Faculty of Science (ETDs)
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Item Mapping and monitoring the impacts of climate variability on rainfed agriculture in Semi-arid North Darfur, Sudan(University of the Witwatersrand, Johannesburg, 2024-02) Altoom, Mohammed Bashar Adam; Adam, ElhadiRainfed agriculture is vital to food security and income in most parts of the world. However, one-third of the population of developing countries population lives in the less favoured rainfed agricultural regions. Around 75-82% of the total cropland areas in the world are under rainfed agriculture and produce more than 60% of the globe’s cereal grains. However, rainfed agriculture is most prominent in some regions of Africa, such as Sub-Saharan Africa, where more than 95% of the cropland is rainfed. This crucial agriculture sector usually depends on the physical environment and, most importantly, the variability and distribution of rainfall. Therefore, rainfed farming is vulnerable to climate-related hazards, and the crop yield is unreliable and difficult to predict. For instance, the spatio-temporal variability of precipitation extreme events often subjects crops to short-term water deficits, causing crop losses. Sudan heavily depends on rainfed agriculture—about 90% of arable land dominates rainfed cultivation, contributing one-third of the country’s gross domestic product (GDP). Rainfed agriculture is the primary source of livelihood for 65% of the population. Unfortunately, agriculture in North Darfur of the west Sudan is characterised by environmental hazards, e.g., frequent droughts and unpredictable low, poorly distributed, and highly variable monthly/seasonal rainfall. Therefore, using various Earth observation data, this study aimed to monitor the impacts of rainfall variability on rainfed agriculture in North Darfur State in Sudan. Firstly, the study aimed to determine the feasibility of estimating rainfall variability across North Darfur State at daily, monthly and annual timescales using six satellite precipitation products (SPPs), i.e., the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), African Rainfall Climatology (ARC), and Climate Hazards Group Infrared Precipitation with Station Data (CHIRPS) were evaluated using four categorical indices, i.e., probability of detection (POD), probability of false alarm (POFA), bias in detection (BID) and Heidke skill score (HSS), and four continuous indices, i.e., Pearson correlation coefficient (r), root mean square error (RMSE), per cent bias (Pbias), and Nash-Sutcliffe model efficiency coefficient (NSE) against ground rain-gauge observations. The other SPPs were Integrated Multi-satellitE Retrievals for Global Precipitation Measurements (GPM) Final Run (GPMIMERG), Precipitation Estimation from Remote Sensing Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR), and the Tropical Applications of Meteorology using SATellite and ground-based observations (TAMSAT). Results of the statistical analysis demonstrated that 1) at the daily timescale, the SPPs underestimate daily rainfall by 6.53–17.61%, and CHIRPS was the best for detecting rainy days, while PERSIANN-CDR performed poorly; 2) monthly and annual scales performed better than daily timescale, and TAMSAT and CHIRPS portrayed better performance than the ther SPPs. Secondly, the study assessed the capability of optical Earth Observation Data (EOD), i.e., Sentinel-2 multispectral dataset, to map crop types in the heterogeneous semi-arid environment of North Darfur using machine learning classifiers in Google Earth Engine (GEE) platform. Five datasets were compared against random forest (RF) and support vector machine (SVM) classification algorithms: (1) 10 Sentinel-2 bands (comprising visible, near-infrared and shortwave infrared bands), (2) Sentinel-2 (10 bands) + 8 vegetation indices, (3) visible bands and near-infrared bands only, (4) visible and shortwave infrared bands only, and (5) 8 vegetation indices. The eight vegetation indices were normalised difference vegetation index (NDVI), enhanced vegetation index (EVI), soil-adjusted vegetation index (SAVI), green normalised difference vegetation index (GNDVI, weighted difference vegetation index (WDVI), red edge NDVI (NDVIre), ratio-vegetation index (RVI) and normalised difference infrared index (NDII). Results showed that the RF algorithm produced the highest classification overall accuracy (OA), i.e., 97% and Kappa coefficient (κ), 0.96, using 10 Sentinel-2 bands dataset. Producer’s (PA) and user’s accuracies (UA) were in the range of 40-97% and 40-100%, respectively. Thirdly, the spatiotemporal trend of drought events and their impact on millet production in North Darfur from 1981 to 2020 was analyzed using standardized precipitation index (SPI) and reconnaissance drought index (RDI) by employing different timescales, i.e., 3- month (June-August), 6-month (June-November), and 9-month (June-February) timescales. Drought-yield