Browsing by Author "Glenday, Julia"

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    Understanding dominant hydrological processes and mechanisms of water flow in a semi-arid mountainous catchment of the Cape Fold Belt
    (Elsevier Ltd, 2025) Jumbi, Faith; Mazvimavi, Dominic; Glenday, Julia
    Improving our understanding of streamflow characteristics, water storage, and dominant flowpaths in mountainous regions is important as mountains play a vital role in delivering water to lowlands, particularly in semi-arid areas. This work characterized water sources, flowpaths, and streamflow characteristics in the semi-arid, mountainous Kromme catchment in Eastern Cape Province of South Africa. Precipitation, shallow and deep groundwater levels, and streamflow data were analysed to identify patterns that indicate the occurrence and/or dominance of certain processes, responses, and flowpaths. Results of the study demonstrated how the catchment responds to rainfall events across seasons and rainfall intensities. Steep and rocky areas that make up much of the catchment contributed to significant flood peaks after high-intensity storms. Quick and slow responses in flow after rainfall events indicated the dominance of both surface and subsurface flowpaths respectively. Furthermore, surface and subsurface flows were significant in recharging the floodplain alluvial aquifer as well as maintaining streamflow during dry periods. Average annual runoff coefficients were low (0.09), which implied large evapotranspiration (ET) withdrawals from dominant flowpaths and/or storage in inactive groundwater. The Kromme catchment has a sizeable floodplain with large alluvial aquifers, which make significant contributions to catchment storage and outflows. Overall, the catchment streamflow was sustained by baseflow (for ∼50% of the time).
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    Variation in soil water content and groundwater levels across three land cover types in a floodplain of the kromme catchment, South Africa
    (Springer Science and Business Media B.V., 2024) Jumbi, Faith ; Glenday, Julia ; Mazvimavi, Dominic
    Invasions of floodplains and riparian areas by alien woody species replacing predominantly herbaceous indigenous vegetation have altered the hydrological and ecosystem functioning in catchments. Although existing studies have examined changes in river flows following the establishment or clearing of alien woody vegetation, our understanding of impacts on soil water content and groundwater remains poor. Limited process knowledge restricts our capacity to reliably model and predict the impacts of land cover changes. As such, this work compared temporal variations in soil water content (SWC) and groundwater levels at three locations with different vegetation types: black wattle (Acacia mearnsii) trees, palmiet (Prionium serratum), and grass (dominated by Pennisetum clandestinum spp), within a floodplain site in the Kromme Catchment in the Eastern Cape Province of South Africa. Soil water content and shallow groundwater levels (< 4 m below ground) were monitored from August 2017 to December 2019 using soil moisture probes and piezometers. Rainfall, vegetation type and antecedent conditions were identified as the major factors controlling observed responses. On average, soil water content and water retention were significantly higher (p < 0.05) at the palmiet site, whilst the wattle site had the lowest SWC among the three sites. Shallow groundwater levels were also higher at the palmiet and grass sites and lowest at the wattle site. Results showed the negative impacts of black wattle trees on SWC and groundwater levels. These results are crucial for improved quantitative predictive capacity which would allow for better catchment management, for example, informing water supply planning and guiding restoration programs focusing on alien plant clearing.