Water resources in Kenya face escalating challenges from rapid urbanization, population growth, and anthropogenic activities that disrupt hydrological processes. This study investigated historical stream discharge trends in the River Ruiru sub-catchment of Kiambu County, Kenya, from 2006 to 2016. The research employed a descriptive quantitative research design using the Mann-Kendall trend test and Sen’s slope estimator to analyse discharge data. The study conducted a comprehensive data validation process before the Mann-Kendall test, revealing 1.3% of the 10-year record as missing values and showing no temporal clustering (χ2 test, p = 0.78). These gaps were considered inconsequential, preserving the original series’ statistical properties. Tukey’s method identified four potential anomalies, two of which were confirmed as legitimate high-flow events. Results revealed a statistically significant declining trend in stream discharge (MK test statistic: -0.3079, p-value: 0.0086) with an annual decrease rate of -0.0502 m3/s over the 10-year period. An anomalous discharge pattern observed between November 2011 and January 2012 coincided with major infrastructure developments and extreme climatic events, demonstrating the complex interaction between anthropogenic and climatic factors. The declining discharge trend aligns with similar patterns observed in other Kenyan watersheds, suggesting regional watershed degradation, which may be linked to rapid urbanization, agricultural expansion, and increased water abstraction. These findings highlight the critical need for integrated watershed management approaches, including protection of forested areas in upper catchments, implementation of green infrastructure to increase infiltration in urbanized areas, establishment of sustainable water allocation systems, and development of climate-adaptive strategies to enhance resilience of water resources in the face of increasing environmental pressures and climate variability.
Cite this paper
Onguru, P. , Macharia, A. N. and Makokha, M. (2025). Stream Discharge Reduction in Kenya’s River Ruiru Sub-Catchment. Open Access Library Journal, 12, e3713. doi: http://dx.doi.org/10.4236/oalib.1113713.
Andualem, T.G. (2015) Impact of Land Use Land Cover Change on Stream Flow and Sediment Yield (A Case Study of Gilgel Abay Watershed, Lake Tana Sub-Basin, Ethiopia). Master’s Thesis, Arba Minch University.
Depetris, P.J. (2021) The Importance of Monitoring River Water Discharge. Frontiers in Water, 3, Article 745912. https://doi.org/10.3389/frwa.2021.745912
Richey, J.E., Nobre, C. and Deser, C. (1989) Amazon River Discharge and Climate Variability: 1903 to 1985. Science, 246, 101-103. https://doi.org/10.1126/science.246.4926.101
Shiklomanov, A.I. and Lam-mers, R.B. (2009) Record Russian River Discharge in 2007 and the Limits of Analysis. Environmental Research Letters, 4, Article 045015. https://doi.org/10.1088/1748-9326/4/4/045015
Phillips, J.D. and Slattery, M.C. (2007) Downstream Trends in Discharge, Slope, and Stream Power in a Lower Coastal Plain River. Journal of Hydrology, 334, 290-303. https://doi.org/10.1016/j.jhydrol.2006.10.018
Déry, S.J. and Wood, E.F. (2005) Decreasing River Discharge in Northern Canada. Geophysical Research Letters, 32, L10401. https://doi.org/10.1029/2005gl022845
Walling, D.E. (2017) Measuring Sediment Yield from River Basins. In: Soil and Water Conservation Society (U.S.), Ed., Soil Erosion Research Methods, Routledge, 39-82. https://doi.org/10.1201/9780203739358-3
Setegn, S.G., Srinivasan, R., Melesse, A.M. and Dargahi, B. (2009) SWAT Model Application and Prediction Uncertainty Analysis in the Lake Tana Basin, Ethiopia. Hydrolog-ical Processes, 24, 357-367. https://doi.org/10.1002/hyp.7457
Sajikumar, N. and Remya, R.S. (2015) Impact of Land Cover and Land Use Change on Runoff Characteristics. Journal of Environmental Management, 161, 460-468. https://doi.org/10.1016/j.jenvman.2014.12.041
Mengistu, T.D., Chung, I., Kim, M., Chang, S.W. and Lee, J.E. (2022) Impacts and Implications of Land Use Land Cover Dynamics on Groundwater Recharge and Surface Runoff in East African Watershed. Water, 14, Article 2068. https://doi.org/10.3390/w14132068
Ngeno, E. (2016) Impact of Land Cover and Land Use Change on Stream Flow in Nyangores Sub-Catchment, Ma-ra River, Kenya. Master’s Thesis, Kenyatta University.
Umukiza, E., Raude, J.M., Wandera, S.M., Petroselli, A. and Gathenya, J.M. (2021) Impacts of Land Use and Land Cover Changes on Peakdischarge and Flow Volume in Kakia and Esamburmbur Sub-Catchments of Narok Town, Kenya. Hydrology, 8, Article 82. https://doi.org/10.3390/hydrology8020082
Waithaka, A., Murimi, S. and Obiero, K. (2019) Assessing the Effects of Land Use/Land Cover Change on Discharge Using SWAT Model in River Ruiru Watershed, Kiambu County, Kenya. International Journal of Research and Innovation in Applied Science, 5, 29-38.
