Dear Jennifer,
I have enjoyed reading Mark's articles at On Line Opinion entitled 'Fired-Up Forests Have More Impact than Loggers' and agree with much of what he says. But he must check his facts regarding thinning in Perth water supply catchments.
The Wungong catchment is only 3.8% of the area of Perth catchments. So it is incorrect to say, "Western Australia has been quick to take advantage... "
This thinning is only a tiny trial, just a PR effort so the West Austraslian government water organisations can trumpet that they are doing something and most of what they say has to have spin "fine tooth combed" out before truth emerges.
The reality of what is happening in Perth water supply catchments can be seen in my graphic at http://au.geocities.com/perth_water/ scroll down to, "Graphic of Catchment Efficiency 1980-2005 showing disastrous falloff 1996-2005 after ceasing catchment management." Click on thumbnail for a larger graphic.
It is perfectly clear from my graphic that the West Australian government is de facto decommissioning Perth catchments. If catchments had been managed post 1996 as they were before that date so as to keep yields steady, Perth would have enjoyed about 90 GL extra water per year on average. Equal to production from two Kwinana sized seawater desalination plants, which require an investment of about $500 million each now. That puts on scale the cost of catchment neglect.
This colossal bungling extends into other areas of water resources.
North of Perth a pine plantation at Gnangara suppresses the potential of the groundwater there by about 100 GL per year. With incremental water valued by investment required in seawater desalination, Govt claims that the pines are needed to support a proposed plywood industry is simply ludicrous. Timber can easily be sourced on the open market if anyone is of a mind to make plywood and the pines must have a negative net present value now in view of their manifest billion dollar damage to groundwater potential.
The Avon, Murray and Collie Rivers pass about twice Perth's total water consumption each year but in a weakly saline state. Surely desalination of a small part of these flows would be cheaper and lower impact than seawater desalination and could take place away from the fragile and crowded coast. In fact a private company, Agritech has been valiantly trying to interest the government in a proposal to desalinate water currently wasted to sea each year from the Wellington dam near Collie. This proposal would be at no capital cost to government and would produce water at half government desalination costs and would I am told use gravity in the process thus cutting back greatly on electricity.
Perth is not running out of water, the water is running out of Perth.
The Ancient Romans were vastly better water managers than the West Australian government.
Regards, Warwick Hughes
To return to the original issue.
Warrick Hughes is less enthusiastic than I am about the value of thinning (plus regular green burning) of forests on Perth's water supply catchments to generate "new" water. We are not talking about clear felling of virgin old growth forests here, but thinning of dense regrowth arising from timber cutting and regeneraton up to 100 yrs ago. The science is well understood. As Mark Poynter correctly points out, properly managed thinning and frequent (about 5 yrs interval) mild burning will result in a significant additional flow into the reservoirs. There will be three other excellent outcomes: (i) additional streamflow and the wetting up of riparian areas and wetlands, enhancing wildlife; (ii) improved health and vigour of retained trees at a time of declining rainfall; and (iii) lower risk of large high intensity bushfires.
However, Warrick is quite correct in saying that there has been a sorry decline in catchment management in WA's forests. Up until a few years ago, these forests were designated as multiple use State forests with the management priority being water production (in the non-salinity risk zones) and catchment protection (in areas potentially at risk from salinity). The government has recently converted the bulk of these forests to national parks where the management priority is biodiversity conservation. In these areas any thinning, which of course involves felling trees, will not be allowed, and green burning is frowned upon. The net result is the management of water catchments as areas which will retain water, especially in a time of low rainfall. Already the outcomes are very evident: reservoirs whcih are almost empty, and an overstocked unthrifty forest in which (during the last three years) there have been three massive high intensity fires. This represents mismanagement of a community asset of the highest order.....and all in the name of conservation!
30 aggreggates. No they're not Louis. You've just got 30 years on the brain after your misadventure with running means and anomalies.
The rainfall decline issue in SW WA has been well documented and investigated by the Indian Ocean Climate Initiative (IOCI.
http://www.ioci.org.au/publications/pdf/IOCI_TechnicalReport02.pdf
Complex interactions between greenhouse forcings, the southern annular mode, and maulti-decadal natural variability have been investigated.
http://www.csiro.au/csiro/content/standard/ps18l.html
And as the Bureau said on 1-Dec-2006
Perth's rainfall over the past 11 months has been at a record low.
The Bureau of Meteorology's Grahame Reader says 462 millimetres of rain fell in the city between January and November, which is almost 46 per cent below the average of 846 millimetres.
"It's a very sad state of affairs," he said.
The Conservation Council of Western Australia's Chris Tallentire says there is no doubt climate change has become a reality and Perth people should do everything they can use water wisely.
"Householders are one part of the tackling of the need for greater efficiency, so to is industry and agriculture," he said.
The council says it looks forward to the State Government's Climate Change Action Plan, which will be released early next year.
Might be also a lack of rainfall?