What would happen if a city of 4 million people ran out of water ?
My view of the situation is that this summer/autumn Melbourne faces the gravest peril any city could face – running out of water.
So why do I fear a “no water/dead city” scenario? As I see it the following factors would contribute to the situation.
1) Record low levels of water in the dams
2) Long term drought which has dried up river flows to again, record low levels
3) Similarly the catchments and countryside are at their driest.. Whatever rain does fall will not run off
4) Fires in the melbourne catchments last year will further reduce run off as new growth takes the little rain that is falling
5) The drought in melbourne will cause further pressure on water supplies as families and councils try to keep trees and gardens alive.
6) Predicted El Niño which will create further pressure as the hotter drier weather destroys our spring rains and creates even higher temperature patterns which reinforce factors 2-6 above.
7) Evaporation from dams increases with El Niño. How much are we losing already ? How much more will we lose?
8) Probability of bushfires creates extra demand for fire fighting water.
9) On going heat wave conditions create demand for extra electricity. As our generators require enormous amounts of fresh cooling water for their operation we see another pressure on the dams.
10) The current and predicted future drought is killing the Goulburn river systems. I believe that even if the North South pipeline is built there simply won’t be any available water to pump down.
Have I missed anything yet? On the supply side I have another grave fear.
A few years ago in the discussions about our water supplies it was made clear that the nominal dam reserves were way overstated. Put simply there is limit below which dams can’t be pumped. We just end up with mud.
I remember that the Thomson dam was supposed to have a bottom line figure of around 17%. Then “someone” found a way to get some super heavy duty pumps that that would take a bit more. But even allowing for that I wonder just how much of the 16.9% of the Thomson’s reserves are accessible? As I now understand it the bottom line is 11% full. D Given that this still represents the largest dam we have the implications of not being able to access three quarters of the remainder are bloody frightening.
And what is the situation with the other dams? When does their effective supply run out ?
According to all history after Sept-October, if we actually get any decent spring rains and run off, there will be no net gains to our dams before June 2010.
How legitimate are these fears ? Is anyone in charge fully aware of the situation and considering what risk management approaches do we take to avoid the situation of Melbourne actually running out of water? What do we need to do preserve our remaining supplies, find new water and somehow survive?
What do other Forum members think - particularly those of us who actually live here...