relationships were assessed using Pearson correlation coefficients (r). Results indicated that RDI is more sensitive to rainfall variabilities than SPI in detecting drought trends. Results revealed that drought events affected North Darfur over broad spatial extents, particularly in 1989, 1990, 1992, 1999, and 2001—an extreme drought event was in 2003. Correlation analysis between the SPI and RDI and the standardized variable of crop yield (SVCY) for millet grain yield showed a strong agreement between them. Moderate to extreme reductions in millet crop yield occurred in 1992, 1999, 2001, and 2003, corresponding to the moderate to extreme drought indicated by RDI. Severe crop losses were in Kabkabiya and Umm Kadadda. Fourthly, this study aimed to map and monitor spatio-temporal dynamics of rainfed agriculture in North Darfur State from 1984 to 2019 using multitemporal Landsat observation data using random forest (RF) classification algorithm. Overall, Landsat Operational Landsat Imageries (OLI) outperformed Landsat Multispectral Scanner (MSS), Landsat Thematic Mapper (TM), Landsat Enhanced Thematic Mapper Plus (ETM+) in monitoring change in agricultural land and other land use land cover (LULC) classes. Overall accuracies ranged between 94.7% and 96.9%, while kappa statistics were greater than 0.90. Results showed that Goz land used for rainfed agriculture increased by 889,622.46 ha between 1994 and 999, while it decreased by 658,568.61 ha between 2004 and 2009. Rainfed cultivation of wadi lands expanded significantly by 580,515.03 ha over the 2014–2019 period and decreased by 182,701.8 ha over the 1994–1999 period. Overall, this study enhances the understanding of spatio-temporal rainfall patterns and current drought trends, aiding in developing more effective policies and resource management strategies. Additionally, it offers crucial spatial data that is currently scarce due to ongoing conflicts, empowering decision-makers to establish sustainable land use monitoring systems. The methodologies used in this study have proved successful in mapping crop types in a fragmented highly heterogeneous fine agricultural semi-arid landscape; such mapping approaches can be applied in other environments with similar characteristics.Item Physical property studies, tunnel numerical simulations and in-mine seismic experiments to image the gold orebody at South Deep Gold Mine(University of the Witwatersrand, Johannesburg, 2024-09) Mulanduli, Omphulusa; Manzi, MusaThe investigation endeavors to assess the physical characteristics of deep borehole cores within the Upper Elsburg Reefs (UER) of the South Deep gold mine of the West Rand goldfield. Specifically, these cores are sourced from three boreholes situated approximately 2.6 km beneath the surface within the confines of the South Deep gold mine. The focal point of this study lies in non-destructive testing methods aimed at elucidating the intrinsic attributes of these rocks, with particular attention directed towards seismic velocities and densities. These measurements hold paramount importance in conducting numerical simulations to designing the in-mine (or tunnel) seismic reflection surveys acquired at South Deep gold mine, as part of the ERA-Min3 FUTURE (Fiber-optic sensing and UAV-platform techniques for innovative mineral exploration) project. Cultivating a profound comprehension of the seismic velocities and densities across diverse rock formations can significantly augment the interpretation of seismic reflections, thereby facilitating more refined assessments of subsurface geology and structural configurations. In pursuit of this goal, our study endeavors to delve into the fundamental acoustic properties of the gold-rich UER, with the overarching aim of deepening our understanding of its seismic reflectivity. To realize this objective, a comprehensive array of physical measurements, encompassing ultrasonic velocities and bulk densities, were conducted on drill-core specimens. To accurately portray the physical attributes of the lithological units under scrutiny, a total of twenty-four samples were subjected to exhaustive analysis for density and seismic velocity utilizing a spectrum of methodologies. Density determinations were procured through a diverse set of techniques, including dimensional assessments, employment of the KT20 MagSus tool, and utilization of the SNOWREX AHW-3 Professional Weighing Scale boasting a heightened sensitivity of 0.01 g. Ultrasonic measurements were undertaken employing the Proceq Pundit PL 2000 ultrasonic pulser velocity tester, equipped with two pairs of transducers boasting a center frequency of 54 kHz. The in-mine seismic survey was acquired to delineate geological structures that crosscut and displace the orebody. The study locale encompasses three distinct rock formations: the UER, gold-bearing conglomerate units (termed reefs), basaltic lava, and dyke specimens. The