End of storm/"wet
season" review
Back to Index
Index 2
General statement
With the figures now confirmed a volume of
water equivalent to 229.5 percent of the capacity flowed over the dam wall in
January 2011. This is in addition to the 55.5 percent that had been released in
October 2010 to December 2010. That total of 285.0
percent was lost without a Megalitre being saved.
It gets worse, 25% of the Wivenhoe has now being
released. This means that during the recent events we are 25% of the Wivenhoe
capacity worse off than when it started.
The dams began filling in 2007 and have been
full since March 2010. This date is well before the La Nina
weather pattern took hold. The
then Deputy Premier Anna Bligh and Minister Hinchcliffe were alerted to this possibility of major losses occurring
within one year on full dams. The alerts were on the 8th January 2008 to Deputy
Premier Bligh and the relevant Minister Sterling Hinchcliffe on 19th March 2009.
It gives me no pleasure to see that I was
right. However it does give me the right to set down an
alternative to these damaging floods. The alternative also gives real meaning to
the words "drought proofing".
There was no reserve supply sufficient to
permit early release of our FSL “drinking water” compartment to avoid
damaging flooding. That water is regained at the back end of the flood.
Flows above and below the dams
According to the Water Resource (Moreton)
Plan 2007 by their official IQQM computer model, the Wivenhoe/Somerset provides 56.5% of all
water that reaches the mouth of the
Brisbane
River. 58.0% below Mt Crosby. 56.5% means that water above the dams was
30% more in volume than below the dams. In this 2011 flood, based on
evidence presented to the Flood Inquiry, it was 65% above the
dams. Again that converts to 85% more in volume than below the dams.
Those who who would have believe that 50% of
flood water comes from below the dams are badly astray. They rely on catchment
areas without the application of rainfall statistics.
The temporary retention of above dam flood
waters clears the way for the
Bremer
River, Lockyer Creek and the
Brisbane
River
itself to run free minimising impact to just 42 percent of the entire flood. In the
case of the 2011 flood it would have been reduced to just 35% of the flood.
This set of numbers following was published by
Engineers GHD in December 2011. It was based on Seqwater Historical Flood Events
Hydrographs. The 1893a flood had only 23.82 percent of the flood below the dams
coming from the main tributaries. Similarly the 2011 flood had only 34.94 per
cent below the dam. I have placed the 1974 above dam total in red and I refer to
my official supporting information. It indicated
the 1974 above dam flood is 2,200,000ML based on official supporting documents.
This reduces the below dam percentage to 42.0 percent.
This brings us to:
Back to Index
Index 3
Flood proofing
Brisbane
From damaging floods to the point of extinction
Mitigating flooding in
Ipswich
and Gympie
In conjunction with a low cost expanded
Borumba Dam to 2,000,000ML for storage and later return to the Wivenhoe/Somerset
system. The cost for the Dam expansion, hydro plant, pipes and pumping equipment
has been costed by engineers at no more than the Tugun Desalination plant.
Click to view the current dam and view from the
ridge
CLICK HERE
to view channel 10's review of this Dam
Flood
volumes
The essential element to flood proofing Brisbane
is to know the inflows that occurred since records were kept from 1890 to 2010.
This is to determine the flood with the largest inflow volume in the
Wivenhoe/Somerset catchments. It is that flood that we must contain.
If we are successful in retaining the
largest recorded flood then 58% of the entire flood is taken out of the equation and
released without harm at the back end of the flood. It is the peak that does the
damage. The 58% is calculated by the IQQM computer model that has the force of
Law in calculating the 66% required for the Ecology.
This permits the
remainder of 42% being the Bremer
River, Lockyer Creek and the Brisbane
River’s own contribution to run free avoiding the backwater
and barrier created by the
Wivenhoe/Somerset outflow.
Reported flood volumes
Seqwater and Brisbane City
Council reports have similar volumes and obviously are reading from the same
gauges.
