Drought

Deficiencies Expand in the Southeast Following a Very Dry October

November 5 2015

October rainfall was below average for most of Australia. Rainfall was in the lowest 10% of historical totals (decile 1) for much of the South West Land Division in Western Australia, a stretch along the southern coast from around Ceduna in South Australia through to South Gippsland in Victoria, all of Tasmania, large areas in central Australia and western Queensland, and smaller parts of southern New South Wales, eastern South Australia, and the Top End. Rainfall was the lowest on record for October for most of Tasmania and an area spanning the southwest of Victoria and southeastern South Australia.

Deficiencies have increased in both severity and extent at all monitored timescales for South Australia, Victoria, and Tasmania. Compared to the last Drought Statement, slight increases in deficiencies have also occurred in southwest Western Australia and Queensland south of the Cape York Peninsula, while on the Peninsula there has generally been little change.

Rainfall in eastern Australia has been very much below average for large areas for periods of about 3 years’ duration (since the conclusion of the last La Niña in autumn 2012). Long-term deficiencies also exist in eastern Australia over the 17 years since 1998.

The southern wet season, which spans April to November, continues to track below average rainfall for the season so far in most of Victoria, southeastern South Australia, Tasmania, and across most of the South West Land Division in Western Australia. For the most recent 3-months (August to October) rainfall has very much below average over most of Victoria (except most of Gippsland and some areas along the New South Wales border), the southeast of South Australia, and nearly all of Tasmania. This particularly dry end to the southern growing season has seen serious deficiencies (lowest 10% of historical observations) extend further north into northwestern Victoria, and severe deficiencies (lowest 5% of historical observations) cover a larger area of Victoria, Tasmania, and southeastern South Australia than at the 6-month timescale.

Rainfall over eastern Australia in recent days (see totals for 1–4 November) has brought cumulative totals of 15 to 50 mm over large areas of eastern Victoria, eastern New South Wales, southern, central and northwestern Queensland, and the central south coast of South Australia; with some townships in western Queensland receiving more than 100 mm of rainfall. Further falls in the range of 15 to 50 mm are expected over eastern Queensland, central to eastern New South Wales, and much of Victoria and Tasmania in coming days (see forecast rainfall for 5–12 November). However, these totals are much less than cumulative rainfall deficits for the 6-month period, which exceed 125 mm in affected areas of Victoria and southeast South Australia, and are between 50 mm and 125 mm in Queensland. Cumulative rainfall deficits for the 37-month period exceed 350 mm over much of Victoria, Queensland, and parts of southeastern South Australia, Tasmania, and eastern New South Wales.

6-month rainfall deficiencies

Below-average October rain resulted in a significant increase in the area of serious rainfall deficiencies (lowest 10% of historical records for similar periods) at the 6-month timescale (May to October 2015) in Victoria, southeast South Australia, and coastal Tasmania. Much of Victoria, southern South Australia, Tasmania, and southern New South Wales have received below-average rainfall for the six-month period and for the cool season to date. Smaller increases were also seen in southwest Western Australia and along a line between the Alice Springs district and central Queensland.

Serious rainfall deficiencies (lowest 10% of historical records) extend from southeastern South Australia and parts of the Fleurieu Peninsula across most of Victoria except the northwest border region and eastern Victoria. Serious rainfall deficiencies are also in place across northern, eastern and coastal western Tasmania, an area of Queensland extending inland from the Central Coast district and smaller pockets between this region and the southwest of the Northern Territory. Severe deficiencies (lowest 5% of historical records for similar periods) persist over most of southwest Western Australia (the area southwest of a line between Jurien Bay and Bremer Bay) and adjacent to the Central Coast district in Queensland, with pockets of severe deficiencies also present in far southeastern South Australia, central Victoria, eastern and west coast Tasmania.

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16-month rainfall deficiencies

For the 16 months July 2014 to October 2015, deficiencies have generally increased in extent or severity in all affected regions.

Severe or serious deficiencies (lowest 5% or lowest 10% of historical records) persist in an area extending from northwestern South Australia, along the coast of South Australia, and across most of Victoria except Gippsland and parts of the Alps. Rainfall for the period remains lowest-on-record for an area spanning southeastern South Australia and adjacent parts of western Victoria. Serious or severe deficiencies also persist across most of Tasmania except an area of the southeast.

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 also persist in western parts of the South West Land Division in Western Australia, and 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.

Click on the map for larger view

37-month rainfall deficiencies

At the 37-month timescale (October 2012 to October 2015), rainfall deficiencies have increased slightly in extent or severity in all affected regions.

Severe or serious deficiencies (lowest 5% or lowest 10% of historical records) persist in an area spanning southeast South Australia and most of Victoria except Gippsland and parts of the Alps, areas of the west and east coasts of Tasmania, and parts of the central South West Land Division in Western Australia along a line roughly from Jurien Bay to Albany. Deficiencies also persist in Queensland, extending from the base of the Cape York Peninsula, through central Queensland into parts of central southern Queensland and northern New South Wales to the west of the Great Dividing Range.

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, and large parts of Queensland having experienced poor wet-season rainfall in successive years.

Click on the map for larger view

Soil moisture

Soil moisture in the upper layer for the week ending 1 November had increased across the eastern mainland and northwestern to central Western Australia compared to the week ending 27 September, but had decreased across the Northern Territory, northern Queensland, South Australia, and the western half of Victoria.

Upper layer soil moisture was below to very much below average in the west of the South West Land Division in Western Australia, across most of the Northern Territory and South Australia, most of Victoria except Gippsland, all of Tasmania, parts of southern and eastern New South Wales, and large parts of western and northern Queensland. Upper layer soil moisture was above average in parts of northwestern, central and southeastern Western Australia and some parts of the east of the South West Land Division, parts of central to southeastern Queensland, extending into some areas of New South Wales west of the Great Dividing Range.

Lower-layer soil moisture for the week ending 1 November decreased in southeastern Australia, compared to the week ending 27 September, markedly along the Great Dividing Range in Victoria and in much of Tasmania, with more moderate decreases also seen in southeastern Queensland and southwest Western Australia. Lower layer soil moisture increased across much of northern Australia.

Lower-layer soil moisture was above average for a large area of Western Australia between the northwest and southeast, the inland Northern Territory, far eastern Victoria and southeastern New South Wales, parts of western New South Wales, and parts of South Australia but not the southeast. Soil moisture was below average in western parts of the South West Land Division in Western Australia, and also for some areas of coastal northern Queensland and around the Gulf coast, an area in the central Top End, areas between central Queensland and northern New South Wales, a large area running from the Great Dividing Range in southeastern New South Wales, across most of Victoria and southeastern South Australia, and much of Tasmania.

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