UPDATES : November 2008
Official statistics of this website indicate that in excess of
20,000 separate computers have accessed this site not all being by this
"home" page. Over 50% have added it to their "favourites".
It would have become clear to the readers that the
Wivenhoe/Somerset System has been living with the prospect
of Dam Failure since 1992. Summer rainfall was clearly inadequate
from that year onwards (see dam level graph below). " Uncommon events" not only
filled our Dams in 1988 and 1989 causing the cancellation of the Wolfdene Dam,
construction of which was well underway, but refilled it a further 4 times to February 2001 when they went
on their quite natural walkabout. This led us to believe that we were experiencing
"the worst drought in 100 years". It was not. 48 years of the 20th
Century in 6 year lots had the same result. The Summer Rainfall for the last 7 years since the
dams were last full compared to the long term average were 99.1% in the
Wivenhoe and 91.4% in the Somerset. We just missed two uncommon events. August
2007 brushed the coast and May 2008 stayed out to sea. January 2008 Monsoon devastated
Central Qld.
This dam level graph provided by SEQWater and overlaid by me with
"uncommon events" tells the story of the Wivenhoe/Somerset system from
1986 (commissioned) to date. One does not have to be a Hydrologist to understand
the previous paragraph.
The answer lies in sufficient storage to control these
events (See actual events
and average yearly gaps attached).
Stage 2 of the Traveston proposal, being the Borumba Dam expansion, is the
answer amended to a Dam twice the size of the Wivenhoe which the Engineers agree is possible
and even larger than that if required. The enlarged Borumba Dam would also
retain its considerable overflow in times of "uncommon events".
Connecting the Wivenhoe/Somerset to the nearby (60klm) expanded Borumba dam and
completing the grid to the Northern Interconnector would provide storage space
for all dams in SEQ connected to the Grid System and allow the Mary River to run
free. From my observations, all parties would be satisfied with this result
although saving the Mary Valley was not a primary intention. The intention was
vast storage facilities to which I was directed by Mr Ron McMah.
The overall additional water available in the
Wivenhoe/Somerset and Borumba Dam is a minimum 171,000ML as compared with the Traveston all
three stages being 150,000ML. The cost is estimated to be $1.9 billion as compared
to the Traveston all three stages of $3.1 billion.
CORRESPONDENCE : Readers
may find correspondence with
decision makers interesting. They are located under the Correspondence
tab
End of updates
What this web-site is all about.
It is acknowledged at the outset that
various parts of
Queensland
and Australia
are, or have been, suffering the ravages of drought conditions. In Queensland in
January/February of 2008, actions of Monsoons have caused a great deal of the State to be
flood declared. These events assist us in understanding the operations of our
Dams systems.
This web-site deals specifically with the catchment areas of the
Wivenhoe, Somerset
and the proposed Traveston site. It identifies the true
root cause of the recent low water levels within the Wivenhoe and
Somerset Dams and proposes a potential long-term solution that is simple,
low cost and effective.
SHORT SUMMARY
Primarily for those who require a quick overview. It
will also give a sense of direction of the web-site. If I have been concise
enough, reading of the first 20 paragraphs should be sufficient for the reader
to gain an understanding and perhaps form a view.
"THE WORST DROUGHT IN 100 YEARS"
In late 2005 and into most of 2006 like all of the people of
South East Queensland I was convinced that we were in the grip of "the
worst drought in 100 years" with variations added such as " but only
in the catchments", "its official, the lowest on record". The
Television commercials and graphic pictures, principally of the Wivenhoe, drove
the message home that a drought was in progress and it was like no other.
Is it a drought?
Although we felt the effects of a drought, things were not
what they seemed to be.
A look at the Bureau of Meteorology rainfall for the six years to 2006 tells us
that the water producing Summer months December to March have been quite normal
compared to the long term averages. This is continuing into the 2007/08 period
with Dam levels in the region of 38 percent in April 2008, a rise of around 20%.
It seems that the source of that
term was a map from the Bureau of Meteorology
(BOM) called a “decile map” which showed the rainfall received in our dams
for 
the 6 years to
2006 was at the lowest level of the historic averages. The
actual rainfall for that period was close to 80 percent of long term average and
that means that the rainfall has never been less
than close to 80% since records were kept. To
me this does not paint the true picture of our rainfall in the past six years
nor does it help in making decisions about how we tackle the problem now.
I think the map
misses a key fact. The water in our Dams comes from two
sources.
The First is normal
rainfall that we see every year – most of it coming from the high impact rain
that falls in the four short Summer
months with little inflow from the remaining months. We have viewed in the above
chart that the deficiency of 20% in the six years to 2006 was all in the non-summer months
which rarely create inflow.
