Browsing by Author "Banda, Vincent Dzulani"

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    Assessment of catchment scale groundwater-surface water interaction in a non-perennial river system, heuningnes catchment, South Africa
    (Scientific African, 2023) Banda, Vincent Dzulani; Mengistu, Haile; Kanyerere, Thokozani
    A significant proportion of the world's river networks are non-perennial rivers that are characterized by segments of dry, standing, and flowing water. However, the role of groundwater and the controlling elements governing the flow processes in these rivers is not widely documented. In this study, aquifer-river interaction was assessed using a combo of geological, hydrological, environmental stable isotope, and hydrochemical data in the Heuningnes catchment, South Africa. Results showed the depth to groundwater levels ranging from 3 to 10 m below ground level and aquifer transmissivity values of 0.17 to 1.74 m2/day. The analytical data indicated that Na-Cl type water dominates most groundwater and river water samples. Environmental stable isotope data of river samples in upstream areas showed depleted δ18O (-4.3 to -5.12 ‰) and δ2H (-22.9 to -19.3 ‰) signatures similar to the groundwater data, indicating a continuous influx of groundwater into the river water. Conversely, high evaporative enrichment of δ18O (1.13 to 7.08 ‰) and δ2H (38.8 to 7.5 ‰) were evident in downstream river samples. It is evident from the local geological structures that the fault in the north-eastern part of the study area passing Boskloof most likely acts as a conduit to groundwater flow in the NE-SW direction thereby supplying water to upstream river flow, while the Bredasdorpberge fault likely impedes groundwater flow resulting in hydraulic discontinuity between upstream and downstream areas. Relatively low conductive formation coupled with an average hydraulic gradient of 8.4 × 10−4 suggests a slow flow rate resulting in less flushing and high salinization of groundwater in downstream areas. The results underscore the significance of using various data sets in understanding groundwater-river interaction thereby providing a relevant water management platform for managing non-perennial river systems in water-stressed regions. Overall, the study provides important insights into the need for maintaining moderately high groundwater levels in shallow and local groundwater systems for sustaining the ecological integrity of non-perennial rivers.
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    Hydrological modelling and climate adaptation under changing climate: A review with a focus in sub-Saharan Africa
    (MDPI, 2022) Banda, Vincent Dzulani; Dzwairo, Rimuka Bloodless; Singh, Sudhir Kumar
    Empirical evidence continues to show that climate change remains a threat to the stability of the hydrologic system. As the climate system interacts with the hydrologic cycle, one significant repercussion of global warming includes changes in water availability at both regional and local scales. Climate change adaptation is intrinsically difficult to attain due to the dynamic earth system and lack of a comprehensive understanding of future climate and its associated uncertainties. Mostly in developing countries, climate adaptation is hampered by scarcity of good quality and adequate hydrometeorological data. This article provides a synopsis of the modelling chain applied to investigate the response of the hydrologic system under changing climate, which includes choosing the appropriate global climate models, downscaling techniques, emission scenarios, and the approach to be used in hydrologic modelling. The conventional criteria for choosing a suitable hydrological model are discussed.
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    Quantifying the influence of climate change on streamflow of Rietspruit sub-basin, South Africa
    (IWA Publishing, 2024) Banda, Vincent Dzulani; Kanyerere, Thokozani; Dzwairo, Rimuka Bloodless
    This study integrated climate projections from five global climate models (GCMs) into the soil and water assessment tool to evaluate the potential impact of climate alterations on the Rietspruit River sub-basin under two representative concentration pathways (RCP4.5 and 8.5). The model’s performance was evaluated based on the coefficient of determination (R2), percent bias (PBIAS), Nash–Sutcliffe efficiency (NSE), probability (P)-factor and correlation coefficient (R)-factor. Calibration results showed an R2 of 0.62, NSE of 0.60, PBIAS of 20, P-factor of 0.86 and R-factor of 0.91, while validation produced an R2 of 0.64, NSE of 0.61, PBIAS of 40, P-factor of 0.85 and R-factor of 1.22. Precipitation is predicted to increase under both RCPs. Maximum temperature is projected to increase under both RCPs, with a major increase in the winter months. Minimum temperatures are projected to decrease under RCP4.5 in the near (0.99 °C) and mid (0.23 °C) futures, while the far future is projected to experience an increase of 0.14 °C. Precipitation and temperature changes correspond to increases in streamflow by an average of 53% (RCP4.5) and 47% (RCP8.5)