How big are the tides in Auckland?

The tidal range in the Waitematā Harbour is about 1.7 metres at neaps and 2.8 metres at springs, with two high and two low waters a day. The tidal streams run strongly through the narrow part of the harbour.

Auckland has a semi-diurnal tide: two high waters and two low waters each day, about six and a quarter hours apart, so the times move later by roughly 50 minutes a day. The range is about 1.7 metres at neaps and 2.8 metres at springs, a little over 3 metres at the biggest tides of the year. Tide predictions for Auckland are published each year by Land Information New Zealand, and appear in tide tables and many apps.

Depths. A range like that makes a real difference. Large parts of the upper harbour, west of the Harbour Bridge, and many bays around the shore are shallow or dry at low tide, with wide mudflats. Some anchorages and the approaches to some marinas and boat ramps need enough tide to use safely. Check the chart, work out the height of tide, and allow a margin.

Tidal streams. All the water filling and emptying the harbour passes through the gap between the city and Devonport, so the stream is strongest there, around North Head and in the channels. The flood runs in, westwards up the harbour; the ebb runs out, eastwards towards the Gulf. At springs it can run at a couple of knots or more, enough to make a big difference to a sailing boat in light wind, and to set you sideways onto moored boats, wharves or marks.

Wind against tide. When the wind blows against the stream, for example a north-easterly sea breeze against the ebb in the harbour entrance, the waves become short and steep. In a small boat this can be uncomfortable or hazardous.

Practical points:

• plan to go out and come back with the stream where you can;
• when picking up a mooring or coming alongside, approach into the stream rather than the wind if the stream is stronger;
• remember that boats on moorings lie to the stream as well as the wind, so they may point in different directions.

More in the book: Chapter 14, Buoys, charts and tides