This footprint varies considerably from country to country, however: the average American, for example, has a water foot-print of 2,483 tonnes (655,000 U.S. gallons) per year whereas the average Chinese has one of 702 tonnes (185,000 U.S. gallons)— part of the difference being due to meat consumption. Countries that are warm and have high evaporation rates use more water to grow food, and thus have large water footprints— examples being Italy and Greece, which both use around 2,300 tonnes per capita annually. Countries whose climate favors efficient food production tend to have lower water use per capita, such as the Netherlands (1,220 tonnes per capita) or Australia (1,390 tonnes per capita). Around one- sixth of the world’s accessible water is used to grow food for export to other countries, making water- poor countries increasingly reliant on those with ample supplies.
Today our freshwater supply is being stretched to the limit. The main reasons include the following. Food demand growth. Since 1950 the area of irrigated land has doubled and withdrawals of water have tripled due to our growing population and even stronger demand for high-protein food. It is conservatively estimated that an additional 6,000 cubic kilometers (or 1,500 cubic miles) of freshwater will be needed for irrigation to meet future increases in global population and food demand.
City growth. Worldwide, 3.5 billion people now live in cities. By 2050, it is quite likely that cities will have 7 billion inhabitants. Current urban water demand of 1,200 cubic kilometers (300 cubic miles) thus could balloon to around 2,500 cubic kilometers (600 cubic miles) or even more.12 As cities are usually richer than farmers, they can afford to buy water once used to grow food and divert it to urban uses, which tends to reduce local food production and cause food prices to rise.
Economic growth. As populations develop eco nom ical ly, their per capita consumption of meat, dairy, sugar, and oils rises, and these food-stuffs require far more water to produce than vegetables and grains do. The more successful we are at overcoming poverty and building our economies, the heavier the demands we place on water resources.
Overextraction. Mechanical pumps powered by fossil fuels allow the extraction of surface and underground water in im mense volumes, which often exceed natural rates of recharge. This is causing the level of ground-water to fall rapidly in most countries where it is used to grow food. Pumping of groundwater also helps to empty rivers, lakes, and wetlands and kills landscapes when water tables sink out of the reach of tree roots. In many countries, governments encourage this destruction and waste by providing cheap hydroelectricity or by underpricing water.
Ignorance. Most communities and many water authorities do not in fact know the true extent of their water resource or the rate at which it is replenished. This makes every decision to use it a gamble— and one that often goes wrong, resulting in a dying river, lake, aquifer, basin, or even sea.
Confusion. Many people, including governments, seem unaware that surface water in rivers and lakes and groundwater drawn from wells and aquifers are often interconnected and that removing one reduces the supply of the other. People often regard well water as a “free good.” Consequently, more water may be withdrawn than the total system receives in recharge.