The fires are not yet out… the death toll not finalised… and Melbourne suffers another blow as projections of some of the long term issues become clearer.
This time the problem is water supply. Rainfall in the catchment area for Melbourne is already at its lowest on record, and the dams are currently only at 30% capacity. Now, with much of the catchment burned and blanketed in ash, when the rains come it’s likely that the water collected will be far too dirty for use. Eventually it will clear of course as sediment settles, but it might take years in order for that to happen because each time it rains… if it rains… the dams will be again polluted by turgid ash filled water.
Despite the problems this will cause, it is nonetheless a short term problem and can be fixed. The issue is far more serious than that and projections have been mooted that suggest the *minimum* period affected will be fifty years, and the situation may not revert to ‘normal’ for up to 300 years!!
So what *is* this problem that is so serious? Basically it’s the possible, actually probable death of hundreds of thousands of Mountain Ash trees. The Mountain Ash is the dominant species throughout the affected catchment area and there are grave fears that the crowns of these trees have been destroyed by the intense heat of the fires.
Whilst it is a Eucalyptus, the evolution of the tree has produced one that *requires* fire in order for seeds to sprout. It is of course, no more fire resistant than others, and these fires were so severe they may not have survived over immense areas. What’s worse is that this variety they won’t shoot new growth from the sides, or the base of the tree. These trees regenerate from seed alone.
This may not sound that serious… until you learn that new growth can use up to 50% more water than a mature tree, and as the growth period of these trees is very extended, the total water supply from the catchment could drop by that amount for the foreseeable future.
What sort of effect this massively reduced water supply will have on Melbourne in the short and long terms is open to discussion, but serious questions are already being asked about the city’s ability to function with water supply so critically threatened. Something will obviously have to be done… the question is, just *what*.
One thing is certain however, the decision of ex-NSW Premier Morris Iemma to push through the building of our desalination plant may well turn out to be a life-saver for Sydney. If similar disastrous fires were to scour the Blue Mountains our water supply, already a bit shaky, would be stretched to the limits and beyond. If that happened, then the plant could be put quickly into full production.
The Eclectic Interweb 