The Water Cycle

The Sun• The sun provides the energy to power the

water cycle• The sun heats the upper ocean causing

evaporation of liquid water into water vapor

• The water vapor rises into the atmosphere and cools

• The cooled water vapor creates tiny water droplets that form clouds

• When clouds become too heavy with water droplets, precipitation falls– rain– sleet– snow– hail

• Once water reaches the earth’s surface:– Infiltrates the surface (soaks in)– Runs across the top of the ground filling rivers,

lakes, and streams (can cause erosion)

aquifer• A natural underground area where large

amounts of ground water collect and create an underground supply of water

• Amount of water stored depends on the porosity and permeability of the sediment

porosity

• Amount of water that a material can hold in the spaces between the pores

permeability

• The measure of how well an earth material can let water pass through it.

percolation

• The downward movement of water from the land surface into soil or porous rock. It is caused by gravity

infiltration

• When water enters the soil surface after falling from the atmosphere

Surface water

• Water located on earth’s surface• Most US cities use surface water– rivers– lakes– streams– ponds– creeks– reservoirs

ground water

• Water located under the ground surface• Reached by using wells• Cleaner and safer

pollution

• Any change to the environment that has a negative effect on living things

• Water sources are especially sensitive to pollution

• Burning fossil fuels can create acid rain

http://www.epa.gov/safewater/kids/flash/flash_watercycle.html

Discussion Questions

Is there a beginning to the water cycle?

What is the power source for the water cycle?

How does water get into an aquifer?