Note : December 2009
The appendix to our
alternative proposal provides a clearer view of pumping requirements
The water involved is:
Borumba dam expansion : Additional 52,000ML. No pumping
requirements. Hydro power available for delivery of existing yield of 35,000ML
to the Mary Valley together with any further allocation out of the additional
52,000ML.
Release of the 93,000ML unallocated in the
Wivenhoe/Somerset system. Pumping required for the initial 1,500,000ML and
replenishing of 760,000ML and 560,000ML. This is the only pumping required in
the period 1888 to 2009.
Release of the additional 80,000ML identified while
considering raising the Wivenhoe Dam wall. The following is relevant.
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Minister Hinchcliffe has left to the last of what he describes as "The second key constraint".
It is contained in pages 3 and 4.
It bears the label "Impact on flood immunity
downstream from Wivenhoe Dam"
*******
The general overview of the linking with the Borumba Dam is
to store water in it for later return to the Wivenhoe/Somerset. It is an adjunct
to storage space in the dam system permitting better control over ecological and
water distribution rights.
It can be done, with or without the use of the flood
compartments.
There is a provision in the Water Resource (Moreton) Plan to
permit this operation of transfer and later return.
The Government's decision to allocate 66% of all water through
the Wivenhoe/Somerset system is the Primary key constraint. It has been
given priority on the HOME PAGE. There appears to
be no other constraint.
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Overview
For clarity, the overall position is this:
The Borumba Dam is expanded to 2,000,000ML
A two-way pipeline is installed, capacity to be determined.
The joint capacities are therefore 3,545,000ML (2,000,000 + 1,165,000 +
380,000ML)
Dealing with the Expanded Borumba first.
The QWC commissioned hydrology report states:
The Borumba catchment is relatively small (approximately 465 sq km) for
a dam 
required under stage 3 McMah proposal (between 1,500GL and
2,000GL
(2,000.000ML) and as
such is likely to fill and spill due to the influence of large scale
meteorological influences which almost always influence the Brisbane River
catchment at the same time. As such Borumba is likely to be overflowing
generally during those times in which Wivenhoe & Somerset are close to Full
Supply Level."
If this were the case, then there would be
no need for the Traveston or the McMah plan as it means that an additional
2,000,000ML is available every 3.7 years on average.
The reality is that in most cases, the
Borumba expanded to 2,000,000ML would fill to 25% or 500,000ML based on stream
flows. The current yield will increase by 50,000ML to 71,000ML. It mitigates the
flooding in Gympie and allows the Mary River to run free.
This leaves approximately 1,500,000ML spare
capacity.
Use of that capacity without the use of
the flood compartments or change to the operational level.
With this spare capacity, the dam managers
have the ability to keep the wivenhoe/Somerset at 50% or lower without use of
the altered operational requirements or the flood compartments. With the
Wivenhoe at 1,165,000ML plus the Somerset at 380,000ML capacities, the joint
capacity is 1,545,000ML. 50% of this figure is available for pumping without
interference. = 772,500ML. At 40% level, the figure is 927,000ML.
A simple example of the backup facility in
operation is that our current 
dam
levels are at 75%. A reasonable rain depression, covering both catchments, will provide around 50% fill
(1996 minor type, see next photo) and thus has 25% going over the spillway uncontrolled to the detriment
of Moreton Bay. By controlling the dam levels at 50%, all of this flood
water would be retained giving us a further benefit of 386,000ML stored in the
Borumba on such an occasion.
A further illustration would occur if the
dams were full and followed closely by another such as occurred in April 1988
and April 1989. The storage in Borumba would benefit by the volume pumped in the
one year gap.
Photo : CM article on
severe degradation of Moreton Bay by flood waters
The event to which this article refers did not have any water
from the main tributaries being the Upper Brisbane River and the Stanley River.
The rain depression did not come far enough west to fully engage the catchments,
with the minor 16% flow being trapped in the dams.
While the last period without these random
but vital events, gave the impression of a drought, they are not 
uncommon
as their name suggest. Our attention should be turned to harvesting them when
they are prevalent. For example, the short life of the Wivenhoe from 1986 to
2001 saw 6 of these events not only fill the dam from scratch to overflow but
refilled it 4 more times, 3 to overflow. These overflows collectively are in the region
of being well in
excess of 2,000,000ML plus. The starting point is April 1988 and April 1989
starting from
scratch to overflow and approximating 1,500,000ML.
Photo : SEQWater dam level graph of Wivenhoe
overlaid by me with large scale rain events
This method is used until the Borumba is
full. The Wivenhoe/Somerset dams then have no where to store overflow water.
Using this method in the short life of the
Wivenhoe, at February 2001 both dams would have been full and the
"drought" period to 2007 covered with ease without the expensive grid
system.
This method releases the 80,000ML held in
reserve "in case". It can be allocated. Together with the additional
yield of 50,000ML from the Borumba expanded to 2,000,000ML, the collective total
is 130,000ML surpassing the Traveston as
now constituted.
The cost of the dam wall and pumping
requirements on engineering advice of the Government and others is $1.9 billion
with the Traveston stage 1 and 2 but not stage 3 estimated to be $2.6
billion.
Use of the flood compartment and change
to the Operational level
That leaves the speed at which it can occur.
The dam managers and those in control of dam safety should consider any use of the flood
compartment together with the size of pumps used. Change to the operational
level will allow some scope. Dam safety requirement is at EL 74Metres above sea
level and reduces the flood compartment to approximately 1,000,000ML in the
Wivenhoe.
Climate change
If what one reads is correct, that drought
and floods are to be larger, longer and more frequent, the use of additional storage is
essential.
Extensive work on pumping requirements
Extensive work has been done on pumping
volumes and requirements. In the area of engineering and pipeline 
requirements,
I was assisted by an engineer who name appears on the Wivenhoe Dam plaque. He is
retired and prefers and enjoys his anonymity. They are contained within pages 20 to 41 in my alternative
to the Traveston lodged with the Coordinator General under the EIS
(Environmental Impact Statement).
His workings have been on view for two years
without critical comment of any kind.
Refer to FINAL
SOLUTION tab
