Baseline Assessment of Water Quality, Quantity, and Sediment Transport in the Kabutie Watershed, Upper Yala River Catchment, Nandi County, Kenya: Implications for Watershed Health and Drinking Water Security

Watershed degradation resulting from soil erosion and organic pollution threatens water security and ecosystem health in many rural catchments of Kenya. The Kabutie watershed, a key sub-catchment of the Upper Yala River in Nandi County, supplies drinking water to Kapsabet Town and surrounding communities, yet baseline information on its hydrology and water quality has been lacking. This study established baseline conditions of water quality, stream discharge, and sediment transport across the Kabutie watershed to support future monitoring and management interventions. A cross-sectional survey was conducted in July 2025 at fourteen monitoring sites. Stream discharge was measured using an Acoustic Doppler Velocimeter. Physicochemical parameters including temperature, pH, electrical conductivity, total dissolved solids, turbidity, and Dissolved oxygen were measured in situ using calibrated field probes. Total suspended solids were determined using APHA standard methods, and sediment loads were estimated from discharge and suspended sediment concentrations. Stream discharge ranged from 0.004 to 1.306 m³/s. Turbidity exceeded the Kenyan drinking water standard of 25 NTU at 85.7% of sampling sites, with Kapyagan Stream recording the highest value (301 NTU). TSS exceeded the recommended limit of 30 mg/L at 42.9% of sites, reaching 282 mg/L at Kapyagan. Dissolved oxygen levels were below the recommended 80% saturation threshold for aquatic life at all sites, with critically low values observed at Kaptilalon Stream (45.5%). Sediment loads ranged from 0.004 to 15.008 tons/day, with the Kabutie River exporting an estimated 5,478 tons of sediment annually. In contrast, pH, conductivity, and TDS remained within acceptable limits across all sites. The Kabutie watershed is experiencing significant degradation driven by soil erosion and organic pollution. Kapyagan Stream, a major drinking water source, was identified as the most vulnerable site. Immediate riparian restoration, livestock exclusion, pollution-source investigations, and long-term watershed monitoring are recommended to safeguard water quality and drinking water security.

Watershed health, Sediment transport, Physicochemical parameters, Upper Yala River

1. United Nations Environment Programme. An assessment of freshwater resources in Africa. Nairobi: UNEP; 2022. [Google Scholar] [Crossref]

2. Intergovernmental Panel on Climate Change. Climate Change 2023: Impacts, Adaptation and Vulnerability. Geneva: IPCC; 2023. [Google Scholar] [Crossref]

3. United Nations Water. The United Nations World Water Development Report 2024. Paris: UNESCO; 2024. [Google Scholar] [Crossref]

4. World Bank. Water Security Diagnostic for Sub-Saharan Africa. Washington DC: World Bank; 2023. [Google Scholar] [Crossref]

5. Mati BM, Mutie S, Gadain H, Home P, Mtalo F. Land use changes and hydrological impacts in Kenyan watersheds. Phys Chem Earth. 2008;33(1-2):55-63. [Google Scholar] [Crossref]

6. Mutua BM, Klik A, Loiskandl W. Catchment degradation and water quality challenges in Kenya. Water Pract Technol. 2019;14(4):847-859. [Google Scholar] [Crossref]

7. Borrelli P, Robinson DA, Panagos P, Lugato E, Yang JE, Alewell C, et al. Land use and soil erosion impacts on freshwater systems. Nat Sustain. 2020;3(3):217-225. [Google Scholar] [Crossref]

8. FAO. The State of the World's Land and Water Resources for Food and Agriculture. Rome: Food and Agriculture Organization; 2021. [Google Scholar] [Crossref]

9. Water Resources Authority. Lake Victoria North Catchment Management Strategy 2023–2027. Nairobi: WRA; 2023. [Google Scholar] [Crossref]

10. Food and Agriculture Organization. Soil erosion and sediment management in agricultural watersheds. Rome: FAO; 2022. [Google Scholar] [Crossref]

11. Keesstra SD, Nunes J, Novara A, Finger D, Avelar D, Kalantari Z, et al. The role of soil conservation in sustainable watershed management. Sci Total Environ. 2021; 754:142306. [Google Scholar] [Crossref]

12. Wetzel RG. Limnology: Lake and River Ecosystems. 4th ed. San Diego: Academic Press; 2019. [Google Scholar] [Crossref]