Wambugu, M., Nyandega, I. and Kithiia, S. (2017) Spatio-Temporal Dynamics of Land Use Practices on Rivers in Tropical Regions: A Case Study of Ruiru and Ndarugu Basins, Kiambu County, Kenya. African Journal of Environmental Science and Technology, 11, 426-437. https://doi.org/10.5897/ajest2017.2325
Wambugu, M., Nyandega, I. and Kithiia, S. (2017) Spatio-Temporal Dynamics of Land Use Practices on Riv-ers in Tropical Regions: A Case Study of Ruiru and Ndarugu Basins, Kiambu County, Kenya. African Journal of Environmental Science and Technology, 11, 426-437. https://doi.org/10.5897/ajest2017.2325
Regional Centre for Mapping of Resource for Development (2019) Kenya Shapefiles. Regional Cen-tre for Mapping of Resource for Development. https://opendata.rcmrd.org/shapefiles
Kundzewicz, Z.W. and Robson, A.J. (2004) Change Detection in Hy-drological Records—A Review of the Methodology/Revue méthodologique de la détection de changements dans les chroniques hydrologiques. Hydrological Sciences Journal, 49, 7-19. https://doi.org/10.1623/hysj.49.1.7.53993
Shein, W.H. and Fitrianto, A. (2017) A Comparative Study of Outliers Identification Methods in Univariate Data Set. Advanced Science Letters, 23, 1422-1427. https://doi.org/10.1166/asl.2017.8366
Sen, P.K. (1968) Estimates of the Re-gression Coefficient Based on Kendall’s Tau. Journal of the American Statistical Association, 63, 1379-1389. https://doi.org/10.1080/01621459.1968.10480934
Chen, Y., Guan, Y., Shao, G. and Zhang, D. (2016) Investigating Trends in Streamflow and Precipi-tation in Huangfuchuan Basin with Wavelet Analysis and the Mann-Kendall Test. Water, 8, Article 77. https://doi.org/10.3390/w8030077
Malik, A., Kumar, A., Najah Ahmed, A., Ming Fai, C., Abdulmohsin Afan, H., Sefelnasr, A., et al. (2020) Application of Non-Parametric Approaches to Identify Trend in Streamflow during 1976-2007 (Naula Watershed). Alexandria Engineering Journal, 59, 1595-1606. https://doi.org/10.1016/j.aej.2020.04.006
Wambugu, G.M., Nyandega, I. and Kithiia, S.M. (2017) Application of Hydrological Models in Poorly Gauged Watersheds: A Review of the Usage of the Soil and Water Assessment Tool (SWAT) in Kenya. International Journal of Scientific & Technology Research, 6, 132-141.
African Development Bank (2025) Thika Highway Continues to Impact Kenyan Lives Five Years on. AfDB and Kenya.
https://www.afdb.org/ar/news-and-events/afdb-and-kenya-thika-highway
-continues-to-impact-kenyan-lives-five-years-on-17519
International Project Planning and Management Consultants (2023) Tatu City: Local Physical and Land Use Development Plan Justification Report. International Project Planning and Management Consultants.
Olang, L.O., Kundu, P., Bauer, T. and Fürst, J. (2011) Analysis of Spatio-Temporal Land Cover Changes for Hydrological Impact Assessment within the Nyando River Basin of Kenya. Environmental Monitoring and Assessment, 179, 389-401. https://doi.org/10.1007/s10661-010-1743-6
Mango, L.M., Melesse, A.M., McClain, M.E., Gann, D. and Setegn, S.G. (2011) Land Use and Climate Change Impacts on the Hydrology of the Upper Mara River Basin, Kenya: Re-sults of a Modeling Study to Support Better Resource Management. Hydrology and Earth System Sciences, 15, 2245-2258. https://doi.org/10.5194/hess-15-2245-2011
Bewket, W. and Conway, D. (2007) A Note on the Temporal and Spatial Variability of Rainfall in the Drought‐Prone Amhara Region of Ethiopia. International Journal of Climatology, 27, 1467-1477. https://doi.org/10.1002/joc.1481
Uhl, A., Hahn, H.J., Jäger, A., Luftensteiner, T., Siemensmeyer, T., Döll, P., et al. (2022) Making Waves: Pulling the Plug—Climate Change Effects Will Turn Gaining into Losing Streams with Detrimental Effects on Groundwater Quality. Water Research, 220, Article 118649. https://doi.org/10.1016/j.watres.2022.118649
Boitt, M., Khayasi, P. and Wambua, C. (2023) Assessment of Groundwater Potential and Prediction of the Potential Trend up to 2042 Using GIS-Based Model and Remote Sensing Techniques for Kiambu County. International Journal of Geosciences, 14, 1036-1063. https://doi.org/10.4236/ijg.2023.1410053
The Department of Water, Environment and Natural Resources (2017) Kiambu Water Steward-ship Partnership Set-Up Brief. The County Government of Kiam-bu.
https://kewasnet.co.ke/uploads/pillarFiles/1726066830_7fc0c30c3de668d5350a.pdf
