Kebede Gurmessa, Siefu.Cahi, Joss Alexander.2025-11-192025-11-1920252025https://hdl.handle.net/10413/24123Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.Understanding surface water–groundwater interactions is essential for effective water resource management, particularly in the context of land use and climate change. This study investigates these interactions at two contrasting sites in KwaZulu-Natal, South Africa: the near-pristine Cathedral Peak Catchment 6 (CP Catchment 6) in the Drakensberg Mountains and the agriculturally impacted Fountainhill Estate (FHE) catchments near Wartburg. These catchments are representative of different climatic, topographic and anthropogenic conditions, offering insights into how land use and land use change influence hydrological connectivity. At CP Catchment 6, intensive field-based monitoring was conducted over two years using a combination of hydrometric measurements, stable isotopes, electrical conductivity (EC), radon (222Rn) and satellite-derived soil moisture modelling (OPTRAM). Sampling occurred across multiple temporal scales (event-based and seasonal scales) to capture both baseline and dynamic hydrological processes. The catchment exhibited stable groundwater contributions facilitated by steep topography, connected wetlands and limited disturbance. Baseflow was sustained by meteoric-origin groundwater, while significant rainfall events rapidly mobilised pre-event water stored in wetlands due to groundwater ridging. These findings validate and expand upon existing conceptual models (e.g., Harrison et al., 2022), highlighting the critical buffering role of wetlands and subsurface flow systems in maintaining perennial streamflow. In contrast, at FHE, hydropedological desktop assessments, historical soil surveys, OPTRAM modelling and EC monitoring data revealed fragmented hydrological connectivity driven by agricultural land use. Practices such as irrigation, soil compaction and fertiliser application in the surrounding farms have resulted in elevated solute loads and episodic flushing during storm events. The presence of farm dams moderated downstream water quality but altered natural flow regimes. The OPTRAM model proved effective in identifying active flow paths and subsurface recharge zones, even in the absence of extensive in-situ data. A comparative analysis underscores how natural and anthropogenically altered systems diverge in their hydrological responses. CP Catchment 6 illustrates efficient, topography-driven hydrology with strong wetland-groundwater interaction, while FHE displays disrupted, highly variable flow paths shaped by land use activities. This research refines conceptual models of runoff generation across diverse landscapes and emphasises the need to incorporate subsurface flow processes into hydrological models. These findings have practical implications for catchment management, especially in balancing water supply, land development and ecosystem sustainability in South Africa’s heterogeneous environments.enCC0 1.0 Universalhttp://creativecommons.org/publicdomain/zero/1.0/Radon.Hillslopes.Hydrology.Thesis