Northern Australia faces water problems

Despite a popular perception northern Australia is water-rich, the region is
actually water-limited and faces serious storage problems, a study shows.
Researchers from the CSIRO have found that northern Australia has little or no rain
for three to six months of the year, while water loss via evaporation is very high.
More than 94 per cent of annual rainfall occurs between November and April, while
there is little or no rain at all during a three to six month period.
The research covered an area of 1.2 million square kilometres from Broome in Western
Australia to Cairns in Queensland.
During a few months in the wet season, daily rainfall can exceed potential
evaporation, and this drives the seasonal streamflow, the study showed.
But it says that on an annual basis, rainfall is insufficient to meet evaporative
demand and the landscape may be described as water-limited.
The CSIRO's Tom Hatton said while it would get worse, the problem of water
availability in the northern part of Australia won't be as bad as the Murray-Darling
Basin.
"We're going to have less rain than we've had in the last 10 years but it's not
going to be the dire situation that's predicted for the Murray-Darling Basin," he
said.
But Dr Hatton says because of the high evaporation rates in the north, surface
storage is a major problem.
"The picture it paints is that if you want to do anything that requires water during
the dry season, you've got to have somewhere to store it."
He said Lake Argyle, Australia's largest inland lake, loses a quarter of its water
every year through evaporation.
"Critically, it means you have to look at alternative storages and the main one
people are turning to is groundwater.
"But groundwater, it turns out, is what keeps those rivers that are perennial going."
He said the problem is the few river reaches that flow year-round have high
cultural, social and ecological value and are generally sustained by localised
groundwater discharge.
"So averting, you mess around with the groundwater, you're potentially going to mess
around with the few reaches of river, and there are only a few, that maintain flows
during the dry season."
The study was undertaken after the Council of Australian Governments (COAG) agreed
to extend the CSIRO research into water availability in the Murray-Darling Basin to
catchments of northern Australia, south-west Western Australia and Tasmania.
It marks the first time a consistent, robust and transparent assessment has been
carried out across northern Australia.