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Droughts are a relatively common feature of the weather in the United Kingdom, with one around every 5–10 years on average. These droughts are usually confined to summer, when a blocking high causes hot, dry weather for an extended period.〔(【引用サイトリンク】title=Drought in the UK )〕 However droughts can vary in their characteristics. All types of drought cause issues across all sectors, with impacts extending to the ecosystem, agriculture and the economy of the whole country in severe cases of drought. The south east of the country usually suffers most, as it has the highest population (and therefore demand) and the lowest average precipitation per year, which is even lower in a drought.〔(【引用サイトリンク】title=2006 Drought in the South East )〕 Even in these areas in severe droughts, the definition, impacts, effects and management are all minimal in comparison to drought prone areas such as Australia and parts of the United States. In recent years however, the summers of 2007, 2008, 2009 and August 2010 were wetter than normal, 2007 being wettest on record. ==Definition and comparison with other countries== A drought is usually defined as an extended period of weather (usually around 3 weeks) where less than a third of the usual precipitation falls. In the United Kingdom an absolute drought currently defined ''as a period of at least 15 consecutive days or more where there is less than 0.2 mm (0.008 inches) of rainfall''.,〔 although before the 1990s a drought was defined as ''15 consecutive days with less than 0.25mm (0.01 inches) rain on any one day''. This previous definition sometimes led to confusion, as many argued that if less than 0.25mm of rain fell in 30 days, is that 2 droughts and if 0.26mm fell after 25 days, is the drought over? This led to the new definition but many believe hindsight is the best way to judge if a drought has occurred.〔(【引用サイトリンク】title=Drought in the UK )〕 In the longer term, drought in the United Kingdom can also be defined as ''a 50 per cent deficit over three months, or a 15 per cent shortfall over two years''. Compared to other countries, the United Kingdom definition of a drought is much less severe. In Libya in the Sahel region, a drought is usually only recognized after two years without any measurable rainfall. If this were to happen in the United Kingdom, the consequences would be disastrous.〔 A different type of drought is the hydrological or agricultural drought whereby moisture is in the soil but little is getting to vegetation, either because it is frozen (which can occur in severely cold winters in the United Kingdom) or because of very high temperatures which means that the rate of evapotranspiration is exceeding the rate of uptake of water from the plant (which can be seen in the United Kingdom, on hot days, when plants wilt as their stores of water are depleted).〔 A hydrological drought can occur, after a relatively dry winter whereby the soil moisture storage, reservoirs and water table have not risen sufficiently to counteract the warm summer weather. These sort of conditions can go over several years, even with above average rainfall at the time as the rainfall only slowly percolates through the water stores and replenishes them.〔 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 the United Kingdom」の詳細全文を読む スポンサード リンク
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