Issued 3 December 2008

Rainfall deficiencies ease over much of Australia

Above to very much above average November 2008 rainfall over much of Australia largely cleared short-term rainfall deficiencies, especially over the NT, SA and WA. However, average to below average falls in western Victoria into southeastern SA maintained deficiencies in these areas.

9-month rainfall deficiencies

For the 9-month period from March to November 2008, above to very much above average rainfall during November has resulted in a general easing of short-term rainfall deficiencies. This was especially evident over southern parts of NSW, northern NT into western Queensland and the southwestern corner of the NT into southern WA and central to southern SA. Below average falls in western Victoria into southeastern SA have maintained deficiencies in these areas. Above to very much above average rainfall fell in eastern Victoria, however, the previous severity of deficiencies in these areas means that they are still present for the period, although they have eased in severity and spatial extent. Generally, areas of serious to severe rainfall deficiencies have persisted over much of southern Victoria (extending into southeastern NSW and the far southeast of SA) and eastern Tasmania. However, there has been a marked decrease in the size and severity of these deficiencies. Small patches of rainfall deficiencies persist in southern SA, northern NT and western Queensland.

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18-month rainfall deficiencies

Rainfall deficiencies for the 18-month period from June 2007 to November 2008 have also eased over large areas, corresponding to the regions that recorded above average rainfall during November. This general easing of long term rainfall deficiencies is not as extensive as was seen for the short-term. Large areas of deficiencies still persist across southern SA into western Victoria. Areas of severe deficiencies have eased somewhat over these areas, although areas of lowest on record still persist in southern SA and have expanded to small patches in southeastern SA. The large area of lowest on record has cleared over eastern Tasmania, although severe deficiencies still persist in eastern and northern Tasmania. Following the very much above average November falls in the southern NT and southern WA deficiencies have largely eased in these areas, however, an area of serious to severe deficiencies still persists in southern parts of the NT.

The deficiencies discussed above have occurred against a backdrop of decade-long rainfall deficits and record high temperatures that have severely stressed water supplies in the east and southwest of the country. The combination of record heat and widespread drought during the past five to ten years over large parts of southern and eastern Australia is without historical precedent and is, at least partly, a result of climate change.

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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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