The water cycle
Water is a key compound for life on Earth. All living organisms need water. Some can survive in a dormant state without it for long periods of time, but all organisms will eventually die without it.
Water is constantly recycled. Energy from the Sun The process in which a liquid changes state and turns into a gas. water from the land and sea forming water vapour. This rises up into clouds and then cools, Condensation is a change of state in which gas becomes liquid by cooling. and falls as rain onto the ground. The water then drains into the sea and the The continuous movement of water on, above and below the Earth. starts again.
These are the key processes in the water cycle.
| Process | What happens to water |
| Evaporation | Water turns from a liquid to a gas when it evaporates. Energy from the Sun can evaporate water from all places on the Earth's surface such as puddles, ponds, lakes and oceans. |
| Condensation | After evaporation water can cool and convert from gas to liquid, often forming clouds. |
| Transport | Water within clouds can be blown many miles by strong winds and so transported to other areas. |
| Precipitation | Precipitation occurs when rain, snow, hail and sleet fall from the sky. |
| Surface runoff | Much water will be absorbed into the ground after precipitation but if a large volume falls or the ground is already wet some water can run along the surface of the ground. |
| Infiltration | This occurs when water that has fallen as precipitation is absorbed into the ground. This can then be stored within underground rocks called aquifers. |
| Transpiration | Plants need to maintain a constant stream of water to their leaves for transport and support. They allow some water to evaporate as water vapour from their leaves so it is continually 'pulled' to their leaves from the soil. |
| Process | Evaporation |
|---|---|
| What happens to water | Water turns from a liquid to a gas when it evaporates. Energy from the Sun can evaporate water from all places on the Earth's surface such as puddles, ponds, lakes and oceans. |
| Process | Condensation |
|---|---|
| What happens to water | After evaporation water can cool and convert from gas to liquid, often forming clouds. |
| Process | Transport |
|---|---|
| What happens to water | Water within clouds can be blown many miles by strong winds and so transported to other areas. |
| Process | Precipitation |
|---|---|
| What happens to water | Precipitation occurs when rain, snow, hail and sleet fall from the sky. |
| Process | Surface runoff |
|---|---|
| What happens to water | Much water will be absorbed into the ground after precipitation but if a large volume falls or the ground is already wet some water can run along the surface of the ground. |
| Process | Infiltration |
|---|---|
| What happens to water | This occurs when water that has fallen as precipitation is absorbed into the ground. This can then be stored within underground rocks called aquifers. |
| Process | Transpiration |
|---|---|
| What happens to water | Plants need to maintain a constant stream of water to their leaves for transport and support. They allow some water to evaporate as water vapour from their leaves so it is continually 'pulled' to their leaves from the soil. |
Learn more about the water cycle with Dr Alex Lathbridge.
Listen to the full series on 大象传媒 Sounds.
Explore the important processes throughout the cycle and what happens to water during each stage.