GOOD rainfall across eastern Australia over the past week has had little effect on dam levels in capital cities.
Melbourne"s dams rose from 39.8per cent full last week to 40.4 per cent yesterday, but the shortage of water is still worse than at any time since the beginning of 1997.
Sydney"s water storages rose 0.4percentage points to 57.4 per cent, while southeast Queensland"s water storages are still very low, on 20.4percent.
National Climate Centre senior climatologist Neil Plummer said: "What we are seeing is what looks like a trend towards a weakish La Nina event, and we would expect to see more rainfall in the areas that it has fallen."
Much of eastern and central northern Australia has been doused with 50mm of rain over the past week.
"There have been some reasonable falls in the Murray-Darling Basin, but as we saw in winter, most of the falls are coming either south or east of the Murray-Darling Basin," Mr Plummer said.
Murray-Darling Basin Commission chief executive Wendy Craik said the outlook for the Murray River was worse than it was at this time last year. She said rainfall over what are traditionally the wettest months - July to October - was very low, and storage levels were at record lows.
Dr Craik said there was a greater than 75 per cent chance that the amount of water available in July at the beginning of the next water season would be less than it was this year.
"It is frightening," she said, describing inflows this year as "incredibly low". "We haven"t broken out of very low inflows, and that is compounded now by our record low storage - it is about 21 per cent of capacity."
This time last year, MBDC storages were at 30 per cent, holding 2820GL (gigalitres or billion litres). Last week they held 2055GL.
Water hydrology professor at Charles Sturt University Shahbaz Khan said the soil through the Murray-Darling Basin was "phenomenally dry". He estimated that it would take about 1000mm of rain to replenish the soil moisture deficit, before there was runoff. In the Murrumbidgee, Professor Khan estimated, the deficit was almost 1400mm. "We need a lot more, and more persistent, rainfall before we will see a real change in inflows to dams," he said.
Dr Craik said the prognosis for the Murray-Darling Basin was for higher-than-average temperatures, which would result in higher evaporation and less inflow.
Wenju Cai from the CSIRO has estimated that every rise in temperature of 1C results in 3400GL being evaporated from the basin.
According to the Bureau of Meteorology, temperatures in the basin since November 2001 have surpassed previous records by considerable margins.
Dr Craik said contingency planning was under way for next season, to ensure Adelaide and river towns had water.
