Wednesday, August 26, 2009

The Hydrologic cycle: condensation, precipitation, infiltration, runoff & evapotranspiration

World Water Supply by Location (

Oceans - 97.08%
Ice Sheets and Glaciers - 1.99%
Ground Water - 0.62%
Atmosphere - 0.29%
Lakes (Fresh) - 0.01%
Inland Seas and Salt Water Lakes - 0.005%
Soil Moisture - 0.004%
Rivers - 0.001%

Only during the ice ages are there noticeable differences in the location of water storage on the earth. During these cold cycles, there is less water stored in the oceans and more in ice sheets and glaciers.

It can take an individual molecule of water from a few days to thousands of years to complete the hydrologic cycle from ocean to atmosphere to land to ocean again as it can be trapped in ice for a long time.

For scientists, five main processes are included in the hydrologic cycle: 1) condensation,
2) precipitation,
3) infiltration,
4) runoff, and
5) evapotranspiration.

The continuous circulation of water in the ocean, in the atmosphere, and on the land is fundamental to the availability of water on the planet.