The Hydrologic Cycle
online meteorology guide

Graphic by: Dan Bramer

Water is the source of all life on earth. The distribution of water, however, is quite varied; many locations have plenty of it while others have very little. Water exists on earth as a solid (ice), liquid or gas (water vapor). Oceans, rivers, clouds, and rain, all of which contain water, are in a frequent state of change (surface water evaporates, cloud water precipitates, rainfall infiltrates the ground, etc.). However, the total amount of the earth's water does not change. The circulation and conservation of earth's water is called the "hydrologic cycle". The Hydrologic Cycle module has been organized into the following sections:

Last Update: 07/21/97
The Earth's Water Budget
The distribution of water among the oceans, land and atmosphere.

The transformation of water from a liquid into a gas, a process which humidifies the atmosphere.

The transformation of water from a gas into a liquid, and the processes that lead to condensation.

The movement of water through the atmosphere.

The transfer of water from the atmosphere to land. Rain, snow, hail, sleet, and freezing rain are discussed.

Water located below ground and how it returns to the surface.

Transfer of water to the atmosphere by plants and vegetation.

Rivers, lakes, and streams transport water from land to the oceans. Too much rainfall can cause excess runoff, or flooding.

Summary and Example
A brief encapsulation of the hydrologic cycle, plus an example of the hydrologic cycle at work.

Those who contributed to the development of this module.

Terms for using data resources. CD-ROM available.
Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.