Water evaporates. It travels into the air and becomes part of a cloud.
It falls down to earth as precipitation. Then it evaporates again. This
repeats over and over again in a never-ending cycle. This hydrologic cycle
never stops. Water keeps moving and changing from a solid to a liquid to a
gas, over and over again.
Precipitation creates runoff that travels over the ground surface and
helps to fill lakes and rivers. It also infiltrates or moves downward
through openings in the soil to replenish aquifers under the ground. Some
places receive more precipitation than others. These areas are usually
close to oceans or large bodies of water that allow more water to
evaporate and form clouds. Other areas receive less precipitation. Often
these areas are far from water or near mountains. As clouds move up and
over mountains, the water vapor condenses to form precipitation and
freezes. Snow falls on the peaks.