The reported flood volumes
are:
2011 2,650,000ML ( revision GHD report Dec 2011 : 2,380,396ML)
1974 1,410,000ML ( revision GHD report Dec 2011 : 1,724,841ML)
1893 2,744,000ML ( revision GHD report Dec 2011 : 2,799,234ML)
If accepted, then 1893 at 2,744,000ML is the largest flood that we have to deal with and nothing further
needs to be examined. We will see that this volume is capable of being
withheld with room to spare. ( GHD report of December 2011 records it at
2,799,234ML)
My review of flood volumes can be examined
in the Flood Review tab.
The review suggests to me that a volume of
3,000,000ML will cover all contingencies.
If further examination is sought click FLOOD
VOLUMES
How has the Wivenhoe Dam performed since installation
in 1985?
The floods of note are 1999 and 2011.
The 2011 flood in the Wivenhoe/Somerset had
an "all up" volume of 2,650,000ML which included the minor flood
before the two large "low pressure systems" and the subsequent
draining of the catchments over a period of many days. Before the Dam was built the largest flood is the first flood of
February 1893 at 2,744,000ML. Basically the largest flood,
and its containment can be measured by the 2011 flood. Both of those floods had
saturated catchments.
The 1974 flood according to my calculations
was close to the 2011 volume. However, it would not have exceeded those volumes in the
previous paragraph.
Seqwater website is very good and tells us
that the Wivenhoe held 88.5% above its FSL (drinking water) and the Somerset
89.7%.
This may be easier to read and
comprehend if one clicks on this photo of the calculations.
This converts to a volume of 1,371,885ML,
held in both flood compartments, that was taken out of the flood. That volume is a
little more than one half of the total flood. This is the volume that was
"mitigated" and did not contribute to the flood.
To maintain no more than this volume, it was necessary to
release 968,000ML up to the flood peak. Otherwise the dam would
overflow. That 
release contributed to the flood
and is acknowledged by Seqwater's Dam Safety expert.
There is considerable
disagreement on the timing and release volumes leading up to the peak of the
flood. Nevertheless the dam could not hold this 968,000ML. The graph on the left
shows the forced coordination of the Wivehoe releases with the Bremer River and
Lockyer Creek that produced the damaging height of the flood. Wivenhoe
releases in red and Bremer/Lockyer in blue. Space every 6 hours from 5th January
2011
To fully contain the
entire flood, further containment of this 968,000ML
plus the run off into the dams after the peak of 310,115ML has to be developed.
This totals 1,298,115ML or close to the volume of the FSL of the Wivenhoe at 1,165,000ML.
With those maximum percentages in the flood
compartments, the Engineers maintained a safety level below the capacities of
the flood compartments.
The flood compartments, on paper, total 1,974,000ML. The
volume held was 1,371,855ML some 575,145ML short of capacity. There is solid
argument that the location of the plugs (called fuse plugs) that ensure dam
safety have reduced the published volumes of the flood compartments.
The calculations of the 1999 flood is also
attached. That event was on normal catchments and spare capacity in the FSL
compartments. It was handled with ease. A situation unlikely in major floods.
With the Wivenhoe/Somerset contribution to
the flood withheld, we now turn our attention to the balance of the flood.
According to the Water Resource (Moreton) Plan 2007 that should be around 42% of
the entire flood.
Review of Bremer River and Lockyer Creek
The impact of the releases from the Wivenhoe Somerset are
clearly seen from these Seqwater produced hydrographs. I have added a red line
at the point where rain ceased.
Photos left to right: Dam releases from the Wivenhoe;
Hydrographs Savages Crossing and Bremer River; Hydrographs Moggill and Brisbane
City; My overlay of Seqwater graph defining the minor and major floods.
Combination of the Bremer/Lockyer/major releases Wivenhoe on the right. Wivenhoe
in red and Lockyer/Bremer in blue. Timing every 6 hours from 5th January 2011
First of all the later releases clearly held up the
flood after the peak at all points. This has little relevance to the peak of the
flood but is an indicator of the " barrier" created at the
Bremer River mouth as mentioned in the Ipswich City Council submission.
The second point is that according to the three major
hydrology firms engaged by the Insurance Council of Australia, the major release
from the Wivenhoe created a rise of 7 metres at One Mile Bridge. The graph of
the releases from the Wivenhoe was constructed by me from the Seqwater flood
submission.
