|
The Water Cycle
About 70% of the Earth's surface is covered in water.
Water is constantly recycled on Earth as rain, snow, oceans, lakes, streams,
hail, and glaciers. The recycling of water is the water cycle.
There are three basic parts to the water cycle:
Capture: Evaporation happens
when lakes, oceans, rivers, and streams are heated by the sun. The
liquid water evaporates into a gas called water vapor. Transpiration is
the name for the process by which plants give off water vapor from
their leaves or needles.
Storage: Collection happens
when the rain, hail, snow, or sleet gathers back into oceans, lakes,
rivers, streams, and glaciers.
Release: Condensation is
when the water vapor comes together to make clouds. Precipitation is
when water from the clouds falls to Earth as rain, sleet, hail, or snow. |
|
Watersheds
Most rivers start high atop a mountain. Rain, snow, fog, underground
springs, and melting glaciers make little trickles of water. The little
trickles come together to make streams, and streams come together to
make rivers, which eventually end up at an ocean. |
|
Rivers can be very powerful. Rivers and streams shape the land as
they move through. As rivers flow downhill, they wear away rock and
soil to form canyons and curves in the land, called meanders.
Rivers with too much water create floods that carry away plants,
trees, and boulders. Although they are sometimes destructive, rivers
and streams support a lot of living things.
It can be a rough place to live, but many animals and plants call
rivers and streams home. Salmon fight their way upstream to spawn,
moss grows on river rocks, frogs lay eggs near the shoreline, and
fish build nests in rivers andstreams.
We find special ecosystems in and around rivers and streams. |
Wetlands
Every single state in the United States has some area
of wetlands. Wetlands are places where the soil is completely saturated
with water. Some wetlands are even covered by a thin layer of water.
It may be a bit soggy, but lots of animals and plants live in wetlands.
Different types of fish, birds, and insects call wetlands home. Crocodiles
and alligators live in swamps. Manatees, beavers, frogs, moss, grasses,
and trees love living in wetlands. Plants really grow well in wetlands,
providing animals with plenty of food.
Wetlands are not just home to different animals and plants, but
they also control flooding andhelp keep the Earth's water clean.
Flood waters move more slowly through wetlands because they have
to go through a barrier of plants and dirt.
Wetlands help stop erosion because the plants stop the soil from
washing away. Plants in wetlands even absorb some types of pollution. |
|
Fish
|
More than 22,000 different species of fish live in the oceans, lakes,
and rivers of the world. Lampreys, jawless fish, suck onto other fish
for food. Stone fish live on ocean bottoms and camouflage themselves
as rocks. Puffer fish blow themselves up like a balloon with spikes.
Fish can breathe underwater with their gills, a bunch of tiny flaps
behind their heads. Gills collect oxygen in water and let out carbon
dioxide.
Fish are sensitive to pollution and other changes to their environment.
Scientists are trying to find out how to restore salmon runs before
the salmon become extinct. |
|
