The recovery in the health of major river systems such as the Barwon-Darling is likely to be delayed well after the return of good rainfall because of policy changes under which irrigators will get the first right to any flows, a new paper says.

The Australia Institute report found that cotton growers in the northern Murray-Darling Basin used about 2000 billion litres last year, or almost 200 times the flow that reached Wilcannia on the Darling River in far-west NSW.

Dry times on a cotton farm near Bourke near the Barwon-Darling in north-west NSW. Credit:Kate Geraghty

However, because of changes to the catchment's water-sharing plans in 2011 - when irrigators were previously deemed to have over-extracted from the river - the farmers were then "owed" 635 billion litres. That total is "almost enough for this year's cotton crop", it said.

"Alas, the Barwon-Darling or Barka [as the river is known to the Indigenous population] does not have the water to pay back these 'debts'," the report said, noting that in years where this water cannot be delivered, the debt is simply ‘carried over’ to the next year.

