Issued 3 November 2006
Drought intensifies over eastern and southern Australia as spring rains fail
rainfall deficiencies have been gradually spreading over southern and eastern Australia during 2006, but the situation has taken a distinct turn for the worse from August, with a near total failure of the late-winter to mid-spring rains. In the historical record dating from 1900, it was the driest August to October period averaged across SA, the second driest averaged over Victoria and the Murray Darling Basin, and the third driest for NSW whose state-average was boosted by above-normal falls along the north coast.
It has also been remarkably warm during the past three months, with mean maximum temperatures being easily the highest on record (for the post-1950 era) averaged over Australia, NSW, Victoria, SA, WA and the Murray Darling Basin. Furthermore, as an indicator of how dry the air and ground have been, the daily temperature range (difference between maximum and minimum temperatures) was the highest on record for August-October averaged over NSW and Victoria, and the second highest for SA. A lack of both atmospheric humidity and soil moisture increases the capacity of the air to gain heat in the day, and to lose heat at night.
Rainfall deficits are also evident over other agriculturally sensitive periods during 2006: the period since May has been very dry across much of southern and western WA (as well as in the southeast of the country), while southeastern Australia (including Tasmania) and southeast Queensland are affected by severe rainfall deficiencies for the period beginning in January.
3-month rainfall deficiencies
For the 3-month period from August to October, generally severe rainfall deficiencies covered most of the southern two-thirds of SA, all of Victoria, northern and eastern Tasmania, most of NSW west of a line from Bega to Tenterfield, the southern one-third of Queensland west of the ranges, and pockets along the south coast of WA. There are other areas analysed further north in both Queensland and the NT, but these are not significant as August to October is a seasonally dry time of year in these parts. A large area extending eastwards from the Far West Coast District of SA across the Eyre and Yorke Peninsulas and into the far west of NSW’s Lower Western District, has recorded its driest August to October on record. Other parts of NSW that had their driest August to October were (i) a region extending north from the ACT to around Dubbo, taking in parts of the central and southern Tablelands, southwest slopes and central west; and (ii) part of the far northwest of the State between Bourke and Broken Hill. Record low totals also occurred around Esperance in southern WA and in smaller patches scattered about southern Queensland.
6-month rainfall deficiencies
For the 6-month period from May to October, severe rainfall deficiencies cover most of western and southern WA. Numerous regions have registered record low totals for this period, most notably near Esperance, Kalgoorlie, and between Carnarvon and Geraldton. Also experiencing deficits for this period are SA southeast of a line from Ceduna to Marree, Victoria (apart from East Gippsland), much of NSW west of the Divide and south of about Tamworth, the southeast inland of Queensland centred on about Miles, and northern and eastern Tasmania. Record low falls have occurred near and to the east of Melbourne, on parts of the Eyre Peninsula and near the Vic/NSW border to the east of Albury-Wodonga.
10-month rainfall deficiencies
For the 10-month period from January to October, serious to severe rainfall deficiencies affect southeast Queensland away from the coast, much of the southern half of NSW west of the ranges, Victoria (apart from East Gippsland), northern and eastern Tasmania, southeastern SA and a coastal strip in WA from Carnarvon to Albany. Record low falls are analysed along Tasmania’s north coast and in the mountainous regions of northeast Victoria and southeast NSW, extending into parts of the southwest slopes.
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.