The Water Cycle
The water cycle, also known as the hydrological cycle, involves the continuous circulation of water on, above and below the surface of the Earth, cycling between the land, ocean, and atmospheric systems. Water is constantly moving, changing between a liquid, vapour and solid state, while interacting with the Earths physical, chemical, and biological environments. Water is stored for varying lengths of time in a number of different forms including atmospheric vapour, lakes and rivers, soil moisture, groundwater, glacial ice, and snow on the ground. Water transfers from one environment to another via processes like surface runoff, transpiration, infiltration, percolation, and wind.
Water is a powerful environmental element, constantly reshaping the face of the earth and allowing life as we know it to exist (Canada). Though the Water Cycle is complex, the three most fundamental processes are:
Evapotranspiration
- Evapotranspiration is the sum of all processes by which water migrates from land or the ocean’s surface, into the atmosphere via evaporation and transpiration. Environmental factors such as temperature, humidity, wind speed and solar radiation all contribute to evapotranspiration, transitioning water from a liquid state into a gaseous, vapour state.
Condensation
- Condensation is the process where water vapour turns into a liquid state. As water vapour rises in the atmosphere, the temperature begins to drop, cooling the water vapour and condensing it into tiny liquid water droplets suspended in the atmosphere that we recognize as clouds, mist, and fog.
Precipitation
- Precipitation is the physical process of water falling to the surface of the earth.
- Gradually, heavier liquid water droplets will accumulate inside clouds until they can no longer remain suspended in the atmosphere. Eventually, gravity causes the larger droplets to fall to the earth surface again in a variety of forms ranging from rain, snow, sleet, or hail, to dew, and frost.
