Category Archives: Water

ACT (Canberra) Government water report makes bizarre and misleading reference to Perth rainfall

I came across this July 2007 report by ACTEW the Canberra based Australian Capital Territory (ACT) Government electricity and water utility. The reports title is “Water Purification Scheme for the ACT”.

My attention was drawn by ridiculous statements on climate change in the first four paragraphs of the Executive Summary. The report holds out Perth as an example of a place with “..greatly reduced long term rainfall averages..”.

Read the Executive Summary for yourself, then check my graphic below for the facts. ACTEW report Executive Summary is in italics

Executive Summary

Context and Purpose

Climate change predictions indicate that the climate would become more variable; droughts are likely to be longer and more severe, storms and flood events are likely to increase and temperatures would continue to rise. These conditions indicate that further investment in new infrastructure is required to address these changes in climate.

Since 2005, ACTEW has implemented a range of actions to increase the reliability of supply for Canberra. However, these measures would not provide sufficient water to ensure a safe, secure and sustainable water supply into the future under this more variable climate.

A significant factor to be considered is that if the recent climate is typical of the future it may be necessary to allow for worse drought events than previously considered and at worst, the possibility that we may have entered into a completely new climate pattern with greatly reduced long term rainfall averages1; as has happened in Perth and is now a real possibility here. The level of uncertainty with any prediction has greatly increased, which means that if a dam or dams are built, it may take many more years for them to fill.

Whilst such a scenario seems unlikely, it is a possibility and must be considered for future water security. Therefore, previous recommendations must be revisited and further investigations must look into options that are less reliant on rainfall. One of these options is to purify our used water.

Reference 1 from the third paragraph.

1 Even worse than assumed in previous modelling which adopted CSIRO predictions for reduced rainfall in the Canberra catchments in future due to climate change.

The rainfall index I quote for the Perth hills is an average of Mundaring PO, Karnet and Dwellingup, places which cover the extent of Perths dams down the Darling scarp.
ACT rain compared Perth dams rain
Perth dam catchment rain for only the wet season May to October, has exceeded Queanbeyan annual rain by about 50% for the last 34 years, the Perth hills May-Oct index has averaged about 920 mm per year for the 34 years, rainfall I would have thought ACTEW would have been very glad to see fall on ACT catchments.

Let’s quickly mention Perth rain history, which is of course longer term than my Catchment Index, noting of course that Perth dam catchment rain in the Perth hills is significantly higher than Perth. Perth region rain did reduce by approximately 10% in the mid-1970’s – scroll down for my graphic and this is what the climate change proponents, such as CSIRO and ACTEW, are referring to when they say “..greatly reduced long term rainfall averages..”.

Update Thursday 30th – long term graphic comparing Perth and Queanbeyan rainfall 1871-2008
Perth rain vs ACT long term
But note by the same token that Perth rain INCREASED around WWI years from previous levels not unlike the lower rain regime post the mid 1970’s. So I would say if “climate change” caused the 10% REDUCTION circa mid 1970’s, then there seems no reason why “climate change” did not cause the INCREASE in Perth rain to over a metre annual average, that took place around WWI. So in reality our long term rain history reflects cycles varying for reasons unknown, there is no evidence of a statistically significant long term reduction.

There is a long term Queanbeyan rain history here, just cyclic variations all within a band for 138 years.

“Our hot, dry future”?

THESE days, it can be hard to imagine how Melbourne ever earned a reputation as the gloomy, rain-filled capital of the south. But, growing up in the 1970s, my memories are full of muddy ovals, local creeks in flood and catching tadpoles in puddles that lasted for months on end. How things have changed.Since 1996, each successive calendar year has brought the city below-average rainfall. With 299 millimetres recorded so far this year, and with just three months to go, it seems virtually certain that this year will become the 12th in a row that has failed to get to the average of 650 millimetres. September 2008 was the driest on record in Melbourne, and the outlook for the remainder of the year suggests that below-average rainfall will continue.So why has it been so dry? The drought started in late 1996, and the subsequent El Nino years of 1997, 2002 and 2006 have each been particularly dry. Ordinarily, these events would have been interspersed with wetter years, but since 1996 the intervening periods have only approached average at best, with the deepening drought particularly evident in our reservoirs and stream-flows.

