Stream Discharge Reduction in Kenya’s River Ruiru Sub-Catchment

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 ( 2 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 m 3 /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.