Updated on 8 April 2015
Rainfall deficiencies continue after drier-than-average month for much of South Australia and the east
March rainfall was generally below average for the eastern two thirds of the mainland, covering most of South Australia away from the southwest; large parts of the Northern Territory; large areas of Queensland, particularly in the west, central north and along the east coast; and extending from northern and eastern Victoria through to central and western New South Wales. Rainfall for the month was above to very much above average for large parts of Western Australia along the west coast extending towards the interior and also above average for western Tasmania.
March 2015 was also a warm month for much of northern Australia, extending into northern and eastern New South Wales. For Queensland it was the warmest March on record in terms of both maximum and minimum temperatures.
Above-average rainfall in the west has cleared rainfall deficiencies at the shorter 9-month timescale, while at the longer 30-month timescale rainfall for the period remains below average in a broad strip along the west coast of Western Australia, although only a very narrow margin along the coast remains in serious deficiency (lowest 10% of records). Deficiencies have increased in both severity and spatial extent in southern South Australia, western Victoria and, at the 30-month timescale, have also increased in inland northern Queensland.
9-month rainfall deficiencies
Compared to the previous Drought Statement, the spatial extent and severity of rainfall deficiencies for the 9-month period (July 2014 to March 2015) have increased across southern South Australia and western Victoria, eased along the west coast of Tasmania, have been cleared from Western Australia, and have shifted affected areas slightly across the Cape York Peninsula in Queensland.
The area experiencing severe or serious deficiencies (lowest 5% or lowest 10% of records) extends from the central West Coast District of South Australia, through southeastern South Australia, across most of western Victoria and just into part of southern New South Wales. An area of coastal South Australia near Ceduna has recorded its lowest rainfall on record for similar July to March periods (and also for similar August to March periods). Deficiencies have lessened in Tasmania but remain in a small pocket of the northwest.
Severe or serious deficiencies persist across areas of Queensland's Cape York Peninsula roughly in a line from north of Kowanyama to Townsville. Deficiencies have increased near Townsville and have emerged on the coast of the Gulf of Carpentaria around the Queensland–Northern Territory border. Isolated pockets of serious deficiencies have also emerged at this timescale around the Queensland–New South Wales border inland of the Great Dividing Range. Very significant deficiencies persist in this region at longer timescales (see next section).
Above-average March rainfall has also helped to moderate rainfall deficiencies at other timescales in Tasmania; rainfall remains below average across nearly all of Tasmania at both the 8-month period (August 2014 to March 2015) and the 16-month period (December 2013 to March 2015) but less severely so than previously. Coastal South Australia is also experiencing significant rainfall deficiencies at the 8-month timescale.
30-month rainfall deficiencies
At the 30-month timescale (October 2012 to March 2015), rainfall deficiencies have increased in severity and spatial extent across northern, central and western Queensland, south of the Cape York Peninsula, as well as in western Victoria and adjacent southeastern South Australia. Severe and serious deficiencies are in place in a broad area extending from south of the Cape York Peninsula, through central and western Queensland, into the areas of central southern Queensland and northern New South Wales inland of the Great Dividing Range. Deficiencies are also in place in an area stretching from southeastern South Australia and western Victoria, away from the coast, to just over the border into southern New South Wales, with a small pocket also around the northeast of Melbourne.
Long-term deficiencies in Queensland are largely the result of below-average rainfall over the 2013–14 and 2012–13 'summer' wet seasons (the northern wet season spans October–April). As there only remains one month in the current northern wet season and the Climate Outlook does not indicate a high probability of above-average April rain over much of the affected area of Queensland, it is unlikely that rainfall deficits will be cleared from this area in the immediate future.
Rainfall for the wet season to date has been below average across most of eastern Australia and South Australia. Despite above-average January rainfall across much of the north and east of the continent, drier-than-average conditions across much of the east during February and March have seen deficiencies persist in large areas.
Above-average March rainfall has cleared serious rainfall deficiencies from Western Australia except for a very narrow margin along part of the central western coast. However, it should be noted that while no longer in serious deficiencies, rainfall for much of the area along the western coast of Western Australia remains below average for the period. The situation is similar for Tasmania.
At even longer timescales, 36-month (three-year) rainfall deficiencies have markedly increased across eastern Australia as the generally wet March 2012 drops out of the analysis period. March 2012 came at the end of the most recent La Niña and was Australia's third-wettest March on record. The La Niña events of 2010–12 also brought Australia its wettest 24-month period on record for April 2010 to March 2012. Compare April 2012 to March 2015 to March 2012 to February 2015.
Soil moisture in the upper layer for the week ending 29 March had decreased, compared to the week ending 22 February, across the mainland southeast, east coast Queensland, and across parts of the Top End. Upper layer soil moisture increased across Tasmania and the west of Western Australia, as well as parts of inland southeast Queensland and northeastern New South Wales.
Upper layer soil moisture at the end of March was below to very much below average across most of the mainland, but above average in the west of Western Australia, parts of inland southeastern Queensland and northeastern New South Wales, the eastern Top End, and across Tasmania.
Lower layer soil moisture for the week ending 29 March was generally similar to the week ending 22 February, decreasing slightly across most of the Northern Territory, and western and central Victoria, while increasing in the northern interior of Western Australia.
Lower layer soil moisture was above average for most of Western Australia, much of the Northern Territory, parts of central eastern Queensland, an area spanning southern South Australia and western New South Wales, an area covering East Gippsland in Victoria and far southeastern New South Wales, and parts of Tasmania. Soil moisture was below average in Western Australia for the northern half of the South West Land Division, extending just into the Goldfields District, areas of Queensland on the north tropical coast and in the central inland north, in an area covering central southern Queensland to eastern New South Wales, with patchy coverage then extending from southern New South Wales and becoming more widespread in central to western Victoria and southeastern South Australia.
Product Code IDCKGD0AR0
The Weekly Rainfall Update describes rainfall over the previous week. It includes a map and a summary table of the highest weekly totals. A discussion of the impact of recent rains on rainfall deficiencies is also presented.
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What is drought?
Drought is a prolonged, abnormally dry period when the amount of available water is insufficient to meet our normal use. Drought is not simply low rainfall; if it was, much of inland Australia would be in almost perpetual drought. Because people use water in so many different ways, there is no universal definition of drought. Meteorologists monitor the extent and severity of drought in terms of rainfall deficiencies. Agriculturalists rate the impact on primary industries, hydrologists compare ground water levels, and sociologists define it by social expectations and perceptions.
It is generally difficult to compare one drought to another, since each drought differs in the seasonality, location, spatial extent and duration of the associated rainfall deficiencies. Additionally, each drought is accompanied by varying temperatures and soil moisture deficits.
Rainfall averages, variability and trends
Lowest on record - lowest since at least 1900 when the data analysed begin.
Severe deficiency - rainfalls in the lowest 5% of historical totals.
Serious deficiency - rainfalls in the lowest 10% of historical totals, but not in the lowest 5%.
Very much below average - rainfalls in the lowest 10% of historical totals.
Below average - rainfalls in the lowest 30% of historical totals, but not in the lowest 10%.
Average - rainfalls in the middle 40% of historical totals.
Above average - rainfalls in the highest 30% of historical totals, but not in the highest 10%.
Very much above average - rainfalls in the highest 10% of historical totals.