Water Cycle (Hydrologic Cycle)
Precipitation: When the clouds become heavy with water particles, the particles fall back to Earth as precipitation in the form of rain, snow, freezing rain or hail, depending on the temperature of the surrounding air. Some of the precipitation evaporates before it reaches Earth. Some lands on plants and is transpired. The water that lands of the surface of the Earth may evaporate, rising up into the atmosphere again. Or it may infiltrate, that is percolate, into the ground or runoff into a nearby body of water.
Evaporation: Water molecules bind together to form a body of water, such as a lake, river or even a puddle. When the sun heats the molecules on the surface of a body of water, they become energized and break away from each other. The molecules evaporate and rise as invisible vapour into the atmosphere.
Transpiration: Plants also give off water vapour in a process known as transpiration. They do this in much the same way that humans perspire. The water that has been absorbed by the plants, usually through the roots, moves to the surface of the plants’ leaves and evaporates into the air.
Condensation: As water vapour rises into the atmosphere, it cools and condenses, often attaching itself to tiny particles of dust in the air. When water vapour condenses, it turns back into a liquid. The water particles collect and form clouds.>
Percolation: Some of the precipitation that falls to the ground seeps into porous soil and cracks in rocks. This water moves downward beneath the Earth’s surface until it settles in an aquifer (a collection of water underground). Water that seeps into an aquifer is called recharge and the land area where water seeps into an aquifer is called a recharge area. Water that percolates through the soil in this way may continue to flow under the ground or it may re-surface somewhere downstream.