Meridian Energy will start spilling water from some of its major South Island hydro lakes from tomorrow because of recent rain and snow melt.

The company said it would start a controlled release of water at Benmore Dam, with releases at Aviemore and Waitaki to follow.

The lakes are currently very high and nearing their maximum consented levels, it said.

Meridian said anyone camping or using any of the areas around Lakes Benmore, Aviemore and Waitaki would need to follow all signage and instructions and ensure they were at a safe distance from the water’s edge.

“The lakes and rivers within the Waitaki catchment are very high due to recent rainfall and snow melt,” the company said.

Meridian has been releasing water from Lake Pūkaki – the country’s biggest hydro lake – since December 3.

High lake levels have depressed wholesale prices across the country, particularly in the South Island.

On Monday, prices at Benmore sank to just $3.00 per megawatt hour (MWh) compared with $109MWh at Otahuhu and $88.91 at Haywards, according to NZX data.

Wholesale power prices are volatile even at the best of times and can vary greatly across the country.

In the winter of 2024, wholesale power prices peaked at $820MWh, driven by low hydro lake levels, calm conditions for wind power, and constrained gas supply.

Gas-powered electricity generation is responsible for about 8% of the country’s power supply.