Water falling on land or sea in the form of rain, snow, or sleet.
Explanation
The hydrological cycle (water cycle) describes the continuous movement of water on, above, and below the surface of the Earth. It involves distinct physical processes that transfer water between the atmosphere, land, and oceans.
Option Analysis:
- Water turning into vapour. is incorrect: This describes Evaporation, the process by which liquid water transforms into water vapour due to heat.
- Water falling on land or sea in the form of rain, snow, or sleet. is correct: Precipitation refers to any product of the condensation of atmospheric water vapour that falls under gravity. The main forms of precipitation include rain, sleet, snow, and hail.
- Water flowing into rivers. is incorrect: This refers to Surface Runoff, the flow of water occurring on the ground surface when excess rainwater, stormwater, or other sources can no longer sufficiently infiltrate the soil.
- Water cooling down to form clouds. is incorrect: This describes Condensation, the process where water vapour cools and changes into liquid water droplets, which is responsible for the formation of clouds.
Key Takeaway:
Precipitation is the primary mechanism in the water cycle responsible for depositing water from the atmosphere back to the Earth's surface.