From the Economist:
...there is some admittedly patchy evidence that, given current patterns of use and abuse, the amount now being withdrawn is moving dangerously close to the limit of safety—and in some places beyond it. An alarming number of the world’s great rivers no longer reach the sea. They include the Indus, Rio Grande, Colorado, Murray-Darling and Yellow rivers. These are the arteries of the world’s main grain-growing areas.
Freshwater fish populations are in precipitous decline. According to the World Wide Fund for Nature, fish stocks in lakes and rivers have fallen roughly 30% since 1970. This is a bigger population fall than that suffered by animals in jungles, temperate forests, savannahs and any other large ecosystem. Half the world’s wetlands, on one estimate, were drained, damaged or destroyed in the 20th century, mainly because, as the volume of fresh water in rivers falls, salt water invades the delta, changing the balance between fresh and salt water. On this evidence, there may be systemic water problems, as well as local disruptions.
Two global trends have added to the pressure on water. Both are likely to accelerate over coming decades.
The first is demography. Over the past 50 years, as the world’s population rose from 3 billion to 6.5 billion, water use roughly trebled. On current estimates, the population is likely to rise by a further 2 billion by 2025 and by 3 billion by 2050. Demand for water will rise accordingly.
Or rather, by more. Possibly a lot more. It is not the absolute number of people that makes the biggest difference to water use but changing habits and diet. Diet matters more than any single factor because agriculture is the modern Agasthya, the mythical Indian giant who drank the seas dry. Farmers use about three-quarters of the world’s water; industry uses less than a fifth and domestic or municipal use accounts for a mere tenth.
Different foods require radically different amounts of water. To grow a kilogram of wheat requires around 1,000 litres. But it takes as much as 15,000 litres of water to produce a kilo of beef. The meaty diet of Americans and Europeans requires around 5,000 litres of water a day to produce. The vegetarian diets of Africa and Asia use about 2,000 litres a day (for comparison, Westerners use just 100-250 litres a day in drinking and washing).
So the shift from vegetarian diets to meaty ones—which contributed to the food-price rise of 2007-08—has big implications for water, too. In 1985 Chinese people ate, on average, 20kg of meat; this year, they will eat around 50kg. This difference translates into 390km3 (1km3 is 1 trillion litres) of water—almost as much as total water use in Europe...
The other long-term trend affecting water is climate change. There is growing evidence that global warming is speeding up the hydrologic cycle—that is, the rate at which water evaporates and falls again as rain or snow. This higher rate seems to make wet regions more sodden, and arid ones drier. It brings longer droughts between more intense periods of rain.
Climate change has three big implications for water use. First, it changes the way plants grow. Trees, for example, react to downpours with a spurt of growth. During the longer droughts that follow, the extra biomass then dries up so that if lightning strikes, forests burn more spectacularly. Similarly crops grow too fast, then wilt.
Second, climate change increases problems of water management. Larger floods overwhelm existing controls. Reservoirs do not store enough to get people or plants through longer droughts. In addition, global warming melts glaciers and causes snow to fall as rain. Since snow and ice are natural regulators, storing water in winter and releasing it in summer, countries are swinging more violently between flood and drought. That is one big reason why dams, once a dirty word in development, have been making a comeback, especially in African countries with plenty of water but no storage capacity. The number of large dams (more than 15 metres high) has been increasing and the order books of dam builders are bulging.
Third, climate change has persuaded western governments to subsidise biofuels, which could prove as big a disaster for water as they already have been for food. At the moment, about 2% of irrigated water is used to grow crops for energy, or 44km3. But if all the national plans and policies to increase biofuels were to be implemented, reckons the UN, they would require an extra 180km3 of water. Though small compared with the increase required to feed the additional 2 billion people, the biofuels’ premium is still substantial.
In short, more water will be needed to feed and heat a world that is already showing signs of using too much. How to square that circle? The answer is by improving the efficiency with which water is used. The good news is that this is possible: vast inefficiencies exist which can be wrung out. The bad news is it will be difficult both because it will require people to change their habits and because governments, which might cajole them to make the changes, are peculiarly bad at water policy...
To make water use more efficient, says Koichiro Matsuura, the head of UNESCO, the main UN agency dealing with water, will require fundamental changes of behaviour. That means changing incentives, improving information flows, and improving the way water use is governed. All that will be hard.
Water is rarely priced in ways that reflect supply and demand. Usually, water pricing simply means that city dwellers pay for the cost of the pipes that transport it and the sewerage plants that clean it.
Basic information about who uses how much water is lacking. Rainwater and river flows can be measured with some accuracy. But the amount pumped out of lakes is a matter of guesswork and information on how much is taken from underground aquifers is almost completely lacking.
The governance of water is also a mess. Until recently, few poor countries treated it as a scarce resource, nor did they think about how it would affect their development projects. They took it for granted...
As is often the way, business is ahead of governments in getting to grips with waste. Big drinks companies such as Coca Cola have set themselves targets to reduce the amount of water they use in making their products (in Coke’s case, by 20% by 2012). The Nature Conservancy, an ecologically-minded NGO, is working on a certification plan which aims to give companies and businesses seals of approval (a bit like the Fairtrade symbol) according to how efficiently they use water. The plan is supposed to get going in 2010. That sort of thing is a good start, but just one step in a long process that has barely begun.