Emerging Diseases

HYDROLOGIC CYCLE

The hydrologic cycle cleans water supplies on the planet by continuously circulating water between the earth and the atmosphere.

Definitions

Evaporation: The process of water vaporizing and entering the atmosphere.

Runoff: Rainfall and snowmelt that does not soak into the ground or evaporate immediately, and therefore travels over the land's surface toward lakes, rivers, or oceans.

Transpiration: The process of water moving through plants and evaporating into the atmosphere from a plant's leaves.

Condensation: The change of water from vapor to liquid, usually because of changes in temperature or atmospheric pressure.

Precipitation: Water that falls to the earth in the form of rain, snow, hail, or sleet.

Percolation: The movement or flow of water through soil or rocks.

Pollution

Air pollution: Atmospheric water vapor mixes with sulfur from industrial emissions and is acidified. Acid rain can affect regions hundreds of miles from the source emissions.

Petroleum products: Since petroleum products do not dissolve in water, oil compounds can become bound with biological debris. Once mired in the sediment, some oil chemicals persist for decades.

Chemicals: Buried chemicals can break down into gases and vapors that enter the atmosphere, while liquids can leach into the groundwater and affect drinking water supplies far from where they were buried.

Excess organic matter: These pollutants are picked up by rainfall or melting snow. They are carried through runoff and percolation into lakes, rivers, ocean waters, and even aquifers and reservoirs.

CREDITS

Subject Matter Expert:

Nancy Pomeroy

Interactive Design:

LaVonne Carlson

Instructional Designer:

Felicity Pearson

Project Manager:

Anne Echtenkamp