World Water Sources
Library of Water

The World’s Water Sources

Water covers roughly 70 per cent of the Earth’s surface, with a volume of 1,386,000,000 cubic kilometres.

However, 97 per cent of this water is undrinkable because it is saltwater from the oceans. Of the three per cent of the world's water supply that is freshwater meaning it has low concentrations of dissolved salts and other total dissolved solids, about 69 per cent is held in glaciers and ice caps, 30 per cent is groundwater held in underground soil and rock crevices, leaving the final 1 per cent as surface water to include lakes, swamps and rivers, according to the National Geographic. Most of the world's freshwater comes from surface and underground water. This includes underground aquifers (gravel and sand-filled underground reservoirs). The rest comes from rainfall, man-made reservoirs, lakes and rivers. The main sources are:

Fresh Water Sources:

  • The Antarctic ice sheet is approximately 8.7 million square miles in size and holds roughly 90 percent of the fresh water that exists on the Earth’s surface.
  • The Greenland ice sheet also contains large volumes of fresh water. Together with the Antarctic ice sheet they account for almost 99 percent of the fresh water ice on the planet
  • The American Great Lakes account for 21 percent of the Earth’s surface fresh water.
  • Lake Baikal in Russia holds almost 20 percent of the Earth’s unfrozen surface fresh water.
  • Lake Victoria, which has borders with Kenya, Uganda and Tanzania, is the second largest freshwater lake in the world by surface area.
  • The second deepest freshwater lake, Africa’s Lake Tanganyika runs through Burundi, Zambia, Tanzania, and the Democratic Republic of Congo.
Antarctic Ice Sheet
We never know the worth of water till the well is dry. Thomas Fuller
American Great Lakes

Clean water

Research into ensuring there is enough clean, drinkable water available to all has become a higher priority with each passing year.

Whilst the world’s supply of water remains the same, the demand for it increases whilst pollutants continue to decrease the amount of available clean, drinkable water. Contaminated drinking water and poor sanitation facilities can lead to diarrhoea, cholera, dysentery, typhoid, polio and more, leading to the avoidable deaths of up to 361,000 children aged under five years. The World Health Organisation asserts that safe water is an essential element for human health, wellbeing and prosperity. Whether used for drinking, cleaning, food production, industrial output or safe sanitation facilities. Yet access to surface water is not always straightforward as legal water rights usually have to be granted first. However, increasing access is not enough. The aim is that by 2030, there will be universal and equitable access to safe and affordable drinking water for all, and access to adequate and equitable sanitation and hygiene for all as a human right. Additional targets that go beyond access are also being considered, such as improving water quality by reducing pollution, and substantially increasing water-use efficiency.

Reduction in sources

Freshwaters is a finite, and in some regions, scarce resource.

The challenge is to balance human needs for freshwater with sustaining long-term supplies which is influenced by political boundaries, economic development and wealth, with much water lost through pipe leaks and evaporation and some countries unable to clean and transport water. At the same time, a study by NASA has said that the world’s freshwater sources are being drained faster than they are being replenished, mostly due to agriculture and food production which use most of the global freshwater. Freshwater is also used for cooling power stations, which are also expected to see a growth in demand over the next several years. Despite the importance of water for development, in a recent sample of 37 countries from Africa, 82 per cent of governments indicated that financing was insufficient to reach national targets for drinking water. The uncertainties brought about by political economy and climate change only add to this sector’s already considerable challenges. It is not surprising that world leaders now rank water as one of their top critical issues. The largest multilateral source of financing for water supply and sanitation in developing countries is the World Bank Group has financed USD13.5 billion in water related operations globally.

Lake Baikal in Russia