EFFECTS OF SEDIMENTATION ON WATER QUALITY IN THE METOLONG RESERVOIR, MASERU, LESOTHO

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dc.contributor.authorMakhakhe, M
dc.date.accessioned2026-04-28T11:24:44Z
dc.date.available2026-04-28T11:24:44Z
dc.date.issued2025-07-01
dc.description.abstractReservoir sedimentation is a significant environmental challenge affecting the sustainability of water resources, particularly in Lesotho, where soil erosion and land degradation are prevalent due to intensive land–use activities and fragile ecosystems. Metolong Reservoir is a critical water supply for approximately two–thirds of Lesotho's population, challenged with rapid sedimentation which lowers the water quality and threatens the long–term viability of the reservoir, yet no known studies have been done to correlate sedimentation and water quality in the area. This study investigated how sedimentation affects water quality in the Metolong Reservoir by quantifying sediment accumulation in the Metolong Reservoir from 2020 to 2022 and analyzing the impact of sedimentation on key water quality parameters. The study employed historical bathymetric and water quality data (2020–2022), complemented by GIS–based spatial analysis and R statistical modeling to assess the spatial and temporal relationships between sediment deposition and changes in water quality parameters, following the causal–comparative research design. Water quality parameters analyzed were aluminum, Electrical Conductivity (EC), iron, manganese, nitrates, nitrites, phosphates, sulphates, TDS and turbidity. Bathymetric analysis revealed a total sediment accumulation of approximately 1,705,583 m3 (2.68% of reservoir capacity) between 2020 and 2022, concentrated primarily near the reservoir’s middle and towards the dam, resulting in an annual storage loss of 1.34%.Linear regression analysis revealed turbidity as the most significant at (p<0.05).The study also identified turbidity and nitrates as key water quality parameters significantly influenced by sedimentation, with turbidity showing the strongest correlation (r = 0.60) and nitrates showing a moderate correlation (r = 0.2) with sediment volume suggesting possible links with upstream land use and nutrient runoff. There was an increase in nutrients and heavy metals concentration from 2020–2022, indicating a need for intervention, though most water quality parameters were still within WHO and South African water quality standards. The findings confirm that sedimentation negatively affects water quality, underscoring the need for integrated catchment management strategies, including sediment control, land–use planning, and systematic water quality monitoring to safeguard reservoir operations and public health.
dc.identifier.urihttps://hdl.handle.net/20.500.14155/2236
dc.titleEFFECTS OF SEDIMENTATION ON WATER QUALITY IN THE METOLONG RESERVOIR, MASERU, LESOTHO
dc.typeThesis
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