My main criticism of the article is that the BoM relies on Melbourne CBD rain data to back up their regional conclusions regarding “climate change” and drought, while the rainfall history is in fact affected by the growing urban heat island.

Melbourne Regional Office 86071 (MRO), a weather station in Melbourne’s CBD is

(a) excluded from their own High Quality (HQ) dataset and

(b) shows a negative trend of 90mm (a stunning 13% of mean annual rain) over the last 153 years when compared to the nearest HQ station, Yan Yean 35 km NNW.

So much of what they say in “Our hot, dry future”, is slanted by this amount, no wonder I am critical of much that the BoM publishes.

153 years of declining rain in Melbourne CBD

Melbourne Regional Office weather station in Melbourne’s CBD which has rain data from 1855, is a site that has undergone enormous changes in its surroundings as the city has been built and expanded over the centuries, resulting in an ever-increasing urban heat island.

Melbourne UHI transect on calm night

The above illustration is from a 1997 BoM paper.

High rise developments have increasingly affected wind and changing pollution levels over the decades could also cause variations in rain formation. Up to post WWII coal burning would have been common leading to much worse pollution than modern times, (note visibility data) and air quality data show improvements over say the last 40 years.

These are just a quick sketch of some reasons why weather data from a large and expanding urban heat island is a most unsuitable source from which to draw conclusions about, climate change, regional changes and long term rain trends.

Finally, the article contains another BoM failed prediction, saying in the second paragraph, “..the outlook for the remainder of the year suggests that below-average rainfall will continue.” Wrong BoM, the 2 month rainfall total for November-December for Melbourne Regional Office was 130.8mm compared to the long term mean of 118.7.

Jennifer Marohasy featured 5 articles on her blog examining the subject during October 2008; the first titled How Melbourne’s Climate Has Changed: A reply to Dr David Jones (Part 1) was posted on 14 October and parts 2 to 5 were later in the month.

Traveston Crossing Dam catchment rainfall trends

Reading recently that the Queensland Premier Anna Bligh had pushed back for five years any action on building the Traveston Crossing Dam I thought the years end was a good time to post some catchment rainfall history.
Traveston dam catchment rainfall histories
Claims by the usual suspects about “worst drought ever”, and variations on this theme are shown to be rubbish. Just a normal, usual drought by the look of it.
A five year postponement sounds like the death knell to me.

2008 update-Perth dam catchments rainfall still OK, Govt will build +$Billion seawater desal plant.

As this graphic shows, Perth dam catchments rainfall has proved remarkably reliable over 34 years in the face of recent WA Govt propaganda spruiking, “our drying climate”, etc etc. See my late 2007 article, “There never was a rain shortage to justify seawater desalination for Perth’s water supply”
and downloadable word doc with several rational proposals vastly cheaper and better than seawater desalination to augment Perth water supply.
Perth dam catchments rain 1975-2008
But the new WA Govt are on the edge of going ahead with the plus $Billion new desal plant at Binningup just north of Bunbury.
Disgraceful waste of taxpayer monies, exactly at a time we are entering economic rough times. Crazy.

New South Wales Premier Rees says Tamworth was in drought but BoM maps say no drought near Tamworth

This is another of these fascinating cases where top Australian politicians seem unable to get the simple facts of rainfall correct. Is this more evidence of a national delusion where rainfall is concerned ?
Premier Nathan Rees is quoted in the ABC Online news story copied below that Tamworth had “..been drought-stricken for some time..”.
I have just downloaded a series of 7 BoM (Australian Bureau of Meteorology) drought maps for all periods, 3, 6, 9, 12, 18, 24 and 36 months, see below and there is no sign of drought near Tamworth for those periods.
It is telling that the article refers says, “While the rain has broken the drought, valuable crops have been destroyed, including one of the best winter grain crops in the region for years.” Nobody has the common sense to ask, how could such a good crop be grown in a drought ?
It may well be that the NSW Govt is still paying out drought relief to the Tamworth region years after any drought (maybe pre 36 months ago) has ended. I have been aware for years that the Govt pays out drought relief to areas where actual rain bears no resemblance to that indicated on BoM drought maps, see my 2005 article, “Are Martians growing Australian wheat ?”.

