Abstract:
The study to determine the impacts of water abstraction in South West Upper Tana Basin which is part of the
larger Upper Tana basin was undertaken in four major rivers, Thika, Kimakia, Kiama and Chania. Data for this
study was obtained from the Kenya Meteorological department (KMD), Water Resources Management (WRA)
and questionnaire surveys. The questionnaires were administered in the period between January 2018 and
December 2018 to determine the impacts of water abstraction in both dry and wet seasons. Regression and
correlation analysis was used to determine the nature and strength of relationships between different variables.
The results of the study indicate that the main impacts of water abstraction are hydrological, environmental and
socio-economic. The hydrological impacts include reduced water levels, changes in stream morphology,
decreased turbidity and reduced siltation. Socio-economic impacts include increased income from crop
production and conflicts while environmental impacts were mainly changes in riparian vegetation. The study
established that the best combination of impacts of water abstraction in the South West Upper Tana Basin were
changes in water turbidity, decline in water levels, improved crop yields, changes in channel morphology and
siltation with a coefficient correlation r of 0.57 and coefficient of determination R2 of 0.52. To mitigate these
impacts, there is a need for better enforcement of legislations on water abstraction and the monitoring of the river
basins to curb water over-abstraction. Public awareness campaigns and involvement of stakeholders could also
minimize these impacts.
