The announcement made on Thursday has raised hopes of millions of residents in the water-scarce Lower Eastern region who are expected to benefit from improved water supply, irrigation and electricity.
The 80.5-metre-high dam, being constructed at the confluence of the Thwake and Athi rivers along the Makueni-Kitui border, was 94.2 per cent complete as of Thursday.
The latest funding follows an additional Sh10.6 billion financing package signed by the AfDB to bridge a funding shortfall that had slowed construction.
In June 2026, the lender announced approval of €68.4 million (Sh10 billion) in additional financing for the dam’s first phase, alongside €15 million (Sh2.2 billion) in counterpart funding from the Kenyan government.
Speaking during a site visit, AfDB director for Water and Sanitation, Mtchera Chirwa, said the bank was also discussing financing for the downstream infrastructure needed to translate the dam’s completion into tangible economic benefits.
“As a Bank, we will ensure the project reaches completion and achieves the benefits. This means provision of water for food security; implementation of the irrigation component, water supply and sanitation for residents and hydropower for energy generation,” Chirwa said.
The dam has a planned storage capacity of 688 million cubic metres, making it one of Kenya’s largest water reservoirs.
It covers approximately 9,217 acres, with a catchment area of about 10,276 square kilometres, according to the programme’s official documentation.
Completing the dam wall is only the first step towards delivering its full economic potential.
The wider programme is structured around four phases, including dam construction, hydropower generation, water supply and sanitation, and irrigation development.
The downstream investments are expected to deliver up to 150,000 cubic metres of treated water daily to about 1.3 million people in Makueni and Kitui, as well as Konza Technopolis in neighbouring Machakos County
The project also envisages a 20-megawatt hydropower plant and an irrigation scheme designed to support up to 40,000 hectares, or approximately 100,000 acres, of farmland.
Water Secretary Samuel Alima said construction had resumed after the funding gap was addressed, with the remaining works focusing on the concrete face slab and a bridge linking the two counties across the dam.
“The contractor has resumed with the concrete face already having some panels, while others are also under preparation. They have also started doing the bridge,” Alima said.
The Ministry is targeting water impoundment by the end of January 2027, followed by commissioning in April, although the timeline will depend on the completion of outstanding works.
The project’s first phase has an estimated cost of Sh42.4 billion, according to official project records, with the AfDB and the Kenyan government sharing the financing burden.
The original design estimated the cost of the entire four-phase programme at 487 million units of account, an AfDB accounting unit whose value fluctuates with exchange rates.
Beyond addressing water scarcity, the dam is expected to help regulate flows along the Athi River, mitigating floods and supporting water availability during dry periods.
The irrigation component could also reduce farmers’ dependence on unreliable rainfall, strengthening food production in the semi-arid region.
Alima said parallel efforts to clean the Nairobi River system, including sewage collection, wastewater treatment and river widening, were underway to improve water quality.
