Issued on 6 September 2010
A very dry year so far in southwest WA
Although much of the country recorded above average falls in August 2010, low rainfall has persisted over southwestern WA. These below average falls have contributed to a continuation of severe rainfall deficiencies in this region, including record low rainfall at some locations. Average to above average falls in southeastern Tasmania were not enough to entirely remove deficiencies in this region. For the southwestern region of WA it has been the second driest start to the year since records began in 1900 (see Special Climate Statement 21). Northern and eastern parts of the country have continued to receive above to very much above average rainfall, with Victoria having its wettest August since 1981. Despite some individual months having below average rainfall in some states, Queensland, NSW and Victoria have all had their wettest starts to the year in more than a decade, with Queensland having its wettest start to the year since 1981. While rainfall in recent months has cleared a number of short-term rainfall deficiencies across eastern Australia, the rains in 2010 have only made limited inroads into the serious deficiencies which remain on multi-year time-scales, especially in southeastern Australia, and continue to affect water supplies; to alleviate these would require above average rainfall for a sustained period.
8-month rainfall deficiencies
For the 8-month period from January to August 2010, serious to severe deficiencies are evident over much of western WA, and areas of lowest on record rainfall have intensified in southwestern parts. In southwest WA in particular (defined as the region southwest of a line from Jurien Bay to Bremer Bay), below average rainfall in the months of April to August has resulted in record or near record low rainfall in the region. Averaged over the region as a whole, it has been the second driest start to the year on record and the driest winter on record. An area of lowest on record rainfall also exists east of Carnarvon. Elsewhere, above average falls in August, have eased the serious to severe rainfall deficiencies in southeastern Tasmania that were present in the previous drought statement. A small area of serious deficiency remains in the south of the state. These rainfall deficiencies have taken place against a background of record or near-record high daytime temperatures during the past eight months in Tasmania and WA.
17-month rainfall deficiencies
For the 17-month period from April 2009 to August 2010, below average falls over the southwestern half of WA during August 2010 further exacerbated areas of rainfall deficiency as described in the previous drought statement, In the last month, areas of severe deficiency and lowest on record became much more extensive in the southwest of the state. Some average to above average falls over the Gascoyne and Pilbara districts have slightly eased some areas of serious to severe deficiency, though large areas still remain, including an area of lowest on record in the Carnarvon region.
Whilst recent rains in eastern Australia have provided, in many cases, short-term relief, sustained periods of above-average rainfall are needed to remove very long-term deficiencies. This is especially true for the very long-term deficiency periods of 8 and 13 years (see the drought statement archive). Rainfall has been below average across much of southwest and southeast Australia since 1997, whilst central and southern parts of the Murray-Darling Basin have experienced below average rainfall since 2002. These long-term deficiencies have taken place against a background of well above average temperatures, including Australia's warmest decade on record. Further information on exceptional rainfall and temperature events across Australia can be found in the Special Climate Statements.
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.
Product Code IDCKGD0AR0