Melbourne water supply issues
June 2005 Update:  Bureau of Meteorology (BoM)/CSIRO  BLOOPER  on Melbourne Region rainfall history statistics.  Oct 2008 update, Yan Yean Monthly rain chart below map.   Plus Melbourne regional rain trends  in chart below that, both from late 1800's.

Misleading BoM/CSIRO rain map
In March 2005 CSIRO  reported to Melbourne Water  on the "Melbourne Water Climate Change Study" which can be downloaded in pdf format at;    This report could be summed up as the usual CSIRO Greenhouse model driven paean to warmer/dryer times predicted for the decades out to 2050. This  Fig 2 eye grabber  of a map (click on for full size) purports to demonstrate that, "..the greater Melbourne Region has had its lowest rainfall on record compared to all other periods of similar length. Source: Australian Bureau of Meteorology."   The period chosen by the BoM was 92 months, from Oct 1996 to May 2004, (ask them why).  Wondering how true this BoM/CSIRO statement was I examined the BoM High Quality rainfall data  closest to Melbourne, Yan Yean with data from Jan 1863.  See graphic of Yan Yean monthly rain and 92 month average trend in blue below.  ( In 2000 I told Melbourne Water that they were making unjustifiable claims about  "the worst drought in Melbournes history". )
Yan Yean monthly rainfall 1863-2005
Clearly the blue 92 month averaged trend at left (click for larger copy) shows the BoM statement  to be false because several periods in our past  show lower values for the 92 month averaged trend. In fact  a total of 160 months centred in the following periods 1867, 1879-1881, mid-late 1890's, and 1940's  all have 92 month averaged rain below the value for Oct 1996 to May 2004. 
The upshot is that the  7 years and 8 months period (chosen by the BoM) looks to be  NORMAL  for a dryer phase of the ever fluctuating, cyclic rainfall patterns in the  Melbourne region .   In 2004 I said  Melbourne was experiencing a cyclic dry spell, see below.  It is also notable that the Oct 1996 to May 2004 period chosen by the BoM marks  EXACTLY a  reversal  point for the blue trend. Well chosen indeed. Assuming Melbourne Water have paid CSIRO for this study, they should ask for their money back and the report should be pulped.  The BoM experts on long term rainfall should carry out a study  into Melbourne Region and catchments long term rain trends with all data involved being made available on their web site.
  Nothing less is adequate with an issue as important as our water supply.

In May 2004 the Victorian Government put out a White Paper on future plans for Victorian water supplies, which summed up means that Melbourne consumers will get less and pay more.
Underpinning this is the notion that the State is in the grip of an "eight year drought"
  The Premier mentions in his introduction to the White paper that water supplies are "..dwindling.."
Yet when we look at long term rainfall data for the Melbourne region we see that we are in a cyclic dry spell  similar to many in the past.
Thus it is crystal clear that the rainfall which feeds Melbourne's water storages is NOT dwindling but is simply in the lower zone of normal cyclic variation.
The real situation then is that  increasing water demands in Melbourne have collided with storage levels affected by perfectly normal cyclic rainfall amounts and planners have chosen not to plan any storage increases for over 30 years.
The Thomson Dam was planned in the late 1960's and Melburnians should be thankful for the vision of those people because there sure is little vision now.  The ill founded dogmas of Green naysayers pumped out through an unquestioning media would make it very hard to build a large new dam anywhere in Australia these days.

In the introduction to the White paper, (the first downloadable pdf file), the following graphic produced by CSIRO is used to portray, presumably what the Government believes are projected climate changes out to 2100 in terms of daytime temperature and rainfall for the Murray-Darling Basin. In the table below I have first shown the CSIRO graphic of model results and then superimposed those CSIRO linear trends 1960-2100 on to historical  mean temperature and rainfall records back to 1882. Click on graphics for larger image.
CSIRO diagram of climate model trends 1960-2100
My Comments

These trends may look convincing to non-scientist politicians but a comparison to real world data history shows they  look very unlikely to come to pass in the decades ahead.
Mean temperature history plus CSIRO moderl

It is my understanding that the rapidly warming model trend for daytime temperatures stems in part from tweaking data with technical corrections that I believe would not stand up to detailed scrutiny.  
In my frank opinion this type of modelling will be an unreliable guide to future trends.
Rainfall MDB 1882-2003 plus CSIRO model
Obviously the CSIRO rain trend must take in data from much lower rainfall areas than those near the NSW - Victoria border.  All rainfall data on this page, both the Melbourne region and these stations from north Victoria plus Deniliquin are from the Bureau of Meteorology (BoM) high quality dataset, of approximately 370 stations Australia-wide.  I have only used data extending to 2003 and the rare missing year has been interpolated.  I would have thought that a White Paper on water resources would have as a cornerstone a peer reviewed paper looking at all rainfall records for the region involved.
  As a further note to the BoM high quality rain data, there are no stations from the main catchments.  
I have seen Melbourne water authority rain data for Maroondah which shows a declining trend, totally at odds with the BoM high quality data and I think the water authorities should forthwith publish all of their rainfall and stream flow data.

There is much mention of  "sustainability", this clever Green buzzword that the Greens and their bureaucratic / regulator / leftie  mates managed to slip past a sleepy Australian population in the last decade.  The implication being that dams are somehow "unsustainable", a notion which the Melbourne population will discover will deliver them increasingly expensive water in years ahead.
Minister Thwaites says smugly, "..dams do not create water..", a misleading little slogan more suited to an advertising jingle than a politician with Premiership ambitions.  Dams certainly do store water in times of plenty for you to use when it suits you and are worldwide the most cost effective foundation for reliable, clean,  public water supplies.
Green claims of environmental harm to rivers downstream of dams will on close examination I believe, turn out to be exaggerated and misleading as are most claims the Greens ever make.
The total area of catchments in say eastern Victoria, affected by dams is very small compared to total catchment area.
In any one catchment affected by a dam, the area not affected by the dam is huge compared to that upstream of the dam.
Rivers have always run low in dry spells, with or without dams.
Rivers have always run low in summers, with or without dams.
Freshwater flora and fauna have survived and evolved for millions of years.
Banning new dams will do very little to benefit wildlife values but is a first step in Green dreams for a return to some pre-industrial Nirvana and is also supporting the mantra of those anti-immigrationists who say Australia can only support this or that population.
I notice from reading further into the White Paper and on the media, claims that irrigator groups are happy with the plan. This leads me to think that there are elements in this of the Government trying to shore up support for itself in rural electorates. For example in eastern Victoria, Independents have done well in the last decade running on environmentalist platforms including returning natural flows to rivers.
Twenty or thirty years ago I would have said it was a ludicrous notion that unscientific and radical fringe groups could influence Government water policy for a major metropolis in a way that equated to a first step in a roll-back of two centuries of progressive improvements to public water supplies and public health.
It is clearly a ludicrous notion that relatively few people in sparsely populated  Gippsland have some greater right to influence water policy on crown lands, than the more numerous people of Melbourne. Presumably because they live closer to the said crown lands and water resources.
Melbourne people will  have to assert themselves at the ballot box to put in place increased dam storage if they find that  Governments are not delivering them an adequate water supply.
Back to front page
Yarra Valley Water front page has link to other Govt. site with downloadable White Paper

A clever little site where you can access the BoM high quality rainfall dataset and generate rainfall trends 1910-1995 for most of the 20C for various parts of Australia. Very well done CSIRO now how about an update through 2003.