Anyway read on to see the reality of the current BoM drought maps for NSW
Continue reading New South Wales Premier Rees says Tamworth was in drought but BoM maps say no drought near Tamworth

Weather experts should check rainfall figures before being quoted by the media

We have all seen articles such as this from The Australian, “Southeast Queensland storms in line with climate change: weather experts”. The article is referring to storms of 18-20 November and the journalist seems intent on getting his headline despite one of the experts cautioning against reading too much into the storms by saying, “..that a series of events by themselves did not “prove” climate change one way or the other.”

The real interest for me is not the ridiculous headline but the two experts quoted state that “..November in southeast Queensland had generally been a dry month over the past decade..”.
These experts are University of Southern Queensland professor of climate and water resources Roger Stone and Queensland weather bureau (BoM) spokesman Gavin Holcombe.
Now what are the facts about November rainfall in southeast Queensland over the past decade ? Lets look at November rainfall for central Brisbane and Gatton, home to the Professor’s University, taking November data for the 10 years 1998-2007 and comparing to long term averages for November.

We find that for Brisbane and Gatton, the November average 1998-2007 is either very close to or exceeds the long term BoM mean(average). So we see that experts much quoted by the media are not fully in touch with simple realities of rainfall statistics, facts they could check in minutes. Is this more evidence of a national delusion about rainfall in Australia ?

The long term rainfall record for Brisbane is “Brisbane Regional Office” which commenced in 1840 and closed in 1994, the November mean is 97mm.
Using this helpful BoM webpage to discover data near the centre of Brisbane I have made the following table from 7 Brisbane stations up to 6.2km from the centre of town, leaving out a few of the most gap ridden stations.
November Brisbane rainfall
BRISBANE REGIONAL OFFICE Site number: 40214 Commenced: 1840 Closed 01 Jul 1994
Mean for November = 97
7 stations up to 6.2 km from 27.47 degrees South – 153.03 degrees East

  • BRISBANE (BCC) ALERT Site number: 40839 Commenced: 1990
  • BRISBANE Site number: 40913 Commenced: 1999
  • HILLTOP GARDENS Site number: 40911 Commenced: 1999
  • BRISBANE SHOW GROUNDS Site number: 40216 Commenced: 1889
  • BRISBANE RPA HOSPITAL Site number: 40767 Commenced: 1988
  • LONG POCKET CSIRO LAB Site number: 40450 Commenced: 1968
  • ALDERLEY Site number: 40224 Commenced: 1899
  • UNIVERSITY OF QUEENSLAND GATTON Site number: 40082 Commenced: 1897

Mean for November = 77.7

My table above gives a Brisbane average of 99.9mm for November 1998-2007, just above the long term mean of 97, that is leaving in the 61mm for station 40839 for 2004 which might be incomplete.

Gatton has a long term record almost free of gaps and has a November mean of 77.7mm. I have not had to look for any other data there and as my table shows Gatton has an average of 90.09mm for November 1998-2007, well above the long term mean of 77.7mm.

With respect to Brisbane data it is interesting that although Brisbane Regional Office closed in 1994 no overlapping station appears on the above BoM webpage to replace it. You might expect the BoM would have started a replacement central Brisbane station before closing BRISBANE REGIONAL OFFICE Site number: 40214.
Maybe there is data somewhere but just not available on the above BoM webpage I have accessed.

Full text of article from The Australian, our national newspaper.

“Southeast Queensland storms in line with climate change: weather experts”
By Andrew Fraser
The Australian
November 21, 2008 12:01pm

ONE of Australia’s leading climatologists has warned the extreme weather that hit southeast Queensland this week is consistent with climate change modelling of weather patterns.

Southeast Queensland was hit with a heavy storm on Sunday night and again in the early hours of yesterday morning, with another predicted for last night and another tomorrow.

University of Southern Queensland professor of climate and water resources Roger Stone and Queensland weather bureau spokesman Gavin Holcombe said that while November in southeast Queensland had generally been a dry month over the past decade, big storms such as the last two were not unusual.

