Water Share

Author : J. V. Hodgkinson F. C. A. Chartered Accountant : Aug 2006 to November 2013    

The principal thrust of this website is
FLOOD PROOFING BRISBANE from damaging floods to the point of extinction. MITIGATING flooding in Ipswich and Gympie. Putting REAL MEANING into "Drought proofing SEQ" and ensuring our water supplies by natural means well into the future

This is my review based on official statistics and documents. It is done in conjunction with Ron McMah, grazier of Imbil and Trevor Herse, retired of the Gold Coast




There is a serious and permanent miscalculation in the division water between the ecology and the residents of South East Queensland. 

It involves a misdirection of 130,568ML to the ecology annually above the volume intended. That volume is the equivalent of the output of three desalination plants of the Tugun size.

Nov 2013: The 1974 flood was not included for simplification. When included the volume When included the deficiency increases to 160,000ML


66% of the water that passes through the Wivenhoe/Somerset is to reach the Brisbane River mouth

The Water Resource (Moreton) Plan 2007 Act requires that 66% of the “mean annual flow” is to reach the Brisbane River mouth. (Page 129 Water strategy). I have no problem with that.

The “node” for the Wivenhoe/Somerset which supplies 57% of the water in the Brisbane River system remains at 66%. Calculation of the “mean annual flow” is where I have a serious mathematical problem.

The way the "mean annual flow" is calculated is laid out in the Water Resource (Moreton) Plan 2007. The once only permanent calculation is as follows

The pre-development flows are added up for a stated number of years

That total is then divided by the number of years

The answer is the "mean annual flow". It is permanent and not calculated again 

The 66% is of that mean annual flow.

As one can see if the period selected as the base has large floods in it then the volume on which the 66% is applied will significantly increase the water allocation for the ecology.

The Technical advisory Panel was aware of this and stated in their supporting literature, when determining the 66%, that the inclusion of large floods would skew the result. However they were imprecise in the selection of the period. They used an approximate time of 110 years and did not state the start and finish dates. The photos below are (1) the Technical Advisory Panel (2) the fact that the inclusion of large floods would "skew" the result and (3) their imprecise selection of the years to be used.
         (1)                    (2)                   (3)

TAP Personnel.jpg (40011 bytes)TAP Mean Annual Flow P52.jpg (77295 bytes)TAP 110 years P 42.jpg (76028 bytes)





The period selected and written into the Act was 01/07/1889 to 30/06/2000. A period of 111 years. It is set out below. It has four major floods in it. Those floods are 1890 as large as 1974, 1893 (two in February) and 1974. Even the uninitiated can see that these floods would increase the volume the 66% would produce compared to a period with the floods excluded.

This chart was produced by the official Government  IQQM computer model

It is in Giga-Litres which is 1,000 Mega-litres per giga-litre

The imprecision of the Technical Advisory Panel has left the selection of the years on which the calculation is to be based to the writers of the Act. Not only did the period written into the Act contain major floods but there was 111 years used which conflicts with their "approximate" 110 years. The presence of the 1890 flood at the beginning and closely followed by the 1893 (Two) would not escape your attention.

The true test of the calculation is its application to the 113 years 1894 to 2006. My calculations below show that the 66% becomes 75% when applied to those years and a volume of water each year of 130,568ML being diverted away from the residents of SEQ. The calculations are below. 

Calculation Page 2 of 2.jpg (50180 bytes)Calculation P1.jpg (136367 bytes)




Simplified calculation below Click to examine

I forwarded more detailed analysis on the 16th November 2010 for Minister Robertson and and his Department’s response to my calculations. My previous requests have been ignored with the exception that Minister Robertson suggested that they be raised in year 2017 when the Water Resource (Moreton) Plan 2007 is up for renewal. The delay would abrogate the solution required. The three desalination plants and the footings for the smaller dam at Borumba would be well under way by then or completed.

