A few wet years can cleanse the memories of last decade, when Canberra was struggling through its worst drought on record. Today, the city's dam levels are up to almost 95 per cent of their capacity and most of our parks, gardens and sportsgrounds are a fertile green. Yet this is the result of a very rare event: two consecutive La Nina cycles over 2010-11 and 2011-12, which dumped a generous volume of rain on the region. Climate scientists say these cycles will occur less often, and tend to be weaker, in the years and decades ahead.
The Bureau of Meteorology's Annual Australian Climate Statement, released last week, jolts us back to the realities of living on a warming planet. The extreme heatwave now affecting most of eastern Australia is not a one-off; forecasters worldwide already fear that 2013 will be the globe's hottest year on record. This not only means more of the intense heat, bushfires and severe storms from which Australians are now sheltering, but a return to the critical question of how we manage our water reserves.
Five-a-half-years ago, Canberra faced a crisis. Water utility Actew reported grimly: ''By June 2007, water levels in our dams had dropped from 50 per cent a year earlier to 30.8 per cent, an all-time low.'' Plans were under way to enlarge Cotter Dam twentyfold and to build a high-tech purification plant that would add treated wastewater (including sewage) to the city's drinking water supplies.
Canberrans' reaction to this latter proposal was surprisingly supportive given the anger with which Toowoomba residents had greeted a similar proposal. Nonetheless, some high-profile opponents emerged, not least Canberra Hospital's head of microbiology and infectious diseases, Professor Peter Collignon. The ACT's then chief minister, Jon Stanhope, eventually dropped the proposal to recycle wastewater, and instead proceeded solely with the Cotter enlargement, which increased our dams' total capacity by 35 per cent.
Today, a near-overflowing Cotter Dam may appear to vindicate Mr Stanhope's decision. The ACT government also has the benefits of the newly built pipeline from the Murrumbidgee River to the Googong Dam and a deal to use it, if needed, to take water from Tantangera Dam in NSW.
Yet the ever-worsening prognoses for our climate suggest we should drink in the sight of a full Cotter now; it may be a very rare luxury. Nor should we assume that, when we need water from Tantangera, other communities in NSW won't make equally strong cases to use it. On top of that, the ACT's population is expected to soar from 370,000 now to about 500,000 in just 30 years. Unless we learn to use much less potable water per household, our demand will soon exceed even the newly expanded supplies of Actew.
It's likely that, sometime in the not-too-distant future, Canberra will again debate whether we should add purified wastewater to our drinking supplies. Perhaps we'll then reflect back on Mr Stanhope's cautious decision, and ask whether it was as wise as La Nina, and her fleeting charity, led us to believe.