At the Farmoor reservoir, a few miles west of Oxford, you cannot tell that anything is wrong. Windsurfers weave among a smattering of dinghies on the water; closer to the shore, a family of ducks and a pair of swans cruise the surface. In this idyllic location, where 136 billion litres are stored, it is hard to believe that there is a water crisis in Britain this summer. But a drought caused by a lack of rain all winter has meant restrictions across the country, with more to come.
Hosepipe bans have already been imposed in parts of Surrey, Sussex and Wiltshire, and Thames Water admits they are "probably imminent" in the capital. The Mayor of London, Ken Livingstone, is urging citizens not to flush the loo "just for a pee". And just across the Channel, French rivers are drying up, "water police" have been drafted in and farmers say their crops are at risk from irrigation restrictions covering more than half of the country. In Spain the situation is even worse, and, some experts say, is a vision of our own future.
The hidden truth of Farmoor is that on the other side of the reservoir, where the swallows tumble around the pumps, the river that supplies it is dwindling to a critical level. Soon, the Environment Agency will tell Thames Water to stop removing water from this upper stretch of the Thames to replenish its supplies.
Natural underground sources that usually trickle into the river during summer are uncommonly low, after the third-driest winter since records began more than 120 years ago. Should its sources dry up, the water in Farmoor reservoir is expected to last for only 90 days.
The winter was unusually dry, global warming being widely blamed for the crisis, which will only get worse. Warnings and restrictions are becoming more strident. But tracing the course of our water supplies from the rain cloud to the tap - or sprinkler, or hosepipe - raises two big questions. Who is using all the water? And why is so much of it being lost before it even gets to the customer?
Last week it was revealed that water authorities around the country are allowing 3,600 million litres a day to leak away through their broken pipes. The situation is so bad that the Environment Agency has forbidden water companies from building any more reservoirs until the pipes are fixed. Thames Water came in for the most criticism, having failed to meet the regulator's target. It actually loses 915 million litres every day from miles of pipes under the city that are rotten, crumbling and up to 150 years old. That amount is the equivalent of 40 Olympic-sized swimming pools, or enough for every household to flush the toilet 30 times a day.
Thames Water must contend with the oldest pipes in Britain being corroded by the clay through which they run, and cracked by the pressure from above ground of heavy traffic. It says a massive project is now under way to replace these crumbling pipes: more than 140 miles of cast iron Victorian mains have been replaced with plastic since 2002, saving about 260,440 litres of water per mile per day. The company plans to renew a further 850 miles of pipework by 2010, at a cost of £540m. And a further £60m a year is being spent finding and fixing leaks.
However, that is not enough, say campaign groups such as WaterWatch. "Thames Water is taking the mickey out of customers and the regulator. It is the height of hypocrisy for Thames Water and others to be telling the public to conserve supplies when they allow this level of leaks," the group says.
"Ofwat [the water industry regulator] should act now to prevent companies like Thames from putting up customers' bills until they can demonstrate they are taking this seriously."
London already receives less rainfall per head of population than Madrid, Istanbul, Syria and even Sudan; less also than Birmingham, which still acquires most of its water via an aqueduct from Wales; and much less than Scotland and the North, which are nothing if not sorted for precipitation. To add to the burden, John Prescott is talking about building 720,000 new homes in the South-east. All of their new inhabitants will want dishwashers and immaculate lawns.
Water is not an infinite resource. Primary school textbooks may suggest that its life is cyclical - from cloud to reservoir to tap to waste pipe to sea to cloud - but the process sullies and depletes the supply. A "national grid" for water, taking supplies from plentiful Scotland to parched London, would be "horrendously expensive" says Ofwat.
Neither would diverting watercourses work: to send the acidic River Severn to serve the capital would introduce aquatic species to water of a different quality that would kill them.
Meanwhile, eight Thames Water boreholes are about to be closed by the Environment Agency. And last week, the company confirmed that it will appeal against a decision by Newham Council to refuse permission for a desalination plant that would turn 10 million litres of salt water a day from the tidal river into drinking water for Londoners. It says it needs this and at least one new reservoir. But the Environment Agency says the company cannot start building it until it stops allowing water to dribble out of the pipes.
Customers, meanwhile, are under increasing pressure to use water more carefully. Scientists are researching better showers and lobbying the Government and planning authorities to make more new houses water-efficient. Any customer who applies can receive a free "hippo" - a water-saving device that reduces a toilet flush by as much as a third. Normally, each flush uses nine litres of water - as much as the average person in the developing world uses for a day's washing, drinking, cleaning and cooking. And that's only the start. Those of us who leave the tap running while we brush our teeth are watching about five litres of water a minute gurgle down the drain. Putting on the washing machine for a few tea-towels and the odd sock uses 95 litres for every load. The worst offender is the garden sprinkler, which squirts away 1,000 litres every hour it is left running.
Public gardens such as Kew are the largest but often the most responsible of water users. "Despite the decrease in rainfall over the past few years, we have cut back drastically on our watering," says Kew. "Without any harm to our magnificent plant collections, the gardens are saving water, money and time." Kew horticulturalists have produced a leaflet telling ordinary gardeners how to do the same. Mulch, mulch, mulch seems to be the secret, together with investing in a water butt to catch the rain and bath water (plants in hard water areas especially like waste water that has been softened by detergents) and letting your lawn grow long.
Golf courses are not lush and green by accident. For every day of play about 10,000 litres are expended on keeping the course green and pleasant. But at St Andrews, where the best players in the world are currently competing for the Open, water is carefully conserved. "We have five-and-a-half golf courses and more than 4,000 sprinklers," says Gordon Moir, the links superintendent. "It is a very sophisticated, modern irrigation system. But we hardly ever use it. The grasses we grow are deep-rooted and very drought-tolerant. The old course has fairway irrigation but we didn't use it once last year and we haven't used it this year yet. On TV you'll see how brown the grass is. Irrigation is only there as an insurance."
At Humberstone Heights Golf Club in Leicestershire, greens-keepers installed an underground tank that collects and stores winter rainwater. Mains water use was reduced by almost 30 per cent. The course's greens are currently watered about every second night; the system is switched on for 15 minutes by a computer at the coolest part of the day to minimise evaporation. In Stockport, the council says it does not water its parks at all - and the city still managed to win the Britain in Bloom competition last year.
The campaign to conserve water is hardly new. During the drought of 1976 - the last time we suffered as dry a winter as the one that has just passed - Princess Margaret grandly announced: "We never pull for a pee" (an interesting use of the royal "we"). But the world has changed since then. Climate change is happening and the need to respond is urgent. Little by little, beneath the swans and sailors at Farmoor and other reservoirs like it, the levels are steadily going down.
DOWN THE PLUGHOLE
30 litres of water go down the drain when you shower for five minutes
80 litres are used in the average bath
5 litres are wasted by running the tap while brushing your teeth
1,000 litres an hour are used by a garden sprinkler
4 litres a day are wasted by a dripping household tap
650 litres of water are used per guest per day in a hotel
10,000 litres a day irrigate an 18-hole golf course
40 litres a day are used by the average family in a developing country; here it is 1,000 litres per family
1 flush of the toilet uses as much water as the average person in the developing world uses for one day's washing, drinking, cleaning and cookingReuse content