Great Sandy Strait

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Celebrating and Defending the Great Sandy Strait

Fraser Island Freshwater Flows

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Fraser Island’s Unique Marine Environment!

The hydrological and nutrient flows between fresh and marine

wetlands are highly significant to flora and fauna in the strait and

contribute to its numbers and diversity of species.

The Great Sandy is mostly a saline water system, but permanent or seasonal flows of fresh water enter most estuaries in the system. Water exchange rates with the open ocean are rapid, owing to the presence of a deep main channel and the absence of mobile, unstable sand bars. In the estuarine conditions of the strait the inflow of fresh water from adjacent catchments can create prolonged conditions of low salinity. The outflow from major streams in the area has a substantial influence on the water quality of the Great Sandy (See Environmental Flows).

Various forms of nutrients and detritus—leaf matter, seeds—are carried out to sea in creeks and streams. The nutrients nourish the seagrass beds. Water flowing from the sand masses contains significant levels of phosphate.

With many other sources of fresh water in the region having been

polluted and exploited over the years, the flows from Fraser Island are

more essential now for marine biodiversity than ever before.

In its educational supplement entitled ‘Maintaining Great Sandy Region’s Environmental Flow’ (click here), the Fraser Island Defender’s Organisation (FIDO) states:

‘It is widely recognized that fish are extremely sensitive to very subtle changes in water quality. Almost imperceptible changes in salinity, pH and turbidity can be significant. All are affected by changes in fresh water flow.

The main flow of fresh water into Hervey Bay in the past came from the Mary, Burrum and Burnett catchments. Diversion for irrigation and other uses has reduced this to a third of its natural flow. This makes maintaining 100% environmental flow from the small streams on Fraser Island critical to maintaining Hervey Bay’s marine vitality. Similarly Tin Can Bay and the Noosa River are such small estuaries that they have little tolerance to any further reduction of environmental flow by tapping of any more of Cooloola’s water.’

Changes to pH levels (the measure of acidity in water) are also detrimental to fish, according to the supplement:

‘… even minor changes can cause ulceration. Release of a small amount of acid resulting from disturbing acid sulphate soil affects not only fish, but even marine algae with deleterious consequences. Thus the natural flow from the myriads of small streams in the Great Sandy Region is critical in maintaining pH.’

¨ ‘Queensland Government Wild Rivers Legislation’ … click here

Go to Environmental Flows

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World Heritage Listed Fraser Island, the largest sand island in the world, forms the western fringe of the Great Sandy Strait and nurtures it in a number of crucial ways.

A permanent supply of freshwater flows into the sea from numerous creeks around the coast of Fraser Island, maintaining in the process a delicate balance in water quality. On its northern beaches the water runs into Hervey Bay, along the eastern surf beach it rushes into the open ocean, and in the Great Sandy Strait it filters through mangroves, creeks and estuaries. The marine ecosystems of the region, and the diversity of marine life they support, depend on healthy mangroves and estuaries for survival.

WILD RIVERS ACT ...

In July, 2006, the creeks and rivers of Fraser Island were declared protected under the Queensland Government’s Wild Rivers Act 2005. This act effectively ensures the island’s water sources cannot be exploited by communities on the mainland. Any development applications which may impact in any way upon a wild river will have to pass a rigorous assessment process.

Woralie Creek running to the sea, north of Moon Point.

Website created by Elisabeth Berry for 2Berries Communications.