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The Hydrosphere • 70% of the earth’s surface is covered with water – Oceans: 97.5% – Land: 2.4% – Atmosphere < .001% The water (hydrologic) cycle The cycle: Evaporation • Water changes from liquid to gas (vapor) • 80% of evaporation comes from the oceans, the rest from waterways and vegetation • Winds transport evaporated water around the globe The cycle: Condensation • Water changes from gas to water droplets as they rise in the atmosphere (gets colder) • Water droplets adhere to particles in the atmosphere and form clouds The cycle: Transpiration • Water evaporates from the leaves and stems of plants • 10% of evaporated water comes from transpiration The cycle: Precipitation • Water transfers from the atmosphere to the earth’s surface • Rain, snow, sleet, hail, freezing rain The cycle: Runoff • Runoff transfers water from lakes, rivers and streams to the oceans. • Runoff also occurs when the ground cannot absorb any more water and it flows on the surface into bodies of water The cycle: Infiltration • Infiltration is the soaking of water into the earth’s surface • Amount that infiltrates affected by – – – – Slope of the land Vegetation Rock types Soil type Water, water everywhere…but not a drop to drink • With almost all of the earth’s water in the oceans, less than 10% is available for human use • Access to water is not equal, due to nature and wealth “The equivalent of 12 jumbo jets of children die everyday from sanitation-related diseases” --UN Water expert • Water pollution is a major problem around the world, including here in Minnesota • Half of the world’s population…3 billion people!...don’t have access to clean water The White T-Shirt Metaphor • Clean water is like a new white t-shirt. Each time you wear it, it gets a little dirtier. Each time you wash it, it is a little less white. • Each time clean water is used, it gets a little dirtier. Each time you “clean” it, it stays a little less clean. CONSERVE WATER!