The Rudd Government will learn from earlier purchases when it opens its next tender process to buy water in Queensland, Climate Change Minister Penny Wong says.
It was revealed yesterday that $50million spent earlier this year to secure 35billion litres of water entitlements would return just 10megalitres the equivalent of 10 swimming pools to the Murray-Darling River system this year.
Greens leader Bob Brown said the result would be laughable if it were not such a serious issue.
Environment Minister Peter Garrett said the buybacks would deliver environmental relief eventually.
He said, ''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.''
Opposition water security spokesman John Cobb said more than 40per cent of the Government's purchases this year were in the Lachlan River or to the north of it ''and it never flows into the Murray River system except once every 50 years''.
Senator Wong said the Government had bought water ''across the basin'' and rejected Opposition accusations that it had bought the cheapest entitlements which were never going to deliver water to the system.
''Unfortunately, there is currently just not enough water in the system to do everything we want to do,'' she said.
''We actually purchased high-security water as well as general-security and low-security water ... We assessed the offers put to us by sellers on the basis of value for money, which included an assessment of how environmentally valuable they would be, so we'll approach this new purchase in the same way.''
Meanwhile, conservationists and the forestry industry are arguing over how Australia's forests can be best used to fight global warming.
The National Association of Forest Industries, in a new report, says carbon stored in timber plantations could meet 20per cent of Australia's emissions reduction target by 2020 depending on its treatment under the proposed carbon reduction scheme and the continuation of existing tax breaks.
Chief executive Allan Hansard said the annual cut of 81million tonnes was a conservative estimate.
But Senator Brown labelled the report ''snide and deceptive'' and instead pointed to a new Australian National University study that found Australia's native forests stored the equivalent of 25.5billion tonnes of greenhouse gases.
It found Australia's old-growth forests could store up to five times more carbon than previously thought, and that natural forests had a higher value than plantations.
Senator Brown wants logging which he says made up 24per cent of Australia's net greenhouse gas emissions in 2005, or more than the transport sector accounted for to be included in any emissions trading scheme.
''The destruction of these carbon banks and the wildlife, the rare flora and water catchments has got to stop,'' he said.
''It is three times worse for climate change than previous assessments estimated, and in tall eucalypt forests like those of Victoria's central highlands or Tasmania's Styx, Weld and Florentine valleys: it is 10 times worse.''