Buoys monitor harbour's sediment

20:13, Mar 17 2014
FLOATING INFO: Auckland Council marine scientist Jerrod Walker puts the finishing touches to the council’s solar powered monitoring buoy. A public information meeting is at the Mangakura Boat Club, Hotea River, tomorrow at 7pm.

Two buoys with scientific instruments will help keep track of sediment entering the Kaipara Harbour.

They will be stationed near the Hoteo River outlet shortly and involve scientists from NIWA, the Auckland Council and the Northland Regional Council.

Murky water affects the amount of sunlight needed for marine ecosystems, so the state-of-the-art scientific equipment will monitor sediment and water clarity.

Sediment and pollutants wash into connected rivers and into the harbour during heavy rain.

Sea life has been seriously affected by runoff. Concerns exist for the last significant sea grass meadows, nursery for various young fish including the entire west coast snapper stock.

The Wairoa River in the north is the biggest culprit. So an estuarine monitoring system (EMS) will go in at Tikonui Wharf near Ruawai.


The Hoteo River also dumps sediment into the harbour, and two slightly different instrumented buoys - one from the Auckland Council and one from NIWA - will be placed near the river mouth and at Orongo Pt, close to the sea grass meadows. The buoys will be used for several years, with NIWA's research vessel Rangitahi also monitoring harbour salinity.

Measures are already under way to reduce runoff sediment from some farms around the harbour through the Integrated Kaipara Harbour Management Group.

A public information meeting about the buoys will be held tomorrow at the Mangakura Boat Club by the Hoteo River, SH16, from 7pm.


The solar powered buoys will provide data the public can use.

Information relating to water temperature, salinity, tidal height, water currents, waves, wind strength and direction, air temperature and sunlight used by the Auckland Council and NIWA researchers will be available for public scrutiny on their websites.

The project has government and regional funding.

The Kaipara Harbour's huge size means it is heavily influenced by weather, therefore making the instrumentation hardy enough to withstand the conditions was a challenge, NIWA coastal scientist in charge of the stations Andrew Swales says. River plumes and water colour changes from algae can be seen in satellite images, so matching what can be seen happening across the harbour with what the buoys are picking up will help to "read" images in the future.

Raglan, Tauranga and Tairua harbours are also considered for a big picture look at how different soil types affect water clarity, Mr Swales says.

Collaboration is needed to get all the environmental outcomes we're looking for, Auckland Council marine scientist Jerrod Walker says.

The buoys join a suite of research projects already under way by the group.

Rodney Times