The water cycle, or hydrological cycle, is the pathway or cycle that water follows underneath the surface, at the surface, and above the surface of the Earth. The water cycle refreshes and renews water on Earth as it moves between the atmosphere, land, and oceans while changing states between liquid, solid, and gas.
Let's take a look at the water cycle beginning with precipitation. Precipitation is water being released from clouds. Precipitation happens in various forms, such as rain, snow, and hail. When rain falls, the water flows above ground as surface runoff. The runoff may flow into streams, rivers, and eventually the ocean.
Infiltration occurs next, as a portion of the rain water soaks into the ground. Some water will remain near the surface, while other water will infiltrate deeper into groundwater aquifers. Additionally, infiltrated water may travel long distances and eventually seep into other bodies of water, such as lakes or streams.
The water that remained near the surface may become plant uptake; that is, water that is absorbed, or taken up, by the root of a plant. After the water is absorbed in the roots, it moves throughout the plant to the farthest and highest leaves and is used for cellular functions and to grow.
Next comes evaporation, which is the process in which water changes states from a liquid to a gas. Most of the water vapor in our atmosphere originates from evaporation of water from the oceans or other large bodies of water. As water is heated by the sun, it evaporates and is released into the atmosphere.
Much like evaporation, water that is absorbed by plants returns to the atmosphere through a process called transpiration. During transpiration, moisture is released from a plant's leaves and is converted to vapor.
After evaporation and transpiration, comes condensation. Opposite of evaporation, condensation occurs as water vapor in the air changes states from a gas to a liquid. Condensation is an integral step of the water cycle as it is responsible for the formation of clouds.
As wind moves clouds through the atmosphere, water is constantly evaporating and condensing. This continual process of evaporation and condensation causes precipitation to form, thus completing a turn in the water cycle.