May 2009 : Since August 2007 the QWC
has applied restriction measures and the requirements are now generally
available to the public. This section is now redundant in favour of the updated
requirements that we must adhere to.
********************************************
Now redundant but retained for
interest
Our normal water requirements
The final calculation is slightly in excess of 1000ML per day.
The SEQ Regional Plan part B uses the expression " business as usual "term which to my understanding means - without restrictions of any kind and
before the "Emergency measures" as described and Legislated in the
Water Commission's web-site. The Requirements are measured on that basis.
In the first instance, the Population serviced by the 
Wivenhoe
and Somerset Dams were determined. Examination of the SEQ Plan part B indicated
the percentages of the areas described as SEQ. The SEQWater web site describes
the areas covered by the 3 Dams which includes the North Pine. The calculation
comes to 85% of the 2.8 million population. The North Pine population is excised
on the basis of Dam capacities. The result is a Population serviced by the two
Dams at 2,113,983 or around 2.1 million.
The second requirement was to adopt the SEQ RP Part B method
being "per person including Commercial and Industrial at 450 litres per day
each". There are adjustments made by me to cater for the Commercial and
Industrial from the main Dams. The revision is 474 litres per person per day.
The break-up is 300 litres Domestic and 174 Commercial and Industrial.
The third aspect of the Requirements was to measure the
calculation with annual depletion of the Dams together with minor estimates of
rainfall. These estimates are fully covered in " Rainfall 2001-06"
button. You will see from the attached document that the requirement
calculations are within tolerance of the annual totals of the depleted Dams
together with rainfall in both "low" and "high" yield years.
It was interesting and understandable that in a high rainfall
year as 2004, the requirements dip by as much as 6% of capacity. This could well
have been the situation in the years 1986 to 2000 covering up to 5 uncommon
events. The year 2004 has an accurate assessment of the Megalitres that inflow
created. See "Wivenhoe Dam" button.
Confirmation from the South East Queensland Regional
Water Supply
The SEQRWSS stage 2 interim report attached confirms 
the
water allocation from the Wivenhoe/Somerset Dams is 374,000 ML per annum. This is the
volume allocated and required but as we have seen, not capable of being supplied
without "uncommon events". It confirms the calculations made above. If
reading of the small print is difficult, it is on their web-site page 8 of the
SEQRWSS stage 2 interim report. They do qualify their calculations to the extent
that effects of a "drought" are not taken into account.
This 374,000ML a year converts to 1024ML per day which agrees
with my calculated requirements. The supply from 
these
Dams in normal times without "uncommon events" is 481ML per day or
176,000ML annually. Uncommon events we have seen are rare and unpredictable. The
South East Queensland regional Water Supply report is based on this 374,000ML.
From my reading of copious other reports, particularly of the Mary Valley
Traveston Dam proposal, they are all based on this calculation. It may be
correct over a great many years but is irrelevant for around 20 year periods.
This amounts to a shortfall of 198,000ML each year until
uncommon events. Those who follow the "drought" mantra, without
thought, will have their calculations severely distorted.
300 Litres Domestic. Further considerations.
Attached
is an extract from a water tank supplier's brochure. They have been in operation for 14 years and
service an area from Bundaberg to the
Victorian border principally to Country clients. The relevant part is the normal household requirements to be
calculated when determining the size of your water tank.
It reveals to us that the normal requirements per
person is
more
than twice the current allowance of 140 litres per day. This is not a
revelation to us all. It supports the selection of the SEQ RP part B. However,
their main sales are Country and Country people are practiced in water
conservation.
The calculations are also
available for those who aspire to self sufficiency. There has been a recent move
by our Brisbane Lord Mayor to limit the rebate on water tanks to those who link
them into household use ( June 2007 ). This is entirely compatible with these
conclusions.
Water
Commission
The public stated aim of the Water
Commission is to reduce the level of water use to 700ML per day. They are 
achieving this through tough water restrictions in operation since May 2005. The Dam releases by SEQWater
indicate that they have been reduced to around 50% of normal. It further indicates
that the normal requirement is in the region of 1400ML per day and my
calculation of our needs may be conservative.
I have not studied the surrounding aspects of water releases
but it obviously plays a part. The calculated 1003ML per day requirement is
maintained.
Conclusion
The
current water requirements from the Wivenhoe and Somerset Dams to resume normal
living is a conservative 1003ML per day.
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.
