Lake Rotorua may be warming from below

Undetected geothermal activity may be the cause of a temperature rise on the bed of Lake Rotorua, says an expert.

Temperatures are 0.3C above normal, said University of Waikato PhD student David Burger.

This could be due to more geothermal activity than first thought, but might also be linked to the lake-bed nutrients warming and releasing the heat.

The lake is about 17C but is expected to increase to about 23C by late January.

"We are talking small, very small, but obviously geothermal activity is a big thing in this lake," said Mr Burger.

Geothermal activity was common near Sulphur Point, he said, but not so much on the northern side of the lake.

- NZPA