TrustPower has been accused of a "corporate takeover" of a Bay of Plenty river ahead of hearings this week on proposed changes to the way it operates its Matahina Dam.

Users of the Rangitaiki River, a popular whitebaiting spot west of Whakatane, say a new resource consent TrustPower has applied for would drastically lower the river's flow rate at times, reducing it to a stream and causing safety and environmental problems.

Locals were shocked by a 2009 trial run that saw water levels in the 37km stretch of river downstream from the dam drop to the point where swathes of weed usually well submerged in water were left rotting in the sun.

Farmer Matt Gow said all he could hear was the sound of stranded fish writhing among the plants, while kiwifruit grower Ian Kinvig said the smell was so bad he could not drive with the windows down for days.

Mr Kinvig, one of 20 submitters against what he called a "corporate takeover", said the lower levels would force him to spend at least $10,000 on new equipment to take river water for irrigation and frost protection.

Whakatane councillor and local resident George Johnston has also claimed the low river flow at a bar near the rivermouth would threaten boaties' lives.

He said he was outraged at TrustPower's lack of concern for the environment and river users and criticised Bay of Plenty Regional Council for relying "entirely" upon interest groups to fight for the river.

Groups and individuals representing the varied river users had been forced to hire consultants and legal representatives to help prepare a defence for what had been labelled by many as a "very slick and impressive" application by TrustPower, he said.

"There is no economic or social benefit for the Bay of Plenty or New Zealand from TrustPower's consent application, only the ability to destroy one of New Zealand's best natural resources.

"The general public's opinion that 'this will never happen' is rightly based on the assumption our resources are being adequately protected by existing legislation and elected bodies - unfortunately TrustPower are very likely to obtain a resource consent that will see generations of New Zealanders deprived of a magnificent natural resource."

One submitter had put the company's chance of getting consent at better than 50 per cent, he said.

Regional council consents manager Helen Creagh said the application was for a "controlled activity" and therefore the consent must be granted.

"However, the way the power scheme operates and controls the flow in the river is a major concern for submitters, and conditions are a decision for the commissioners."

TrustPower spokesman Graeme Purches said there had never been a set minimum flow rate and the application requested one.

"We've worked with a whole bunch of parties where we've been able to identify potential mitigations for the lower flow."

The hearings start today and run into next month, when a decision is expected..


At 86m, the Matahina Dam is the highest in the North Island and its hydroelectric power scheme pumps the national grid with an average output of 290GWh each year.


The application seeks to set the minimum output of the dam to 20 cumecs (10MW), except when inflow to Lake Matahina was less than that. Other changes would remove the limit on the number of operational peaks at the dam each day and boost "ramping" flow rates through it.