Raupo choking the Aronui Dam will be cleared this summer after the Central Otago District Council agreed to restore the site back to its 2015 condition.

Friends of Aronui Dam representative Ken Churchill spoke to the Vincent Community Board this week. He said volunteers could no longer keep up with the fast-spreading weed.

“It is now beyond us,” Ken said.

The volunteer group has spent years maintaining the popular picnic spot and has repeatedly used diggers to remove raupo. Despite their efforts, Ken said “there is virtually no clear water left in the dam.”

Raupo is a tall wetland plant that thrives in shallow, fertile water and can grow up to two metres. It provides breeding habitat for waterfowl but can quickly dominate small ponds.

The dam and surrounding reserve were vested to the Central Otago District Council in 2016 after being transferred from the Department of Conservation.

Ken told the board the overgrowth was now affecting the stability of the dam wall and causing leakage into nearby properties.

“It’s prolific, this stuff, and very difficult to get out,” he said.

Two Australian coots with their new babies on the Aronui Dam. Photo: The Central App.

The council recently commissioned geo-engineers to assess the dam. They found the structure was not considered stable due to its age, similar to a number of older dams in the district. Although the

southwest embankment shows visible deformation, engineers did not believe failure was imminent except in an earthquake.

Constructed in 1909, the Aronui Dam originally supplied water to gold mining operations. It later became part of Alexandra’s water supply and feeds water to the nearby Lanes Dam. 

Shortly after its construction, the western wall began to bulge and a buttress was added. 

The board has now approved a dam break risk assessment, funded through the Long Term Plan and agreed for council staff to remove raupo back to its 2015 levels while retaining a small section for

bird breeding.

Council staff will also work with the Friends of Aronui Dam on future maintenance and funding needs.