Most of this water is locked up in ice, and another Rivers make up 0. Although rivers account for only a small amount of freshwater, this is where humans get a large portion of their water from. Source: Gleick, P. In Encyclopedia of Climate and Weather, ed. Do you really like lakes? Or maybe you'd rather sit by the ocean, or maybe a waterfall is your favorite? Visit our interactive Activity Center and submit your vote for your favorite water body? See how thousands of others all over the world voted.
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 millions of years.
The air is full of water, even if you can't see it. Higher in the sky where it is colder than at the land surface, invisible water vapor condenses into tiny liquid water droplets—clouds. When the cloud droplets combine to form heavier cloud drops which can no longer "float" in the surrounding air, it can start to rain, snow, and hail 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. 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.
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. 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.
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.
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 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. Skip to main content. Search Search. Water Science School. Freshwater Lakes and Rivers and the Water Cycle. This is an example — given trees require a certain minimum level of precipitation to grow — of a positive feedback loop.
The term evapotranspiration captures the combined effects of evaporation and transpiration. Much smaller amounts of water vapor are also contributed by other processes such as the respiration of animals and volcanic eruptions.
But needless to say its atmospheric residency is incredibly important from the standpoint of refueling the land-based portion of the water cycle. Water vapor condenses into liquid droplets or sublimates to ice particles to form clouds when the airmass containing it cools sufficiently. Humid maritime air masses laden with moisture evaporated off the oceans reach land by advection , the horizontal movement of air. When the droplets and ice particles in a cloud grow large and heavy enough, they fall as precipitation: rain, snow, freezing rain , hail, graupel, sleet and the like.
This provides an input of water into the terrestrial system. Trees, for example, wring moisture from low-hanging or ground-hugging clouds by providing a surface for water condensation. This fog drip can supply significant amounts of moisture to the soil. Air at ground level that cools overnight can also condense water on vegetation and other surfaces in the form of dew.
Much is funneled over the surface as runoff via overland flow, creeks and rivers to eventually shuttle into the ocean. Share this page. Related Links. Footer pod May 20, All rights reserved. Privacy Policy Donor Privacy Policy. Quicklinks Footer quicklink May 20, Footer quicklink May 20, Remember me.
Create new account Request new password. Commands Support portal Log in.
0コメント