The Rudd government has defended its water buyback scheme following reports $50 million spent this year will return just 10 mega litres to the Murray River.
The opposition says the government bought the cheapest allocations possible which were never going to deliver water to the system.
But Environment Minister Peter Garrett says the buybacks are well-chosen and will deliver environmental relief down the track.
"In the medium and the longer term they are well-chosen, deliberate buybacks which will provide, once we get some water into the system, the type of relief the river does need," Mr Garrett told Sky News.
Australia was in the grip of a "really significant and serious drought" which meant water wasn't available to be returned to the Murray-Darling Basin this year, he said.
The government has estimated its $3 billion buyback scheme will enable nearly 24,000 megalitres to be returned to the environment each year for the next decade.
But it now admits that won't be happening this year.
"There's no water there for farmers, there's no water there for irrigators, there's very little water there for the buybacks," Mr Garrett said.
"We're committed to making sure that we do start to get some water into the river system to help the environment ... but the fact is that, particularly with some of these licences at this point in time, there's a shortage of water."
The opposition says the government bought water it knew couldn't be delivered.
"All they did was buy the cheapest water they could to make it look like they've got the 35 gigalitres they're aiming for which can't be delivered," water security spokesman John Cobb told AAP.
"Over 40 per cent of what they bought (this year) was in the Lachlan River or north and it never flows into the Murray River system except once every 50 years.
"Down the bottom in the Murrumbidgee and the Murray, the water they bought was general security and there is no general security for irrigators at the moment."
Nevertheless, Mr Garrett insisted this year's buybacks had been "cost-effective".
