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?