One Mile Bridge on the Bremer River is 47 Klm from the Bremer
River mouth.
This, of course, would have a significant bearing on the
flooding in Ipswich from the One Mile Bridge to the Bremer River mouth.
Those Hydrologists ignored altogether the minor flood which
also occurred in the Bremer prior to the major flood. This supports my
observation that a minor and major flood occurred.
The above is all related to the flood of 2011. My
correspondents from Ipswich assure me that the flood of 1974 had a very
different result.
This discussion is continued under the Ipswich Tab. With the
Wivenhoe/Somerset out of play.
Logic of flood mitigation in Brisbane
* The flood volumes from the Wivenhoe/Somerset of 2011 and
1893, according to Seqwater, are almost the same.
* They are the largest floods experienced.
* There is evidence in rainfall data in Ipswich that any flood
of 1893 did not exceed the flood of 1974 or was at least equal to any of them.
* The hydrologists now agree that the major release of Wivenhoe
water was the major cause of damage in Ipswich and Brisbane.
* Overall a volume equivalent to almost the capacity of the
Wivenhoe was released from that dam, before the flood peak, to mingle with the
Bremer and Lockyer and other tributaries of the Brisbane River.
* With the Wivenhoe/Somerset taken out of play, therefore
there is minimal damage, if any, in Brisbane. This is our objective.
To follow this subject and further calculations, click on this tab IPSWICH
Flood mitigation in Gympie
The Borumba Dam stands on Yabba Creek. It is researched
throughout this website as it was the subject of our submission to replace the
proposed Traveston dam.
My calculations for the 1999 flood is that Yabba Creek
provided 34.8% of the total flow through Gympie. To review click on Hydrology
Mary Valley
As we will see later on this page, the major part of this
proposal is the expansion of that dam from the current 45,000ML to 2,000,000ML.
It will provide ample opportunity to mitigate flooding in Gympie to the extent
of 34.8% of the flood.
Yabba Creek in full flood 2011(Gympie times photo)
1841 and prior
The
Queensland Parliament at the time of the 1893 floods recorded that the 1841
flood was 7 inches (.2 of a metre) above the 1893(1) flood. The archaeological
find at Indooroopilly, being up river, may well come in under the 1893(1) flood
because up river heights are much higher.
******
For those who appreciate an easier read than the language of
this accountant, click on Trevor
Herse for his "Water woes result from misunderstanding and blunders". Trevor and I,
together with Ron McMah, grazier, of Imbil, have worked together on this project since 2006. We
represent no one and have in mind only the interests of citizens of South East
Qld.
*********
The containment of a flood to 3,000,000ML is the target.
Back
to Index
Index
4
How to deal with major floods
Saturation rain
Saturation rain
preceded all of the floods under review. It is certain that the FSL “drinking
water” compartments were, or would have been, full.
Flood
compartments available
The official flood
compartment volumes are Wivenhoe 1,450,000ML and 
Somerset 524,000ML for a total
of 1,974,000. This represents 170 % as a percentage of the Wivenhoe capacity for
easy measurement. Mr Ian Chalmers, the chief supervising engineer in the
construction of the Wivenhoe has suggested in his submission the relocation of
the fuse plugs to maintain these volumes.
FSL or commonly
known as “drinking water” compartments
These compartments
are not normally reduced as the metrological events that fill them come on
average every 3.7 years. Their fill usually represents 95% of the water in the dams.
Click to
view official dam statistics Wivenhoe/Somerset
These compartments
measure Wivenhoe 1,165,000ML and Somerset 380,000ML. The total is 1,545,000ML.
This total represents 132 per cent of the Wivenhoe capacity.
Total capacity
to retain floods if all the compartments are available.
The flood
compartments total 1,974,000ML or 170 %. The FSL or “drinking water”
compartments total 1,545,000ML or 132%. The combination is 3,519,000ML or 302%.
