Where rivers meet the sea – two North Auckland estuaries

The murky green water at the Matakana Wharf looked rather less inviting than the array of delicious artisan produce at the nearby Matakana Market. But we were paddling, not swimming, and the Auckland Council’s most recent (2011) monitoring rates the river as having “good” water quality, rather than “fair” as in many other rivers which drain rural catchments.  Several hundred metres downstream of the wharf where large trunked mangroves edged the river and the tidal influence was more obvious, the water looked cleaner.

Mangroves on the Matakana

The Matakana River and estuary, the proposed marina at Sandspit and nearby Whangateau Harbour were the focus of this Dirty Water Tour.

Improving water quality in the river requires a significant upgrade of the existing Matakana sewerage system which is at capacity. It collects primary treated wastewater from septic tanks and filters it through a wetland before discharging poor quality wastewater into the river 300 metres downstream of the wharf. High levels of stormwater infiltration during wet weather can lead to discharges which exceed the consented volumes.

Auckland Council’s plans to “solve” Matakana sewage problems by piping wastewater to the existing Jones Road treatment plant near Omaha risk increasing the nutrient loading on nearby Whangateau Harbour.

Whangateau Harbour is the most natural mainland estuary in the Auckland region. A nationally important scientific reserve with regenerating kahikatea forest and saltmarsh wetlands fringes part of the harbour’s southern arm.  It is increasingly popular for snorkelling, and has some of the best cockle beds in the Auckland region. The cockles help sustain an array of wading and shorebirds and fish and their ability to filter impressive amounts of seawater each day is a major reason for the harbour’s clear water.

Whangateau has been closed to cockle takes since 2009 when there was a mass die off in the shellfish. The annual cockle survey organised by Whangateau Harbourcare suggests the beds are gradually recovering.

Roger Grace sampling cockles on the Whangateau Harbour

I was lucky enough have living legend, marine biologist Dr Roger Grace as a guide. It was fascinating  exploring the sandflats at low tide with Roger pointing out the sandy depressions where eagle rays had fed and explaining how they siphon up seawater and use it like a high pressure water drill to expose shellfish.

Safeguarding Whangateau’s existing high water quality should be a priority. Adding Matakana’s sewage to the Omaha plant and irrigating the sandy Omaha golf course with more treated effluent risks significant nutrient leaching into the harbour. As part of its 10 point plan Whangateu Harbourcare instead proposes that wastewater be treated in the catchment where it is generated. Less “convenient” in the short term  but more sustainable in the long term.

Our Matakana flotilla included the memorable Wendy House on a pontoon boat. It has a mooring in the estuary and at high tide it rests on the mudflats. Al, one of our trip participants, who designs and builds these modular boats, is no fan of the proposed Matakana marina which I have written about previously.

Wendy’s pontoon boat

Estuaries are prone to sedimentation. With the Matakana and Glen Eden rivers meeting the sea at Sandspit, a marina here risks burdening ratepayers and residents with a disfigured estuary and the costs of dredging and maintenance. The stories of other marinas at estuarine sites, such as Westpark and Milford Marinas, have been ones of bankruptcy (in the case of Milford Marina on the North Shore) and high dredging costs.  The controversial Whangamata marina is now being dredged regularly with local councils and ratepayers expected to foot the bill.

Sedimentation on the estuary at Sandspit

In 2011, Michael Taplin wrote a paper entitled Marinas Private Asset-Public Liability which he presented to the Hauraki Gulf Forum. It contains some telling information about the ongoing cost of marina dredging to ratepayers. Dredging of the Westpark Marina in the Waitemata Harbour is reported to cost a whopping $800,000 per year (referenced within Michael’s paper).

Auckland Council needs to recognise the many values of the estuary at Sandspit and rethink the consent it has given for a poorly conceived development.

Many thanks to Roger, Frances, Mike, Al and others for a great day on the Matakana River and Whangateau Harbour and for their efforts to protect these special places as individuals, and as part of Whangateau Harbourcare, Forest and Bird and other groups.

One thought on “Where rivers meet the sea – two North Auckland estuaries

  1. Is there somewhere one could sign up to hear about future events on this tour? I would have gone to Matakana but only heard about it (through Auckland Canoe Club) until the night before.

Comments are closed.