Perth and Catchments Rainfall History and Water Resources

On 15 April The West Australian ran front page headline, "Perth faces another dry winter disaster" Click for 1 September dam storage graphic from Water Corporation showing dams starting to take inflow early this year and inflows increasing after a wet August.  Dams

Tim Flannery Tim Flannery statement The West Australian 25 June that "...Perth will die..." gets me to start a press page. Click on Dr. Tim.
I can cope with a politician, the WA Premier making para-normal statements about water resources ("..we are in a 25 year drought...") but for a scientist to swallow  CSIRO climate modelling as though it is written on tablets of stone, has me puzzled.  Could it be the Federal election  due soon ?  Could this talk scare a few more waverers into voting Green ?  Any comments welcome.

Up to date prediction for just above average SW WA rainfall in May-June-July 2004 from modelingwinter2004 by Scripps Institution of Oceanography.  Click to see  global prediction.These pages have been posted by Warwick Hughes a free lance earth scientist who thinks there is room for  more scientifically based input into the debate over the future of Perth's water supply.  Comments can be emailed to   Updated April 2004
Drought in Australia web site

Main contents:
rainfall history
forecasting rainfall
misleading WaterCorp graphic
climate change
forest thinning 
Harvey water 
Cloud seeding 

Questions for Water Corporation

Perth Waters Users Group
Including comments on Government 29 July go ahead for seawater desalination plant
Feb 05 comments on WaterCorp press claims re MANJIMUP water supply issues

Read how CSIRO Chief made incorrect claims re SW WA rainfall data on ABC TV 7.30 Report
Summary: The 2001-2003 water shortage in Perth and low dam levels represents a  challenge for ratepayers and voters.
The Government line is that climate change is the cause and expensive new desalination facilities are a part of the solution.
The truth is that decades of forest regrowth and a lack of catchment management due to prevailing Green dogmas  has suppressed streamflows and made a significant contribution to the current situation along with slightly lowered rainfall of the last 30 years.  The process of catchment degradation is continuing, wasting too much of  catchment rainfall.
2003 rainfall for Perth at 853 mm was above the average (791) for the years since 1975 and figures for 2004 ; dam levels have improved and there seems no rational reason to expect that rainfall ahead will not oscillate around the 800 mm PA level, as it has for 130 years that we know about.   A more balanced approach is required by the Government before Perth people are saddled with the most expensive city water in Australia.  Unnecessary  spending on a massive desalination plant to augment the Perth water supply must affect other Government expenditure on schools, hospitals etc, there is no bottomless pit of public money. .

Perth rainfall history 1876-2004

The above graphic demonstrates clearly that there has been no decline in rainfall which would imperil supplies to the point where we have to consider expensive desalination options.  2001 was only the 15th dryest year since records began in 1876. What has happened to cause our water shortage is that consumption is ever rising, catchments are being steadily degraded by scrub regrowth impairing runoff and we have been less than prudent over a decade or more in putting off projects that could have brought on new supplies from dams.  

sw wa rain contours Rainfall near the catchments is of course more relevant to dam storage than Perth rain and this map by Martyn Keen, WA Dept. of Agriculture shows how catchment rain is so much higher than Perth. Click on map for larger version. Click here for full map and legend.
Click for Dwellingup rain history and we see that 2001 was a dryer year relatively than in Perth.  How blessed we are to be averaging a metre of rain per year so close to Perth.  Government proponents of the "Perth water crisis" including the CSIRO often say that since the mid 1970's there has been  a 20% reduction in rainfall in SW WA including Perth.  My figures for Dwellingup show an average of 1313.8 mm 1934-1974 then 1181.8 mm from 1975-2003, so there has been 132 mm decrease since 1974 which to my way of thinking equates to a 10.05% reduction.  

In the case of Perth, there was an average 880.3 mm of rain per year from 1876 to 1974 and 791.2 mm 1975 to 2003, a drop of 89.1 mm per year which equates to a 10.12% reduction in annual rainfall.   I am still looking for the 20%.

What the Government should do in 2004/5.

All too easy but Hey !!, would the Greens be happy ?

The composite graphic below sums up major trends relevant to the debate on  Perth water supplies, data (except BoM rain fall) extracted from Water Corporation Annual Reports.

Salient points are;

I am sure readers will correct me if I am wrong here but the contents of this web page are based on the assumption that our society through elected Governments plans for its future needs and welfare employing experts such as engineers, scientists and economists who should have due regard to rational facts and the most accurate histories of natural data possible.   If this is not done we run the risk of basing policy on belief, which  puts us closer to  Witch Doctor or Cargo Cult societies.

The issues I am commenting on critically are mainly those that I can see have been inadequately dealt with to date.
These are;

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