring networks, IoT sensors, historical documents, social media and many others.
Application of enviromental and hydrochemical analysis to characterize flow dynamics in the Sakumo Wetland, Ghana
(University of the Western Cape, 2018) Laar, Cynthia; Xu, Yongxin
This research focused on understanding the current hydrogeology of the Sakumo wetland by developing a conceptual flow model and simulating the groundwater flow system. The purpose of the model is to assist in understanding the groundwater flow system and quantify the water fluxes contributing to the wetland water storage. The research adapted quantitative, qualitative and mixed analysis to characterize the water flow in the basin. This involved the use of numerical modelling techniques to determine the zones of groundwater discharge to the wetland and zones of wetland water released for groundwater recharge. Field investigation were carried out to estimate the hydraulic parameters and sample rainwater, wetland water and groundwater. The Sakumo wetland aquifer is situated in the quaternary unit consisting of sandy clay and weathered quartzite. The average annual precipitation in the study area from 1970 to 2016 was estimated at 760 mm/yr. Groundwater recharge rate was estimated as 5% of the mean annual rainfall which provided inputs into the numerical groundwater flow model. Evaporation from the wetland and evapotranspiration from the basin estimated using the Hargreaves and Samani method were 1341 mm/a and 546 mm/a, respectively. The hydrogeologic conceptual model was developed from the geology, borehole lithology, groundwater and wetland water levels.
Application of geochemical characterization, multivariate statistics and geological modelling in assessment and prediction studies on selected coal and gold mine waste in South Africa
(University of the Western Cape, 2023) Abegunde, Oluseyi Blessed; Opuwari, Mimonitu
Over the years, South Africa has generated vast amounts of coal fly ash and gold slime tailings, constituting over 70% of the country's waste materials. These byproducts contain elevated levels of trace metals, posing a potential threat to the environment upon release. Addressing this issue requires a comparative study of the environmental impact of coal fly ash and selected mine tailings on water resources and land pollution. This research aims to investigate and compare leachability, metal release, oxidation effects, and environmental pollution between coal fly ash and gold tailings. By contrasting these aspects, the study seeks to enhance understanding of the potential risks associated with these materials, aiding informed decision-making for their management and regulation. Additionally, the research explores the correlation between gold tailings' acid potential generation and coal fly ash's alkaline potential generation in terms of leachability, metal release, oxidation effects, and environmental pollution. The research employed comprehensive laboratory experiments and analytical investigations, including leaching tests under simulated weathering conditions. A total of 51 gold tailings samples and 66 coal fly ash samples were analysed through SEM and XRD for mineralogical insights and ICP-MS and XRF for geochemical analyses. Statistical analysis revealed the significant roles of pH, Fe ions, Ca2+, and Mg2+ in metal extraction from both materials. Notably, the study identified key factors contributing to the environmental impact of coal fly ash and gold tailings. SEM imagery highlighted heterogeneous characteristics in gold tailings, while factor analysis indicated the potential release of ferrous ionic species, contributing to acidity. Trace elements like Ni, Zn, Pb, and Cu were predominantly associated with Fe/Mn oxides during leaching experiments, facilitating their mobilization with acid-generating ions.
Application of multivariate statistics and Geographic Information Systems (GIS) to map groundwater quality in the Beaufort West area, Western Cape, South Africa
(UWC, 2013) Solomon, Henok Goitom; Siad, Abdi Mohamoud
Groundwater in arid and semi-arid areas like the Karoo region of South Africa is an important source of domestic, agricultural and industrial source of fresh water. As a scarce resource, it requires extensive quality control and protection through innovative methods and efficient strategies. The town of Beaufort West and its vicinity use groundwater as a major source of municipal and private water supply. Forty nine groundwater samples were collected from spatially referenced boreholes located in and around the town of Beaufort West and were analyzed for EC, pH, TDS,TH, SAR, TA, Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, NO3- and SO42- according to SANS 241 standards and tested for ionic balance. The groundwater of the study area was characterized using WHO and South African drinking water quality standards as well as TDS and Salinity hazard classifications. These comparisons and classifications characterized the groundwater of the study area as hard to very hard, with low to medium salinity hazard. These results are in accordance with the dominance of the ions Ca2+, Na+, HCO3 - and Cl- in the groundwater samples. Linear relationships between the hydrochemical variables were analysed through correlation and multiple regression analysis to relate the groundwater quality to the underlying hydrogeochemical processes. These linear relationships explained the contribution of the measured variables towards the salinity, hardness and anthropogenic contamination of the groundwater. The groundwater of the study area was also assessed using conventional trilinear diagrams and scatter plots to interpret the water quality and determine the major ion chemistry. The conventional methods highlighted the sources of the hydrochemical variables through analysis and interpretation of rock-water interaction and evaporations processes. To supplement these conventional methods and reveal hidden hydrogeochemical phenomenon, multivariate statistical analyses were employed. Factor analysis reduced the hydrochemical variables into three factors (Hardness, Alkalinity and Landuse) that characterize the groundwater quality in relation to the source of its hydrochemistry. Furthermore, combination of Cluster (CA) and Discriminant analyses (DA) were used to classify the groundwater in to different hydrochemical facies and determine the dominant hydrochemical variables that characterize these facies. The classification results were also compared with the trilinear diagrammatic interpretations to highlight the advantages of these multivariate statistical methods. The CA and DA classifications resulted in to six different hydrochemical facies that are characterized by NO3 -, Na+ and pH. These three hydrochemical variables explain 93.9% of the differences between the water types and highlight the influence of natural hydrogeochemical and anthropogenic processes on the groundwater quality. All the univariate, bivariate, multivariate statistical and conventional hydrogeochemical analyses results were analyzed spatially using ArcGIS 10.0. The spatial analysis employed the Inverse Distance Weighted (IDW) interpolation method to predict spatial distribution of unmeasured areas and reclassification of the interpolation results for classification purposes. The results of the different analyses methods employed in the thesis illustrate that the groundwater in the study area is generally hard but permissible in the absence of better alternative water source and useful for irrigation.
Application of multi‑method approach to assess groundwater–surface water interactions, for catchment management
(Springer, 2018) Madlala, T.; Kanyerere, Thokozani; Oberholster, P.; Xu, Y.
Globally, the dependence of river systems to delayed discharge of subsurface water to augment flows during dry seasons is well documented. Discharge of fresh subsurface water can dilute concentrated river flow quality during reduced flow. Observed and reported results on the Berg River’s declining water quantity and quality are a concern to the regions socio-economic growth and environmental integrity. Understanding the role of subsurface water discharges on the quantity and quality of receiving surface water courses can improve their management during dry periods. A case study was designed and implemented in the upper Berg River catchment in the Western Cape Province of South Africa to assess the influence of groundwater–surface water interaction on water quantity and quality. This study aimed to quantify and characterize the quality of subsurface water available in the upper catchment to improve observed declining water quality downstream. Hydrograph separation provided estimates of water fluxes during 2012–2014 low and high flow periods, while hydrochemical analysis provided insights on impacts of major land use activity in this catchment on water resources. Hydrograph separation analysis indicated that the Berg River is 37.9% dependent on subsurface water discharges annually. Dominant Na–Cl-type water indicates the quality of water from the upper Berg River is largely affected by natural processes including short residence times of aquifer water, rock–water interactions and atmospheric deposition of NaCl ions. These results provide insights for suggesting management options to be implemented to protect subsurface water for continued dilution and water resources management in the lower catchments.

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