The Pacific has now moved out of its La Nina weather pattern, which is associated with wetter conditions over Eastern Australia. Although rain has been falling recently, Melbourne's water supply conditions have worsened after a dry Autumn. The catchments have been so dry that the winter rains are not running down into the reservoirs in anything like their usual fashion: the thirsty ground is just soaking up the water.
The climate gurus say that we are now in a ‘neutral’ weather pattern, and another La Niña could develop in 2009, which would bring back the drought.
Over the past twelve years, Melbourne’s water supply has been dropping by about 5% a year. There have been two years when our water supply dropped 20% in a single year (1997, 2006). For this year our water inflows seem to be a pattern similar to 1999 and 2002, the years when the water supplies dropped by 10%. On the other hand, there has only been one year in the past twelve with an increase of more than 5%.
If we don't get above average falls in the next three months, and are unfortunate enough to have another year in 2009 like 1997 0r 2006, Melbourne’s water supplies could drop down to 10% by Christmas 2009. I suppose that at that point, the water in our reservoirs will just be mud.
I am no expert on long-term weather trends, but just based on recent years, there would seem to be at least a one-in-five chance that Melbourne will have no water at all in two years’ time. On the other hand an increase in reservoir supplies of even 10% seems a very remote possibility indeed.
In any case, within five or so years we will have run out of water, based on recent patterns. BUT the good news is, Victoria is planning a water desalination plant, which will produce 150 billion litres a year. This is due to start construction in 2009, with water on tap by January 2012. Still, questions abound. Will it be finished on time? Will there be any water left in our dams when it starts up? Will 150 billion litres be enough? This water is supposed to supply parts of Gippsland, Philip Island and Geelong, as well as Melbourne If, say, 100 billion litres comes to Melbourne, that is only 6% of total reservoir capacity, which is about what we have been short each year on average. So even with this extra water, it might take us a hundred years to fill up the reservoirs again! We would also still be highly vulnerable to a sequence of dry years. We can look forward to decades of water shortages.
Then there is the cost factor. Once the desalination plant is built, the main running cost is electricity. The price of power will definitely go up, as oil prices spiral upwards and the government implements a carbon tax. Although the Victorian Government has promised that the cost of water will no more than double after the desalination plant comes on stream, it seems more likely that cost increases will be much greater than this.
There are some ‘known unknowns’ here. Perhaps our decade of drought will be broken, and we will have a decade of rain, and all will be fine for a few more decades. On the other hand, perhaps power costs will shoot up, water consumption will rise, the drought will worsen, and we’ll be trucking in water from the Northern Territory or dragging in icebergs from the Atlantic! No doubt our planners are hoping for wet years ahead.
Prayer seems a very wise policy. And a water tank.