Power back on in Rotorua

After nearly 20 years of controlled management, the Rotorua geothermal field has its energy back and is undergoing a major review.

Unrestrained extraction of hot water by bores caused a startling decline in the field's thermal activity between the 1970s and late 1980s, affecting the performance of famous geysers such as Pohutu.

But the situation improved after restrictions on use were introduced in 1986 and a ban imposed on drilling new bores within a 1.5km radius of the tourist drawcard Whakarewarewa.

A senior environmental scientist with the Bay of Plenty regional council, Dougall Gordon, said yesterday that the renowned geothermal area was now in "fairly good health" and Environment Bay of Plenty was beginning a full assessment of the Rotorua geothermal management plan which guards the resource from overuse.
The plan, in operation for the past five years, was designed to protect the field's geothermal surface features - such as geysers and flowing springs - while allowing a certain amount of controlled extraction for domestic and industrial use, said Mr Gordon.

Containing one of New Zealand's last remaining areas of notable geyser activity at Whakarewarewa, the Rotorua field was unique because of its location under a regional city, he said.

Geothermal activity was a huge tourist attraction and of vital economic importance to Rotorua and the region. Tourism brought more than $300 million a year into the district.

Controls imposed in the 1980s meant about 90 per cent of water was now returned, compared with only 5 per cent in 1985.

Monitoring showed that water and temperature levels in the underground aquifers had stabilised but surface features had recovered more slowly, especially at Whakarewarewa, Mr Gordon said.

"The field now appears to be in a stable dynamic state, within the natural variations expected for thermal activity."

The outcome of the review would be public at the end of the year.

Tapping the earth

* Thermal energy underlying much of the city and the southern edge of Lake Rotorua was used from the 1800s for bathing and cooking.

* From the 1950s modification to springs and manipulation of flows to provide for bathing and spa development started to take a toll.

* Population growth and energy crises in the 1950s and 1970s resulted in still more bores, with no regard for sustainability.

* In the 1980s controls were imposed.

* About 90 per cent of geothermal water was now returned, compared with only 5 per cent in 1985.