I presented my calculations to the Department of Environment and Resource Management on the 25th February 2010 for critical analysis. No response or acknowledgement has been received. Two members of the Technical Advisory Panel and Peer Review were advised of my calculations with requests for clarification (19/03/2010). They have been strangely silent on the matter. One of the Technical Advisory Panel was Professor Greenfield, Vice Chancellor of the Queensland University. He twice refused acknowledge receipt of my information. He has since resigned his position.

Minister Robinson has now responded and suggests that the matter be raised in 2017 when the Water Resource (Moreton) Plan 2007 is up for review. He correctly states that this Act was widely canvassed but the flaw, based on page 42 above, of the inclusion of the floods was not fixed as the pre-development flows were not published. I was aware of these floods but an argument could not be developed without them. 

The "approximation" of the years included in the "Simulation period" seems to be a breach  of the standards laid down by the Technical Advisory Panel (TAP) particularly where a sizable difference is proven. The failure to be specific in the actual years start and finish in the published documents above, in my view, undermines the credibility of the TAP conclusion. 

A meeting with DERM senior officers left us in no doubt that they were unhappy with the 66% allocation made by the Technical Advisory Panel. They viewed it as insufficient for the environment and had no hesitation in advising us that they had moved to increase this volume. No doubt they have that authority or authorisation and sound reasons for any departure from the TAP information. They did not explain how this was applied.

However Minister Roberson letters of the 6/08/2009 and 02/06/2010 are in conflict as he relies specifically on the TAP report. 

Structural implementations such as desalination plants will occur before 2017 and at great initial and ongoing costs to our community.

Permanent “once only” calculation ignoring the advice that major floods would “skew” the result

A simplified version that excludes all three floods. The 1974 flood is included in the detailed version.

(1) Known major floods in the Wivenhoe/Somerset catchments)

The known pre-development inflows of the major floods as shown be the official graph below total 16,100,000 ML. (1890 4,300.000ML 1893 (2 in February) 7,500,000ML and 1974 4,300,000ML = 16,100,000ML) As per the official pre-development flow chart above.

(2) Known floods in the whole of the Brisbane River

Major floods cover all of SEQ including the other tributaries of the Brisbane being the Bremer River , Lockyer Creek and others. The Wivenhoe/Somerset provides 58% of the total inflows according to the official IQQM computer model.

Therefore the total flow from the three major floods = 27,758,621ML being the Wivenhoe/Somerset contribution of 16,100,000ML = 58%. 100% being the whole of the Brisbane River = 27,758,621ML.

(3) The period covered in the calculation is 111 years. Reduce to annual

The annual contribution by these major floods is therefore 250,078ML. (Total flood inflow of 27,758.621ML divided by 111 years = 250,078ML

(4) Overstatement of the Ecology proportion being 66%

Overstatement of the Ecology share is 165,051ML annually. (66% of 250,078ML) Note : The detailed version includes the 1974 flood for continuity and includes years 2001 to 2006.

End of simplified version  Click to return

Strangling the true potential of the Wivenhoe/Somerset dams

It also means that no further water, other than the 286,000ML annual allocations already made to us, can be extracted from the Wivenhoe/Somerset system until the Act is changed to represent the correct allocations. This means that the massive infrastructure of the Wivenhoe/Somerset dams has been confined to providing a little more than the equivalent of the output of 6 desalination plants of the Tugun size.

SEQWater in their 2000 and 2001 reports had set the yield (available water) from the Yields_Annual_SEQWater_web.jpg (114473 bytes)Wivenhoe/Somerset System at 445,600ML annually. The South East Qld Water Strategy Mark 1 had set the yield at 373,000ML but were concerned about "droughts" now overcome by the Borumba Plan. Either way the Wivenhoe/Somerset System falls well short of its true potential by the use of this calculation of the volume including the 1890 and 1893 and 1974 major floods.





The structure of the SEQ Water Strategy, the fate of desalination and lower water costs now rest largely on this calculation.