In meteorology, precipitation (also known as hydrometeor) is any product of the condensation of atmospheric water vapor that is deposited on the earth's surface. It occurs when the atmosphere (being a large gaseous solution) becomes saturated with water vapor and the water condenses and falls out of solution (i.e., precipitates).
Air becomes saturated via two processes, Cooling and Adding Moisture. Precipitation that reaches the surface of the earth can occur in many different forms, including rain, freezing rain, snow, sleet, and hail. Virga is precipitation that begins falling to the earth but dries up before it reaches the surface.
Precipitation is a major component of the hydrologic cycle, and is responsible for depositing most of the fresh water on the planet. Approximately 505,000 km³ of water falls as precipitation each year, 398,000 km³ of it over the oceans.
However, worldwide more than 1 billion people live in areas where water is in short supply and more than one-third of the world's population has no access to sanitation facilities because of this. Unfortunately, this water crisis is predicted to worsen.
In the last century, global water consumption rose six-fold, more than double the rate of population growth. As freshwater resources continue to disappear the World Bank estimates that by 2035 there will be 3 billion people with no access to any safe water, period.
Most of these people will be living in developing countries which lack the infrastructure and support systems of industrialised nations to deal with this impending crisis.
"Problems cannot be solved at the same level of awareness that created them."