May 2009 : No change since August
2007.
The basis of this web site is Bureau of Meteorology rainfall
Stations in the catchments and the Web-site of SEQWater, the Dam managers. Their
Annual Reports reveal that they are a truly professional body. Their public announcements have been helpful and they are to be
commended.
This
is an example of the data provided by the Bureau. It is obtained through
identification of the Rainfall Station numbers and then by request to the data
section. A small fee is required. You will observe that the information is in
EXCEL spread sheet format which gives easy access to assessing the required
information.
The
Bureau of Meteorology measures rainfall against the 30 year average (or
mean) 1961 to 1990.
To maintain statistical purity, I have used all the rainfall stations that have
been in continuous operation from 1961 to 2006. The remaining stations were
mostly closed prior to 2006 but have been inspected for possible aberrations.
These
charts were initially used to confirm the rainfall maps. The Qld. Govt. Climate
Change Centre
for excellence has since confirmed the overall percentage as 76.2%. The
relationship of the Somerset and Wivenhoe dams is one of the central ingredients
of this examination. The Somerset is on the Stanley river and the Wivenhoe on
the Brisbane River at the junction of the Brisbane and Stanley Rivers. It backs up to the foot of
the Somerset.
They have separate catchments but as we will see the Somerset
is the dominant partner.
The
North Pine Dam is completely separate to the other dams. (SEQWater verbal advice). It experiences similar
rainfall patterns. A reading of the "water grid" indicates that the
proposed Traveston dam will feed into the North Pine dam.
Because
it is separate, it is excluded from these observations. The Dam levels quoted
contain all three Dams. The North Pine Dam however mirrored the Somerset Dam. It
is also much smaller than the Wivenhoe and Somerset and therefore has little
influence on all calculations in this web-site. The statistics compared to the
total of the three Dams are : Capacity 12.2 % : Yield 10.9 % : Catchment area
4.7 %. Annual Rainfall is listed by SEQWater as : Wivenhoe 940mm : Somerset
1230mm : North Pine 1175mm.
