Lake Manapouri is key to the country's hydro generation capacity. Photo / OJB
An agreement has been reached to boost hydro generation at Lakes Manapōuri and Te Anau at lower operating levels in an effort to ensure energy security.
The changes, agreed to by Meridian Energy and the Guardians of Lakes Manapōuri and Te Anau, are expected to deliver an additional 45GWh of energy from the Manapōuri Power Scheme each year – enough to power around 6000 homes.
It’s being described by Energy Minister Simon Watts as an “important step in the Government and the sector’s work to protect the security of our energy supply for the future”.
“Last winter, New Zealand faced an energy shortage that led to significant price increases for consumers, in part due to low hydro lake levels. This Government will not accept a repeat of last winter and is working at pace to ensure we have a reliable and affordable energy supply.”
The two lakes are linked by a river system and provide generation for Manapōuri Power Station, the country’s largest hydro station. It’s operated by Meridian Energy.
The lakes’ levels are subject to operating guidelines, which include outlining what high and low operating ranges are and what rates of drawdown are allowed. The rate of drawdown is the rate at which hydro generation can reduce the levels of the lakes.
The agreement, which was announced by Watts on Friday evening, will change the drawdown rates when the lakes are in their low operating ranges to enable Meridian to generate more flexibly at their lower ranges.
Requirements on how long the lakes can stay within the first band of their low operating ranges will be removed to allow Meridian to generate more often when hydro levels reach these stages.
Equinoctial requirements will also be removed. These set limits on how hydro generation could affect the two lakes twice a year during windier periods.
“Lake Manapōuri and Lake Te Anau are not only environmentally and culturally significant, but they are also essential to New Zealand’s energy system,” Watts said.
“However, in recent years the lower operating ranges of these lakes have been underutilised, impacting our energy supply and risking the health of plant life along their shorelines.
“The agreement reached today allows for more flexible drawdown rates once the lakes reach lower operating levels, enabling Meridian to continue generating when lake levels are low. The changes balance the needs of our country’s electricity system with the environmental impact on the lakes and their surrounding areas.”
The Guardians of Lakes Manapōuri and Te Anau were established in 1973 after a campaign opposing the raising of the lake levels for hydro generation. The Guardians, along with Meridian, can make recommendations to the Government about issues relating to the operation of the power station.
“I am pleased to have enacted the Guardians and Meridian’s recommendations by amending the relevant legislation and publishing in the New Zealand Gazette,” Watts said.
“I acknowledge the expertise of the Guardians, who are responsible for advising on environmental, ecological and social effects of the power station on the lakes, and Meridian, as operator of the Manapōuri power station.
“I thank them for working together to recommend a path forward that better protects the existing patterns, ecological stability and recreational values of the lakes, while optimising hydro generation.”
The Government is attempting to avoid a similar situation to the “power crisis” that hit New Zealand last winter. Energy costs rose significantly amid low hydro-lake levels, a lack of wind and sun and what was considered an inadequate supply of natural gas. Several mills closed in the second half of last year, citing in part high power prices.
Jamie Ensor is a political reporter in the NZ Herald press gallery team based at Parliament. He was previously a TV reporter and digital producer in the Newshub press gallery office. In 2025, he was a finalist for Political Journalist of the Year at the Voyager Media Awards.