New South Wales is currently weathering its driest year on record since 1965 and Australia’s new drought envoy Barnaby Joyce has joined the ranks of politicians calling for environmental water to be diverted to farmers. In this climate, it seems pertinent to investigate how to save water by irrigating more efficiently.
However, a team of researchers, led by Professor Quentin Grafton of the Australian National University (ANU) Crawford School of Public Policy, has found attempts to make irrigation systems more efficient can actually lead to more water use.
In a paper published in the journal Science, Grafton and his co-authors outline what they call the ‘paradox of irrigation efficiency’.
They write that governments spend billions of dollars annually to subsidise irrigation technologies such as sprinklers or drip systems with the aim of increasing irrigation efficiency. This is often done on the premise that more efficient irrigation will save water, which can then be reallocated to cities, industry or the environment while maintaining or even increasing agricultural production.
However, the researchers found increases in irrigation efficiency can result in greater on-farm water consumption, groundwater extractions and water consumption per hectare. This is due to increased water use by existing crops, a switch to more water-intensive crops or an expansion of irrigated areas.
“This paradox, that an increase in irrigation efficiency at a farm scale fails to increase the water availability at a watershed and basin scale, is [also] explained by the fact that previously non-consumed water ‘losses’ at a farm scale (for example runoff) are frequently recovered and reused at a basin scale,” the paper states.
As irrigation accounts for 70% of global water extractions and provides about 40% of the world’s calories, Grafton said understanding how increases in irrigation efficiency affect water availability is critical to solving the world’s water problems.
He said governments need to take decisive action in order to tackle “one of the greatest policy dilemmas of the world – how to reconcile increasing freshwater demands with finite freshwater resources”.
The researchers suggest this action should include: robust water accounting and measurements; a cap on extractions; an assessment of risks and uncertainties; the valuation of trade-offs; and a better understanding of the incentives and behaviour of irrigators.
“This research shows current irrigation efficiency policies must change to include farm and basin-scale water accounting and limits on irrigation water diversions,” Grafton said.
“Unless current irrigation policies are reformed, the world will not achieve the Sustainable Development Goals. We know what to do. We must act now to avoid a global water tragedy.”