Describe the forces that drive the hydrological cycle

The driving force for the hydrologic cycle is the sun, which provides the energy needed for evaporation just as the flame of a gas stove provides the energy necessary to boil water and create steam.

Precipitation that falls as snow in glacial regions takes a somewhat different journey through the water cycle, accumulating at the head of glaciers and causing them to flow slowly down valleys.

The ecological water cycle describes how water moves through phase changes and from oceans to the atmosphere to the land. Heat from the energy of the sun is the underlying or driving force for the water cycle.

Key Concepts

Though the amount of water on Earth remains constant, it is regularly cycling through the ecosystem through various processes.

Earth's water supply is stored in a variety of ways, from ice sheets to oceans to underground reservoirs.

Like other processes occurring on Earth, the hydrologic cycle is affected by global warming and, as a result, influences climate and weather patterns.

The water cycle is driven primarily by the energy from the sun. This solar energy drives the cycle by evaporating water from the oceans, lakes, rivers, and even the soil. Other water moves from plants to the atmosphere through the process of transpiration. As liquid water evaporates or transpires, it forms water vapor and clouds, where water droplets eventually gain enough mass to fall back to Earth as precipitation. The precipitation then becomes run-off or ground water, and works its way—over various timescales—back into the surface reservoirs. The water cycle is essentially a closed system, meaning that the volume of water that is in the hydrosphere today is the same amount of water that has always been present in the Earth system.