The impacts of water abstraction in tropical rivers: a case of South West upper Tana basin, Kenya



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The study to determine the impacts of water abstraction in South West Upper Tana Basin which is part of thelarger Upper Tana basin was undertaken in four major rivers, Thika, Kimakia, Kiama and Chania. Data for thisstudy 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 andDecember 2018 to determine the impacts of water abstraction in both dry and wet seasons. Regression andcorrelation 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 andsocio-economic. The hydrological impacts include reduced water levels, changes in stream morphology,decreased turbidity and reduced siltation. Socio-economic impacts include increased income from cropproduction and conflicts while environmental impacts were mainly changes in riparian vegetation. The studyestablished that the best combination of impacts of water abstraction in the South West Upper Tana Basin werechanges in water turbidity, decline in water levels, improved crop yields, changes in channel morphology andsiltation with a coefficient correlation r of 0.57 and coefficient of determination R2 of 0.52. To mitigate theseimpacts, there is a need for better enforcement of legislations on water abstraction and the monitoring of the riverbasins to curb water over-abstraction. Public awareness campaigns and involvement of stakeholders could alsominimize these impacts.




Journal of Environment and Earth Science, Vol.9, No.5