Hydrodynamic models

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Hydrodynamic models

Council has built up a picture of what is happening in the waters of the Queen Charlotte Sound/Tōtaranui and Pelorus Sound/Te Hoiere with the help of NIWA scientists, their supercomputer, and the Ministry for Primary Industries.

Hydrodynamic models simulate how the tides and currents flush in and out of the Sounds, how nutrients come and go and the ecological effects of marine farming and land-uses.

The 2014 Queen Charlotte model (below) has confirmed what many fishermen, boaties and Sound residents have always believed – Tory Channel/Kura Te Au is like a vital artery connecting Queen Charlotte Sound with Cook Strait to refresh and flush out the water and nutrients

If Queen Charlotte Sound was emptied of all its 9.9 billion cubic metres of water, the amount of water through Tory Channel would refill it in about 3.8 days.

The 2015 Pelorus Sound model (below) showed that the Pelorus River is a powerful engine that drives the circulation of water throughout the entire 50 km long system.

Every second an average of 5,000 cubic metres (equivalent to two Olympic swimming pools) is exchanged with the deeper waters of Cook Strait at the entrance of Pelorus Sound.

With the current number of consented fish and mussel farms, the model suggests there is unlikely to be a marked change in nutrient levels in the ecosystem.

Since these reports were produced, the Ministry for Primary Industries commissioned further modelling in 2016 and 2017 to better understand the effects of proposed salmon relocations.

Council will continue to monitor water quality to track key indicators such as nutrient loading, which will also help verify the predictions of the models.

To find out more email Council's Coastal Scientist