Free-flowing estuary vital to healthy river

I am a Murray-Darling Basin food and fibre producer, and I'm very aware of how much water our operations use. My company, Twynam Agricultural Group, also invests in research and development constantly to improve water-use efficiency so we can produce more food and fibre with less water.

But the bottom line is that food and fibre production requires water, so on average there is less water flowing to the Murray Mouth, Coorong and Lower Lakes. Food and fibre producers don't take all the water. In fact because of upstream storages there is more water on average in the Murray River during drought, including the recent drought, than there was historically.

This last summer the Murray Mouth, Lower Lakes and Coorong have flooded, not because of government water reform or because rice and cotton were not planted, but because the drought broke with good flooding rains.

A few South Australians who farm near the Lower Lakes are still complaining they are not getting enough fresh water from upstream, even after the flooding rains. But should they be farming at all around Lake Albert if they can't make a go of it in such a good season?

In a story in The Australian "Efficiency gains 'just don't hold water' " (The Australian, June 3), Mark Schliebs quotes irrigator Sam Dodd, whose family began farming at Meningie in 1940 with water pumped from Lake Albert.

Dodd says that when the lake dried up in 2007 he was forced to use mains water on the farm and sold half his herd of dairy cows.

What readers weren't told, however, is that 1940 is the same year that 7.6km of barrage were finished and sealed, preventing saltwater inflows from the Southern Ocean, in effect destroying the Murray River estuary. Before the completion of the barrages the waters in the lake were often too salty for farming.

Upstream irrigators did not significantly affect downstream flows before 1925. During the drought of 1915 the Southern Ocean penetrated beyond the Lower Lakes for about 250km up the Murray River.

Consistently low salt levels have been a feature of the lower reaches of the Murray only since 1940, after the construction of the barrages.

During the recent drought the barrages could have been opened, allowing sea water to fill the area, as once happened naturally. But instead the South Australian government chose to keep the barrages closed, so they acted as dykes and the Lower Lakes started to dry up.

Either way, there would not have been enough fresh water for Dodd. The reality is that the upstream storages are just not large enough to supply the Lower Lakes reliably with fresh water during prolonged drought. The federal government has allocated billions of dollars to fix the Murray-Darling. But so far there has been no consideration of the needs of the Murray River estuary.

The estuary was crippled with the completion of the barrages in 1940; reduced in size by 90 per cent according to the 2000 report by the South Australian Department of Environment, Heritage and Aboriginal Affairs titled River Murray Barrages Environmental Flows: An Evaluation of Environmental Flow Needs in the Lower Lakes and Coorong.

This and many other studies explain that the Murray River estuary was destroyed by the barrages and as a consequence the Lower Lakes region continues to decline in health.

Just as wetlands need fresh water, rivers need estuaries. The problems of the Murray are exacerbated by the five barrages that separate salt water close to the river mouth from fresh water in Lake Alexandrina and Lake Albert.

Fresh water needs to come down the river to trigger spawning of fish and flow out the Murray Mouth to take nutrients to creatures such as the Goolwa cockle but salt water is also required for the estuarine ecology. In summary, the health of the Murray River and its estuary is dependent on more than the amount of water coming downstream.

Restoring the Murray River estuary would affect Dodd and a few other farmers who started farming at the Lower Lakes after the barrages were put in place.

These issues need to be discussed; yet in all the arguing about the new plan for the Murray-Darling Basin there is no discussion about the Murray River estuary or the barrages.

Estuaries are healthiest when fresh water from rivers flows into and mixes with salt water from the ocean, creating a transition zone rich in ecology with nutrients from the land and also from the ocean.