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Hydrological Cycle
6th Grade
Review: Hydrological Cycle (Water Cycle)What are the 3 major components?
–1) Evaporation–2) Condensation–3) Precipitation
EVAPORATION
• Changing from a liquid to a gas
• Molecules gain energy
• Ex. Letting your wet hair after a shower air dry = evaporation
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
PRECIPITATION
• When water vapor condenses and becomes too heavy, liquid water falls to the ground– Ex. Rain
Basic Hydrological Cycle
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
What about sleet and hail? Why do they form sometimes instead of snow?
• http://www.youtube.com/watch?v=dhr46zLnwbg
• Start at :37: http://www.youtube.com/watch?v=69Y7c14pEFI
Other parts of the Hydrological Cycle
• Surface runoff
• Subsurface runoff (groundwater)
• Transpiration
Hydrological Cycle = more complex
Surface Runoff
• Water from rain or snowmelt that flows on the Earth’s outer surface
Subsurface Runoff: rain water that is absorbed into the ground
Transpiration –when plants draw in water from the soil through their roots, water is given off through the leaves as water vapor
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
Fresh Water Distribution
Fresh Water Distribution
GlaciersGround waterSurface Water
Glaciers – 75% of fresh water (mostly at North and South poles)
Groundwater –almost 25% of fresh water
Surface water –streams, rivers, ponds, lakes = less than 1% of all fresh water
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