4618.0 - Water Use on Australian Farms, 2011-12 Quality Declaration 
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 31/05/2013   
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2011-12 was a generally wet year for Australia as La Nia conditions returned for a second year, although it was not as extreme as 2010-11. Averaged nationally, rainfall was 24 per cent above the 1961-1990 mean, the ninth-highest value in 112 years of records, with all states and territories above normal. Daytime maximum temperatures were very close to normal, while overnight minima were slightly below normal.

The vast majority of Australia had above-normal rainfall in 2011-12. The only significant areas which were drier than normal were western Victoria and adjacent parts of southeastern South Australia, parts of Tasmania, and the west coast of Western Australia south of the tropics. Most inland areas of New South Wales (which had its eighth-wettest year on record) had rainfall above the 90th percentile, as did southern inland Queensland and Gippsland in Victoria. There were also scattered areas with rainfall above the 90th percentile in the western and central interior. Whilst 2011-12 did not see the widespread record-breaking rainfalls which occurred in 2010-11, a few records were set near the New South Wales-Queensland border around Goondiwindi, and in east Gippsland.

The high rainfalls were concentrated in the period from October to March, with national averages mostly drier than normal, despite some locally heavy falls, in July to September 2011, and April to June 2012. October, November and March were especially wet, all having nationally averaged rainfalls at least 50 per cent above normal; the core of the October-March period, the summer months December to February, were only slightly wetter than normal at the national scale. March, the fourth-wettest on record (77 per cent above normal), contained much of 2011-12’s most significant flooding, with large parts of northern Victoria and southern New South Wales (especially the Murrumbidgee) affected in the early part of the month. The Murrumbidgee, Lachlan and Upper Murray catchments all had weekly rainfalls which were nearly double the previous record.

Bureau of Meterology map Rainfall Deciles (AWA grids 1900-pres.)

Bureau of Meterology map Rainfall Deciles (AWA Analyses)

Temperatures were generally above normal in the second half of 2011, and below normal in the first half of 2012. The most extreme months of the year were August (mean temperatures 0.9C above normal, tenth-highest on record) and March (mean temperature 1.2C below normal, ninth-lowest). For the year, maximum temperatures averaged over Australia were 0.04C above the 1961-1990 mean, and minimum temperatures 0.22C below the 1961-1990 mean.

Maximum temperatures were generally below normal in the tropics, as well as in eastern New South Wales and Queensland. The west coast of Western Australia south of Carnarvon had temperatures for the year about 1C above normal, while Tasmania, the western half of Victoria and the agricultural areas of South Australia were up to 1C above normal. Large parts of all of these areas were above the 90th percentile, especially near the coast. The area with the most significant below-normal temperatures was the Kimberley in Western Australia, with temperatures about 1C below normal in the region’s east; much of Australia’s northern interior was at least 0.5C below normal.
Bureau of Meterology map, Max. Temp. Anom. (ACORN 1961-1990)

Similar to maximum temperatures, minimum temperatures were generally below normal in northern Australia and above normal in the south. However, the area of above-normal minimum temperatures was more limited than its daytime counterpart, covering the south and west of Western Australia, most of South Australia, Victoria and Tasmania, and coastal New South Wales. Most southern coastal areas (including Tasmania), as well as Western Australia southwest of an Esperance-Carnarvon line, had minimum temperatures above the 90th percentile, and some records were set around Perth and in southern Tasmania. In contrast, scattered areas across the northern interior had minimum temperatures for 2011-12 more than 1C below normal (the start of the 2012 dry season, in May and June, was particularly cool), and some places had their lowest annual minimum temperatures on record, especially in the Kimberley.

Bureau of Meterology map, Min. Temp. Anom. (ACORN 1961-1990).