Issued 2 November 2007

Another dry month for central and south-eastern Australia

Short-term rainfall deficits remain over SA and southeastern parts of the country as a result of widespread below to very much below average October rainfall. Unless November is wetter than average, 2006-07 will be one of the very few instances in history where the Murray-Darling Basin (MDB) has suffered a winter-spring drought in successive years. The other years when this has occurred were 1918-19 (the latter was extremely dry), and 1940-41, with 1940 being very dry. In each of the years 1927, 1928, and 1929, large parts of the MDB had a winter-spring rainfall total in decile 3 or lower, although individually none of the years was extremely dry.
See October rainfall pattern

5-month rainfall deficiencies

Since the start of winter, South Australia has been the worst hit state, with the five-month average being the second lowest on record at just 36 mm. At the yearly time-scale (not shown), rainfall deficiencies have weakened somewhat compared with the situation at the end of September as October 2007 has generally had higher rainfall totals than October 2006.

For the 5-month period from June to October 2007, an area of serious to severe rainfall deficiencies covered most of SA, southwest Queensland, western NSW, northern Victoria, regions in the southern NT, scattered parts of WA and an area in northeastern Tasmania. Large areas of lowest on record covered South Australia and southwestern Queensland into southeastern NT.

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6-month rainfall deficiencies

Rainfall deficiencies for the 6-month period from May to October 2007 were widespread across the southern half of Western Australia as May rainfall was also below average in this region. SA was also affected, but to a much lesser extent than for the five-month period. There were small areas of lowest on record in these areas.

The deficiencies discussed above have occurred against a backdrop of multi-year rainfall deficits and record high temperatures that have severely stressed water supplies in the east and southwest of the country. Several years of above average rainfall are required to remove the very long-term deficits. Furthermore, the combination of heat and drought during the past five to ten years over the MDB and southeastern Australia, is outside the typical range of variability experienced during the previous 100 years. For more information go to a recent Special Climate Statement on the six years of widespread drought in southern and eastern Australia, November 2001 to October 2007.

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Click on the map for larger view
Black and white | High resolution colour

Definitions

Lowest on record - lowest in the historical analysis, which runs from 1900.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.

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.

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