What is the Earth's "water cycle?"
The water cycle, also known as the hydrologic cycle, describes the continuous movement of water as it makes a circuit from the oceans to the atmosphere to the Earth and on again.
Most of Earth's water is in the oceans. The sun, which drives the water cycle, heats water in the oceans. Some of it evaporates as vapor into the air. Rising vapor cools and condenses into clouds. Cloud particles grow and fall out of the sky as precipitation.
Some precipitation accumulates as ice caps, glaciers, and snowpacks; in warmer climates, snow melts in the spring and flows into streams. Most precipitation falls back into the oceans or onto land, where it flows over the ground as surface runoff. A portion of runoff enters rivers and continues toward the oceans. Runoff and groundwater seepage can also accumulate and get stored as freshwater in lakes.
Some runoff soaks into the ground where it replenishes groundwater aquifers or seeps back to the surface.
Over time, this cycle continues again and again.
Learn more: USGS Water Science School: The Water Cycle
Related Content
How much water is used by people in the United States?
How much natural water is there?
How do we benefit from USGS streamgages?
What is groundwater?
Summary of estimated water use in the United States in 2010
About 355,000 million gallons per day (Mgal/d) of water was withdrawn for use in the United States during 2010, a decline of 13 percent from 2005 and a substantial change from the level of about 400,000 Mgal/d reported from 1985 to 2005. Withdrawals for 2010 were lower than withdrawals estimated for 1970. Fresh surface-water withdrawals (230,000...
Barber, Nancy L.
The water cycle for kids
The U.S. Geological Survey (USGS) and the Food and Agriculture Organization of the United Nations (FAO) have created a water-cycle diagram for use in elementary and middle schools. The diagram is available in many languages. This diagram is part of the USGS's Water Science School, in which the water cycle is described in detail.
Neno, Stephanie; Morgan, Jim; Zonolli, Gabriele; Perlman, Howard; Gonthier, Gerard
Ground water and surface water; a single resource
The importance of considering ground water and surface water as a single resource has become increasingly evident. Issues related to water supply, water quality, and degradation of aquatic environments are reported on frequently. The interaction of ground water and surface water has been shown to be a significant concern in many of these issues....
Winter, Thomas C.; Harvey, Judson W.; Franke, O. Lehn; Alley, William M.
How Much Water Do We Use?
The USGS National Water-Use Science project has documented 60 years of water-use from 1950 to 2010 in an interactive map. Choose a year and pick a category to see how much water your state uses.
The Water Cycle for Schools and Kids
Learn About Water!
The U.S. Geological Survey (USGS) and the Food and Agriculture Organization of the United Nations (FAO) have teamed up to create a water-cycle diagram for schools and kids. It is available in over 30 languages and also in an interactive version made for online
...
El Ciclo del Agua - The Water Cycle, Spanish
El Ciclo del Agua
El ciclo del agua describe la presencia y el movimiento del agua en la Tierra y sobre ella. El agua de la Tierra esta siempre en movimiento y constantemente cambiando de estado, desde líquido, a vapor, a hielo, y viceversa. El ciclo del agua ha estado ocurriendo por billones de años, y la vida sobre la Tierra depende de él; la
...
All of Earth's Water in a single sphere!
This image shows blue spheres representing relative amounts of Earth's water in comparison to the size of the Earth. Are you surprised that these water spheres look so small? They are only small in relation to the size of the Earth. These images attempt to show three dimensions, so each sphere represents "volume." They show that in comparison to the volume of the globe,
...
Diagram of the water cycle, showing natural and human processes
Diagram of the water cycle showing natural and human processes.
El Ciclo del Agua Para Niños, The Water Cycle for Schools, Spanish
El Ciclo del Agua Para Niños
El Servicio Geológico de los Estados Unidos (USGS por sus siglas en inglés) y la Organización de Alimento y Agricultura de las Naciones Unidas (FAO) han colaborado en la creación de un diagrama sobre el ciclo del agua para niños de las escuelas elementales e intermedias.
El Ciclo del Agua
Qué es el ciclo
...
The Water Cycle (Natural water cycle)
The Natural Water Cycle
Earth's water is always in movement, and the natural water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the Earth. Water is always changing states between liquid, vapor, and ice, with these processes happening in the blink of an eye and over
...
Le Cycle de l'Eau - The Water Cycle, French (PDF)
Le Cycle de l'Eau pour les Enfants
Vous pouvez penser que chaque goutte de pluie qui tombe du ciel, ou chaque verre d'eau que vous buvez, est tout nouveau, mais, en fait, il a toujours été là et fait partie du cycle de l'eau.