Tides and circulation

More information about circulation and watermixing is available in section 2.1 - Stratification of water and section 2.1 - Circulation and tidal flows

The waters of Princess Royal Harbour have good circulation and are generally well-mixed.

Water circulation in Oyster Harbour varies according to the season. In winter, brackish, nutrient-laden water from the King and Kalgan rivers and other creeks and drains, crosses the surface of the harbour into King George Sound. It doesn't mix much with the water of the harbour. This surface water flow is important because it carries nutrients out of the harbour and into the open sea, preventing them entering the harbour's ecosystems. In summer, less fresh water flows into the harbour. The sun heats the water so that there is warmer and less dense water on the surface and colder, denser water below.

Princess Royal Harbour and Oyster Harbour are open to King George Sound. Flushing rates in Oyster Harbour are higher than Princess Royal Harbour. It is estimated that under average conditions surface waters remain in Oyster Harbour for two days or less, and bottom waters stay in the harbour for 10-20 days. A typical 90% flushing time for Princess Royal Harbour is about 20 days. Other estuaries on the southern coast of Western Australia have flushing times of months or years.

The mean tidal range in the sound and the harbours of Albany is 0.4 metres. Semi-diurnal tides are common, although diurnal tides do happen. For periods of time, tidal levels can remain static. Tides in the harbours are also affected by changes in atmospheric pressure.