The water level was lowered in 2022 to allow some infrastructure to be removed, investigated and replaced.
"This included replacing valves located at the bottom of the reservoir tower, 15m below the top of the dam, and the installation of new brackets to support the valve spindles," a Dunedin City Council spokesman said.
"This has been a complicated piece of work, in part because of the tight working space involved and working at such depth."
The work had been completed successfully, he said.
The council has been raising the water level in 1m stages since August.
"We expect the refilling of the reservoir to be completed later this week, by which time 150,000cu m of water will have been added to the reservoir."
The full project is expected to cost about $120,000.
