The natural water cycle

IN THE SUPPLY AND SANITATION

The processes of evaporation, condensation and precipitation form part of the the Natural Water Cycle.

The natural water cycle

Evaporate

The energy of the sun causes huge quantities of water to evaporate from the Earth’s surface (for example, from seas, oceans, rivers, living beings and landmasses). All of the resulting water vapour rises into the air where it is as invisible as all of the other gases that go to make up our atmosphere. 

Evaporation

Condenses

When the air cools, the water vapour it contains condenses and minute droplets of water form. These droplets of liquid water then accumulate to form clouds. On occasion, the droplets increase in size and precipitate or fall in the form of rain, snow or hail. 

Condenses

Surface runoff water

Part of the water that falls runs straight off the land into rivers and lakes (this is known as surface runoff water), while the rest of it filters down through the land, either directly whenever it rains, or through the beds of rivers and lakes, forming what is known as groundwater. In time the rivers and streams transport the water to seas and lakes where it once again evaporates, thereby restarting the entire process.

Surface Runolf Water