Thiba Dam, which is among President Uhuru Kenyatta's flagship projects in Mt Kenya, is complete.
Rice farmers in the expansive Mwea irrigation scheme are expected to start using the dam in May.
National Irrigation Authority officials say they expect the dam to be filled by heavy rains expected in the country this month.
Eng Charles Muasya, the authority's Infrastructure Development boss, said it would take two months to fill the 15 million cubic meters reservoir.
A spot check by the Star revealed that the dam's 42-metre embarkment, spill way, and associated works are complete.
"We project that the dam would be 100 per cent ready next week," Muasya said.
The project, he said, has cost the taxpayers Sh11 billion to construct. The dam was financed by the JICA - Japanese International Corporation.
"Because we have finished the dam early, we are likely to save some money," Muasya said.
Water will be bound in the dam and the gates will be opened based on the demand downstream.
"The control rooms are complete. We have also completed the sand trap at the top," he said, restating that the critical components are complete.
Workers were spotted doing finishing touches to a road running around the 1km wide dam.
The dam is projected to the close the countries rice supply deficit by 86,000 metric tonnes.
Kenya's annual rice consumption is 450,000 metric tonnes of which only about 200,000 metric tonnes is supplied.
Mwea irrigation scheme is served by two rivers - Thiba and Nyamindi.
"We seek to increase the acreage of rice in Mwea by 10,000 acres. The water harvested will allow us do two crop seasons. We currently do one season meaning we will put a total 70,000 acres in a year," the NIA boss said.
The number of people involved in farming is projected to increase to 180,000 households.
Following a request by the surrounding community, NIA has created three new schemes with a total acreage of 2,000 - Rumbuini, Rukenya, and Kibithe.
Tana Water Services Board are also working on a water supply component that will be attached to the dam.
The dam is expected to boost the economy by Sh6 billion every year, with 350,000 direct jobs set to be realized through the project.
President Kenyatta unveiled the project in November 2017, which was among the first one after his reelection. Works kicked off in March 2018.
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