Warm temperatures and low rainfall over the past two months have resulted in a significant drop in the level of Lake Wānaka and it now hovers just millimetres from its lowest ever recorded level, in 1935.

“Lake Wānaka’s level … is still … above the lowest recorded level which was measured on September 25, 1935 at a level of 276.26 metres above sea level,” Guardians of Lake Wānaka chair and Wai Wānaka trustee Don Robertson said.

At the time of writing Lake Wānaka was at 276.32 metres above sea level, 66 millimetres above its lowest recorded level and 4.06 metres below the December 2019 flood level of 280.38 metres above sea level.

Don said it was possible the low water levels could have some negative effects on aquatic biodiversity in the lake but noted that it could have some positive outcomes, too.

The Bullock Creek delta extends well out into the lake.

“It was impossible to know the specific effects of exposure to the dryness and the solar radiation on the biodiversity as they would be microscopic,” Don said.

“The impacts on the biomass of those organisms which would have lived in the exposed areas is unfortunate but I don’t think it is anything that can be addressed by the Guardians or anyone else”, he said.

“We are at the mercy of the rain and snow.”

The lake level has been on a steady decline since early February.

On the flip side, patches of the invasive waterweed lagarosiphon which are exposed may die off.

“It is quite likely that that’ll be suffering,” Don said. “I think events like this will certainly reduce the population of lagarosiphon in a number of areas.”

Unlike Lake Hāwea, Lake Wānaka’s water level is not controlled for the purposes of electricity generation and is protected under the Lake Wānaka Preservation Act 1973.

“When the National government’s ‘think big’ campaign got underway around 1970, Wānaka and the Upper Clutha were being looked at for several high dams, one of which would have backed up water into Wānaka and would have raised the lake several metres,” Don said.

“There was substantial community opposition to National’s project. The Labour Party promised to protect Lake Wānaka forever if they won the election in 1972, which they did, and rapidly wrote and passed the Lake Wānaka Preservation Act 1973.”

Occasional rain is forecast over the next two weeks but conditions are generally dry. The lake may still threaten the low level of 1935.

PHOTOS: Wānaka App