The Environment Agency and water firms in south-east England are asking for the public's help to beat the region's drought crisis.
Hosepipe bans are in place in much of south-east England
Eight water companies launched the new advice website Beat The Drought on Monday at Bewl Reservoir in Kent.
Standpipes or supply cuts may be used as a last resort without sustained rain, the Environment Agency warned.
Three firms have asked the government for powers to ban non-essential water use such as watering parks.
The applications to the Department of Environment, Food and Rural Affairs (Defra) for the drought measures came from Southern Water, Sutton and East Surrey and Mid Kent water companies.
If the orders are granted, the bans could apply to watering public gardens, parks, cricket pitches, bowling greens, allotments and other open spaces including natural or artificial surfaces for sport or recreation.
'Global warming policies'
Car washing, filling of privately-owned swimming pools, spas and splash pools would also be affected.
The last time such orders were in place in Britain was in 1991.
Paul Kent, regulatory manager for Southern Water, said: "We are not entering into this lightly. We are in the driest period we have had for 70 or 80 years and we need to conserve the water so that it is sufficient for basic hygiene throughout the rest of the year."
He said it was "possible" that similar bans would be necessary next year and said water companies were ready to change their long-term policies if it seemed that global warming was permanently reducing rainfall in the UK.
Paul Butler, managing director of Mid-Kent Water, said it was "essential" the powers were granted by Defra if water levels remained depleted.
Visitors to beatthedrought.com website will be encouraged to take steps such as turning off the tap while they brush their teeth and repairing leaking taps to cut down the amount of water they use.
The South East has had two consecutive winters with below-average rainfall.
The period between November 2004 and January 2006 was the driest for more than 80 years, surpassing even the notable drought of 1974-76.
Although some reservoirs have relatively high levels of water, below-average rainfall has left many aquifers depleted.
Aquifers - also known as ground reservoirs - are underground layers of rock that collect water.
Andrew Marsh, of the Consumer Council for Water, said: "In the last 18 months it's been very, very dry and there's now a genuine water resources problem."
Three Valleys Water, which serves three million people in the South East, announced on Monday that it was imposing hosepipe and sprinkler bans from 3 April.
The area covers Essex, Bedfordshire, Buckinghamshire, Hertfordshire, north London and Middlesex.
Last week, Britain's biggest water company, Thames Water, announced a ban on hosepipes and sprinklers that will affect eight million customers.
The announcement by Thames follows decisions by Sutton and East Surrey Water, South East Water, Southern Water, Mid Kent Water, and Cholderton and District Water to ban hosepipes.