The largest flood
of 3,000,000ML represents 258% of the Wivenhoe Dam FSL. This can be held by the
flood compartments of 1,974,000 plus the FSL of the wivenhoe at 1,165,000ML
which totals 3,139,000ML or 270% of the Wivenhoe capacity. The Somerset FSL is
not needed.
How does this work?
There is always
the quandary “will flooding rains come or will they not?”
Our weather
forecaster are becoming more reliable in predicting 
major
events in our weather patterns. This article written by Brian Williams of the
Courier appeared in their paper on the 1st October 2010. He points out that all
dams are full and the weather patterns that produce flooding rains were
entrenched. I have observed that throughout the flood period Brian Williams was
accurate in reporting all events of the flood and that his reports could be
relied upon.
It is necessary to
early release the FSL “drinking water” compartments with the recent Bligh/Robertson
decision in progress (28/02/11). As events unfold and the flood is reasonably
certain, further releases from these compartments should be made at the front of
the flood thus allowing the Bremer River, Lockyer Creek and the Brisbane River
to run free.
This avoids the
backwater and congestion of the Wivenhoe/Somerset releases. The extent of the early
release will depend on the Meteorologists and their telemetry equipment.
It is a considered
gamble on weather predictions.
If the rains do
not come then you lose heavily as you have released your precious drinking water
with almost no chance of recovery until the next “uncommon event”.
If the flooding
rains come, you win well. Not only have you assisted in reducing damaging flood
levels by taking the water from the Wivenhoe/Somerset out of play but most, if not all of the water
released, can be recovered at the back of the flood.
How do you cover your gamble if it does not pay off?
Example of a
feeble attempt but a step in the right direction
Minister Robertson supported by Premier
Bligh made the decision to release 25% of the capacity of the Wivenhoe dam’s
“drinking water”. The backup explained by the Premier was the Wyaralong Dam
which represents 6% of the Wivenhoe capacity.
The additional backup is the Tugun
desalination plant and the recycled water that a lot of people dislike. The
Tugun plant takes 34 years to fill the Wivenhoe/Somerset dams from scratch if we
do not take water out. The recycled water takes a bit longer.
The consequence is that we will be out of
water in 3 to 4 years 
if an “uncommon event” does not appear in the normal
average of 3.7 years. It is a very high price to pay for such a small gamble on
the weather. The Wivenhoe dam level chart with red lines shows that we rely
almost entirely on "uncommon events" to refill our dams.
Click to view "uncommon
events" in the Wivenhoe dam 1988-2007
When one exceeded the average in 2001-2007
it was misrepresented as a "drought".
The
obvious major reserve supply – Borumba Dam.
The reserve supply needs to be in place
permanently. The decision making process on release will depend on the
concentration of the rain and will determine how much is
released without the flood event happening.
It is most likely that no more than 60% of
the Wivenhoe capacity would be released without the flood event occurring. This
volume is 700,000ML. It is stored for later return if needed by the
Wivenhoe/Somerset system.
A proposal to maintain a significant
percentage permanently in the Borumba Dam and have a corresponding permanent
reduction of the FSL- "our drinking water" has merit. It will give the
dam operators more flexibility to early release.
This is well within the storage capacity of
the Borumba Dam expanded to 2,000,000ML. This capacity is larger than the
Wivenhoe/Somerset dams total capacity.
A brief resume of that dam follows.
The dam already exists
It is a hard rock natural amphitheatre ideal
for minimal evaporation.
Has its own small but efficient catchment.
We own all the land and no disruption to people of the Mary
Valley
.
It is 60klm over the hill in the Mary Valley.
The
Queensland
Water Commission has expansion to 350,000ML in the SEQ Water Strategy
Engineers say it can be expanded to 2,000,000ML or larger than the
Wivenhoe/Somerset dams.
1,500,000 for storage and 500,000ML for the Mary
Valley
Partial flooding of Gympie avoided. Yabba Creek on which it stands provides 34%
of flood water to the Mary River.
Regeneration
of the Mary Valley from its damaged state which resulted from the scrapping of
the Traveston Dam proposal.
