What is the water cycle?
The water cycle is the movement of water around the earth.
As a result of natural processes, water transfers between the land, rivers, creeks, ocean and atmosphere in a continuous cycle.
The amount of water on earth stays fairly constant over time, but it is naturally cleaned and replenished though the water cycle. It takes about 10,000 years for a drop of water to complete the cycle.
As water moves through the cycle it changes state, from liquid in the waterways and oceans, to gas in clouds, and to solid in the form of snow and ice.
The water cycle is an essential ecosystem that supports all life on earth.
The natural water cycle
Runoff
Runoff
Runoff is water that has not soaked into the ground and flows across land instead, making its way to the waterways.
Infiltration
Infiltration
Infiltration is when water that falls from the sky soaks into the ground. Infiltration replenishes waterways and soil moisture, supporting plant life and ecosystem function. The water is also cleaned as it filters through the earth. Water that has not been absorbed by plants soaks deep into the earth where it collects in layers of rock and sand called aquifers. This type of water is known as groundwater.
Precipitation
Precipitation
Precipitation is when water falls from the sky as rain, snow or sleet. When enough water droplets have clumped together that the air cannot support its weight, water falls from the clouds back to the Earth’s surface. Depending on the air temperature, the water can fall
as a liquid (rain), or solid (snow, sleet or hail).
Transpiration
Transpiration
Transpiration is when water evaporates from plants and back into the atmosphere as a gas. This process cools the air.
Condensation
Condensation
Condensation is the process of changing water from gas to liquid.
As water vapour rises into the atmosphere it becomes cooler and changes back into small water droplets. These droplets clump together and form clouds.
Evaporation
Evaporation
Evaporation is the process of changing water from liquid into gas. When the water in rivers, oceans or lakes is warmed by the sun, the molecules break apart. These molecules become water vapour or steam and rise through the air into the atmosphere. Any salt, minerals or metals in the water is left behind when it evaporates.
Move your mouse over the picture to learn more about the natural water cycle.
