1. The Water Cycle

2. Water is…  The only common substance that exists as a solid, a liquid, and a gas.  Present everywhere on Earth.  In a continuous state of change and movement.

3. The Water Cycle  Definition: the combination of all of the different movements of water  Also known as the hydrologic cycle  A flow of matter (water) and energy  Called a “closed” system –A material [water] moves from place to place but nothing is gained nor lost.

4. The Water Cycle The Water Cycle

5. Major Processes of the Water Cycle  Evaporation and Precipitation  There is more evaporation than precipitation over the surface of the Earth’s oceans.  There is more precipitation than evaporation over the surface of the Earth’s continents.

6. Evaporation  Definition: the change of state of matter from a liquid to a gas.  Heat is absorbed.  Example: boiling water to steam

7. Oceans  Cover about 75% of the Earth  Ocean water is constantly evaporating into the atmosphere (becomes water vapor)  When water vapor cools: –Forms clouds at higher altitudes –Forms fog if close to the ground

8. Precipitation  Definition: water that falls to the surface from the atmosphere as rain, snow, hail, or sleet

9. After the precipitation  Water can take different routes: –Evaporate –Ground Water –Soil Moisture –Surface runoff

10. Evaporation  Back into the atmosphere  The higher the temperature, the faster evaporation occurs.

11. Ground Water  Water soaks into the ground until it reaches a zone where all of the pores are filled with water.  Example: underground streams, aquifers

12. Soil Moisture  Water that remains in the surface layer of soil  the roots of plants absorb this water. –Travels up through the stems and branches of the plant into the leaves and is released into the atmosphere as vapor in a process called transpiration.

13. Surface Runoff  Water that flows downhill into streams and rivers  Eventually empties into the ocean

14. What makes the ocean salty?  Water flows from the surface of the continents into the oceans  This water carries sediment particles and dissolved minerals into the ocean.  When ocean water evaporates, it leaves the sediments behind.  Over time, the ocean becomes more and more salty.

15. Reservoir vs. Flux  Reservoir – a place in the Earth system that holds water. –Ex. Oceans, Atmosphere, Clouds, etc  Flux – the movement of water from one reservoir to another.

16.  Energy is required to make water flow from one reservoir to another.  On average, the total amount of water in all reservoirs combined is nearly the same.  The amount of water stored in any one reservoir varies over time.