Even before January's floods had receded, people with zero experience of water resource management, including me, were pontificating about how water should have been released from Wivenhoe Dam long before it coincided with abnormally heavy rainfall over an already saturated catchment area. It was obvious, wasn't it? And conspiracy theorists joined in, opining that it hadn't been released because Seqwater wanted to maximise their profits from selling their excess water to needy drier regions.
The Queensland Floods Commission of Inquiry's interim report* determined that there was room for improvement in all areas: dam management; disaster frameworks, preparation and planning; forecasting, warnings and the distribution of information; the co-ordination of local and state emergency responses; and the maintenance of essential services.
So far, this November has been without rain. People are already commenting on how dry everything is. I suppose it's a novelty: ever since we got here virtually, all they've been talking about is how wet it's been.
So, in line with flood mitigation measures and reservoir** capacity management, the Wivenhoe Dam today started to release 57,000 megalitres (8,000 megalitres a day for a week) – I have no idea how that relates to the volume of Sydney Harbour, before you ask. This will reduce the reservoir's capacity from 80 per cent to 75 per cent, the level recommended by the Flood Enquiry if a wet summer has been forecast. Which it has†.
But the people aren't happy. Fuelled by the Courier Mail's scaremongering this morning††, talk-back radio callers expressed their concern that security of water supplies was being compromised by flood mitigation.
Queensland's Natural Resources Minister, Rachel Nolan, is advised by the Bureau of Meteorology, the Water Commission, the Department of Environment and Resource Management and SEQ's Water Grid Manager. And I'm sure she's learned by heart the Flood Commission's recommendations.
Ms Nolan claims that the security of Brisbane's water supply is higher than would normally be in place for a city of its size, and that flood mitigation and capacity management are reasonably balanced in the decision to release water this week. She has been advised that there is a one in 25 chance that reservoir levels will fall to 60 per cent in the next five years. A DERM spokesperson adds that it would take until 2017 for levels to reach critical (40 per cent), necessitating water recycling and the activation of the Gold Coast Desalination Plant.
These figures are based on probability (which in turn is based on rainfall and water use records). Few people understand probability adequately: they think that if the probability of an exceptional flood is one in a hundred, then it will only happen once in a century. So if there's one now and another in 50 years, they tend to conclude that the figures were wrong.
Forecasters failed to predict the continuation of La Niña beyond last autumn; topsy-turvy drought-flood cycles are characteristic of Australia's climate; and climate change is making predictions far more difficult for statisticians.
The Intergovernmental Panel on Climate Change (IPCC), the group of the world's leading climate scientists convened by the UN, has just released a 'special report on extreme weather', compiled by more than 200 scientists over two years. The report's findings were summed up by the policy and communications director of The Grantham Research Institute on Climate Change and the Environment at the London School of Economics, Bob Ward:
'This expert review of the latest available scientific evidence clearly shows that climate change is already having an impact in many parts of the world on the frequency, severity and location of extreme weather events such as heatwaves, droughts and flash floods.This is remarkable because extreme events are rare and it is difficult to detect statistically significant trends in such small sets of data. What is more, these trends have been identified over the last few decades when the rise in global average temperature has been just a few tenths of a centigrade degree.'#
On the whole, I think we have to trust Ms Nolan's judgement. She must be a tad relieved, however, to see that heavy rain is forecast by next Wednesday.
** 'dam' if you're an Australian reading this
† Eastern Australia is still experiencing a La Niña event
# source: The Guardian online
This post was last updated on 20 November 2011