River Murray's mighty struggle ends in South Australia at Lake Alexandrina and ocean

The River Murray-Darling system is the catchment for one seventh of the Australian land mass.
Image courtesy National Parks South Australia

The River Murray, Australia’s longest at 2,508 kilometres rises in the Australian Alps and eventually as it flows to the northwest into South Australia where it turns south at Morgan for its final 315 kilometres, reaching the Southern Ocean at Lake Alexandrina and the Coorong.

The Murray River is part of the 3,750-km combined Murray-Darling system that’s a catchment for one seventh of Australia’s land mass. Between 2.5 and 0.5 million years ago, the Murray terminated in the vast freshwater Lake Bungunnia, formed by earth movements that blocked off the river near Swan Reach in South Australia. Deep clays from the lake are evident in cliffs around Chowilla. The lake drained away about 600,000 years ago, at the apparent end of the river basin’s wet phase.

In 2010, the Murray River system received only 58% of its natural flow due to irrigation takes for crops. The river’s health has declined greatly since being regulated by European settlement, threatening native fish such as the Murray cod, trout cod, golden/silver perch and eel-tailed catfish. Introduced fish species, especial carp that has taken over some segments of the river, have also taken a big toll on native species and water quality.

Other aquatic species like the Murray short-necked turtle, crayfish, broad-clawed yabbies, and the large-clawed Macrobrachium shrimp share the struggle with long-necked turtles, small clawless paratya shrimp, water rats and platypus. The Murray River also supports corridors and forests of the river red gums put under stress by extreme droughts on top of the Murray’s usual variable flow.

Since the 2000s, 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.

The Murray has significant cultural relevance to Aboriginal Australians. According to the peoples of Lake Alexandrina, the Murray was created by the tracks of the great ancestor Ngurunderi as he pursued Pondi, the Murray cod.

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