Proposed Malewa dam in Kenya: Adequate adaptations to original design

Abstract

Malewa dam in Kenya was first studied in the 1990s at preliminary design stage, through a study funded by Japanese Government who entrusted JICA with it. At that time, its main purpose was water supply to Nakuru, Naivasha and Gilgil cities in the Rift Valley. Thirty years later, its design was reviewed within the frame of a feasibility study funded by World Bank to account for revised needs -now excluding Nakuru- also taking into account increased awareness of environmental impact on downstream Lake Naivasha (Ramsar zone), management of the water scarcity, climate change trends, reliability issue, quality of water, sedimentation, as well as growing concern with operation and maintenance costs. Among studied solutions, focused on supply by gravity for economic reasons, and as ground water poses a serious health problem in this area due to a high fluoride content detrimental to human consumption, the construction of Malewa dam was confirmed to be the best solution after a decision making process, subject to some changes to the basic design, such as using the compensation flow to generate hydro-power to pump water to a WTP nearby the dam, mixing water with groundwater, building check dams and implementing water management and compensation measures.