Issued 4 June 2007
Short term relief but long term drought persists
Autumn rainfall was average to above average over much of inland NSW, northern and western Victoria, Tasmania and southern South Australia, thereby providing some short-term relief to many agricultural systems and an easing of the severe drought caused in part by the 2006/07 El Niño event. However, some areas missed out, most notably eastern Queensland, southern Victoria (especially around Melbourne) and western WA.
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.
12-month rainfall deficiencies
Long term deficiencies remain in parts of western and eastern Australia
Average to above average rainfall during May in NSW, Victoria and Tasmania eased the intensity and extent of 12-month rainfall deficits in comparison with the situation at the end of April, but severe deficiencies still remain. In contrast, below average rainfall in WA saw little or no improvement in that State.
For the 12-month period from June 2006 to May 2007, there were serious to severe rainfall deficiencies over southern and eastern Australia in an arc extending across southeastern SA, much of southern and eastern Victoria, and the tablelands and western slopes in southeastern NSW. A large part of southeast Queensland was also affected, as were northern and eastern Tasmania and WA west of a line from Dampier in the north to Bremer Bay in the south. Record low 12-month falls were recorded between Dalby and Goondiwindi in southern Queensland, near much of WA’s west coast, in northeast Tasmania and in a large area around Melbourne.
The worst of the long-term deficiencies are likely to remain for some time. For them to be removed by the end of August, for example, falls over the next three months would need to be in the highest 10% of the historical record in many areas, especially in Victoria 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.
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