How do the lakes work?

The Tuggerah Lakes estuary features three inter-connected coastal lagoons which are separated from the ocean by a sand barrier. Tuggerah Lake has a narrow connection to the ocean at The Entrance channel. Tidal currents are strong at The Entrance but only cause micro-tides within the lagoon.

Coastal lagoons are the most common type of estuary in New South Wales. In their natural state, coastal lagoons are only intermittently or weakly connected to the ocean. Lagoons are a brackish water environment at times with high rainfall but can become more salty than the ocean during droughts. The brown colour of the water is caused by the sediment and tannins that are washed into the lagoons from the catchment.

Fresh water flows into the lagoons from catchment tributaries (Wyong River, Ourimbah Creek, Wallarah/Spring Creeks, Tumbi Creek and Saltwater Creek). Tuggerah Lakes are shallow, so winds mix this fresh water with the more salty lagoon water. Salty ocean water spills into Tuggerah Lake when the ocean level rises. Lagoon water discharges to the ocean when the lagoon is higher than the ocean.

Because of its large surface area, large amounts of water evaporate from the lagoons.

map of Tuggerah Lakes indicating water movement and influences

Diagram showing how the water moves around the lakes.

Wind and water

Wind-driven currents in the lakes are so powerful they can mix the estuary vertically in about three hours and the whole lake system within about 12 days.  This is due to the unique characteristics of the lake which include its large expanse of open water, shallow water depth, small tidal range and freshwater inflows.

Find out what happens when the water circulates in the lakes.