Water use is increasing everywhere. The world's six billion people are already appropriating 54 per cent of all the accessible freshwater contained in rivers, lakes and underground aquifers. By 2025 humankind's share will be 70 per cent. This estimate reflects the impact of population growth alone. If per capita consumption of water resources continues to rise at its current rate, humankind could be using over 90 per cent of all available freshwater within 25 years, leaving just 10 per cent for the rest of the world's species.

Currently, on a global basis, 69 per cent of all water withdrawn for human use on an annual basis is soaked up by agriculture (mostly in the form of irrigation); industry accounts for 23 per cent and domestic use (household, drinking water, sanitation) accounts for about 8 per cent. These global averages vary a great deal between regions. In Africa, for instance, agriculture guzzles 88 per cent of all water withdrawn for human use, while domestic use accounts for 7 per cent and industry for 5 per cent. In Europe, most water is used in industry (54 per cent), while agriculture's share is 33 per cent and domestic use 13 per cent.

Agriculture
 
Almost 70 per cent of all available freshwater is used for agriculture. Overpumping of groundwater by the world's farmers exceeds natural replenishment by at least 160 billion cubic metres a year. It takes an enourmous amount of water to produce crops: one to three cubic metres to yield just one kilo of rice, and 1,000 tons of water to produce one ton of grain.

Land in agricultural use has increased by 12% since the 1960s to about 1.5 billion hectares. Current global water withdrawals for irrigation are estimated at about 2,000 to 2,555 km³ per year. Pasture and crops take up 37 percent of the Earth's land area.

Poor drainage and irrigation practices have led to waterlogging and salinization of approximately 10 percent of the world's irrigated lands (30 million hectares of the world's 255 million hectares of irrigated land) according to the UN Food and Agricultural Organization (FAO). A combination of salinisation and waterlogging affects another 80 millions hectares.

Agriculture is responsible for most of the depletion of groundwater, along with up to 70 per cent of the pollution. Both are accelerating. Many of the world's most important grainlands are consuming groundwater at unsustainable rates. Collectively, annual water depletion in India, China, the United States, North Africa and the Arabian Peninsula adds up to a hefty 160 billion cubic metres a year - an amount equal to the total annual flow of two Nile Rivers.

Industry
 
Water withdrawals for industry:

 World: 22% of total water use
 High-income countries: 59% of total water use
 Low-income countries: 8% of total water use

The annual water volume used by industry will rise from 752 km3/year in 1995 to an estimated 1,170 km3/year in 2025.

In 2025, the industrial component is expected to represent about 24% of total freshwater withdrawal.

Some 300-500 million tons of heavy metals, solvents, toxic sludge, and other wastes accumulate each year from industry.

Industries based on organic raw materials are the most significant contributors to the organic pollutant load with the food sector being the most important polluter.

Contribution of the food sector to the production of organic water pollutant:

 High income countries: 40%
 Low-income countries: 54%

More than 80% of the world's hazardous waste is produced in the United States and other industrial countries.

In developing countries, 70% of industrial wastes are dumped untreated into waters where they pollute the usable water supply.

Energy
 
World energy demand, especially for electricity, will increase greatly during this 21st century, not only because of demographic pressures, but also because of improved living standards, urban and industrial growth, and rising expectations.

Hydropower is the most important and widely-used renewable source of energy; it represents 19% of total electricity production. Worldwide there are now about 45,000 large dams in operation. Canada is the largest producer of hydroelectricity, followed by the United States and Brazil.

Built to provide hydropower and irrigation water and to regulate river flow to prevent floods and droughts, they have had a disproportionate impact on the environment. Collectively, they have inundated more than 400,000 square kilometres of mostly productive land - an area the size of California. Fully one-fifth of the world's freshwater fish are now either endangered or extinct. Somewhere between 40 and 80 million people have been displaced by dams, forced to relocate to other , often less productive, land.

A study by the World Commission on Dams, published in 2000, found that large dams have a very mixed record.

On one hand:

 In 140 countries, dams provide cheap hydroelectric power. On a global scale, dams account for 19 per cent of the world's electricity generation and supply; through irrigation, almost 16 per cent of the world's food.
 Some dams continue to operate after 30-40 years, providing water and electricity.
 Hydropower plays a major role in reducing greenhouse gas emissions: developing ½ of the world's economically feasible hydropower potential could reduce greenhouse gases emissions by about 13%.

On the other hand:

 Large dams have led to the loss of forests and wildlife habitat and the loss of aquatic biodiversity - both upstream and downstream.
 Large dams have, in most cases, systematically failed to assess and account for the range of potential negative impacts on displaced and resettled communities. With up to 80 million people displaced from their homes and many more living downstream suffering from unintended effects (e.g., loss of fisheries), mitigation efforts have, for the most part, been cosmetic and ineffective.

According to the Commission, large dams may be on their way out:

 Mini-hydropower plants have proved to be far cheaper to build and more economical to run than originally forecasted; plus they have minimal impacts on the environment.
 Better management to reduce the demand for water has great potential to reduce water stress and hydropower requirements.
 Improved systems management, particularly for irrigated agriculture, has tremendous potential for reducing waste, while increasing the efficiency of irrigation systems.

Sources: World Water Assessment Programme, People and the Planet