The
Second and most significant source of our water comes
from unseasonal deluges – typically associated with Monsoons, Cyclones or large Low pressure
systems. They do 
not occur every year but, on average, every twelve years in tight groups of two
or three years. When they do come they generally cover the whole of South East
Queensland and have the capacity to fill and overflow our dams. They can
occur at any time during the year.
As
an example, in a few days the dams can take in the water of 9 years of
normal average rainfall. The Television pictures of the Fairburn Dam in Central
Qld of January 2008 remind us of the Monsoon's powerful ability to fill large
Dams in a few days. SEQWater is to the point and calls them “uncommon
events”.
The chart above has been compiled from
Bureau of Metrology rainfall data. It reflects the rainfall required by SEQWater
to produce an uncommon event. The Bureau's flood information chart, on the
right, has permitted me to form an opinion that the rainfall requirements are
accurate and the past uncommon events are clear. Notice that flooding below the
dams since 1986 represents water not able to be held by the dams.
The
reality to me is that, as our population increased, we
have come to rely more and more on the store of water from these large deluges (
uncommon events ) – the regular 
summer rains have long since been insufficient
to meet the needs of the region. They provide 11% annually to our dam capacities
and the population requirements are 22% under business as usual conditions. The
draw down from full dams in times where these deluges are absent is therefore
11% which is 9 years supply. In the 6 years to 2006 we have seen that happen. The
dams were full in 2001 and were around 18% capacity in late 2007 rising to around
38
percent in April 2008 with above average Summer rain for 2007/08.
Dam levels and uncommon
events in the life of the Wivenhoe : In the short life
of the Wivenhoe commencing in 1986, the Wivenhoe/Somerset system received
5 out of the 17 
uncommon events of the Twentieth Century. They occurred
between 1988 and 2001. This graph supplied by SEQWater shows the constant fill
to overflow and draw-down of our requirements until the next uncommon
event. The uncommon events finally ceased in 2001 with the draw-down in
requirements continuing.
The previous uncommon event was the 1974 flood. Under current
conditions, the surplus water would have lasted 9 years to 1983 leaving a gap of
5 years to 1988.
The Twentieth Century type gaps that normal summer rains have to bridge are
listed in the the previous charts. They are :-
14
years. 1974 to 1988
10 years. 1956 to 1967
27 years. 1928 to 1955 with one in 1950 intervening
19 years. 1908 to 1927
10 years. 1898 to 1908
The Bureau of Meteorology Flood information
chart above shows that large gaps were not evident in the last 60 years of the
19th Century. Natural climate change was evident in the first half of the 20th
Century. A return of an 1841 or 1893 flood compared with the 1974 flood would
make for very interesting calculations.
What does this
mean?
The good news
is that the grid
system excluding the Traveston Dam will go close
to providing sufficient water to make up for the absence of uncommon events. The
bad news is that it will not
provide relief for a genuine drought and does not provide for any increase in
population nor does it provide for a refill of the dams.
The whole system awaits an uncommon event to
take the pressure right off and provide insurance against a real drought. There
is no requirement to draw against it at least for some time as the Grid
and Summer rains take care of our unrestricted needs.
The longest gap between uncommon events in the twentieth century was 22
years with the last gap from 1974 to 1988 being 14 years. We are 7 years into a
gap, from 2001 to 2008. The filling of the Hinze Dam in January/February of 2008 has
provided some relief. In addition, the current above average fill in the
Wivenhoe/Somerset of around 20% to 38% of capacity from above average summer
rains will provide more than sufficient time to bring the grid system on-line in
year 2008.
What the Queensland Water Commission
believes the situation to be.
In their "Water report" published in the
Sunday Mail on the 20th April 2008, the second paragraph leads off with
"Smart water use is now a way of life - even when
this drought breaks".
To me, the known facts are that we have
survived totally on Summer Rainfall December to March since February 2001. The
Dams were full at that date and have been reduced to the current April 2008
level of 38%, a period a little over 7 years. You will see that the Summer
rainfall overall has been quite average. The first 3 to 4 years were with unrestricted
use with no apparent concern by those in charge of the developing situation.
It follows that the "Uncommon
events" are included in the Water Commission's definition of a "drought".
It is clear from the above information on "Uncommon events" that their
provision to our water supply, while very large, is completely unreliable in
timing. The
last gap, 1974 to 1988 was for 14 years. On that basis, it is my view that the Water Commission
type "drought"
may not break until year 2015.
The answer lies in the management of the water
from "Uncommon events".
Understanding the Dams and their catchments
It is useful at this point to gain an understanding of the
operations of the Wivenhoe and Somerset Dams and their catchments. In my view, a
comparison with the Traveston proposal can then be measured.
