Water covers 71% of the Earth's surface; the oceans contain 97.2% of the Earth's water. The Antarctic ice sheet, contains 90% of all fresh water on Earth. Condensed atmospheric water can be seen as clouds, contributing to the Earth's albedo.
Clean, fresh drinking water is essential to human and other life forms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world. There is a clear correlation between access to safe water and GDP per capita. Water plays an important role in the world economy, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70 % of fresh water is consumed by agriculture.
The human body is between 55% to 78% water depending on body size.
To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water.