"The little water-saving gestures, like putting a bucket in the shower or turning the tap off while you brush your teeth — while they are good measures, and I do them myself — are exactly that, gestures. "They are going to contribute almost nothing to solving Australia's water crisis and we are deluding ourselves if we think it's going to be enough," Dr Byron said.

He said two or three large irrigators, such as dairy or cotton farms, would use "in a couple of days" the water the entire city of Melbourne could save in a year. Earlier this month, Victorian Water Minister John Thwaites praised Melburnians for their water-saving efforts over summer. The city of Melbourne had saved, on average, 209 megalitres (million litres) of water every day. "This is a great savings effort equivalent to a saving of around 19 billion litres of water over summer," Mr Thwaites said.

But by comparison Australia's largest irrigator, Queensland cotton farm Cubbie Station, has a water allocation in excess of 400,000 megalitres a year. It has on-farm water storages bigger than Sydney Harbour.

When water is available, it uses an average of 1095 megalitres every day, more than five times the amount saved by the 3.7 million people of Melbourne. The 19,000 megalitres of water saved by Melburnians over the three months of summer would be used by Cubbie Station alone in about 2½ weeks. Australia uses about 24 million megalitres of water a year. About 75 per cent is used in irrigation, 20 per cent goes to urban and industrial uses and 5 per cent to other rural uses including for stock and domestic needs.

Dr Byron said household water-saving gestures should still be encouraged. "One of the good things about these small gestures is they indicate public interest and buy-in, that is the public care about this issue, they're concerned about it, and they want to help.

"That's terrific for when it gets to the really serious stage, and we really need to do something that involves a little bit of pain, the public is already onside," he said. "But these little gestures will not even get us close to where we want go. If every man, woman and child in Australia was to do it, the difference in water use would be negligible. "The problem is the big actions carry with them a pretty big tag, but rather than bite the bullet and adopt some of the big changes needed, we're told to be satisfied with making these symbolic gestures."

Unless large-scale water-saving methods were adopted by governments, state and federal, Australia's water crisis would only worsen, Dr Byron said.