UER primarily comprises quartzites, exhibiting a P-wave velocity range of 5202-5802 m/s, an S-wave range of 3037-4768 m/s, and bulk densities spanning from 2.66 - 2.71 g/cm³. Conglomerate reefs exhibit a P-wave velocity range of 4467-5970 m/s, an S-wave range of 4040-4854 m/s, and bulk densities ranging from 2.67-2.94 g/cm³. Lava samples extracted from the boreholes showcase a P-wave velocity range of 5916 - 6711 m/s, an S-wave range of 3275-5659 m/s, and bulk densities spanning from 2.75-2.90 g/cm³. Singular dyke samples were encountered, exhibiting a P-wave velocity of 5921.5 m/s, an S-wave velocity of 5385 m/s, and a density of 2.85 g/cm³. The study employed the synth-seis code to simulate 1D seismic responses based on borehole data collected from the mine, aiming to validate findings from velocity and density measurements. Analysis of the seismograms indicated notable contrasts between conglomerates and quartzites, particularly evident in density and S-wave measurements, suggesting potential for improved rock discrimination with alternative seismic sources. Additionally, 2D numerical simulations were conducted to model wave propagation in the Upper Elsburg Reef (UER), revealing discrepancies between simulated and synthetic seismogram results, indicating potential limitations in seismic imaging. Furthermore, ray tracing was used to design a seismic survey inside the mine along the tunnel floor to image VCR (Ventersdorp Contact Reef) orebody and other geological structures. The real seismic survey was finally conducted inside the tunnel (SDT1), demonstrated the value of in-mine reflection seismic surveys for mapping geological structures at significant depths, which would otherwise be costly and logistically challenging. Despite noise interference from mine operations, processing algorithms enabled extraction of reflections and structural mapping from the dataset, underscoring the importance of such surveys in mining exploration and planning.Item The perceptions of Moretele residents of small scale agriculture: The case of Ga-Moeka village in the North-West Province(University of the Witwatersrand, Johannesburg, 2024-02) Malivhadza, Takalani; Pillay Gonzalez, SaritaIn South Africa, small-scale agriculture is hindered by various obstacles such as the lack of structural initiatives towards land reform, the dominance of agri-business, and related difficulties of penetrating and flourishing in the market. This research sought to understand perceptions of rural residents of Ga-Moeka (in the North-West province in South Africa) of small-scale agriculture for positive rural development. Small-scale agriculture in rural areas like Ga-Moeka is perceived and practiced as a leisure activity. While the economic potential of small-scale agriculture is recognised, it is not necessarily considered as a primary mechanism to drive positive rural development. Perceptions of small-scale agriculture in the area indicate there is a need to further explore the economic potential of rural areas in a non-binary manner. Additionally, a significant and unexpected finding was the need to also challenge the definition of rural areas and stray away from binary definitions of urban/rural. The findings in this research may support policy makers to assess and put strategies in place that are in alignment with the public’s interest, enhancing their participation in government initiatives and fast-tracking rural development.Item The Stratigraphy of the New Tuli Basin Fossil Sites in Zimbabwe(University of the Witwatersrand, Johannesburg, 2024-09) Zondo, Michel; Choiniere, Jonah; Broderick, Timothy; Munyikwa, DarlingtonThis thesis investigated new fossil-bearing outcrops of the Mpandi Formation of Zimbabwe, exposed at Sentinel Ranch in the Tuli Basin, at sites named “Wedding Hill “and “Pimwe Hill”. The Mpandi Formation exposures at Sentinel Ranch reveal strata that were deposited in fluvial environments that occasionally experienced flooding in otherwise usually dry and hot climatic conditions. These fluvial systems deposited facies that are mostly dominated by fine sediments and their facies have similarities with those found in the main Karoo Basin of South Africa. The use of borehole data helped establish the thickness of the Mpandi Formation and the explorable portion of the formation was estimated to be around 54 metres. Detrital zircons collected from main Sentinel outcrops were used to estimate the maximum depositional age of the sediments using inductively coupled plasma mass spectrometer (LA-ICPMS) methods. Although sparse, the youngest zircons in these samples yielded ages of 199.2 ± 5.1 Ma and 200.8 ± 5.8 Ma, with error bars suggesting maximum depositional ages in the earliest Jurassic or possibly the latest Triassic. A bonebed at the Wedding Hill site produced many postcranial bones of sauropodomorphs, including the articulated leg of a very large individual sauropodomorph, and the