Which processes drive the continuous circulation of water through the Earth-atmosphere system?

In hydrologic sciences, the continuous circulation of water through the Earth-atmosphere system is known as the hydrologic cycle. This cycle is primarily driven by energy from sunlight and the force of gravity.1

The cycle involves several key processes that transfer water between various reservoirs, such as the oceans, atmosphere, and land surface:23

• Evaporation: Solar energy heats water surfaces, providing molecules with sufficient kinetic energy to transition from a liquid to a gaseous state, replenishing atmospheric water vapour.143
• Transpiration: Water is also released into the atmosphere through vegetation.43
• Precipitation: Atmospheric water vapour condenses to form clouds and eventually falls back to Earth’s surface as precipitation, such as rain or snow.153
• Runoff and Infiltration: Once on the surface, water may flow as runoff into streams and lakes or infiltrate the soil to become groundwater, eventually returning to the oceans under the pull of gravity.13

These processes collectively maintain the Earth's water balance and are essential for sustaining life and shaping the planet's climate.36