Mokau River power station application declined

Joint media release: Environment Waikato and Waitomo District Council

A proposal by King Country Energy to build a hydro-power station on the Mokau River near Aria has been declined.

After hearing extensive evidence, both the Waitomo District Council and the Waikato Regional Council have turned down the application on the basis that it would have significant actual or potential adverse effects on the environment.

The applicant had proposed to construct an earth dam on the Mokau River, located approximately 4.3 km downstream from the existing Wairere Falls dam. The dam would have had a height of around 44 metres, crest length of 160 metres and have a footprint length of around 200 metres, with the capacity to generate around 9.6 MW of electricity – which is typically enough to power 5500 households.

The water behind the dam would have formed a lake with a maximum surface area of around 50 ha when full. All generation flows would discharge into the tail race, which would discharge approximately 50-100 metres downstream from the dam.

The joint hearing committee concluded that the merits and benefits of the hydro electricity generation proposal did not, on the evidence presented, outweigh the adverse effects to the environment that would arise.

The committee noted that while generating electricity enables people and communities to provide for their wellbeing, the definition of sustainable management clearly envisages that these benefits are not to be gained at all costs, and that “certain environmental bottom lines are to be met, or adverse effects remedied or mitigated.”

The hearing committee concluded that there were a number of areas where environmental impacts could not be avoided, and noted that no mitigation of these areas was proposed by the applicant.

“One of the key adverse effects is quite simply associated with the dam. We note that the features of the river which make it attractive for the applicant are the same features that make it attractive to recreational users, that is, the rapid change in gradient,” the committee noted.

“Damming the river as proposed will replace 6.2 km of flowing water with still water which will have adverse environmental and recreational effects.”

In particular, the hearing committee noted that while some effects could be mitigated (for example fish passage issues and vegetation loss), the effects on downstream aquatic fauna as a result of the fluctuating flows would be significantly adverse.

In addition, there would be:

• an adverse effect on aquatic biodiversity.
• the loss of the pa tuna sites and other cultural heritage sites and values, which were found to have a highly significant effect on iwi
• the effects on landscape, visual and amenity values within the Mokau Valley would likely range between “more than minor” and “significant”
• the recreational effects would be significant particularly with respect to the loss of regionally significant whitewater rapids.

The joint hearing committee comprised three representatives from the Waikato Regional Council, Councillors Lois Livingston, Ian Balme and Angus Macdonald, and one representative from the Waitomo District Council, Commissioner Robert Eyeington.