On Monday I posted a graph of rainfall history and suggested that it indicated south east Queensland was not experiencing the worst drought in 100 years - that the current dry spell is not unusual in the scheme of things.
I was surprised how many comments in the thread following the post, and also in the many emails I received, were supportive of the notion that this is a worst drought ever.
Some argued that I didn't understand definitions of drought and that a drought could simply be a result of too many people squashed into a region without the infrastructure to supply adequate water. Comment was also made that it would be interesting to see the rainfall history for the catchment averaged over 10 years.
Warwick Hughes has sent me the following graph, showing the rainfall history averaged over 10 years:
Mr Beattie has been reported in the Courier Mail stating that:
"Rainfall in the region has been well below average for the past six years and in fact it is the worst 10-year period in history," he said. "It has been dry after dry, year after year, which has led to major storage deficits in our dams."
Looking at the above graph Beattie may be technically correct, we may have had the worst 10-year period in recorded history, and those who want to define drought based on 'supply' rather than 'rainfall' may also be correct because we have never had so many people living in south east Queensland and probably never as many trees growing in the catchment.
But the above graph, and the graph posted on Monday, does indicate that south east Queensland has experienced comparative periods of low rainfall during the 1920s and 1940s. The current dry period is not unusual in the scheme of things.
My point is that: If we can not reconcile ourselves with our history, how can we hope to prepare for the future? It is important we understand what is special about this drought.
If we could perhaps start to acnowledge that rainfall has not been exceptionally low, we might, for example, be able to more clearly focus on other variables, including population.
There is also the issue of tree cover. A heavily timbered catchment generally produces less runoff. Page 7 of yesterday's The Land reports Malcolm Turnbull, federal parliamentary secretary for water, explaining that the West Australian Water Corporation is thinning catchment forestry to increase run off by 6,000 megalitres a year. Mr Turnbull said the method could deliver "new water" at about 20c/kilolitre - far cheaper than piping or desalination.
I am not necessarily advocating tree clearing in the Wivenhoe catchment, but rather my issue is that here in Queensland, we tend to invoke 'exceptional circumstances' whenever there is a flood or a drought rather than taking a more evidence-based, and dare I suggest, more responsible approach.
I'll need a bigger shovel. And OK, if it will make you happy, Wivenhoe is in drought, possibly the worst for donks. But Maroon Dam is not anywhere near Logan Treatment works where the weather station is.
Ian - lets talk median not averages with rainfall. But yep happy with tanks and no dams if you can convince the electorate - good luck !
And one more interesting stat. This years rainfall at Wivenhoe has been only 500mm or just over half of the annual average. Run-off from the catchment has been effectively zero but is normally about 5% of rainfall. Evaporation from the dam is about 2000mm.
So a houseboat floating on Wivenhoe over the past year would have saved four times more water than actually fell on it's roof. Each square metre of houseboat roof, or deck, would deliver the same water volume as 40 square metres of catchment.
The median house size, if built on stilts in the dam, would collect all the water it needs from the roof and save enough water from evaporation to supply two more houses.
Luke, as a person who can actually remember surfing the Pass without backpacker-rage, I can advise that I have not actually been to "the Bay" (as real locals call it) for a decade because it is all so very, very sad. And it is not so much the tourists that offend me but, rather, the "11 month locals" who think they own the place but invariably slip away to be replaced by another set of cliche's before handing a feral minority a rented electoral mandate.
And as for Dams. Why is it that it is OK for us to drink overly expensive recycled sewerage but we cannot allow waterfront housing on the banks of our Dams? Nothing improves a dams catchment efficiency like urban development. Wivenhoe has over 500km of waterfront land which could take all the pressure off the coastal strip. At even modest rates of development and density it could produce value increases that could completely idiot-proof our hospital system, fix our roads and increase the supply of storm water to such an extent that no new dams would be needed.
But that would involve decision making by government that is not afflicted by asynergy. The collective intellect of what we've got is significantly dumber than the sum of the individual intellects involved.
Beattie isn't "technically correct", he's "correct". The fact that some others run a close second, doesn't change the fact that this is indeed the worst drought in 100 years, just as he claimed.
The question of whether this is a bad draw from a stationary distribution or reflects a contribution from anthropogenic climate change can't be settled by the kind of eyeballing that's going on here.
Ian I'm going with the BOM and my disused lawn mower on this one - SE Queensland in general and Brisbane and north in particular are in drought.
As it appears the houses have been built where the dams should have been, the whole plan for dams must be wrong.
Instead of building dams in rural areas, where the rain isn't falling, the dams should be built in the urban areas where it is falling.
So you can build tin & plastic dams, [tanks], or you can resume a few thousand suburban houses & build dams.
It makes sense to me. As the dams are for the exclusive amenity of the urban population, surely the pain should de distributed in the same area.
Can you imagine the NIMBY scream if it happened. Suddenly the idea of new dams would become a whole lot less attractive.
Yes Ian a dam reliant urban community's drought can be an arboreal mammal's good season. There's a fair bit of grass out there waiting for the usual pyros to light it up. Cooler rainy weekend has taken the edge off. And yes areas near the coastal strip are having better rainfall. But the argument is for the Wivenhoe catchment. FOR HEAVENS SAKE !!! If you want to say that Brissos' rainwater tanks might be OK on the coastal strip that's another debate. How much of this can a Koala bear?
And was it you who wrote "Brissos go home" on the rocks at Byron Bay?
Simon C, Strathpine, in the north also has a similar data set showing above average rainfall for more than 12 months last year. Mt Gravatt in the middle had a slightly below average year.
So no matter what spin you try on, the statement "we are in our worst.." is untrue because some of us are not.
And when we look at the monthly breakdowns there have been some very good seasons during the past decade. The point is, there has been an unusual but not rare sequence without very large rainfall events on which dams rely. The wildlife, in contrast, have had some good years during this time where a lower volume of rain has been spread out more evenly to maintain the nutritional value of leaf, bark and flower stocks.
A dam reliant urban community's drought can be an arboreal mammal's good season.