Some 70% of the earth's surface is water, but most of that is ocean. By volume, only 3% of all water on earth is fresh-water, and most of this is largely unavailable. About three-quarters of all freshwater is locked away in the form of ice caps and glaciers located in polar areas far removed from most human habitation; only about 1% is easily accessible surface freshwater.

Globally, between 12.5 and 14 billion cubic meters of water are considered available for human use on an annual basis. This amounts to about 9,000 cubic meters per person per year, as estimated in 1989. By the year 2025 global per capita availability of freshwater is projected to drop to 5,100 cubic meters per person as another 2 billion people join the world's population. Even then, this amount would be enough to meet human needs if it were distributed equally among the world's population .

Global per capita figures on water availability give a false picture, however. The world's available freshwater supply is not distributed evenly around the globe, throughout the seasons, or from year to year. In some cases water is not where we want it, nor in sufficient quantities. In other cases we have too much water, in the wrong place, at the wrong time.

As populations grow and water use per person rises, demand for freshwater is soaring. Yet the supply of freshwater is finite and threatened by pollution. To avoid a crisis, many countries must conserve water, pollute less, manage supply and demand, and slow population growth.

Today 31 countries, accounting for under 8% of the world population, face chronic freshwater shortages. By the year 2025, however, 48 countries are expected to face shortages, affecting more than 2.8 billion people-35% of the world's projected population. Among countries likely to run short of water in the next 25 years are Ethiopia, India, Kenya, Nigeria, and Peru. Parts of other large countries, such as China, already face chronic water problems

In much of the world polluted water, improper waste disposal, and poor water management cause serious public health problems. Such water-related diseases as malaria, cholera, typhoid, and schistosomiasis harm or kill millions of people every year. Overuse and pollution of water supplies also are taking a heavy toll on the natural environment and pose increasing risks for many species of life.