Rainfall deficiencies for the 24-month period from May 2006 to April 2008 are evident in southwest WA, Tasmania, southeast Queensland, northern SA and in a band stretching from the Bight coast of SA across much of Victoria and the western slopes and plains of southern NSW. The pattern is very similar to that observed at the end of March, but as April 2008 was drier than April 2006 in most areas, there was a slight increase of these two-year deficits. One exception was southwest WA which had a wetter April this year so the 24-month deficits eased somewhat. Record-low falls remain evident on the Eyre Peninsula in SA and in southwest WA where they are smaller in area. Compared with a month ago, record low falls at this time-scale expanded near Melbourne and in eastern and northern Tasmania.
The worst of the long-term deficiencies are likely to remain for some time. For example, above to very much above average rainfall (deciles 8-10) is needed in the rainfall deficient areas over the next six months just to elevate totals since May 2006 out of the lowest decile. Furthermore, due to the seasonally dry period in northern parts of Australia, short-term rainfall deficits in the NT are also likely to remain over the coming months.
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. Several years of above average rainfall are required to remove the very long-term deficits. 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. For more information go to a Special Climate Statement on the six years of widespread drought in southern and eastern Australia, November 2001 to October 2007.