1. Hydrological Cycle 6 th Grade

2. Review: Hydrological Cycle (Water Cycle) What are the 3 major components? – 1) Evaporation – 2) Condensation – 3) Precipitation

3. EVAPORATION Changing from a liquid to a gas Molecules gain energy Ex. Letting your wet hair after a shower air dry = evaporation

4. CONDENSATION Changing from a gas back to a liquid Molecules lose energy Ex. When you fog up a window by breathing on it, invisible water vapor in your breath is cooled by the window and forms drops of liquid water

5. PRECIPITATION When water vapor condenses and becomes too heavy, liquid water falls to the ground – Ex. Rain

6. Basic Hydrological Cycle

7. Why does precipitation sometimes come down as snow instead of rain? * When it is 32 degrees Fahrenheit or 0 degrees Celsius, when the water vapor turns to liquid, it freezes and falls as snow flakes

8. What about sleet and hail? Why do they form sometimes instead of snow? http://www.youtube.com/watch?v=dhr46zLn wbg http://www.youtube.com/watch?v=dhr46zLn wbg Start at :37: http://www.youtube.com/watch?v=69Y7c14p EFI http://www.youtube.com/watch?v=69Y7c14p EFI

9. Other parts of the Hydrological Cycle Surface runoff Subsurface runoff (groundwater) Transpiration

10. Hydrological Cycle = more complex

11. Surface Runoff Water from rain or snowmelt that flows on the Earth’s outer surface

12. Subsurface Runoff: rain water that is absorbed into the ground

13. Transpiration –when plants draw in water from the soil through their roots, water is given off through the leaves as water vapor

14. Distribution of Water on Earth: What percent is salt (saline) water and what percent is fresh water? 97% = salt water – oceans 3% = fresh water – 75% of fresh water is frozen (glaciers) – Almost 25% is groundwater – Tiny fraction surface water

15. Fresh Water Distribution

16. Glaciers – 75% of fresh water (mostly at North and South poles)

17. Groundwater –almost 25% of fresh water

18. Surface water –streams, rivers, ponds, lakes = less than 1% of all fresh water