Sustainable Food Guide
|Environmental Practice at Work © 2005|
|The Dynamics of the Water Cycle... |
1. Energy from the sun evaporates water from the surfaces of masses of water, such as oceans and lakes. This is collected in the atmosphere. The energy enables the water to evaporate from the surface of the earth.
2. This, together with water vapour returned to the air during respiration, and from plants transpiration, are taken up by warm air in the atmospheric cycle. This evaporated water rises and condenses into clouds.
3. As clouds rise they cool down and are unable to contain the water vapour. This is then deposited as rain, hail, fog and snow.
4 Gravity moves water from upland areas across the earth and back to sea. Some water penetrates the soil called infiltration, where it may be taken up by plants. Some water sinks through porous rock becoming part of the groundwater mass.
5. Other water flows into lakes and rivers and returns to the seas carrying sediments from plants and animals as well as from the geological cycle.
Human activity traps and uses a quantity of available water. In Northern and Western developed countries water is often treated as a free resource.
|Photos courtesy of http://www.usda.gov|