The Somerset and Wivenhoe Dams are placed at the junction of
two Rivers. The Stanley River, which is closest to the coast, and the Upper
Brisbane River. The Stanley River feeds 
into the Somerset Dam as a temporary
measure which then releases all its water into the main storage Dam, the
Wivenhoe. The Upper Brisbane River feeds directly into the Wivenhoe at that
junction and the Wivenhoe releases, when required, into the lower reaches of the Brisbane River.
The catchment of the Stanley
River is 1/3 the size of the spread out
catchment
of the Brisbane River but three times more efficient. The Stanley River receives
30.8% more rainfall which converts to a much higher inflow figure ranging beyond
50% additional water. Most of this water is stored in the Wivenhoe which also
has a flood mitigation compartment larger than the normal water supply.
The Bureau of Meteorology has
confirmed that in three year periods, the catchments have never received less
than close to 80% of the long term average.
The Stanley River
catchment, which feeds
into the Somerset Dam, is by far our largest water supply source. In
the most recent rainfall from the 4th January 2008 to the 12th February 2008,
the Stanley River provided a flow of 147,595ML into the Somerset Dam. The Upper
Brisbane River provided a flow of 78,199ML into the Wivenhoe Dam (SEQWater
website). There were minimal releases to that point. That amounts to 65% of our
water supply coming from the Stanley River which is about equal to my
calculations in this website.
Traveston Dam proposal
Our Leaders look to the future with the Traveston Dam. The
Traveston dam catchment rainfall has
almost exactly the same pattern and timing as the rainfall in the Wivenhoe and
Somerset Dams. It is not surprising as they
are adjacent. Its Supporters say that it stands up to Hydrological modelling.
The most recent and rare August 2007 low pressure system over the Sunshine Coast
is quite a minor player in size and location.
It is my view that the Traveston Dam
will eventually be in the same position
and at the same time as the Wivenhoe and
Somerset
in attempting to bridge the gaps between uncommon events.
The solution.
Wivenhoe/Somerset system
In 1974 and in the recent period of 1988 to
2001, a great deal of water from the catchments found its way into
Moreton
Bay. In addition the Wivenhoe Dam was filled from scratch in 1986. Our historic
experience is that unless we can harness the surplus water from these deluges,
we are not likely to see a long term solution to our water supply problem.
Government appointed Engineers quantify this
water as 80,000ML annualised over a 110 year period. Of course it occurs
in large bursts.
The people of the
Mary
Valley
have pointed out that the Borumba
Dam expanded to 2 million ML is an ideal 
storage
dam. The provision of a suitable dam wall would increase its capacity to
twice the size of the Wivenhoe dam. It
has been reviewed on the basis of a normal dam and discarded. My review of the
reports used did not disclose any evidence that it has been seriously considered as a
storage dam for the surplus waters that would normally go over the spillways of the
Wivenhoe/Somerset system and the Borumba Dam during these uncommon events. This
most likely occurred because, in my view, the Consultants were not provided with
a suitable "Terms of Reference". My
views on the reports used are expressed in pages 4 to 8 of the Environmental
impact study (EIS) in this website.
This surplus water is now out of our control through lack of storage capacity. The draw down from Borumba would
occur when these large gaps between uncommon events are encountered. As we are
replacing the water taken from the Wivenhoe, the Wivenhoe/Somerset system
dynamics are unchanged and, as you will see elsewhere in this website, vastly improved for this stressed
system.
Borumba Dam
As explained, the Engineers advise that
this small dam can be expanded to 2 million ML and beyond if required. This is
almost twice the size of the Wivenhoe/Somerset system. The Borumba Dam is just over the hill from the Wivenhoe Somerset
system (60klm). With the very 
large excess flood holding capacities of the Wivenhoe Somerset system, the
pumping time required would be adequate. The flood holding capacities of
the two dams is 1,974,000ML, almost twice the size of the Wivenhoe Dam.
In times of deluge the Borumba Dam is no
slouch with a rock hard catchment. In 1999 a volume of water equivalent to one
half of
Sydney
Harbour
went over the dam wall in a single day. The event lasted 5 days.
The official statistics confirm that
91,000ML flowed over the Borumba Dam wall for its entire life since 1964 on
an annualised basis. It does not happen annually as it is the product of
"uncommon events".
Storage space for uncommon events
With the introduction of the Grid System to
replace uncommon events, there will be little requirement to draw on the dams.
After the dams are replenished by the first one, the rest will largely go over
the spillway with possible major flooding.
The Traveston proposal locks up permanently
the Borumba Dam to 40,000ML annually ( it is part of the 150,000ML of the
proposed dam) and the Dam footings will block the creation of the 2 million ML plus Borumba storage dam.
Calculations reveal in this website that
125,000ML, on an annualised basis, can be stored in the expanded Borumba if the
Traveston proposal does not proceed.
THE SOLUTION SUMMARY
The mathematics are :-
My proposal
