10 June 2016

Watercare commissions game-changing study of Manukau Harbour

Manukau Harbour’s ecological health will be put under a scientifically-backed microscope for the first time in a complex hydrodynamic study commissioned by Watercare.

Auckland’s water and wastewater services provider is funding a three-year research programme by the National Institute of Water and Atmospheric Research (NIWA), which will establish a coupled hydrodynamic and water-quality model of New Zealand’s second largest harbour.

The work is part of a strategic partnership between Watercare and NIWA, and will provide much-needed information on how nutrients enter the harbour and how they subsequently move around the harbour and the lower levels of the foodweb.

Watercare chief executive Raveen Jaduram says the model will establish a very clear understanding of the various factors that affect the health of the Manukau Harbour.

“Finally we will have a sound, scientific basis for collaborative decision making in the harbour. This will ensure planning decisions and debate is based on facts, not opinions,” says Jaduram.

In Auckland Council’s 2014 State of Auckland Marine Report Card, the harbour received a D grade for water quality, contaminants and ecology, the result of years and, in some areas, decades of deterioration.

NIWA Auckland regional manager Ken Becker says the initial phase of the project will focus on nutrients and nuisance algal blooms.

“Our scientists will then be able to use the model to conduct ‘what-if?’ studies. For example, what if nutrient inputs increase due to Auckland’s growth and increased flows at the wastewater plant? What about climate change? How will sea-level rise influence the flushing time of the harbour?”

Surface water and discharges from a large and complex land catchment – that includes Onehunga, Mangere and Takanini and stretches as far south as Waiuku – converge in the Manukau Harbour.

Watercare's Mangere Wastewater Treatment Plant, which collects and treats wastewater from across the city, discharges the treated wastewater to the harbour.

Jaduram says: “We are part of the Manukau Harbour community and feel strongly about sustaining the health of the harbour environment.”

Although Watercare is funding the initial stages, he says the model is a collective resource and harbour stakeholders, including Auckland Council, are encouraged to provide expertise and funding to enhance the research and understanding of the harbour, particularly in relation to sedimentation.

Manukau Harbour Forum chair Jill Naysmith says the forum is delighted that Watercare has stepped up to fund the first major step of the model.

“We are looking forward to collaborating with Watercare and other harbour stakeholders to develop the sediment and contaminant components of the model.”

Auckland councillor Denise Krum says for too long the Manukau harbour has been the poor cousin to the Waitemata and Watercare’s commitment to undertake modelling is a massive step forward.

“Knowledge is king and the reason why I pushed through an amendment to Council’s 10-year budget to raise the hydro modelling topic.

“Increased focus on the harbour will be incredibly important for our city given the population growth expected all along our shores. As a keen and competitive ocean swimmer, I’m excited to one day swim in a clean and safe Manukau.”

ENDS

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