Drought
Rainfall deficiencies and water availability

Australia's driest September on record increases rainfall deficiencies

September rainfall was below average across the majority of Australia, and especially so across the southern mainland. It was the driest September on record nationally, and the second driest September on record for Victoria, third driest for Western Australia, and fourth driest for South Australia.

Rainfall totals were in the lowest 10% of historical rainfall totals for the month in large areas including greater southwestern Western Australia (southwest of a line between about Geraldton and Esperance), South Australia from Ceduna east across the Eyre Peninsula and agricultural districts, much of the western half of New South Wales, and nearly all of Victoria except parts of South and West Gippsland. Total rainfall for the month was the lowest on record for September at many sites in Victoria and Western Australia, and a handful of locations in New South Wales and Tasmania.

The year to date has also been exceptionally dry over the mainland southeast, with significant rainfall deficiencies continuing to affect large areas of eastern Australia at timescales out to around two years duration. Compared to other January to September periods since 1900, year-to-date rainfall has been the second lowest on record for the Murray–Darling Basin, third lowest for New South Wales, and eighth lowest for Victoria.

Deficiencies have increased in both extent and severity at each of the 6-, 9- and 18-month timescales across eastern Australia and parts of Western Australia. Deficiencies have increased for much of New South Wales, with the area of severe deficiencies now extending further into eastern and northern Victoria, eastern South Australia, inland southern Queensland, and south coast Western Australia than compared to periods ending August 2018.

Accompanying recent low rainfall have been unusually high day-time temperatures, which add to the impact of reduced rainfall, e.g. as seen through reduced soil moisture. Australian maximum temperatures for 2018 to date have been the second warmest on record with an anomaly of +1.36 °C (behind 2013 with an anomaly of +1.54 °C). Both New South Wales (+2.17 °C) and the Murray–Darling Basin (+2.10 °C) have experienced their warmest January–September period on record.

6-month rainfall deficiencies

The southern rainfall season spans April to November and corresponds to the southern agricultural cropping season. For 2018, the southern rainfall season to date has so far seen 6 consecutive months of below average rainfall across much of Australia. Serious or severe rainfall deficiencies persist across much of the eastern mainland, affecting northern and eastern Victoria, nearly all of New South Wales except along the northern coast and a pocket of the central inland north, large areas of Queensland apart from the inland northwest to Gulf Coast region, and eastern South Australia between about Adelaide and the New South Wales/Queensland border. A large area of northwestern New South Wales, and smaller pockets in the southwest New South Wales and along the ranges in the east of the State, and in southwestern Queensland, have received lowest on record total rainfall for the six months April to September 2018.

Large areas of serious or severe rainfall deficiencies are also in place for Central Australia and Western Australia's Interior District, and across an area along the south coast of Western Australia and much of the southern Goldfields District.

Compared to the 5-month period ending August 2018, deficiencies have increased in severity across southern Western Australia, eastern South Australia, northern and eastern Victoria, and much of the affected areas of New South Wales and Queensland, particularly in western New South Wales and southern Queensland.

9-month rainfall deficiencies

For the year to date, deficiencies have increased in severity across southeastern Australia to southern Queensland, and on the south coast of Western Australia. The area affected by deficiencies has expanded between Albany and Hopetoun in Western Australia, and in central southern Victoria. Across the east of South Australia (but excluding the far southeast), northern and eastern Victoria, New South Wales (excluding the northern coast), inland southern Queensland, and a pocket of Queensland adjacent to and inland of Mackay serious or severe deficiencies persist, and have generally increased in strength.

18-month rainfall deficiencies

Similar to deficiencies for other monitored periods in this Drought Statement, rainfall deficiencies have increased across nearly all affected areas for the 18 months commencing April 2017, although changes in absolute severity are smaller than for shorter periods due to the larger total accumulated rainfall deficits over the longer period.

Serious or severe rainfall deficiencies are in place across most of New South Wales except the northeast and parts of the southern border country, across eastern to central southern Victoria, much of southern, central inland, and southwestern Queensland, much of eastern South Australia except the far southeast, and along parts of the west and south coast of Western Australia.

Compared to the 17-month period ending August 2018, the area affected by deficiencies has increased in south coast Western Australia, now reaching to Busselton and inland towards Kalgoorlie, across the northern Eyre Peninsula and Murraylands and Riverland districts of South Australia, across southern New South Wales, and in central southern Victoria.

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Soil moisture

Following a very dry September, lower-layer soil moisture (from 10 cm to 100 cm deep) has decreased over much of Australia. Warmer than average maximum temperatures and high potential evapotranspiration again contributed to low soil moisture.

Soil moisture for September was below average for most of the eastern mainland States, except southwestern Victoria and parts of Queensland's northwest to central inland north. Below average soil moisture extended into eastern South Australia, affecting areas adjacent to northwest Victoria and reaching the eastern Eyre Peninsula and north to Lake Eyre / Kati Thanda, and also affected most of the Northern Territory and the Kimberley in Western Australia. Parts of the western half of Western Australia, particularly inland areas and along the south coast, also observed below average soil moisture for the month.

• September was Australia's driest on record
• Rainfall was very much below average nationally, and particularly low across the southern mainland
• Rainfall deficiencies have increased across eastern Australia and southern coastal areas of Western Australia at each of the 6-, 9- and 18-month timescales
• Lower-level soil moisture was below average for September across eastern and northern Australia, and parts of inland and southern Western Australia