1. 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.

2. 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.

3. The Water Cycle

4. 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.

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

6. 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

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

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

9. Evaporation Water moves into the atmosphere as a gas(water vapor).
The higher the temperature, the faster evaporation occurs.

10. Ground Water
Water soaks into the ground through a process called infiltration until it reaches a zone where all of the pores are filled with water.
Example: underground streams, aquifers

11. Infiltration
Infiltration is an important process where rain water soaks into the ground, through the soil and underlying rock layers.
Some of this water ultimately returns to the surface at springs or in low spots downhill.

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.

17. We just said energy is required to make water flow from one reservoir to another.
Where does the energy come from?
The sun.

19. The Water Cycle

20. Earth’s Water Supply
The total amount of water on the Earth has not changed much since early in its history.
The same water is cycled over and over.
The water you drink at lunch was probably drunk by a dinosaur millions of years ago!