In full page newspaper advertisements in Perth on the 7th and 8th of July the Western Australian government controlled water Authority, Water Corporation, published this graphic with a blue trendline (Govt. statistical experts say 1960-2006 average ??) showing water supply from rain ending in about a decade from now.
The graphic is headlined, “Why we can no longer rely on the rain”.
The graphic above is dodgy in its construction because the stream flow data is certainly not homogenous over its timespan 1911-2006. There is a range of flow data post the 1970’s whereas pre-1970’s the data is ONLY from one tiny catchment, Wungong which is only 3.8% of the area of Perth catchments. Note also this huge change in the data available is exactly at the period of this mid-1970’s fall off in rain and inflows. I have asked WaterCorp for the historic flow data and they refuse to give it to me on grounds I might use it on the internet.
The Govt. Dam inflows graphic conveys more serious mis-information, spin, propaganda, one could say lies, in that the fall off in flows in the last ten years is not due to declining rainfall, to the extent they claim.
Inflows are falling off because catchment vegetation understorey and regrowth is NOT being managed (thinned) as it was pre 1995. My graphic below (added May 2008) demonstrates how catchment rainfall continues in an average band (~900 mm per year each May to October), yet inflows continued to decline.
The graphic below from a WaterCorp publication shows clearly the huge benefits of catchment thinning, we could easily aim for inflow yields of 6% instead of the current near 3%. Incremental water production is now priced at an investment of a $Billion per 45 GL of water per year, from the estimated cost of the proposed Binningup seawater desalination plant. That means that just in the four years 2002-2005, by refusing to manage catchments to an average yield of 6%, the Government has wasted inflows of circa 100 GL per year, that would cost an extra $2Billion investment in seawater desalination to produce each year. To put this inflow on scale I have inserted a small 2 on the Govt inflow graph, above the red bar for 1982, when inflows were 98.3 GL. To get that water each year by seawater desalination, which is the direction the Govt. is heading, we need to invest more than $2Billion, then there are running costs and other impacts the Govt. tries to minimise.
It is perfectly clear that if catchments had been sensibly managed post 2001 we would have had an extra ~100 GL per year in our dams over that period and would not have needed to waste precious taxpayer money on high impact seawater desalination.
There is an impression out in the media, carefully fostered by Govt., that catchments are being managed. This is just more Govt. spin, in fact Water Corporation are engaged on a 12 year TRIAL, and only in the tiny Wungong catchments, only 3.8% of total catchment area.
For background and possible reasons why the WA Govt acts as strange as it does re water.
Who would have thought we could be so cursed with a profligate multi-$Billion dollar money wasting Government who will not go and sensibly harvest available rainwater.