Most of us have probably heard of and learned about the water cycle. On this page you will find a brief overview, along with some extra details you might not know!
- Water in oceans and lakes is evaporated by the sun and rises in the form of water vapour.
- As it rises, it cools and forms clouds.
- Water falls from the clouds in the form of snow and rain.
- Snow and rain runs off the land in rivers and streams back into the oceans and lakes.
- Evaporation completes the cycle.
The water cycle is also called the hydrologic cycle. Basically, it involves three steps: water collected in an ocean or other source evaporates into the air and becomes clouds; the water then gathers together to become heavy enough to fall as rain. The rainwater eventually collects in pools of water which evaporate again. This is a cycle, so it always continues – water never stops moving.
The “first” step in the water cycle is when water in oceans, lakes, or other bodies / collections of water is warmed up by the Sun. Heat adds energy to matter. This causes the molecules in the water to move faster and farther apart, until they move so far apart that they become a gas instead of a liquid – the water becomes water vapour.
Eventually the water vapour condenses into clouds. This means that the particles in the water vapour slow down and cool off, resulting in them becoming water droplets. These water droplets group together to form clouds. This is why a parachutist unfortunate enough to fall through a cloud would end up covered in water droplets.
When enough water droplets (remember, these are usually very small to begin with) form ‘inside’ clouds, they become heavy enough to fall towards the Earth. This is usually observed as rain, but Precipitation can also occur as snow, hail, sleet, etc., depending on temperatures and humidity.
Runoff is when water travels across land. Rain will land in the ground, streets, oceans, and in streams and rivers. Eventually it makes its way to a body of water (not necessarily an ocean, these can be streams, puddles, even a glass of water you leave outside). After a while, the water is evaporated and the water cycle repeats.
Although the processes mentioned above are the most common, there are other parts to the water cycle. These include:
Snowmelt “Snowmelt” is when snow melts into water, and is a form of runoff. Sometimes extreme snowmelt results in flooding. Sublimation Sublimation is when a solid turns directly into a gas, instead of first becoming a liquid. In the water cycle, this is seen when ice or snow is heated up enough to turn directly into water vapour.