The costing by engineers of the dam wall is $1.4 billion including the Hydro plant. Engineering view is that the pipes and
pumping equipment are in the region of $0.5 billion. Deduct the QWC proposed dam
of 350,000ML and we arrive at a cost about the same as the Tugun Desalination
plant.
This compares with the Insurance Council of Australia assessment in 2007 that a
1974 type flood "represents a potential insurance loss of $1.8 billion and a
simply staggering loss for both Government and the affected community"
Back to Index
Index 5
Drought
proofing SEQ.
Sub
Index
1.
Wolffdene Dam cancellation assurances not met.
2. Drought in the catchments. Conclusive proof
that it did not exist.
3. Different approach to "drought
proofing".
Sub-index
1
1.The
Wolffdene Dam cancellation assurances not met
Extract
from the Ministerial Statement by Hon. E. D. Casey (Mackay-Minister for Primary
Industries) ALP member. Statement was made on the 1st March 1990 setting
out the reason for the cancellation of the Wolffdene Dam.
Click
for Full statement
He
had this to say on future water supplies: "On present
indications, an additional source of supply is unlikely to be required before
the year 2010. However, it is recognised that the actual timing will
depend very much on future population growth in the South East Urban corridors."
"Adequate
time is available to properly plan to meet those water needs. The people of
Brisbane and surrounding areas can be assured that the Goss Government (ALP) has
such planning well in hand."
Obviously,
this assurance made on behalf of the Government, was not met! Two years
later in 1992 it was clear that normal summer rainfall was inadequate for our
needs and that the Wivenhoe/Somerset dams were reliant on random "low
pressure systems" to fill them as explained in the leader to this
page.
Much
larger dam space is needed to control them for the Ecology and our use. This
website recommends enlargement of the Borumba Dam and connection to the
Wivenhoe/Somerset Dams.
Partial
correction of the oversight has unnecessarily cost us billions of dollars so
far. It is fair to say that a backup water supply in the Wolfdene Dam would have
permitted prior reduction in our water supply to counter the 2011 flood thus
reducing the damage to our citizens of SEQ.
The
2011 flood was true to form. The saturation rains of "low pressure
systems" had filled our dams by March 2010. This is well before the weather
pattern of two major "low pressure systems" had set in and the
Wolffdene Dam, like the Wivenhoe and Somerset dams, would have been full.
The
"drought" excuse was used for non-compliance to the assurance which leads to:-
Sub-index
2
2. Conclusive proof that there was no
hydrological drought in the
catchments
Former Premier Beattie, Premier Bligh and now Minister
Robertson claim that South East Queensland is "drought proofed".
This section provides a different view suggesting that this
phrase is misused to justify an expense in the region of $9 billion according to
Mr Kim Wood CEO of Allconnex water (Refer WATER COST). An
expensive cost brought about by those who should have displayed more diligence in
the control of our water supplies.
This phrase "drought proofing" belongs with the "worst drought in 100
years" when related to the low levels of water in our dams. The evidence
presented in this section is
that while there was drought in most parts of the State, there was no drought in the
catchments.
I have overlaid the Wivenhoe dam level graph with
"uncommon events" as described by Mr Drury of SEQWater in the header
above. The dam decline from each refill is marked in red.
That decline was obvious soon after the Wolffdene dam was 
cancelled
for political reason in 1989. By 1992 it was obvious that normal "summer
rain" was inadequate for our needs and we relied heavily on these
"uncommon events". A longer period beyond their 3.7 year average
would, and did, bring us grief with no provision by those in charge.
Click to view "uncommon events" in the
Wivenhoe Dam 1988-2007
A convenient statistical aberration of a "decile"
map was used to avoid scrutiny. The "decile" map was showing
"lowest on record" for the rainfall, while the corresponding "percentage" map
read 80% of the long term average. This can be viewed at DECISION
MAKERS
The Bureau of Meteorology rainfall stations in the catchments
were at the same time showing 99.1% for the Wivenhoe and 91.4% for the Somerset
for summer rainfall December to March. Viewed at the bottom of the RAINFALL DEFICIENCY
page.
