Australia: The Land Where Time Began

A biography of the Australian continent 

Murray-Darling Basin

This basin includes 26 major catchments covering a total area of more than 1/7 of the Australian continent. It is Australia's biggest river system, but even in good times, and including all the water taken by farming along its routs, its annual flow is less than 1 day's flow of the Amazon. This situation is not unexpected, considering the fact that it is on the world's driest inhabited continent. It continues to flow throughout the year, but only because some of its flow is from relatively well watered regions, most of its drainage being from arid areas with erratic, occasional rain. It is essentially inward-flowing. Some of the tributaries that combine to form the Darling River arise in the Great Divide, but they cross some very arid country before reaching the Murray River, so they lose a lot of their water to evaporation in the hot dry areas they pass through. They contribute 12 % to the Murray flow.

Tributaries of the Murray in New South Wales flow westward from the Great Divide, those in Victoria drain a part of the Great Divide where it curves westwards, so they flow northwards. 13 % of the Murray flow is contributed by the Murrumbidgee system. 75 % is contributed by tributaries of the Murray River upstream of the point where it is joined by the Murrumbidgee.

The Darling system receives most runoff from summer rain, while the Murray system depends more on winter rainfall. The extremes of the climate means that the flow of the Murray-Darling System is also very variable, depending on the highs and lows of the ENSO weather system.

Because the Murray-Darling system passes though Australia's major food bowl, most of the water coming down the Murray is diverted for irrigation long before it reaches the sea. The amount reaching the sea before the present extremely dry time was only about 20 % of its full potential. Now it is danger of stopping flowing completely, as the farmers along various sections of its flow are reluctant to give up their irrigation water to keep the river flowing. The result is that the system is dying. It can no longer supply sufficient water to irrigate crops and still continue to flow to its mouth.

One of the biggest problems for the continued flow of the Murray River in dry times is the growing of cotton at several places along its tributaries. Cubbie Station, the largest irrigated property in the Southern Hemisphere, is one of the biggest users of water from the system, with its water storage the size of Sydney harbour, using between 200,000 and 500,000 megalitres of water to irrigate its crops with a total area of 130 km², of which cotton has a large water requirement, made even more environmentally unfriendly by the necessity to apply large amounts of pesticides and herbicides. Some say crops such as cotton and rice should not be grown in Australia because of the large water requirements.

In New South Wales, other cotton producers withdraw large amounts of water from the Lachlan River, though on a smaller scale than Cubbie Station, but enough for the pumps to have caused the river to flow 'backwards' towards the pumps in dry times. 

There are 26 sub-catchments in the Murray-Darling Basin - Avoca, Benanee, Border, Broken, Campaspe, Castlereagh, Condamine-Culgoa, Darling, Goulburn, Gwydir, Kiewa, Lachlan, Lake George, Loddon, Lower Murray, Macquarie-Bogan, Mallee, Moonie, Murray Riverina, Murrumbidgee, Namoi, Ovens, Paroo, Upper Murray, Warrego and Wimera-Avon.

Trees of the Murray-Darling Basin

Lachlan Fold Belt

Sources & Further reading

1. Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003
2. Mary E White, Running Down, Water in a Changing Land, Kangaroo Press, 2000
3. Geology of the Murray-Darling Basin - Simplified Lithostratigraphic Groupings

Hydrology

Bass Basin

Bremer Basin

Canning Basin

Carnarvon Basin

Carpentaria Basin

Duntroon Basin

Drainage Patterns

Eromanga Basin

Eromanga Sea

Eucla Basin

Great Artesian Basin-GAB

Murray Basin

Murray-Darling Basin

Officer Basin

Otway Basin

Perth Basin

Torquay Basin