By Boyd Champness

MUCH of Australias breadbasket river system will be poisonous to humans and crops within 50 years – devastating agriculture, endangering country towns and creating massive regional unemployment across eastern Australia.

In what is shaping as the biggest man-made disaster in Australian history, the salinity overload of the Murray-Darling river system cannot be transformed without a revolution in agriculture, involving the conversion of dryland and irrigated farms to massive tree-planting.

The Murray-Darling Basin Ministerial Councils salinity audit, released last week and reported in the Sydney Morning Herald, predicted that water in New South Wales and Queensland tributary rivers that feed into the Darling River would be undrinkable by 2020.

The salinity problems of the Murray-Darling river system – one of the longest river systems in the world – have implications for all four of Australias eastern seaboard states.

The Darling River originates in southern Queensland before winding its way through NSW and linking with the Murray River on the NSW-Victorian border.

The Murray River then continues east through South Australia before eventually flowing into the ocean at Adelaide.

The Federal Environment Minister, Senator Hill, told the Morning Herald the audit was an “alarm bell” ringing after 100 years of agricultural practices, including land-clearing – which still occurs on a large scale in central north-west NSW and southern Queensland.

The Agriculture Minister and chairman of the Murray-Darling Basin Ministerial Council, Mr Warren Truss, told the newspaper that the audit revealed a “disaster area” and illustrated the need for Australia to become “the clever farming nation”.

Gross agricultural production in the Darling-Murray basin is worth A$20 million a year and provides 40% of the nations agricultural wealth.

“Its quite clear from the audit that there are many warning signals,” Mr Truss told the paper.

“If nothing is done, within a few decades large areas which are currently highly productive will cease to be able to contribute to the communities that are so dependent upon them.

“So business as usual is simply not a viable option. There will need to be changes in land use on a regional, catchment and farm scale.”

The key to ending dryland salinity problems is to reforest the catchment areas with deep-rooted trees.

According to scientists, some of these catchments will have to have 50% of their areas reforested.

In the past, irrigators have been routinely blamed for Australias salt problems. But this latest audit is the first to proportion blame on dryland farming to such a large extent.

Dryland salinity is caused where salt rises from deep beneath the surface, where it has been for millions of years.

Before vast areas of land were cleared, deep-rooted trees would soak up the majority of rainfall, with the rest running into river systems.

However, once the trees were felled, the water pumping process was removed, so the water table started rising, bringing salt towards the surface.

But its more than just an agricultural and environmental issue, with much of South Australia – and particularly Adelaide – relying on the Murray River for drinking water.

Since 1989 work on the Murray River has reduced salinity to below 800 EC (E coli), which is the World Health Organisation threshold for desirable drinking water.

But upstream poisoning of the river from irrigation, farming practices and catchments in NSW and Queensland is jeopardising Adelaides water supply.

The audit predicts lower Murray River salinity will rise from an average 570 EC currently to 790 EC in 50 years and 900 EC in 100 years.