Water Shortage in the UK
A drought in the UK used to be defined as 15 consecutive days with less than 0.25mm rain on any one day, but this definition was abandoned in the mid-80's after running into problems. Different organisations couldn't decide whether the drought had ended or not, so it seemed easier if each made their own definitions.
The strict definition, was always coming under scrutiny and often caused confusion. If after 20 days there is 0.26mm rain, is the drought officially over? If there is less than 0.25mm rain for 30 days is that 2 droughts? It is far more sensible to judge each drought on its own merits and even then it is always hard to determine whether a drought has ended.
In a country affected by several weather fronts it is hard to imagine how the UK can be affected by droughts. In between the fronts are ridges of high pressure. These are often short lived, but sometimes a large area of high pressure called a 'blocking high' can dominate the weather for up to a month. As their names suggests these 'block' other weather fronts and force the fronts to skirt around them.
These high pressures can cause long dry spells, and eventually droughts. This is what caused the drought in 1976, when a blocking high dominated our weather for much of the summer. The drought of the mid - 80's on the other hand dragged on for years as the winter rain was not sufficient to replenish the ground water supplies.
Exactly how frequent droughts are in the UK is hard to pinpoint. 1976 was definitely a drought, as were the mid 80's. There was also one in the mid 90's, but different companies may well have other periods that they would also like to include in that list. The trend since the 1960's is for wetter winter and drier summers, this trend has been accentuated since the 70's. This seasonal cycle is strongest in the south and east of the country and if this trend continues then we can certainly expect more droughts in the future.
When there is a chronic shortage of water, the water companies can impose and apply various restrictions (see here for more info) to limit the amount of water used domestically and for industrial/agricultural purposes. For the latest information on the current water shortages please see http://www.environment-agency.gov.uk/homeandleisure/drought/31749.aspx and http://www.environment-agency.gov.uk/research/library/publications/33995.aspx (Water situation for England and Wales rainfall and river flows)
Concerned about irrigation and water demand please contact your Environment Agency regional co-ordinator/officer http://www.environment-agency.gov.uk/aboutus/organisation/35671.aspx
If you are concerned about how water shortages may affect some of your Environmental stewardship options please contact your local catchment sensitive farming officer http://www.defra.gov.uk/foodfarm/landmanage/water/csf/catchments/csfos.htm
For further information of water restrictions in Scotland please go to: http://www.sepa.org.uk/about_us/news/other/sepa_guidance_on_current_low_r.aspx | 
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