Water Cycle Chapter 15
Movement of Water on Earth Water Cycle: the continuous movement of water between the atmosphere, the land, and the oceans 2/3 of Earth is cover in water The atmosphere has water vapor and liquid water (found in clouds and fog) Earth’s water is constantly cycling
Evapotranspiration: the total loss of water from an area by evaporation and transpiration into the atmosphere. Evaporation: comes from bodies of water such as lakes, rivers, and oceans. Transpiration: comes from animals, plants and soils. Each year, about 500,000km 3 of water evaporates into the atmosphere. About 86% comes from the oceans.
Condensation: the change of state from a gas to a liquid When water vapor rise into the atmosphere it cools and expands. As it cools some will condenses and forms water droplets that form into clouds.
Precipitation: any form of water that falls to Earth’s surface from the clouds; includes rain, snow, sleet, and hail. About 75% goes into oceans About 25% ends up as runoff and ground water. All water will end back up in the atmosphere to begin the water cycle again.
Water Reservoirs Reservoirs% Ocean97 Glaciers/Ice caps2 Groundwater.7 Atmosphere.01 Freshwater Lakes.3 Saline lakes and inland sea.01 Rivers.001
Water Budget Precipitation: income Evapotranspiration and runoff: expenses Precipitation = Evapotranspiration and runoff ‘World’s’ Water budget is balanced! Local water budget (an given area) is not balanced!
Watershed: Local Water Budget
Factors that Affect the Water Budget General Factors: Temperature, vegetation, wind, and the amount and duration of rainfall Local factors: geography (landscape) and seasons
Water Use Average person usage in US in a year: 95,000 L (20,890.5 gallons) Population increase = more demand on water 90% of water used in cities and industry is returned as wastewater into rivers and oceans, which includes pollution
Conservation of Water Two ways to ensure fresh water for the future Conservation or use water wise Find alternative methods of obtaining fresh water Desalination a process of removing salt from ocean water Expensive and impractical for large populations What other ways can you think of?