Specific questions on water quantities
Specific questions on water use and the amounts of available water on earth
Approximately 1385 million cubic kilometres of water are available on earth. 97,5% of the water is salt water that can be found mainly in oceans. Only 2,5% is freshwater that can be used by plants, animals and humans. However, nearly 90% of this freshwater is not readily available, because it is centred in icecaps of the Antarctic. Only 0.26% of the water on this world is available for humans and other organisms, this is about 93.000 cubic kilometres. Only 0.014% of this water can be used for drinking water production, as most of it is stored in clouds or in the ground.
Increases in world population means increased water use and less availability on a per capita basis. In 1989 there was some 9,000 cubic metres of freshwater per person available for human use. By 2000, this had dropped to 7,800 cubic metres and it is expected to plummet to 5,100 cubic metres per person by 2025, when the global population is projected to reach 8 billion.
People already use over half the world's accessible freshwater now, and may use nearly three-quarters by 2025. Over the twentieth century, the world annual water use has grown from about 300 km3 to about 2,100 km3 (see chart).
In this chart the annual water consumption is shown, as withdrawal and use. These two concepts are separated, because much of the withdrawn water is later returned to the water cycle, after application. An example is cooling water; it is used for power generation and is immediately released for further use downstream.
Global consumption of water is doubling every 20 years, more that twice the rate of human population growth. According to the various water research agencies, the world water use is expected to triple in the next 50 years.
Water scarcity is caused by dry climates, drought, desiccation, or water stress. Water scarcity caused by drought has killed over 24,000 people a year since the 1970's. Over 40% of the world's population now experiences water shortages that threaten their agriculture and industry and also their personal health. Today over a billion people do not have access to clean drinking water and by 2025 at least 3 billion people in 90 different countries are expected to face severe water stress. The main problem that causes this is not a shortage of water, but the wasteful and unsustainable use of available water supplies.
The costs of a cubic meter of water are known to differ between countries. In this chart, the costs of one cubic meter of water are shown, for 14 different countries.
When water is desalinated through the Reverse Osmosis (RO) treatment, the costs are as follows:
The costs should decline within the next 10-50 years, as membranes become cheaper and more efficient. However, the costs are mostly energy related, so the energy use should be taken into account.
Global population now exceeds 6.2 billion, more that double what it was in 1950, and is currently projected to rise to between 7.9 billion and 10.9 billion by 2050. Even when the population does not increase, water use will still grow. A population increase will only make the global water use rise faster.
For more answers to your questions on water quantities, move to our Water Quantity FAQ
For the answers to your questions on drinking water, move to our Drinking Water FAQ