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
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
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.
cycle diagram from USGS