A one-off algae treatment has been carried out at Onepoto Lake in response to community concerns about persistent algal blooms.
The treatment funded by Kaipātiki Local Board and facilitated by Auckland Council’s Healthy Waters and Flood Resilience team, aims to improve water quality and reduce nuisance algae that has affected recreation and caused odours at the popular reserve.
Shallow water levels, reduced to just 10 to 30 centimetres in places due to sediment build-up, combined with warmer temperatures, have made the lake more prone to nuisance algae. The decomposition and subsequent release of gases contribute to unpleasant odours.
Council’s Wai Ora Urban Partnerships team is facilitating the application of a safe algaecide spray, supported by alum dosing to limit the nutrients that feed algal growth.
“It’s been really tough this year,” said Brian Christensen, a member of the New Zealand Radio Yacht Squadron, which regularly sails on the lake. “The algae comes in earlier than expected, and our boats end up tangled in it. Sometimes people wade in to rescue them, which isn’t safe.”
“The water usually clears up in winter, but since last year’s green algae died back in June, it’s stayed murky and a strange colour. There’s a constant flow of runoff over the path into the lake that looks the same.”
“We’ve been keeping a close eye on Onepoto Lake this week and were quite surprised to see a bloom appear so early in the year,” says Jack Dickens, Senior Healthy Waters Specialist.
“The algae is a result of high nutrient levels, sunlight heating the water surface and very low flows through the lake, preventing the mixing of water. For now, we want to continue monitoring the lake to see how the algae develops.”
The board has provided funding for this one-off intervention to address community concerns. However, ongoing lake management is not part of the project.
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