Every time there is a drought, water companies can be found dusting off their plans for new reservoirs. After another dry winter in the UK, this year is unlikely to be an exception. Thames Water is preparing plans for the largest man-made structure in Britain -- a £700 million (US$1.22 billion) reservoir covering 10km2, with banks rising as high as a church tower above the flat farmland near Abingdon in Oxfordshire.
The scheme, designed to store water from the Thames in winter and release it downstream in summer, is due to be unveiled this week. Thames Water had booked the local village hall, but then canceled. The firm denies the story, but many believe that the delay is because Thames Water has been put up for sale by its German owners.
Even so, it has pencilled in a public inquiry for 2008 and, if it gets its way, the Vale of the White Horse will be under water by 2020. The alternative could be standpipes in the capital, say the firm's engineers.
But few of those engineers will be aware that 30 years ago, before Thames Water was privatized, an economic study by their public sector predecessors concluded that saving water by plugging leaks in water mains and installing new valves for every toilet cistern in London would be cheaper and just as effective.
Britain is a modest user of water, consuming a sixth as much per head as Egypt, for instance. This is mainly because a moderate temperatures, reasonable rainfall and cloudy skies ensure that British crops mostly grow without artificial irrigation.
But water engineers in the UK share with their colleagues the world over an obsession with dams and pipes and concrete. They want to supply ever more water, and are deaf to calls for investment in demand management.
DRY BEDS
And, as I have discovered in a five-year investigation of the world's water, this supply-side fixation is creating a global hydrological crisis that threatens the survival of some of the world's largest rivers.
The world atlas no longer tells the truth. Today, dozens of the greatest rivers are dry long before they reach the sea. They include the Nile in Egypt, the Yellow River in China, the Indus in Pakistan, the Rio Grande and Colorado in the US, the ancient Oxus that once fed the Aral Sea in Central Asia, the Murray in Australia, and the Jordan, which is emptied before it reaches the country that bears its name.
The biggest demand on the world's water is irrigated farming, which takes two-thirds of all the water abstracted from rivers and underground reserves. This is largely due to the green revolution.
The "high-yielding" plant varieties that have kept the world fed as populations have doubled over the last 30 years turn out to be high-yielding only when measured against land area. Measured against water use, they are generally worse than the crops they replaced. They produce less crop per drop.
As a result, the world grows twice as much food as it did a generation ago, but abstracts three times as much water to do it.
The UN Food and Agriculture Organization says that on at least a third of the world's fields today, "water rather than land is the binding constraint" on production.
This profligacy is present in every supermarket trolley. The amount of water needed to grow our everyday food is staggering. To grow a kilo of rice takes between 2,000 and 5,000 liters of water -- more than many households use in a week. It takes 20,000 liters to fill a kilo jar of coffee, up to 4,000 liters to grow the fodder that will deliver a liter of cow's milk, and up to 11,000 liters to make a quarter-pound hamburger.
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