first theropod bones recorded from the Mpandi Formation at Sentinel. The discoveries improve our knowledge of the fauna diversity of the Mpandi Formation, permitting more accurate biostratigraphic correlation and enhancing our understanding of the Triassic- Jurassic interval.Item Taphonomy and palaeoecology of a monospecific microvertebrate bonebed: behavioural implications for the late Permian (Lopingian) parareptiles(University of the Witwatersrand, Johannesburg, 2024-06) Mukwevho, Lutendo; Choiniere, Jonah; Smith, RogerSociality in the vertebrate fossil record is a dynamic and fast-expanding area of research. Natural history observations of living animals are crucial for understanding and categorizing sociality, but these observations are not feasible for extinct species. Monotaxic bonebeds provide unique opportunities to conceptualize the social behaviours of these extinct animals. An unusual bonebed (SAM-PK-K11289) discovered in the uppermost Permian strata of the Balfour Formation, Karoo Supergroup, in the Eastern Cape presents a window into the sociality of Late Permian reptiles. The use of propagation phase-contrast synchrotron X-ray microcomputed tomography permitted the 3D reconstruction of skeletal elements in SAMPK-K11289, allowing the taxonomic identification of the individuals in the bonebed as most likely belonging to Owenetta. This is the largest aggregation of Owenetta individuals known to date, with a minimum number of 31, which are all very similar in body size. The ontogenetic profile of SAM-PK-K11289 was interpreted by analysing the size distribution of duplicate elements and by making comparisons with other Owenetta and procolophonid specimens. The specimens in the bonebed are all osteologically immature, indicating that they are juveniles. The bonebed occurs in a pedogenically modified ripple cross-laminated siltstone suggesting that a low-energy fluvial sedimentation likely contributed to the modification, disturbance and disarticulation of elements before the bonebed was buried at or very close to the death site. This bonebed provides novel information that directly challenges the popular belief that reptiles and their ancestors are non-social or asocial. Considering the overall circumstances of the bonebed, I hypothesize that Owenetta rubidgei juveniles were socially gregarious and this behaviour may have been induced or influenced by environmental changes during the early extinction phase of the end Permian mass extinction in the Karoo Basin.Item Metagenome sequencing of the lichen species Flavopunctelia flaventior and Parmotrema tinctorum from Gauteng, South Africa(University of the Witwatersrand, Johannesburg, 2024-06) Katane, Malebogo Dimpho; Botes, Angela; De Maayer, PieterLichens are defined as a mutualistic association between fungi (mycobiont) and an algal and/or cyanobacterial photobiont. Increasing evidence suggests that lichens comprise more diverse microorganisms than initially thought, where lichens represent an interaction between archaea, bacteria, filamentous fungi, green algae, yeasts, and viruses. Not many comprehensive studies have been done of South African lichen species. The present study employed metagenome sequencing to investigate the lichen microbiomes of Flavopunctelia flaventior and Parmotrema tinctorum sampled from Bryanston, Gauteng province, South Africa. Furthermore, the roles played by the members of the lichen microbiome within symbioses were also studied by functionally annotating the assembled metagenomes of the two lichen species. This study sets the groundwork for future studies on South African lichen species. In Chapter 1, an extensive literature review on lichens, their ecology, taxonomy and biology is discussed. Furthermore, it delves into the existence and shape of the microbiome beyond the mycobiont and the photobiont. Additionally, possible roles that the lichen microbiome may play in sustaining the lichen symbiosis is also discussed. In Chapter 2, the metagenomes of two lichen species were sequenced, the quality of the reads were assessed, and taxonomic classification was performed to elucidate the composition of microorganisms associated with each lichen species. Both microbiomes were dominated by bacteria, with limited fungi, viruses, and archaea. The majority of the identified phyla and genera were found to be common between the two lichen species. Similarities in the core microbiome was accounted for by the fact that F. flaventior and P. tinctorum were sampled from the same location and they are both members of the Parmeliaceae family. In Chapter 3, the metagenomic reads were assembled and functionally annotated using various bioinformatics tools. We demonstrate that the members of the lichen microbiome are involved in the cycling of nutrients such as carbon and nitrogen. We also found differences in carbon fixation pathways, which were attributed to the accessory microbiome. Finally, a summary highlights key results and recommendations on future work that could be undertaken to further provide insight into biological pathways essential to sustain the lichen symbiosis.Item Exploring the Structure, Function and Stability of Glutathione Transferases Engineered from Intra- and Inter-class Consensus Sequences: How Forgiving is Nature?