A further example of timing of "uncommon events" is
this comparison. With a time period of 3 years and 9 months, the February 1992
to 
November
1995 was right on average of 3.7 years. The dam level dropped from
100% to 44.3%. Bureau of Meteorology maps show that there was no drought in that
period with rainfall 90% to 100% of the long term average.
Click to view comparison
Comparing the same 3 years and 9 months period of the
"drought" February 2001 to November 2004, the level dropped from 100%
to 53.4%. We held
9.1% more in reserve than in a
period with
no drought.
It is now certain that there was no drought in the catchments 
for the 2001 to 2007 period. It was simply the operation of low pressure
systems. The 2001/07 period was an object lesson in how the 3.7 average works.
Most are below that average so the few that are above can be quite
lengthy.
More recently there have been attempts to extend the
"drought" to years 2008 and 2009. I have forwarded to the Qld Flood
Inquiry the Bureau of Meteorology Rainfall graphs for those years which show the
rainfall in the catchments 125% of the long term average.
Premier Bligh
and Minister Hinchcliffe were warned of this mathematical certainty that Low
Pressure Systems would return and overfill our dams.. Click to move to these
warnings.
The importance of this is that forward planning by the
Queensland Water Commission in its strategy for SEQ is related to preparing for a
"drought".
Our main water supply is low pressure systems. They are random and can occur at
any time of the year and for much longer than any "drought". They
are oblivious to the conditions prevailing at the time.
Sub-index
3
3. It requires a different approach to drought proofing.
It requires a different approach from the present stance of
"drought proofing" SEQ.
The current claim of "drought proofing SEQ" is in
the same category as "worst drought in 100 years". They both do not
stand up to scrutiny by a long way.
The current "drought proofing" relies on the
Desalination plant at Tugun which can produce 45,000ML a year. The recycled
water produces almost the same based on Premier Bligh's most recent comments.
Seqwater spokesman advised that the current release of 25% was
one year's "drinking water". That is 291,000ML a year. The official "allocations" made from the Wivenhoe/Somerset dams are 286,000ML so
the spokesman is near the mark. Deduct the
90,000ML from Desalination and recycled water and we have a shortfall of
200,000ML each year for the length of the "drought".
On
the other hand the two-way pumps between the Wivenhoe and Borumba Dams can have transfer rates of up to 4,000ML per day compared to using the expanded Borumba Dam
storage of the Wivenhoe/Somerset water for later return
The
objective is to maintain the wivenhoe/Somerset dams above 40% level before recycled
water is introduced. This is on 
the basis of a yield of 373,000ML which is
considerably higher than the 286,000ML presently allocated.
Click to view the simulated levels in the Wivenhoe
Dam for the last 100 years
On the past history of 120 years, it would
require no more than 500,000ML to be retrieved from the Borumba Dam for a period of three to four years at the
bottom of the drought cycle. It would have happened only twice in those 120 years.
Pumping
to the expanded Borumba Dam would be undertaken when dam levels are high
creating space in the Wivenhoe/Somerset dams to capture as much as half of the
55.5 per cent overflow created in October/December 2010.
Engineers
have costed the dam wall to $1,397 million. It includes a hydro plant. Add to
that an engineers estimate for the pipes and pumps of $500 million and deduct
the unknown cost of the Water Commission dam wall to 350,000ML and we have a
cost equivalent of one desalination plant of the Tugun size.
Compared
to the high cost desalination, the operating costs are minimal. The spare
capacity can be filled over a number of years with little draw down required.
The Hydro Plant will be operating full time as water is already used by the
Gympie and district people.
The
proposed three desalination plants will not be required.
Back
to Index
Index
6
The
WATER SHARE Tab is recommended reading to this
proposal. It is examined on the "Water Share" Page in this website.
In
essence the well credential Technical Advisory Panel who examined this
allocation recommend that 66% of all water that passes through the
Wivenhoe/Somerset dams must reach the Brisbane River mouth. It is now the law
(March 2007). I
have no problem with that percentage.
However
in the writing of the Act the Technical Advisory Panel's advice, that large
floods should not be included when calculating the permanent base on which the
66% is calculated, was ignored.
