Issued on 4 August 2010
Short-term deficits remain over western WA
Although much of the country recorded above average falls in July 2010, below average falls over southern and far-western parts of the country have contributed to a continuation of serious to severe rainfall deficiencies in western WA and southeastern Tasmania. For the southwestern region of WA it has been the third driest start to the year since records began in 1900. Despite the drier than average July in southern parts of Australia, northern and eastern regions have continued to receive above to very much above average rainfall, with Queensland having its wettest start to the year since 1981, despite a dry May and June. While rainfall in recent months has cleared a number of short-term rainfall deficiencies across eastern Australia, serious deficiencies 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.
7-month rainfall deficiencies
For the 7-month period from January to July 2010, serious to severe deficiencies are evident over much of western WA, and areas of lowest on record have developed in the west Gascoyne and near the south coast. In southwest WA in particular (defined as the region southwest of line from Jurien to Bremer Bay), below average rainfall in the months of April, May, June and July has resulted in record or near record low rainfall in the region, with the third driest start to the year on record. Elsewhere, there is a region of serious to severe deficiency in southeastern Tasmania, which has intensified in the past month, with a small area of lowest on record developing. These rainfall deficiencies have taken place against a background of record or near-record high daytime temperatures during the past 7 months in Tasmania and WA.
16-month rainfall deficiencies
For the 16-month period from April 2009 to July 2010, below average falls over the western half of WA during July 2010 further exacerbated areas of rainfall deficiency as described in the previous drought statement, with areas of severe deficiency becoming much more extensive in the southwest part of the state. An area of lowest on record has developed in the eastern Great Southern district. Serious to severe rainfall deficiencies remain evident over much of the Pilbara and Gascoyne districts and areas of lowest on record rainfall have developed 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