Water Science School

Water Cycle Components

Earth's water is always in motion, 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 millions of years.

The Water Cycle for Schools and Kids

The Water Cycle for Schools and Kids

Use our Water Cycle for Schools area to introduce water-cycle science to elementary and middle-school students.

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The Water Cycle for Adults and Advanced Students

The Water Cycle for Adults and Advanced Students

We offer extensive analyses about all of the parts of the water cycle; this area is recommended for high-school students to adult ages.

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Filter Total Items: 133
Date published: July 7, 2019
Status: Completed

How Much Does a Cloud Weigh?

I don't know anyone who is afraid to walk underneath a cumulus cloud because they are afraid it might fall on them. We don't think of clouds even having weight because they are floating. But, clouds are made up of a physical substance, water, and water is quite heavy, so clouds must have weight. We will explain this "paradox" to you if you read on.

Contacts: Ask USGS
Date published: July 6, 2019
Status: Completed

Rain and Precipitation

Rain and snow are key elements in the Earth's water cycle, which is vital to all life on Earth. Rainfall is the main way that the water in the skies comes down to Earth, where it fills our lakes and rivers, recharges the underground aquifers, and provides drinks to plants and animals.

Contacts: Ask USGS
Attribution: Water Resources
Date published: July 5, 2019
Status: Completed

Water Science Photo Galleries

Learn about water using pictures

Contacts: Ask USGS
Date published: June 12, 2019
Status: Completed

Streamflow and the Water Cycle

What is streamflow? How do streams get their water? To learn about streamflow and its role in the water cycle, continue reading.

Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human interference.

Contacts: Ask USGS
Date published: June 12, 2019
Status: Completed

Snowmelt Runoff and the Water Cycle

Perhaps you've never seen snow. Or, perhaps you built a snowman this very afternoon and perhaps you saw your snowman begin to melt. Regardless of your experience with snow and associated snowmelt, runoff from snowmelt is a major component of the global movement of water, possibly even if you live where it never snows. 

Note: This section of the Water Science School discusses the...

Contacts: Ask USGS
Date published: June 11, 2019
Status: Completed

A Víz Körforgása , The Water Cycle, Hungarian

A Víz Körforgása , The Water Cycle, Hungarian

Contacts: Ask USGS
Date published: June 8, 2019
Status: Completed

Evaporation and the Water Cycle

For the water cycle to work, water has to get from the Earth's surface back up into the skies so it can rain back down and ruin your parade or water your crops or yard. It is the invisible process of evaporation that changes liquid and frozen water into water-vapor gas, which then floats up into the skies to become clouds.

Note: This section of the Water Science School discusses the...

Contacts: Ask USGS
Date published: June 8, 2019
Status: Completed

Condensation and the Water Cycle

The air is full of water, as water vapor, even if you can't see it. Condensation is the process of water vapor turning back into liquid water, with the best example being those big, fluffy clouds floating over your head. And when the water droplets in clouds combine, they become heavy enough to form raindrops to rain down onto your head.

Note: This section of the Water Science...

Contacts: Ask USGS
Date published: June 8, 2019
Status: Completed

The Atmosphere and the Water Cycle

The atmosphere is the superhighway in the sky that moves water everywhere over the Earth. Water at the Earth's surface evaporates into water vapor which rises up into the sky to become part of a cloud which will float off with the winds, eventually releasing water back to Earth as precipitation.

Note: This section of the Water Science School discusses the Earth's "natural" water...

Contacts: Ask USGS
Date published: June 8, 2019
Status: Completed

Infiltration and the Water Cycle

You can't see it, but a large portion of the world's freshwater lies underground. It may all start as precipitation, but through infiltration and seepage, water soaks into the ground in vast amounts. Water in the ground keeps all plant life alive and serves peoples' needs, too.

Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human...

Contacts: Ask USGS
Date published: June 8, 2019
Status: Completed

Surface Runoff and the Water Cycle

Runoff is nothing more than water "running off" the land surface. Just as the water you wash your car with runs off down the driveway as you work, the rain that Mother Nature covers the landscape with runs off downhill, too (due to gravity). Runoff is an important component of the natural water cycle.

Note: This section of the Water Science School discusses the Earth's "natural"...

Contacts: Ask USGS
Date published: June 8, 2019
Status: Completed

Sublimation and the Water Cycle

Solid, liquid, and gas - the three states of water. We see water freeze and turn to ice and we see water evaporate and turn to gas but... have you ever seen ice evaporate directly to gas? This process is called sublimation and you can read all about it below.

Note: This section of the Water Science School discusses the Earth's "natural" water cycle without human interference....

Contacts: Ask USGS