The water cycle
Water is a key compound for life on Earth.
Water is important for:
- maintaining habitats
- allowing nutrients to flow between organisms and the environment
- survival of organisms
Some organisms can survive in a dormant state without water for long periods of time, but all organisms will quickly or eventually die without it.
Processes in the water cycle
The The continuous movement of water on, above and below the Earth. is easiest to understand in terms of its processes and what happens to the water in each stage.
| 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 is transported to other areas. |
| Precipitation | Precipitation occurs when rain, snow, hail and sleet fall from the sky. |
| Surface run-off | Much water will be absorbed into the ground after precipitation but if a large volume falls or the ground is already wet then 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 photosynthesis, support and transport of minerals. They allow some water to evaporate as water vapour from their leaves so that more water is continuously '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 is transported to other areas. |
| Process | Precipitation |
|---|---|
| What happens to water | Precipitation occurs when rain, snow, hail and sleet fall from the sky. |
| Process | Surface run-off |
|---|---|
| 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 then 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 photosynthesis, support and transport of minerals. They allow some water to evaporate as water vapour from their leaves so that more water is continuously '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.