Murray Mouth

Murray Mouth (35°33′S 138°53′E / 35.550°S 138.883°E / -35.550; 138.883) is the point at which the River Murray meets the Southern Ocean.

When early European explorers looked for the Murray Mouth they had high hopes of finding a natural harbour suitable for shipping. Had they found such a harbour, the Murray would have been used far more as a means of connecting many parts of inland Australia with the coast and beyond. Instead, what Captain Charles Sturt found was a treacherous river mouth that punched a channel through sand dunes into the sea.

At the time we had arrived at the end of the channel the tide had turned and was again setting in. The entrance appeared to me to be somewhat less than a quarter mile in breadth. Under the sandhill on the off side the water is deep and the current strong... The mouth of the channel is defended by a double line of breakers admidst which it would be dangerous to venture except in calm and summer weather... Thus our fears of the impracticability and inutility of the channel of communication between the lake and ocean confirmed.

— Charles Sturt, 12 Feb 1830, quoted in South Coast Story, J.C. Tolley 1968

The Murray Mouth's location is changeable. Historical records show that the channel out to sea moves along the sand dunes over time. At times of greater river flow and rough seas, the two bodies of water would erode the sand dunes to create a new channel leaving the old one to silt and disappear. The mouth is between two sandhill peninsulas. Sir Richard Peninsula on the northwest separates the Goolwa channel (the main river channel) from the ocean. The much longer Younghusband Peninsula separates the Coorong from the ocean on the southeast of the mouth. The Murray Mouth is separated from Lake Alexandrina by a row of low islands. The largest one, directly facing the mouth, is Hindmarsh Island. A series of barrages join the islands, separating the salt water from the fresh water of the lakes and river. The barrages can be opened during high river flow.

What made the Murray Mouth so dangerous to shipping in the past was the unpredictability of the currents and the depth of the channel. At high tides, seawater flows in through the channel and into the Coorong National Park's lagoon system. At the Mouth, the Murray flows eastward until it turns south for the last few hundred metres. To the east of the mouth river water and high tide seawater can continue eastward for over a 100km into magnificent saltwater lagoons protected from the fierce ocean by tall sand dunes.

River Murray water is used by farmers for irrigation in four of Australia's states, as well as supplying water to most towns along the river, and many further away through various pipelines. It has been widely accepted that too much water is being extracted, however business and political concerns make it difficult to remedy the problem. A visible symptom of the over extraction of river water is the closing of the Murray Mouth. Since October 2002, two dredging machines have operated at the Murray Mouth, moving sand from the channel to maintain a minimal flow from the sea and into the Coorong's lagoon system. Without the 24-hour dredging, the Mouth would silt up and close, cutting the supply of fresh seawater into the Coorong, which would then warm up, stagnate and die. In mid-2006 the dredging was scaled back as a result of the improved conditions at the mouth. Now only one dredging machine operates, and permission was granted to one commercial operator to navigate the channel between Goolwa and the Coorong, passing the mouth.

• South Coast Story, John C Tolley, Rowett Print, Mt Compass SA, 1968 ISBN 0-9587964-3-2