Tracing the Impacts of Land-Use Change on Reservoir Sedimentation: Insights from the Ruiru Basin, Kenya

Human activities have profoundly influenced sediment dynamics in tropical regions, altering the functionality of critical water infrastructure. This study focuses on the Ruiru Reservoir, a key water supply source for Nairobi, Kenya, constructed in 1949. Using a novel "source-to-sink" approach, we begin by integrating sediment core analysis, geochemical and stratigraphic profiling, and historical land-use reconstructions to examine sedimentation dynamics over the past seven decades (1949 - 2017).

The findings highlight six major sedimentation periods corresponding to heavy rainfall events and extensive land-use changes. Peaks in sediment accumulation align with transitions from forested landscapes to agriculture and urbanization, coupled with episodic climatic events. Advanced geochemical fingerprinting methods would enable the identification of sediment source areas, linking elevated sediment loads to hotspots of erosion caused by deforestation, agricultural expansion, and infrastructural development.

This multi-proxy analysis underscores the reservoir’s role as an environmental archive, documenting the Anthropocene’s imprint on hydro systems. It provides actionable insights into managing erosion and sedimentation under intensifying anthropogenic and climatic pressures. The research emphasizes the importance of sustainable catchment management and highlights how retrospective sediment analyses can inform future policies to enhance the resilience of tropical water reservoirs.