The Water Cycle Illustrated


	During Evaporation, the sun evaporates water from seas and land masses and converts it to vapor, or gas, which ascends into the atmosphere. Water vapor can condense as fog or mist, but most often it collects to form clouds.

	When clouds become saturated with water vapor, Precipitation occurs. Water falls to the Earth as a raindrop, snow crystal or hail, depending upon the climate, season and topography. Not all precipitation reaches the earth -- some will evaporate between the sky and the land and reenter the water cycle.

	Water that reaches the Earth either runs off across a land surface, falls into a body of water, or infiltrates soil to collect underground. Infiltration is the process where water is filtered through nonporous rock and soil to collect in aquifers and underground streams. Through wells and irrigation, the water may be pumped out of the ground for our use.

	Water that infiltrates soil may be taken up through the roots of plants and then transpired through the leaves. During Transpiration, plants use solar energy, water and minerals to create nutrients--water vapor is a by-product of photosynthesis. Prolific plant life explains the high humidity of the rain forest and tropical regions where transpiration returns high levels of water vapor to the atmosphere.

	During Combustion, automobiles, motors and engines release water vapor into the atmosphere as a by-product. In addition to water, they also release waste products. High concentrations of sulfur and nitrogen oxides can form sulfuric and nitric acids that fall to Earth, leading to the phenomena known as acid rain.

	Small amounts of water are retained and held by animals. When animals breathe, their lungs release water vapor to the atmosphere. This process is called Respiration.

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