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Drought in Australia is defined by the Australian Bureau of Meteorology as rainfall over a three-month period being in the lowest decile of what has been recorded for that region in the past. This definition takes into account that drought is a relative term and rainfall deficiencies need to be compared to typical rainfall patterns including seasonal variations. Specifically drought in Australia is defined in relation to a rainfall deficiency of pastoral leases and is determined by decile analysis applied to a certain area. Note that this definition uses rainfall only because long-term records are widely available across most of Australia. However, it does not take into account other variables that might be important for establishing surface water balance, such as evaporation and condensation. Historical climatic records are now sufficiently reliable to profile climate variability taking into account expectations for regions. Bureau of Meteorology records since the 1860s show that a ‘severe’ drought has occurred in Australia, on average, once every 18 years. State Governments are responsible for declaring a region drought affected and the declaration will take into account factors other than rainfall.〔 The worst drought to affect the country occurred in the 21st century–between the years 2003 to 2012. Nonetheless, many regions of Australia are still in significant drought and rainfall records have showed a marked decrease in precipitation levels since 1994, with many scientists attributing this to climate change and global warming. ==Droughts in the 19th century== * 1803 Drought in NSW that produced severe crop failures. * 1809 Beginning of an unusually severe drought in NSW that continued until 1811. * 1813−15 Severe drought in NSW that prompted searches for new pastures. * 1826−29 Severe drought in NSW that caused Lake George to dry up and the Darling River to cease flowing. Since 1860, when adequate meteorological recording commenced, the most severe droughts have occurred commonly at intervals of 11 to 14 years. Major droughts that were recorded later in the 19th century include: * 1829 Major drought in Western Australia with very little water available. * 1835 and 1838 Sydney and NSW receive 25% less rain than usual. Severe drought in Northam and York areas of Western Australia. * 1838−39 Droughts in South Australia and Western Australia * 1839 Severe drought in the west and north of Spencer Gulf, South Australia. * 1846 Severe drought converted the interior and far north of South Australia into an arid desert. * 1849 Sydney received about 27 inches less rain than normal. * 1850 Severe drought, with big losses of livestock across inland New South Wales (NSW) and around the western rivers region. * 1864−66 (and 1868). The little data available indicates that this drought period was rather severe in Victoria, South Australia, New South Wales, Queensland and Western Australia. * 1877 All States affected by severe drought, with disastrous losses in Queensland. In Western Australia many native trees died, swamps dried up and crops failed. * 1880 to 1886 Drought in Victoria (northern areas and Gippsland); New South Wales (mainly northern wheat belt, Northern Tablelands and south coast); Queensland (1881–86, in south-east with breaks – otherwise mainly in coastal areas, the central highlands and central interior in 1883–86); and South Australia (1884–86, mainly in agricultural areas). * 1888 Extremely dry in Victoria (northern areas and Gippsland); Tasmania (1887–89 in the south); New South Wales had the driest year since records began; Queensland (1888–89) had a very severe drought, with much native scrub dying and native animals perishing; South Australia had one of its most severe droughts; and Western Australia (central agricultural areas) lost many sheep. *1897 Drought in much of Queensland, compared to 1883-4 droughts. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Drought in Australia」の詳細全文を読む スポンサード リンク
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