Why Does the Water Cycle Keep Going?

The water cycle changes because cycles of day and night, the seasons and the movement of water in any of its forms changes its environment, specifically its temperature. As water in oceans or on surfaces gets warmer, it evaporates, and the resulting water vapor moves along with the wind, often rising and cooling. The cooling vapor condenses into water droplets, forming clouds and eventually precipitation.

Fluctuations in heat from the sun ultimately drive the water cycle. It is a complex process, often involving many stages.

One relatively simple cycle occurs with what is known as lake effect snow. Solar warming of a large lake causes a large amount of water vapor to be released. Cold, dry winds above capture the moisture and cool it rapidly, causing it to condense into tiny water droplets. These droplets then freeze, forming clouds of ice crystals. As these clouds are pushed toward shore, the ice crystals grow too large to keep suspended in air and fall as snowflakes. Any hills along the shoreline force the air upward and increase the rate of snowfall. The snow falls on the shore, and when conditions are warm enough, begins to melt. The resulting liquid water either flows back into the lake or is absorbed as groundwater.