Issued 5 August 2015
Deficiencies increase slightly in the east, develop in southwest Western Australia
July rainfall was below average for most of the South West Land Division in Western Australia, extending into part of the Southeast Coastal district. The month was also drier than average for much of Tasmania, coastal regions of southeastern Queensland and central New South Wales, large parts of South Australia, and western to central Victoria. The southern wet season, which spans April to November, continues to track below average rainfall for the season so far in central to western Victoria, southeastern South Australia, Tasmania, and across the greater southwest of Western Australia.
Compared to the last Drought Statement, deficiencies have generally remained similar to those for the preceding period or have increased slightly in areal extent and severity. The most notable increases have been in Queensland, western to central Victoria (at the 13-month, July 2014 to July 2015, timescale), parts of coastal Tasmania, and the west coast and adjacent inland of the South West Land Division in Western Australia. Serious or severe rainfall deficiencies have been observed in parts of the southeast for various medium-term periods since late 2013, and for longer-term deficiencies for various periods to around 2 years duration. Deficiencies are also evident over large areas of eastern Australia for periods of about 3 years' duration.
At the shorter term, rainfall deficiencies have continued to build over the southwest of Western Australia with severe deficiencies (lowest 5% of historical records for similar periods) now in place across a large area at the 3-month timescale (May–July 2015). A number of locations within this region have seen record-low falls.
3-month rainfall deficiencies
Despite some recent heavy falls across the Central Wheat Belt district in Western Australia at the close of July, rainfall deficiencies have emerged at the 3-month timescale (May to July 2015). Below-average rainfall during recent months followed a good start to the growing season with above-average monthly rainfall during April. The growing season spans April–November, with the bulk of the rain received in the cooler months of the year. However, daily totals as high as those received in the wheat belt between 29th July and 1st August are unusual for the region and the time of year.
Severe deficiencies (lowest 5% of historical records for similar periods) for the period cover much of the South West Land Division in Western Australia and some smaller areas further inland. Small pockets of deficiencies are also seen in parts of northern Australia, although this period typically corresponds to the dry season there.
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13-month rainfall deficiencies
For the 13 months July 2014 to July 2015, severe or serious deficiencies (lowest 5% or lowest 10% of records) persist in areas of northern Queensland extending across the southern and central Cape York Peninsula, roughly from Kowanyama to Townsville, along the southern coast of the Gulf of Carpentaria, and in an area of inland central Queensland near Longreach. Deficiencies have increased slightly compared to the previous period, although July rainfall is typically low in most of northern Queensland.
A substantial area of lowest-on-record rainfall was observed in southeastern South Australia and western Victoria, with serious or severe deficiencies also present along a broad band extending from west of Ceduna in South Australia, into the western edge of the Northeast district of Victoria. Much of southeastern Australia has seen below-average April–November rainfall during three of the last four years, with monthly rainfall also below average from August last year for much of this region (apart from well-above-average January rainfall, and above-average March and May rainfall in Tasmania). Deficiencies increased in extent slightly in northwestern Victoria. Deficiencies also increased in western and northwestern Tasmania and on the west coast of southwestern Western Australia.
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34-month rainfall deficiencies
At the 34-month timescale (October 2012 to July 2015), rainfall deficiencies have increased slightly in both extent and severity in some parts of central to northern Queensland. Serious and severe deficiencies are in place from the base of the Cape York Peninsula, extending through central Queensland into parts of central southern Queensland and northern New South Wales to the west of the Great Dividing Range.
Deficiencies have also increased in extent in western to central Victoria while increasing in severity in southeastern South Australia and have emerged in parts of the central South West Land Division in Western Australia.
Deficiencies also persist at a range of even longer timescales, with most of eastern Australia having received below-average rainfall following the conclusion of the 2010–12 La Niña events.
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Soil moisture
Soil moisture in the upper layer for the week ending 26 July had increased across the Pilbara and the region around Derby in the Kimberley, both in Western Australia, and parts of the Cape York Peninsula in Queensland, while generally decreasing across the rest of Australia, compared to the week ending 28 June.
Upper-layer soil moisture at the end of July was below average for much of the South West Land Division in Western Australia, although rainfall in the last days of July has likely raised soil moisutre in parts of this area. Soil moisture was also below average in parts of the eastern Kimberley and Victoria River district of the Northern Territory, as well as smaller areas of the coastal Roper–McArthur district of the Northern Territory and large parts of the Alice Springs district and adjacent parts of Queensland. Soil moisture was also below average in numerous pockets along the east coast of Queensland and New South Wales, between southeast South Australia and South Gippsland in Victoria, and across eastern to central Tasmania. Soil moisture was above average across the eastern Top End, a large area of the Pilbara and western Gascoyne in Western Australia, and in a large area of inland eastern Australia between far eastern Victoria and southern Queensland.
Lower-layer soil moisture for the week ending 26 July was generally similar to that for the week ending 28 June, although having decreased slightly in Western Australia and moving slightly closer to average values in eastern Australia.
Lower-layer soil moisture was above average for most of the northwest and interior of Western Australia, the central to southern Northern Territory, scattered areas along the east coast, eastern Victoria, and parts of South Australia but not the southeast. Soil moisture was below average in most of the northern half of the South West Land Division in Western Australia, extending just into the Goldfields District, and also for areas of coastal northern Queensland, around the Gulf coast, parts of the Top End, some areas between central Queensland and northern New South Wales, and much of central to western Victoria and southeastern South Australia.
