Dream of swimable Lake Rotoroa long way off as water flatlines

Thursday, 7 August 2025

Anglers try their luck at the 2025 fishing competition at Lake Rotoroa.

While walkers and runners aren’t paying much attention to water quality at Hamilton lake, the city council is now keeping close tabs on it. They say it has landed on a “plateau”: stable, but still far from safe for swimming.

Back in January, the council installed a high-tech monitoring system to keep tabs on the lake’s health, tracking everything from water temperature to nutrient levels. While it’s too early to see long-term trends, the raw data is now online for anyone to dive into.

Councillor Anna Casey-Cox says it’s a step in the right direction for a much-loved landmark that locals dream of swimming in again. “There’s a shared aspiration in the community and at council for it to improve,” she says, “so we do need to put in some mitigation.”

Swimmers in Lake Rotoroa Hamilton Lake, circa 1927.HCL_01021

‘It’s so well used now, I mean it’s such a lovely lake,’ retired University of Waikato science professor Brendan Hicks said.

Some of the actions already underway include pest control, stormwater improvements, planting projects, and managing the local goose population. But progress is slow, and Casey-Cox says limited council resources make a full-scale restoration plan challenging.

Once swimmable, lake Rotoroa is now, at least, not getting any worse.

“We have to be really careful about how we invest, making sure those investments are going to make a difference,” she says. “It’s going to take not just one thing, but a mix of efforts to bring real change to the lake.”

She envisions a future where Hamilton children can once again swim safely in the lake – something not seen since the 1980s.

But that vision is met with some scepticism from retired University of Waikato science professor Brendan Hicks, who has studied Lake Rotoroa for decades. “People have talked about dredging the lake – not really feasible, expensive, and probably wouldn’t achieve anything,” he says.

Hicks led aquatic science research at the university for 30 years. He recalls a 2006 project that removed large numbers of fish from the lake, but found it had little impact on water quality.

“There are really no easy solutions when you look at the root causes,” he says. “For me, it’s about education – teaching people the value of the lake.”

Hicks and Casey-Cox may differ on the path forward, but both agree Lake Rotoroa is an ecological and cultural taonga. Sitting at the heart of Hamilton, it’s a space worth fighting for – even if restoration is slow.