Millions of householders across southern and eastern England will be banned from using hosepipes from today as drought grips parts of the country.
Seven water companies are introducing restrictions on water use following one of the driest two-year periods on record, with domestic customers facing a £1,000 fine if they use their hosepipe in defiance of the ban.
Thames Water, Southern Water, South East Water, Anglian Water, Sutton and East Surrey, Veolia Central and Veolia South East are bringing in the restrictions today, affecting about 20m people.
Customers will no longer be able use their hosepipes for watering their gardens, washing cars or boats, hosing down patios and paths and filling swimming pools, ponds, fountains and paddling pools. Public parks and allotments will also be hit.
The firms insist they are necessary to preserve essential water supplies and protect the environment, in the face of drought which has left groundwater below 1976 levels in some places and rivers running dry.
Despite some rain in the past few days, March was another dry month and the whole of the South East and East Anglia and parts of Yorkshire are officially in a state of drought.
Yorkshire Water has said it does not anticipate bringing in hosepipe restrictions as yet.
The Environment Agency said most reservoirs were now below normal levels and river flows were decreasing. All rivers are experiencing lower than normal flows, with two-thirds "exceptionally" low.
The water firms bringing in restrictions say they are investing significant resources in fixing leaks, moving water resources from wetter to drier areas and encouraging their customers to save water.
But the Environment Agency has urged companies to do more to tackle leakage rates.
Water companies across England and Wales leaked more than 3.3bn litres a day in 2010/11, according to Ofwat, the economic regulator of the water and sewerage industry. Anglian and Southern were among the companies to fail to meet their water leakage targets last year.
But the water companies say the main problem is that it has not rained enough in the past two winters to restock supplies.
Peter Simpson, managing director of Anglian Water, said: "Two dry winters have prevented rivers, reservoirs and aquifers from refilling with the water we treat and supply the rest of the year, especially during the hotter months when demand rises."
Martin Baggs, chief executive of Thames Water, said: "Imposing restrictions on the use of hosepipes, although regrettable, is the most sensible and responsible next step in encouraging everyone to use less water so we can maintain supplies for as long as it stays dry, and reduce the risk of more serious restrictions later in the year."
Southern Water estimated that the hosepipe ban would reduce water demand by around 5% while Thames Water said its last ban in 2006 reduced demand by 10%.
Mike Hegarty, Sutton and East Surrey Water's operations director, said: "We have said from the outset that we very much regret having to impose this bar but this drought is becoming increasingly serious.
"We have no choice if we are to protect our customers by ensuring the long-term security of their water supply."
He warned that the drought could continue, saying: "We must be mindful of the possibility - albeit unprecedented - of a third dry winter."
Companies have warned of wider restrictions, including extending the hosepipe ban to businesses.
But Gavin McHale, head of operations at Veolia Water Southeast, stressed there was no likelihood of standpipes being needed, although he urged customers to do everything they could to save water.
Thames Water said prosecuting customers for breaching the ban, which is a criminal offence, was the "last thing we want to have to do" and urged people to work with water companies to use water as sparingly as possible.
Environment Secretary Caroline Spelman said: "These temporary restrictions will help protect the public's water supply in the areas most affected by the record low levels of rainfall we have experienced.
"We can all help reduce the effects of drought by respecting these restrictions and being smarter about how we use water. Taking action now to reduce how much water we use will help us all in the future."
As part of its measures to tackle water shortages, Thames Water has been running its desalination plant in Beckton, East London, which was built to convert sea and fresh water from the Thames Estuary into drinking water in times of drought.
The plant, which can supply enough water for one million people, has now been taken offline for a service, but will be treating water again shortly. Thames Water plans to keep it running throughout the summer if needed.
Conservation groups called on the public to support the hosepipe ban as part of efforts to deal with a drought that could have serious impacts for the countryside.
Phil Burston, RSPB water policy officer, said: "Reducing demand now will help keep more water in the environment, keeping rivers flowing for longer and protecting their precious wildlife.
"Every indicator, whether river flow or groundwater level, is telling us that this is a very serious drought that could be worse than the infamous 1976 event.
"It is really important for us all to reduce the water we use in our homes and gardens now to hopefully avoid further environmental damage and restrictions in use later in the year."
He said the drought was already hitting RSPB wetlands, threatening to affect the breeding seasons of birds such as snipe, redshank and black-tailed godwit.
The Environment Agency called for businesses, as well as householders, to save water, warning hosepipe bans for residents were effective, but "not a silver bullet".
Trevor Bishop, head of water resources at the government agency, said: "While households have a very important role to play in helping to cut water use during the current drought, businesses, farmers and water companies must all play their part too, by using water wisely to ensure that the water that we do have goes further.
"Being water efficient makes good business sense, and can help businesses save money.
"It will also ensure that there is enough water to produce food, products and services, and in the environment for wildlife."
The Environment Agency urged companies to carry out water audits to identify where savings could be made, for example by fixing leaks.
Other suggestions include considering investing in rainwater harvesting and waste water recycling systems, ensuring taps are off and cleaning windows and fleet cars less often, while maintaining health and safety standards.
Shadow environment minister Gavin Shuker said: "The hosepipe ban and water restrictions are further bad news for households worried about the weather.
"We have seen the driest 12 months on record and drought conditions will become more common in future.
"Lack of water could mean food prices go up, wildlife will suffer and, in the worst case, construction and energy industries affected.
"The Government needs to stop dragging its feet and legislate for the long awaited reforms we need to protect our water supply."