The Water Cycle Explained

The Water Cycle

The water cycle (also called the hydrological cycle) is the continuous movement of water through Earth's systems. Water changes state between liquid, vapor, and ice, moving through the atmosphere, land, and oceans.

Key Stages

The Cycle in Detail

1. Evaporation

The sun's energy heats water at the Earth's surface. When water molecules gain enough energy, they break free from the liquid and become water vapor (a gas). This process happens mainly in oceans, which cover about 71% of Earth's surface.

The amount of evaporation depends on temperature, surface area, and wind speed. Hotter days produce more evaporation.

2. Condensation

As water vapor rises, it cools down. Cooler air cannot hold as much moisture, so the vapor condenses around tiny dust particles to form water droplets. Billions of these droplets together form clouds.

3. Precipitation

When water droplets in clouds combine and become heavy enough, they fall back to Earth as precipitation. The form it takes depends on temperature:

• Rain — when temperatures are above 0°C
• Snow — when temperatures are below 0°C
• Hail — strong updrafts in thunderstorms
• Sleet — rain that freezes as it falls

4. Collection

Precipitation collects in various places:

• Surface water — rivers, lakes, and oceans
• Groundwater — water that soaks into the soil and fills underground rocks (aquifers)
• Glaciers — snow that compacts into ice in cold regions

Water Distribution on Earth