Keeping the Murray Mouth open

The Murray Mouth, near Goolwa in South Australia, is part of a dynamic system influenced by the flow of River Murray water from Lake Alexandrina via barrage releases and tidal movement from the Southern Ocean.

When the flow to South Australia is low, barrage releases are low and sand deposits occur inside the mouth causing restrictions and increasing the risk of closure. Continuous barrage releases of about 2 GL (2 000 ML) per day are desired to assist in maintaining an open mouth. Much larger volumes are required to provide a scouring effect, removing sand from the mouth.

It is important that the Murray Mouth remains open to maintain connectivity between the river, the Coorong and the Southern Ocean, to discharge salt and other nutrients out to sea, and to maintain healthy ecosystems in the Coorong.

The best way to maintain an open Murray Mouth is through high flows and barrage releases. In the absence of high flows, dredging is considered the most effective method of keeping the mouth open in terms of cost and environmental outcomes, when compared with other intervention methods.

Periods of low flows have presented management challenges in the past. Due to low flows, in 2002 the Murray Mouth threatened to close, and dredging was required for eight years to keep it open. In 2010, the drought was broken with a high flow event and dredging ceased. With the return of low flows, in 2014 the condition and openness of the mouth deteriorated, with dredging recommencing in January 2015. Two dredges are currently operating in the Goolwa and Tauwitchere channels to maintain an open Murray Mouth.

Maintaining an open Murray Mouth is a key objective under the Murray-Daring Basin Plan, which was adopted in 2012. The Basin Plan seeks to ensure that the mouth remains open without the need for dredging 95% of the time under the 3 200 GL water recovery scenario.

For more information regarding activities being undertaken as part of Project Coorong click here.