(University of the Witwatersrand, Johannesburg, 2024-10) Mulenga, Thabelo; Achilonu, Ikechukwu; Sayed, YasienProtein folding is an enigmatic biochemical process that is foundational to the structural and functional requirements of a cell. The problem of protein folding, in a nutshell, concerns itself with the rate of protein folding as well as the conversion of amino acids from a linear sequence to a fully folded structure. This problem is partly answered by the existence of folding pathways. The folding funnel was conceptualised as a depiction of folding pathways, and it is a framework that illustrates that native proteins naturally favour the lowest energy state, encountering kinetic and thermodynamic barriers as they fold. Consensus protein design, based on this understanding, aims to: (1) enhance stability and (2) navigate the pitfalls of folding by modifying the folding funnel of a protein. This approach can also shed light on the significance of evolutionarily conserved residues. In this study, consensus protein mutants were generated for the Alpha and Mu glutathione transferases (GSTs) classes. The consensus proteins were then benchmarked against the parental proteins that were chosen (hGSTA1-1 and hGSTM1-1). The Alpha consensus mutant had 11 consensus mutations, including a notable M50L mutation, which affects the dynamic behaviour of helices α2 and α9, while the Mu consensus mutant had 13 unique mutations. Protein production and purification showed that the Mu consensus mutant had larger and purer yields. Data from far-UV circular dichroism studies and root-mean-squared-fluctuation (RMSF) from molecular dynamics (MD) simulations showed that the secondary structural components of the Alpha and Mu proteins remained largely the same, although the Alpha consensus mutant displayed a far lower molar residue ellipticity reading than its wildtype counterpart, indicating the disruption of secondary structural elements, likely caused by the M50L mutation. The ANS binding results showed that the M50L mutation in the Alpha consensus protein caused an increase in exposure of the surface area of the H-site, while the Mu consensus protein had a decrease in the solvent accessibility of its H-site. Thermal shift assay results indicated the consensus proteins had increased thermal stability. Enzyme kinetics results showed that the functionality of the proteins was severely diminished in the consensus mutants, particularly the Alpha consensus mutant. MD simulation results showed that there was an overall increase in the rigidity and compactness of the consensus mutant proteins, further affirming the improvement of thermal stability, while signalling the loss in functionality. The results produced herein have the potential to facilitate the proliferation of engineered GSTs for biotechnological applications that require proteins with an increased half-life and greater stability.Item Natural resource use and environmental perceptions in different types of rural villages in Bushbuckridge, South Africa(University of the Witwatersrand, Johannesburg, 2024-09) Mbedzi, Mary Emma; Twine, WayneHouseholds in rural communities in developing countries rely on natural resources that contribute to income generation, food, medicine, cooking energy, and act as livelihood safety nets. Levels of dependency vary between households within communities due to factors such as wealth status and household size. However, less is known about differences in household resource use between communities within an area. Environmental awareness, values, and preferences are shaped by various factors including, local context. Thus, perceptions of the environment and natural resources, and changes in these are likely to vary between communities. This study aimed to compare the levels of natural resource use and environmental perceptions across village types and determine if there is any relationship between the level of natural resource use and environmental perceptions across village types in the Bushbuckridge Local Municipality in the Mpumalanga province, South Africa. Village types were defined and categorised based on their size, socio-economic factors, access to basic services, connectedness, and remoteness. The level of natural resource use was analysed using existing data from a survey of 491 households across 12 villages located in the Agincourt Health and Demographic Surveillance System (AHDSS) site. This included data on the use, collection, buying, and selling of a range of natural resources used locally (e.g., wild foods, firewood, and medicinal plants), annual