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