It’s relatively easy to talk about keeping more environmental flows in the Murray River.
Stop extracting water for farming. Keep more for the environment.
That should provide more water for the wetlands along the Murray and its tributaries, and maintain the level of the huge Lower Lakes in South Australia. Not hard to visualise at all.
But there are some tougher and more complex issues to consider when you look at the Murray-Darling Basin, and there are just a few uncomfortable ones to address.
When you talk to South Australians about the Lower Lakes and the Coorong, at the mouth of the Murray River, very few volunteer to talk about how South Australia is contributing to the environmental problems.
South Australia occupies only about seven per cent of the Murray-Darling Basin and its biggest urban water consumer, Adelaide, is not even in the basin but draws on Murray River water.
While the state complains about being at the end of the river system and having to accept poor water quality, salinity statistics show that the Murray’s salt load considerably lifts when the river enters South Australia.
In the 1980s and 1990s, upstream states spent millions of dollars addressing salinity and — to the credit of northern Victorian farmers — the march of salt has been largely halted.
But one of the biggest issues that South Australia is only now beginning to address is a historic drainage scheme that has diverted overland freshwater flows away from the Coorong and into the sea.
South Australia is wanting more environmental water to maintain the level of the Lower Lakes, flush the Ramsar-listed wetlands in the Coorong and to keep the Murray Mouth open.
But a succession of South Australian state governments have presided over a system of drainage that has diverted water away from the southern Coorong.
The Murray-Darling Basin Authority acknowledges that the Upper South East region of South Australia is a biologically rich, yet highly modified landscape.
‘‘Broad scale land clearance and the construction of an extensive drainage network has altered the wetland-dominated landscape in favour of agricultural production,’’ one report remarks.
The South Australian Government notes: ‘‘Historically, quantities of freshwater flowed into the Coorong South Lagoon from the South East and this source of freshwater has been reduced by drainage works in the South East over the past 150 years.
‘‘Reduced inflows have raised salinity in the Coorong South Lagoon to a hyper-saline range, ie, a very high salt concentration, making it too salty to support important species.’’
The South Australian Government is introducing some modest drainage works to redirect the water back to the Coorong South lagoon, which could result in tipping an extra 26Gl into the lagoon.
Just one drain, Blackford Drain, has a combined annual discharge into the sea of about 136.4Gl, according to a Federal Government report.
In wetter years the potential is huge.
‘‘For example, in 2000 the combined total discharge was 449.9Gl,’’ the Federal Government report said.
‘‘Without the drainage network in place, a considerable proportion of this water would have flowed into the Coorong South Lagoon.’’
Victorian Shadow Water Minister Steph Ryan has called on governments to look at more engineering projects to improve the Coorong and Lower Lakes, without having to send large volumes of water down the Murray River, much of which is evaporated anyway.
She believes South Australia needs to concentrate on projects which allow the state to use water more efficiently, rather than simply insisting on volumes of flows.