Putting Murray River where its Mouth Is

As a cause, Environmentalism has a lot going for it.  Promise to "save" something and you may not only feel righteous superiority but, if you are the leader of the Federal Opposition, it may help you stem the flow of votes from your party to the Greens.  Hence Mark Latham's recent promise to "save the whole Murray River" starting with an allocation of, "450 gigalitres (of water) needed to keep the mouth of the Murray open" (Murray plan a priority, The Land, January 22, pg. 17).

The Australian Conservation Foundation has made the River's mouth a symbol of River health and impressed upon the Australian public the belief that the mouth runs dry because irrigators take too much water from the river.

The reality is much more complex.

Before irrigation, the famed explorer, Charles Sturt, writing in the early 1800s, commented on the nature of Australian rivers, "Falling rapidly from the mountains in which they originate into a level and extremely depressed country;  having weak and inconsiderable sources, and being almost wholly unaided by tributaries of any kind;  they naturally fail before they reach the coast, and exhaust themselves in marshes or lakes;  or reach it so weakened as to be unable to preserve clear or navigable mouths, or to remove the sand banks that the tides throw up before them".

Under natural conditions during drought, the Murray River's main channel would run dry or reduce to a series of saline and stagnant pools.  As a consequence of the dams built over the last 100 years, however, even during the severe drought of the past few years there has been water in the River.

At Wellington the Murray runs into a large lake system.  A series of barrages constructed in the early 1900s at the bottom of Lake Alexandrina stops freshwater flowing out to sea and stops tidal flow into Lake Alexandrina, and the adjoining Lake Albert.

The barrages help maintain this now artificial freshwater system at a more constant water level.  This is considered important for boating and tourism in South Australia.  Evaporation from the lakes is estimated to be in the order of 600 to 1,000 gigalitres per year.

The Murray's mouth could reasonably be considered to be where the River enters the Lakes at Wellington.  However, the official "Murray Mouth" is the narrow, often blocked passage through the coastal sand barrier downstream of the barrages.  Any extra water for "the mouth" must thus pass through the Lakes.

Last year, as a consequence of the "Save the Murray Campaign" the concept of water flowing out the narrow passage downstream of the barrages became a national preoccupation.  Yet all the while water was flowing at Wellington and evaporating from the Lakes.  When it did rain in September, the barrage at Goolwa was lifted and water flowed from Lake Alexandrina out to sea.

In reality, more water for the "Murray Mouth" is likely to be a case of providing more water for evaporation from an artificial lake system at the expense of River Red Gums and Irrigators upstream.  The nonsense is illustrative of how both sides of politics have become too eager to sign up for environmental causes that may deliver no environmental benefit.

ADVERTISEMENT