Objective: Students will learn the hydrologic cycle is controlled by natural laws. This
lesson provides a basic understanding of the water cycle.
Materials: Water Cycle crossword puzzle, answer key, ice, lamp stand, 40 watt light
bulb, 5 lbs plaster of Paris, duct tape, transparent plastic box with lid (about 6"x12"x4"),
knife, water, tempera paint (green and brown), brushes, clear acrylic spray, clear plastic
Background: The water cycle or hydrologic cycle, is a continuous process in which
water is circulated between the earth, plants and animals, and the atmosphere. The total
amount of water circulating through the water cycle never changes. However, the form in
which the water exists - either gas, liquid, or solid - does change.
When precipitation, such as rain or snow, falls onto the earth's surface, it meets one of
several fates. About 85% of precipitation falls directly into the oceans. Some
precipitation which falls on land may run across the surface of the soil (runoff) into
oceans, lakes, ponds, rivers, and streams. The water that remains at the earth's surface
in oceans, rivers and other bodies of water is called surface water. Precipitation may
also infiltrate or soak into the soil. This water may be absorbed by plants, or seep down
through the soil until it reaches a saturated zone where all the pores between the rock
and soil particles are filled with water. Water that reaches this saturated zone is called
groundwater. The upper boundary of the groundwater in the soil is called the water table.
Groundwater will eventually reach the earth's surface once again (though it may range
from many years to only a few hours) as a spring or seep, by flowing through the soil
into a stream or lake, or by being pumped up to the surface. Surface water and water in
the soil is warmed by the sun or by being pumped up to the surface. Surface water and
water in the soil is warmed by the sun and changes into a gas or vapor. This process is
called evaporation. Water in plants may also become vapor through a process known as
transpiration. The term evapotranspiration is used to describe the combined process of
evaporation of surface water from soil and transpiration from plants.
When water vapor condenses into a liquid or solid and forms clouds, the water cycle
starts all over again. It is important to remember that while the form of the water
changes, the total amount of water remains the same. This is nature's way of recycling.
Imagine, the water you used to wash your face today has been recycled since long
before people ever lived on earth.
Distribute the Water Cycle crossword puzzle. Pass out copies of the water cycle picture
that is part of The Fountain. Upon completion, have students share responses to the
crossword and use the words to introduce the water cycle.
Construct a water cycle model. Raise one end of the plastic box about two inches. Mix
plaster of Paris and water to a pancake batter consistency. Pour the mixture into the end
of the box that is not elevated. Leave about two inches of the elevated bottom free of
plaster of Paris. When the material starts to set up, use your fingers to make hills and
valleys. Allow the plaster to dry for at least 12 hours. Paint the landforms after the
plaster is hard. Use browns and greens. After paint is dry, spray the landforms with at
least two coats of acrylic spray.
Cut a 3" x 3" hole in the plastic lid and tape a piece of clear plastic in the hole as
illustrated below. Note: place the lid face down on a piece of cardboard and cut the hole
in the lid with a sharp knife.
The model is now ready to operate. Add enough water to form a lake at the low end of
the tray. Then place the lamp near the lake. Add ice to the plastic bag and wait for
Note: This water cycle box is a very good investment. It really works and can be used
over and over again.
Condensation: The change of water from a gas to a liquid
Evaporation: The process of converting or changing into a vapor
Groundwater: Water that infiltrates into the earth and is stored in usable amounts in the
soil and rock below the earth's surface
Precipitation: Water droplets or ice particles condensed from atmospheric water vapor
and sufficiently massive to fall to the earth's surface, such as rain or snow
Surface runoff: Water (usually originating as precipitation) that flows across surfaces
rather than soaking in
Transpiration: Direct transfer of water from the leaves of living plants or the skins of
animals into the atmosphere
Water cycle: The cycle of the earth's water supply from the atmosphere to the earth and
back which includes precipitation, transpiration, evaporation, runoff, infiltration, and
storage in water bodies and groundwater
SD Standards for 4th grade:
4.E.1.1; Nature of Science Indicator 2
Interpretation, Critical Thinking
Prior Preparation: Collect materials
to construct the water cycle model.
precipitation, water cycle, evaporation,
transpiration, groundwater, surface