Update on October 2010 rainfall event (5th
October 2010) At bottom of
this page
Update on late February/early March rainfall and inflow
(8th March 2010)
The Late February/Early March rainfall of 2010 saw our dams
increase from 69% to 97% as 
at the 13th March 2010. A click on
this photo will give one a comparison of the rainfall at flood time for all
large events in the short life of the Wivenhoe since its commissioning in 1986.
Five rainfall stations that were in existence for the whole of the period were
used for consistency.
Photo : Rainfall comparison
The Department of Environment and resource Management (DERM)
have been good enough to provide me with the inflows
that would have occurred if the dams and other 
infrastructure were not present.
This provides us with sufficient information to judge the inflow from the recent
February/March 2010 event which inundated Western Queensland. Our catchments
benefitted from the same weather system. Comparison is made with all major
events in the short life of the Wivenhoe.
Photo : Inflow comparisons
All
of these events overflowed the dams with the exception of 1996.
With no large events to fill our dams from 2001 to 2007, four
near-misses rescued us from 2007 to 2009 the largest being May 2009 which failed
to come west enough to cover the Wivenhoe catchment. Cyclone Hamish missed us
altogether.
Photo : Wivenhoe dam level graph
These large scale events are random with an an average of 3.7
years from 1841. Most 
occur
below 3.7 years and as a consequence, a small number exceed this average by a
wide margin. Their absence was misread as a drought. There was no provision for their extended
absence although it was evident in the dam level graph, even to the unpractised
eye, that eventually extreme difficulty would be experienced in a
protracted absence.
Photo : Frequency of "uncommon events".
The evidence is now conclusive that Large Scale Events are our main water supply.
We have all just witnessed a 30% fill from the recent event. While it was a
major event out west it was a comparatively minor event in our catchments as
evidenced by the rainfall comparison. The short history of the Wivenhoe shows us
that 5 out of 6 overflowed the dam. Our dams are too small to accommodate these inflows and
control our water supply for the benefit of our ecology and residents of South
East Qld. We have the solution and it follows below.
October 2010 "uncommon event"
This 5 day event was unusual in that it did not have a low
pressure system to support it. Never-the-less it provided sufficient rainfall to
overflow our rivers and creeks causing some residents harm.
The release of water from all dams was spectacular.
Alert to Minister Hinchcliffe
The following is an
extract from my letter to Hon. Mr S. Hinchliffe, the then Minister for
Infrastructure and Planning, sent on the 23rd April 2009 three weeks before the
May 2009 "uncommon event" mentioned above. 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 Traveston battle was
lost by the Government but the use of the Borumba Dam expanded to 2,000,000ML
for storage, or almost twice the size of the Wivenhoe, is still valid. It will
eliminate the need for 3 more desalination plants of the Tugun Plant size.
Further reading Borumba
Dam Proposal and Borumba Dam Appendix