The
base on which it was calculated included the four major floods of 1890, 1893
(two) and 1974. The result is that when applied against the 113 years 1894 to
2006 (excluding 1974) the percentage rises to 78%.
It cannot be disputed, it is straight forward simple arithmetic. Readers will have no difficulty understanding this when they view the official
chart of inflows into the dams for 1890 to 2000 on the "water share" page.
The
effective result is that a volume of water equivalent to the proposed, and now
cancelled, Traveston dam is redirected from our consumption to the ecology every
year. That is 160,000 ML.
In
today's terms the massive infrastructure of the Wivenhoe/Somerset Dams, which
cost $550 million, would equate to a cost more than $1 billion. It has been reduced from
SEQWater's public records of 446,950ML annual yield to allocations of just
286,000ML by the introduction of this Law in March 2007. The fundamental
arithmetic flaws need to be corrected. (A yield is the volume that a dam can
produce in a year without running dry. It is calculated in this case over 111
years).
While
this fundamental arithmetic flaw exists, the Water Strategy for South East
Queensland is severely affected and will involve major costs on the drawing
board that are not necessary.
Back
to Index
--------------------------------------------
*******************
Advice offered to Deputy
Premier Bligh and the relevant Minister Hinchcliffe
I offered the following advice to these Ministers. It was
not prophetic. It was not climate change. It was straightforward mathematics.
The following is an
extract from my letter to Hon. Mr S. Hinchcliffe, the then Minister for
Infrastructure and Planning, sent on the 23rd April 2009 three weeks before the
May 2009 "uncommon event". The alert to the Minister followed a meeting with him in January
2009. The meeting had the support of the senior policy advisor to the PM (Kevin
Rudd).
"The way I see it, the difficulty for you and all who support the
Traveston is that on the mathematical certainty of the return of the
“uncommon events” the dams will overflow. That by itself should have people
in SEQ questioning if those in charge understand what they are doing.
Historically there has been 11 “uncommon events” within 1 year of each other
(April 1988 & April 1989 for example) and there will be a tremendous loss of
water over spillways with full dams. In my view justification of the Traveston
will be under severe stress and storage in the Borumba Dam together with its
additional yield, vindicated."
The following is an extract from my letter
to Premier Anna Bligh on the 18th January
2008 when dealing with the Traveston Dam project.
“Uncommon
events” proved to be the lifeblood of SEQ from 1986 to 2001, filling the Dams
to overflow four times and covering expanding population requirements with ease.
Although the official records disclose there was
an absence of “uncommon events” between 1974 and 1988, there were five such
events in the short life of the Wivenhoe Dam (1988 to 1999 and a topup in
Feb.2001). A high proportion of those events flowed over the spillway
and were lost because of lack of storage.
They will return. When the uncommon events return, we will not
have sufficient storage space to retain the surplus water from
them, except for the first one. Most of that water from uncommon events
would now be lost whereas they were our main provider for the 16 years to 2001.
End
quote
The Traveston is now historical but the alert to Minister
Hinchcliffe and the use of the Borumba Dam as its replacement is still valid.
The alert to Premier Anna Bligh was on the same subject. This
procedure eliminates the planned three desalination plants and avoids most of the
construction and ongoing costs. Further reading Borumba
Dam Proposal and Borumba Dam Appendix
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hodgkin@powerup.com.au
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February 2007. Output from the
Government IQQM computer model, covering the 111 years 1890 to 2000, has proven Mr Drury correct. In essence 300mm of
rain in the catchments in a few days is a flood and, in the right circumstances,
can fill the dams from scratch. On the other hand 3 months of 100mm a month is a
comparative
trickle. These facts can be buried in official overall rainfall statistics the
use of which in dam performance can and did throw up statistical aberrations.
records from 1841 reveal that
they occur on average every 3.7 years with most below that average. Therefore
those above can extend well above that average such as the recent period of 2001
to 2007.
Mr Drury also provided dam level charts
which were not published by the Courier Mail. They provided clear evidence of
the importance of "uncommon events" and the inability of the
"Summer wet season" to provide sufficient water from as far back as
1992. 
Extract
