Sea will save Murray River's mouth27, August 2011
Sign Up for free e-mail updates!
THE Murray-Darling Basin is the food bowl of Australia and for years has been considered an ecological disaster.
Later this year the government will release a plan that is supposed to place the Murray-Darling on a sustainable environmental footing, and already $10 billion has been set aside for the plan's implementation. But if the guide released last year gives any indication of what to expect, then it will do nothing to restore that part of the system most affected by agriculture and most in need of saving: the Lower Lakes and Murray mouth, once the Murray River's estuary.
The estuary was destroyed when 7.6km of concrete barrages were built across the bottom of the Murray in the 1930s. If nothing is done about this enormous structure there is no guarantee water will get to the Murray's mouth even if South Australia gets the 4000 gigalitres it is demanding as part of the water reform (4000GL has a market value of $3.2bn ato $8bn, depending on where in the Murray-Darling it is purchased).
Top 50 Media
The barrages have turned the coastal terminal lakes into a permanent and artificially freshwater system, to the detriment of the local environment and the river.
The problem is restoring the estuary to something like it was before the barrages would not only upset local dairy farmers but could also create a problem for Adelaide because the city's water supply is dependent on the Lower Lakes being entirely fresh water.
This situation needs to change. But instead of spending time and money finding solutions, politicians and environmentalists during the recent drought, for example, used the drying of the Lower Lakes to campaign against upstream rice and cotton farmers. Never mind that there was a natural and local solution: letting in the ocean by opening the barrages.
I've been in SA for the past two weeks meeting past and present water ministers, bureaucrats, scientists, activists and others. It strikes me from these discussions that many South Australians have a limited understanding of the natural history of the Lower Lakes and want to deny the effect the barrages and farming are having on the local environment.
The Lower Lakes were once the estuary for the Murray River. In summer and each autumn when the southwesterly winds picked up, the Southern Ocean would roll in, bringing the famous mulloway fish. This was an issue for the farmers who settled around the lake from the 1850s. They didn't want the salt water, instead wishing the lakes were always "sweet".
In 1902, during the height of the Federation drought, sea water took over the lakes and the local farming community was forced to sink more wells. This was the situation again in 1915 when the ocean not only flooded into the lakes but extended up the Murray River proper for about 80km. This was the natural state.
I live just north of the Fitzroy River in central Queensland and I know it is the sign of a perfectly natural and properly functioning estuary to taste the sea water tens of kilometres upstream, particularly in winter and during drought. But in SA, even in 1902 when there were no significant upstream diversions, the salt water was blamed on upstream irrigators.
A significant lobby, beginning in the late 1880s, claimed barrages were needed. The lobby was spearheaded by dairy farmers, who drained wetlands and swamps along the Lower Murray to provide pasture. They have changed the landscape and created the requirement for always fresh water, but this is not natural or healthy.
Newspaper articles from the 1850s show a battle between the farmer-settlers in SA and the fishermen, who lost out to the farmers.
The barrages were completed and sealed in February 1940, and that year the mulloway tried to come in but were defeated, thrashing against the Goolwa barrage on each tide.
In 1939, the annual mulloway catch by commercial fishermen was 595 tonnes.Last year it was 30 tonnes, all from the nearby Coorong. There are no longer any mulloway in the Lower Lakes.
The technical literature explains the barrages reduced the size of the estuary by 89 per cent and flows to the Murray mouth by 75 per cent. We are left with freshwater lakes full of carp instead of an estuary with mulloway, crabs, waders and the biodiversity that comes when there is natural mixing of fresh and salt waters.
Disappointingly, the Australian Conservation Foundation that is supposedly leading the campaign to restore the Murray appears reluctant even to talk about the barrages. They are arguably a bigger problem than upstream diversions because they not only reduce flow out but have destroyed the tidal prism that once, particularly in autumn, scoured the Murray's mouth.
There is no mention of the barrages in the guide, and discussion about their removal or modification is taboo in official discussions on saving the Murray.
Present planning revolves primarily around how to buy back water from irrigators and improve infrastructure to make more fresh water available for the Lower Lakes. Mike Young, from the Wentworth Group of Concerned Scientists, has calculated that the commonwealth is looking at spending $588,000 an irrigator towards this end.
But it is not more fresh water that the environment of the terminal coastal lakes needs, it is more salt water; and this should be allowed to roll in at no cost to the taxpayer each autumn and for longer periods during protracted drought.
Jennifer Marohasy is a biologist and adjunct research fellow at Central Queensland University.
Published in The Australian on August 27th 2011
Sign Up for free e-mail updates!