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Seasonal assessment of water quality and major ion chemistry in the lower region of Lake Kariba, Zambia

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Abstract

Lake Kariba is a major freshwater resource in Southern Africa that sustains livelihoods, biodiversity, and regional economic activities, yet faces pressures from land-use practices and climate variability. This study assessed the effects of surrounding land use on lake water chemistry, with emphasis on anions, cations, and key nutrients. Fifty-three water samples were collected from downstream sites during hot-dry, cool-dry, and rainy seasons to capture temporal variability. Ionic composition and potential sources were determined using Ion Chromatography and Inductively Coupled Plasma techniques. Dominant ions, including Mg (3.3–3.9 mg L⁻¹), SO₄²⁻ (> 2 mg L⁻¹), Cl⁻ (1.2–1.6 mg L⁻¹), and Si (> 4 mg L⁻¹), remained relatively stable across seasons. Parameters such as pH, F⁻ SO₄²⁻, Cl⁻, TDS, EC, and temperature exhibited greater seasonal variability, with significant differences (p < 0.05) associated with land-use activities. Areas influenced by aquaculture and agricultural activities showed comparatively elevated nutrient concentrations relative to sites dominated by natural vegetation. Although localized impacts were evident, the Water Quality Index (13.1–13.6) consistently classified the water as excellent. Overall, the lake maintains good water quality, but continued monitoring and targeted management are necessary to address land-use pressures and safeguard its ecological integrity.

Data availability

All data supporting the findings of this study are available within the paper and its Supplementary Information. Microsatellite primer sequences are provided in Supplementary Table 2, along with original reference describing the microsatellites used in this study.

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Acknowledgements

The authors gratefully acknowledge the National Research Foundation (NRF) for their support through the trilateral collaborative agreement between Japan, Zambia, and South Africa (A-J CORE), as well as the University of the Witwatersrand, without which this study would not have been possible. Gratitude is also extended to Mr Bob Mwangala from the Zambezi River Authority (ZRA) and the fisheries local authority at Siavonga district for all the support during the sampling processes.

Funding

This work was supported by the National Research Foundation for the WELCOME project [No. 132802] and the University of the Witwatersrand.

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Authors and Affiliations

  1. Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Private Bag X3, Johannesburg, 2050, South Africa

    Mokgaetji Monyai, Mbongiseni L. Dlamini, Heidi Richards, Hlanganani Tutu & Luke Chimuka

  2. School of Education, University of the Witwatersrand, Private Bag X3, Johannesburg, 2050, South Africa

    Sinegugu Khulu

  3. School of Mines, Integrated Water Resources Management Centre, University of Zambia, P.O. Box 32379, Lusaka, Zambia

    Kawawa Banda

  4. Copperbelt University, P.O. Box 21692, Kitwe, Zambia

    Imasiku Nyambe

Authors

  1. Mokgaetji Monyai
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  2. Mbongiseni L. Dlamini
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  3. Heidi Richards
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  4. Sinegugu Khulu
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  5. Hlanganani Tutu
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  7. Imasiku Nyambe
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Contributions

Mokgaetji Monyai: Data curation, Formal analysis, Investigation, Methodology, Validation, Writing – original draft, Writing – review & editing. **Sinegugu Khulu** : Investigation, writing – review and editing, Mbongiseni Dlamini: Writing – review & editing, Software. Luke Chimuka, Heidi Richards & Hlanganani Tutu: Conceptualization, Funding acquisition, Methodology, Supervision, Writing – review & editing, Project administration. **Imasiku Nyambe & Kawawa Banda** : Conceptualization, Funding acquisition, Project administration.

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Mokgaetji Monyai.

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Monyai, M., Dlamini, M.L., Richards, H. et al. Seasonal assessment of water quality and major ion chemistry in the lower region of Lake Kariba, Zambia.
Sci Rep (2026). https://doi.org/10.1038/s41598-026-44457-w

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Keywords

  • Anions
  • Cations
  • Water quality
  • Downstream
  • Water quality index
  • Lake Kariba

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