Borumba Appendix
AN OBSERVATION OF THE CONFLUENCE OF STATISTICAL ABERRATIONS, DAM RATIOS, TIMING AND UNCOMMON RAINFALL EVENTS THAT COMBINED TO HAVE OUR LEADERS DRAW INCORRECT CONCLUSIONS. THEIR INFLUENCE ON ACTIONS TAKEN.

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

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APPENDIX

This appendix will demonstrate that the expanded Borumba Dam is a far superior option to Desalination plants and recycled water.

The Water resource (Moreton) Plan was enacted in March 2007.It laid out the flow requirements of all segments of the Brisbane River that would have occurred in pre-development times.

The principal objective was that 66 percent of all water that flows through the system must reach the Brisbane River mouth and the remaining 34 percent is for our purposes. 

Being enacted by legislation, I have requested this information. It has not been forthcoming at this time but not denied.

It should be noted that the sister legislation that is designed to monitor and enforce this legislation has not been enacted although on the internet since January 2009.

The QWC has confirmed that the following graph is an accurate representation of the movement of dam levels created by inflow and extraction of the Historical Yield No Failure (HYNF) of 373,000ML annually.

It does not represent the actual dam levels influenced by the containment of allocations of water to 280,000ML. For example, in June 2006 the Wivehoe level was 30% and the Somerset 33%. Water restrictions from late 2005 also influenced the actual dam levels. The unallocated water of 93,000ML is held in reserve for contingencies such as prolonged drought.

What it does give is a reliable insight to the following:

 
(1) The draw-down on reserves from the expanded Borumba Dam required to maintain the 40% level adopted by the QWC for introduction of recycled water.
(2) The Comparison of Desalination plant and recycled water to match the reserves from Borumba.
(3) The influence of large scale rainfall events on dam levels.
(4) The approximate inflow of one of these events

What it does not give us is:

(5) The flow information on the overflow of these large scale events. Almost all of them overflowed the dams with very few exceptions.
(6) the basis of assessing the contribution towards the 66% required of the Wivenhoe/Somerset dams.  

The above graph is now expanded and overlaid with relevant information. It identifies most of the large scale rainfall events in the 120 years since 1888 when records began to 2009. It illustrates the vital gaps in these events and the backup ability of this proposal, desalination plants and recycled water to fill those gaps.

The Gaps are designated "A", "B" and "C". The QWC use of the 40% requirement to introduce recycled water is taken as the minimum dam level for security of our water supply. "A" and "B" are our main consideration with "C" requiring little attention.

Of particular note is that periods "A: and "B" did not experience a large scale rainfall event within the normal period of 3.7 years. The gap in "A" was 10 years 1898 to 1908. The gap in "B" was 7 years with 4 "near misses" taking their place.

Period "A" received no such boost from 1888 when it was full until 1903 when it was held in check by a series of minor inflows. It was finally rectified by the 1908 large scale event.

Period "B", being the one just experienced, saw no such boost from February 2001 to January 2008. It was then rectified by four "near misses in the catchments" being fills of 14.1% in January 2008, 8.0% in November 2008, 11.3% in April 2009 and finally 16.0% in May 2009 with the Premier declaring the "drought" over.  

(1) The draw-down on reserves from the expanded Borumba Dam required to maintain the 40% level adopted by the QWC for introduction of recycled water.
(2) The Comparison of Desalination plant and recycled water to match the reserves from Borumba.

Both of these items are clearly illustrated in the following schedule". They relate to the release of the 93,000ML, currently held in reserve, for consumption.

Pumping requirements: To service both "A" and "B", an initial withdrawal of 2,000,000ML is required then 760,000ML and 560,000ML to be replenished. This is permitted under the Water Resource (Moreton) plan enacted in March 2007. These are the only requirements over a period spanning 120 years.

Additional benefits of the Borumba expanded : In addition to releasing 93,000ML now held in reserve mainly for drought contingencies, there is an additional 52,000ML provided from the Borumba's own catchment. 

Costing generalisations : The estimated cost of the Borumba dam wall and two-way pipeline is $2 billion. The download and replenishing amounts to less than 10 years in the 120 years observed.

The cost of desal plants based on Tugun is $1.2 billion each plus pipes. As there are 5.5 required, this totals $6.6 billion plus pipes. The electricity requirement is 5.5 times the electricity requirement of Mt Isa each year.

Recycled water cost is unknown. It cannot retrieve the situation by itself.

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The remaining information mainly relates to the additional 80,000ML annually identified by engineers GHD when considering raising the Wivenhoe Dam wall.

(3) The influence of large scale rainfall events on dam levels.
(4) The approximate inflow of one of these events

What it does not give us is:

(5) The flow information on the overflow of these large scale events. Almost all of them overflowed the dams with very few exceptions.
(6) the basis of assessing the contribution towards the 66% required of the Wivenhoe/Somerset dams. 

(3) Influence of large scale rainfall events on dam levels : 
One can see that almost all "large scale rainfall events" overflowed the dams. They are marked in red. What we do not know at this stage is by how much.

(4) The approximate inflow of one of these events:
The event of 1908 was the only one contained within the Wivenhoe/Somerset system. It was of medium size at approximately 1,200,000ML. The only other fully internal event was 1996, being comparatively minor, when the Wivenhoe was retrieved from 47% to 90% with the Somerset full. 

(5) & (6) This area determines the availability of the remaining 80,000ML identified by engineers GHD. 

We are not in possession of the overflow from these large scale rainfall events. Calculations have been made under the "Brisbane River 66%" tab. Understandably, with the yield of 373,000ML representing our share of 34%, the 66% must result in an annual figure equating 724,000ML provided by large scale rainfall events and is flood water. The combined Wivenhoe/Somerset at 1,545,000ML capacity is clearly unable to control them as they do not happen every year and thus the figure is cumulative.

I recently received advice that the Wivenhoe/Somerset system provides 40% of the water in the Brisbane River. Under revised calculations, the 66% requirement at the Brisbane River mouth would require an adjustment to 63% for the additional 80,000ML. If the advice is not accurate, it may be required to be adjusted to around 60%.

What is certain is that almost all of the water available to the Brisbane River is flood water and as the rainfall systems generally cover all of SEQ, they combine with other flood waters that are particularly damaging to Moreton Bay as outlined in our proposal.

The release of 3% to 6% would have to be reassessed on the basis of control of these flood waters via the doubling of capacity of the Wivenhoe/Somerset by expansion of the Borumba dam to 2,000,000ML. 

An Environmental Impact Study (EIS) is required as Moreton Bay is involved. We would welcome this as it will enable all to understand the Brisbane River requirements under these changed conditions.

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