consumptions, ownership of resources made from natural resources, and livestock (cattle) ownership. The survey included questions on respondents’ perception of the change in the supply of natural resources over the past 5 years (2016-2021) before the survey. Focus group discussions were conducted in 10 of the study villages asking participants their perception of the changes in the environment and the causes thereof, the importance of the natural environment, natural resources used for their daily needs, income generation, their culture, as well as the changes in availability of natural resources and impacts on their livelihoods. The study villages were classified according to a village typology that had been developed for the AHDSS study site, based on factors such as connectedness, access to amenities and services, and the proportion of Mozambican refugee households. ANOVA and Kruskal Wallis tests were used for continual data, while the Chi-squared test was used for categorical data to test for significant differences across village types in the quantitative part of the study. For qualitative, responses of participants from each village were recorded and grouped into village types, and an overall picture of the perception of natural resources that participants used was developed using the focus group schedule. Similarities and differences in natural resources between villages were assessed by grouping widely and less used resources by villages and village types. There was no significant difference (p>0.05) in the mean prevalence of use, collection, buying, and selling of natural resources, or annual consumption of natural resources across villages and village types. Households in better-serviced villages owned more products from natural resources and were to greater extent, likely to own livestock than poorly-serviced villages. As to environmental perceptions, more respondents in the poorly serviced village types (refugee settlements (RS) and underdeveloped communities (UC)) perceived a decrease in the supply of natural resources than better-serviced village types (established communities (EC) and central communities (CC)). Participants in focus group discussions also noted a decrease in the supply of natural resources across all villages and village types. There was a relationship between village types, natural resource use, and perceptions of change in natural resource availability. Established communities correlated with a higher number of resources perceived as decreasing and central communities were associated with higher cattle ownership. Underdeveloped communities and refugee settlements were associated with a higher number of resources used/owned, a higher number of resources used often (more than 4 times a month), and a higher number of resources sold, and buying firewood. Natural resources were more highly used in, better-serviced village types (central communities, and established communities), than in poorly-serviced village types (underdeveloped communities, and refugee settlements), which was unexpected. However, there were quite a few proxies such as the collection and selling of resources, which were used that did not help back up these findings which could explain the unexpected results. Most respondents in remote and poorly-serviced village types perceived a change in the supply of natural resources, the greatest decrease being in the supply of natural resources. This is associated with awareness of the value of the environment and high reliance on natural resources for these poorly-serviced village types. This study suggests that differences exist in resource use patterns between villages, even in the same area. However, village characteristics were not a good predictor of all aspects of resource use. Changes in proxies of resource utilization and re-evaluating the existing village typology would be useful for further studies.Item Evaluating the impact of land use activities in and around Lake Kariba on the presence and levels of anions and cations in the water body(University of the Witwatersrand, Johannesburg, 2024-09) Monyai, Mokgaetji Andelina; Chimuka, Luke; Tutu, Hlanganani; Cukrowska, Ewa; Richards, Heidi L.Huge seas, lakes, and rivers come to mind when we think of surface water. Surface water is vulnerable to water pollution, with consequential repercussions for the well-being of both human and aquatic environments. Furthermore, the diminishing levels of oxygen have a profound effect on the natural ecological equilibrium within river and lake ecosystems. Lake Kariba, situated in the Southern African region, is a vital freshwater ecosystem supporting local communities, wildlife, and regional economies. However, it faces threats from human activities and erratic weather. This study investigated the influence of land use activities in and around Lake Kariba on water composition and the concentration of anions and cations. The research