13. Maina CW, Sang JK, Mutua BM. Influence of livestock activities on stream water quality in Kenyan highlands. Environ Monit Assess. 2020; 192:624. [Google Scholar] [Crossref]

14. Mango LM, Melesse AM, McClain ME, Gann D. Impacts of land-use change on water quality in Upper Yala catchment. Hydrol Process. 2021;35: e14218. [Google Scholar] [Crossref]

15. World Health Organization (WHO). Guidelines for Drinking-water Quality. 4th ed. Geneva: WHO; 2022. [Google Scholar] [Crossref]

16. Bilotta GS, Brazier RE. Understanding turbidity and suspended sediment impacts. Water Res. 2008;42(12):2849-2861. [Google Scholar] [Crossref]

17. Rasmussen PP, Gray JR. Sediment monitoring and turbidity relationships. J Hydrol. 2018; 560:287-299. [Google Scholar] [Crossref]

18. Sutherland AB, Meyer JL, Gardiner EP. Effects of sediment on stream ecosystems. Freshw Biol. 2020;65(4):763-779. [Google Scholar] [Crossref]

19. Wynants M, Solomon H, Ndakidemi P, Blake WH. Soil erosion dynamics in East African agricultural catchments. Earth Surf Process Landf. 2021;46(8):1571-1585. [Google Scholar] [Crossref]

20. Kiplagat JK, Onywere SM, Kirui WK. Water quality degradation in Nandi highland streams. Afr J Aquat Sci. 2020;45(3):289-299. [Google Scholar] [Crossref]

21. Odongo VO, Onyando JO, Mutua BM. Sediment transport and water quality in Upper Yala tributaries. Hydrol Sci J. 2019;64(10):1231-1244. [Google Scholar] [Crossref]

22. Walling DE. Human impacts on sediment transport. Geomorphology. 2019; 340:34-45. [Google Scholar] [Crossref]

23. Sillanpää M, Ncibi MC, Matilainen A. Drinking water treatment technologies. Water Supply. 2019;19(2):355-367. [Google Scholar] [Crossref]

24. World Health Organization (WHO). Water Safety and Turbidity Management Guidance. Geneva: WHO; 2023. [Google Scholar] [Crossref]

25. Mwangi HM, Thenya T, Kiemo K. Effectiveness of riparian buffers in reducing sediment loads in Kenyan watersheds. Environ Chall. 2021; 5:100280. [Google Scholar] [Crossref]

26. Zhang X, Liu X, Zhang M, Dahlgren RA, Eitzel M. Riparian vegetation and water quality improvement: A meta-analysis. J Environ Qual. 2019;48(6):1452-1462. [Google Scholar] [Crossref]

27. Connolly NM, Crossland MR, Pearson RG. Dissolved oxygen thresholds and aquatic ecosystem health. Freshw Biol. 2020;65(9):1562-1574. [Google Scholar] [Crossref]

28. Dodds WK, Smith VH. Nitrogen, phosphorus and oxygen dynamics in freshwater ecosystems. Inland Waters. 2019;9(2):123-135. [Google Scholar] [Crossref]

29. Kilonzo F, Gikuma-Njuru P, Onywere S. Organic pollution in rural Kenyan streams. Water Environ J. 2021;35(3):776-787. [Google Scholar] [Crossref]

30. Mugo RM, Owuor PO, Kipkorir EC. Drivers of dissolved oxygen depletion in East African rivers. Ecohydrol Hydrobiol. 2022;22(4):659-669. [Google Scholar] [Crossref]

31. APHA. Standard Methods for the Examination of Water and Wastewater. 24th ed. Washington DC: American Public Health Association; 2023. [Google Scholar] [Crossref]

32. Nyairo WN, Wekesa PW, Omondi EO. Physicochemical water quality characteristics of agricultural catchments in western Kenya. Water Pract Technol. 2022;17(5):1187-1201. [Google Scholar] [Crossref]

33. Lal R. Soil conservation and watershed restoration in developing countries. Land Degrad Dev. 2021;32(8):2453-2467. [Google Scholar] [Crossref]

34. United Nations Development Programme. Integrated Watershed Management Guidelines. New York: UNDP; 2022. [Google Scholar] [Crossref]

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