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For the 12-month period ending 31st July 2007
Most states still affected by rainfall deficiencies
At the yearly time-scale, rainfall
deficiencies are evident in all states and territories, with the
exception of the Northern Territory.
As
July 2007 was wetter than July 2006 in western WA, Victoria and
southeast SA, there was a slight easing of 12-month deficits in those
regions compared with the situation at the end of June. However,
southeast Queensland, Tasmania and the Eyre Peninsula experienced a
drier July this year thereby causing 12-month rainfall deficiencies
to expand and intensify.
For the 12-month period from August 2006 to
July 2007, there were serious to severe rainfall deficiencies
over southern and eastern Australia in an arc extending across the
Eyre Peninsula and southeastern SA, southwest, south-central and
northeast Victoria, and the tablelands and western slopes in
southeastern NSW. A large part of southeast Queensland was also
affected, as were Tasmania (except for the southwest), and parts of
western WA between Carnarvon and Perth as well as areas between Wagin
and Albany.
Record low falls for this particular 12-month period were recorded
southeast of Melbourne, in much of northern and central Tasmania, in
the far southeast of SA and along WA’s west coast between Shark Bay
and districts to the south of Geraldton.
Over the past three months (May to July), rainfall deficiencies have
developed in southwest WA between Geraldton and Kalgoorlie and between
Kalgoorlie and Esperance, these being areas largely unaffected by
12-month deficiencies.
The worst of the long-term deficiencies are likely to remain for some time. For
them to be removed by the end of October, for example, falls over
the next three months would need to be in the highest 10% of the
historical record in some areas, especially near Melbourne, in
northern Tasmania, western WA and southeast Queensland.
The deficiencies discussed above have occurred against a backdrop of
multi-year rainfall deficits that have severely stressed water supplies
in the east and southwest of the country.
An important consideration in the recovery from drought is the different
rate at which systems respond to rainfall deficiencies. At the current
time, many catchments in eastern Australia are excessively dry from a
very protracted period of below average rainfall and above average
temperatures. This means that it will take above average rainfall just
to produce average runoff, and very considerable rainfall to make a
material difference to water storages.
Rainfall
deficiency maps for standard periods out to three years are
available.
Note: The terms used to describe rainfall in these
Drought Statements have the following meanings -
Serious deficiency
- rainfalls in the lowest 10% of historical totals,
but not in the lowest 5%
Severe deficiency
- rainfalls in the lowest 5% of historical totals
Lowest on record
- lowest since at least 1900 when the data analysed begin
Very much below average
- rainfalls in the lowest 10% of historical totals
Below average
- rainfalls in the lowest 30% of historical totals,
but not in the lowest 10%
Average
- rainfalls in the middle 40% of historical totals
Above average
- rainfalls in the highest 30% of historical totals,
but not in the highest 10%
Very much above average
- rainfalls in the highest 10% of historical totals
For more information regarding this rainfall
deficiencies statement, please contact the following
climate meteorologists in the National Climate Centre:
Grant Beard on (03) 9669 4527
Blair Trewin on (03) 9669 4623
Lyn Bettio on (03) 9669 4165
External Sites Relating to Drought
The Bureau of Meteorology does not make formal drought declarations
as these are done by either the relevant State Governments or by the
Australian Government. The Australian Government Program is called
Exceptional Circumstances
and it is administered by the Federal Department of Agriculture,
Fisheries and Forestry (DAFF). General information about Australian
Government drought assistance is available at
http://www.daff.gov.au/droughtassist.
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