employed a combination of field surveys and laboratory experiments to identify potential sources of ions. Sixty-nine (69) water samples (53 downstream and 16 upstream) were collected during different seasons in October 2021, July 2022 and April 2023. The Ion Chromatography, Inductively Coupled Plasma equipped with Optical Emission and Mass Spectroscopy detectors were used to concentrations of various anions (Fˉ, Clˉ, NO3ˉ, SO4 2ˉ, and PO4 3ˉ) and cations (Ca, K, Mg, Na, Si, Al, Cr, Fe, Mn, As, Cu, Ni, Ti, and Zn) respectively. Acidic water was notably observed upstream in two sampling areas, namely the Malasha and Kanzinze rivers. The Malasha River exhibited pH levels ranging from 3.71 to 4.81, while the Kanzinze River showed a pH of 6.01. The electrical conductivity (EC) for Malasha ranged from 1035 to 1484 µS/cm, whereas for Kanzinze, it measured 878.0 µS/cm. These areas exhibited significantly elevated levels of both anions and cations. In the Kanzinze River, the detected concentrations showed the following descending order: SO4 2ˉ> Clˉ > NO3ˉ> Fˉ> PO4 3ˉ (anions); Ca > Mg > Na > K > Si > Fe > Al > Zn > Cu > Mn > Ni > Cr > Ti > As (cations). Conversely, the Malasha River, exhibited the following order for anions: SO4 2ˉ > Clˉ > NO3 ˉ > Fˉ > PO4 3ˉ, and for cations: Ca > Fe > Mg > Na > Si > K > Al > Mn > Zn > Cr > Cu> Ni > Ti > As. The significant presence of SO4 2- and NO3 - indicates that human activities and agricultural practices in certain areas of Lake Kariba's catchment can have a considerable impact on the lake's water quality. Despite this, the corresponding Water Quality Index (WQI) indicated that the water quality from Kanzinze and Malasha rivers was unsuitable for drinking purposes. The findings revealed variations in ions concentration at different sampling points, with discernible patterns corresponding to specific land use types, such as mining in the upstream that elevated the levels of SO4 2- and some heavy metals and also NO3 - levels in the downstream due to commercial cage fish farming. Statistical analysis showed significant downstream variations (p < 0.05) in water chemistry parameters related to land use, while upstream areas exhibited no significant differences (p > 0.05). Water quality index ranged from 13.1 to 230.0, categorizing water quality from "excellent" to "very poor." The study underscores the complex interplay between land use activities and water chemistry in Lake Kariba, emphasizing downstream impacts. These findings contribute valuable insights for sustainable management and conservation efforts in the region, considering the dynamic nature of the ecosystem and potential threats posed by anthropogenic activities. Continuous monitoring and mitigation strategies are crucial to reserving the ecological balance of Lake Kariba and safeguarding the well-being of its surrounding communities and wildlife.Item Surface water dependencies and activity patterns of mammalian herbivores in South Africa(University of the Witwatersrand, Johannesburg, 2024-10) Padayachy, Janiel; Hetem, Robyn; Strauss, Willem Maartin; Venter, JanAn increase in aridity in Africa may make water availability more variable, thus understanding how animals respond to these conditions is important for future wildlife management and conservation. However, mammalian herbivores with varying water requirements may respond differently to changes in water availability and predation. Using camera trap data, I analysed the spatial distribution relative to surface water sources and the 24-hour activity of 16 mammalian herbivores across 10 sites in South Africa. As expected, water dependent herbivores were generally closer to water, but only at sites where lions were absent. Herbivores with low water requirements were more nocturnal, potentially reducing water required to cool themselves evaporatively when active during the heat of the day. But that nocturnal activity was reduced when lions were present, likely reducing predation risk, increasing water requirements to dissipate heat and forcing herbivores to remain close to water. Nocturnal activity increased with body size in mixed-feeders and grazers, but decreased with body size in browsers, potentially reflecting more time spent foraging by large browsers. Using a novel approach of multistate diel occupancy models I showed that herbivores were generally active during both the day and night, and that the presence of lions impacted occupancy of preferred prey species (blue wildebeest, gemsbok and zebra). Diel occupancy of water-dependent prey (blue wildebeest) was influenced by an interaction between lion presence and distance to water sources. Thus environmental factors as well as physiological and morphological features affected the timing of activity and spatial distribution of several mammalian herbivore species in South African wildlife areas, which should be considered for future research and management of these species.