Whangarei District Councillors have approved a long term strategy to develop the Wairua River as the next water source for the Whangarei water supply area, and to put on hold the investigation into a dam on the Ngunguru River.
Infrastructure & Services Manager Simon Weston said the proposal to use the Wairua River represented a significant saving and would have a lower environmental impact than the proposed dam.
“Changes to projected growth patterns in the District, public opposition to the Ngunguru River proposal and the need to think creatively given our limited financial envelope, led us to think about the project in a different way,” he said.
“We thought about establishing an emergency supply rather than a source that would be available all year round, and this opened up the possibility of using the Wairua River only when the main water supply, the Whau Valley Dam, falls below 55% full. A resource consent already existed for taking water from the Wairua River. Although it had lapsed, an application to renew it had been lodged with the Northland Regional Council to continue the use of this source some ten years ago.
“The strategy was modelled using new District growth data and the results showed this approach would provide enough water for Whangarei for the next 50 years.”
With the agreement of Northpower, which is entitled to use the majority of water in the river for its power generation plant just downstream of the proposed take point, Council has been granted a new resource consent to take up to 21,000 cubic metres of water per day from the Wairua River when the Whau Valley Dam level is below 55% full. When drought conditions reach this point the power generation capacity of the river is limited.
Council proposes to use the raw water line owned by the Maungatapere Water Company to pipe the water, but has yet to reach agreement with the water company regarding access.
A new treatment plant will be required to treat the water from the Wairua River and Council already owns the land on which it could be built. Staff say this could be done by upgrading the Poroti water treatment plant, which treats water from the Poroti Springs, or by building a second plant. Despite the cost of upgrading or building a new treatment plant, short term savings of around $30 million have been identified compared with the cost of constructing a dam in another location.
Construction of the water treatment facility is programmed for 2017 with public input sought by way of the 2012 Long Term Plan process.