The National Center for Atmospheric Research | UCAR | UOP
Home Our Organization News Center Education Research Tools Libraries

Weather and
Climate Basics

Weather Wonders
Climate Change

The Water Cycle
Water on the Move

“It’s good to see you again,” said Mr. Thompson to the familiar mountain lake he camped beside every year.
“Have we met?” asked the lake.

The water you see in a lake is not always the same. In fact, water is always on the move through the water cycle, being constantly recycled, sustaining life and creating dramatic weather worldwide. To better understand the water cycle we can follow a bit of the lake water through its journey.

Under the Ground
Some of the water in the lake may seep below the surface of the Earth, becoming groundwater. The water does not stay in the ground forever, but does stay put much longer than surface water.

Down the River
The mountain lake drains into a small stream that eventually joins a larger river, which carries the water down to lower elevations and eventually empties the water into the ocean.

Into the Air
Water at the surface of the ocean evaporates as the Sun hits it, allowing it to enter the atmosphere as water vapor. It is joined by water vapor released from plants during transpiration. Winds often push the water vapor hundreds of miles and high into the atmosphere. There it cools and clouds are created as water vapor condenses into small droplets or forms tiny ice crystals.

Falling to Earth
The tiny droplets within a cloud are able to fall to Earth as precipitation, such as rain, snow, and hail, if they combine together to be large and heavy enough. Some of the precipitating water falls as snow on a glacier of a high mountain peak, adding to the glacier’s size.

Back to the Lake
As the mountain snow and glaciers slowly melt in warm weather, water travels in steams to the lake where Mr. Thompson likes to camp.

Through this cycling, water is continually reused. In the past, the lake water may have been gulped by thirsty dinosaurs or sipped by medieval kings. In the future, some of that same water might fill the clouds above a distant city or be part of an unexpected blizzard.

Delve Deeper...

Water cycle diagram from USGS