“They generally are a one-in-20-years event, but that doesn’t mean that you won’t get two or even more in the one week,” said Professor Stone.

“But this sort of violent weather activity is consistent with climate change predictions. We’re coming off a long drought in southeast Queensland, and that has been an extreme weather event. Now we’re getting these storms, and they’re also extreme weather events.”

He cautioned against reading too much into the storms, saying that a series of events by themselves did not “prove” climate change one way or the other.

Weather bureau records show that Brisbane generally has 11 rainy days during the month of November, but Mr Holcombe said that during the past decade rainfall in the month had been well under previous averages.

“But back in the 70s and 80s we did have plenty of Novembers which were very wet indeed. I just think people are now thinking of the sort of dry Novembers that we’ve had over the past decade as the norm, but if you look over the long term, there have been plenty of wet Novembers,” Mr Holcombe said.

He said there could be a bigger storm tomorrow. “The sort of warm winds over southeast Queensland combined with an upper trough moving over southeast Australia are the sort of conditions that allow a lot of storms,” he said.


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Brisbane-Toowoomba floods 18-20 Nov 08 highlight failure of 28 Oct BoM rain Outlook

In three short weeks the BoM rain Outlook prediction gets shot to pieces by real world weather.
BoM predicted rain Nov08-Jan09

This inset map shows the BoM predicted on 28th October that the Brisbane region had only a 45% chance of average rain for the November to January period.

To see the original map select the 28th October 2008 rain prediction.

Sadly for the BoM prediction a series of high rainfall storms hit the region from the 18th-20th November
Real world rain 1-23 Nov08

see map inset of rain anomalies from 1st to 23rd November.

You can make various rain maps at this BoM site

See earlier articles re BoM rain Outlook failures:

Long term rainfall trend updates Melbourne region, Canberra, Warragamba catchment (Sydney Australia)

While digging around for rain data I thought I would update my “Melbourne water supply issues” page. Look for the Yan Yean monthly long term chart (below the red map) and below that my composite Melbourne region long term rainfall.
This lead on to charting the Queanbeyan Bowling Club trend complete from 1871.
Queanbeyan long term rain trend 1871-2008
Then Taralga from the Warragamba catchment.
Warragamba catchment (Sydney Australia) rain trend from 1885
Compare with my Uriarra district (Canberra, ACT) long term chart.
All of these long term data show that the recent decade is nothing exceptional, in every case the 5 year trend has been lower in earlier periods. Yet to listen to the media you would believe we are in a “long drought” caused by IPCC Greenhouse Global Warming. A bizarre national delusion. Who knows what the future brings, if rainfall long term trends do slide further into uncharted territory we can be sure that our policy response will be based on irrational notions and not on considered logic.

Deterioration in BoM rainfall data quality this decade

While chasing updates for Perth Dam catchments rainfall data I have been hit by how common it is to find a marked fall of in data quality this decade. I want to emphasize I have not searched for these cases, they just jumped out in the normal course of checking data. Then I had a quick look at stations relevant to catchments east of Melbourne incl the Thomson, very poor data there.
I wonder why, considering Australia is widely believed to be in the grip of a national rain / water crisis. Our pioneers have little trouble collecting data reliably for the best part of a century and just when the nation is hit by a downturn in rainfall, the BoM appears to drop the ball on what must be one of its prime reasons for existence. I would suggest there needs to be a reallocation of resources in the BoM; more effort on archiving weather and water data history and presenting it free on the www in a usable form and less resources wasted on climate change fairy stories.
Here are the examples, I have taken a screen shot of the gap ridden recent years and you can click the station name links to see all the data for each station at the new and very useful BoM web page. The columns are monthly rain in mm, Jan to Dec left to right, with the annual total in far right column.
MUNDARING WEIR Site number: 9031 Commenced: 1900, full data to end 1996, missing Jul 1987, then OK till 2001, then just as national “water crisis” hits, missing data increases. First 4 from Perth hills Western Australia then a few from catchments east of Melbourne.
Mundaring Weir rain data gaps
Continue reading Deterioration in BoM rainfall data quality this decade