Unit 3 – The Water CycleHow Do Californians Get the Water They

Need?

California Science Standard3.e Students know the origin of the water

used by their local communities.

Shasta Dam, California

Where does the water in the Sacramento River come from?

Is the water in the river fresh water or salt water?

Why would a community consider building a dam?

VocabularyWatershed – The area of land in which water

runs off into a particular system of creeks and rivers.

VocabularyDam – A barrier across a river that controls

the river’s flow.

VocabularyReservoir – A body of water stored for future

use.

VocabularyAqueduct – A pipe or channel that is used to

transport water.

VocabularyGroundwater – Water that is in soil and rocks

below Earth’s surface.

Water ResourcesFreshwater is vital to human health.It is also necessary for growing many kinds of

plants that people rely on for food.

Water ResourcesFresh water is vital to human health.It is also necessary for growing many kinds of

plants that people rely on for food.

What are some other ways that people use freshwater resources?

What are some ways that people use saltwater resources?

Local Water SourcesMost communities in California get their fresh

water from lakes and rivers.These communities’ water supply depends on how

much rain and snow falls during the year.When rain or snow falls it collects in a watershed.

As snow melts from the top of a mountain, it flows down in small creeks.

The creeks join to form rivers.The rivers join to form larger rivers.

This system of creeks and rivers “drains” the watershed.

Local Water SourcesA community may be able to take its water

directly from the rivers of a watershed.The amount of water in a river changes from

season to season.During spring, rivers may have plenty of water

from melted snow.Dry seasons, the water level may be very low.

There may not be enough water to meet the community needs.

Local Water SourcesMany communities build dams to store water

for dry seasons.In California, dams are often used to hold

water.Water collects behind a dam to form a

reservoir. This water is being stored for future use.

Local Water SourcesIf a community uses more water than is

available from its watershed, it may need to bring in water from another watershed.The community would use an aqueduct, a pipe

or channel, to transport water.

Local Water SourcesLos Angeles uses two large aqueducts.

The first aqueduct was built in the early 1900’s. As the city grew, so did it’s need for water. The

second aqueduct was build in 1970.

How has Los Angeles provided its citizens with water?

GroundwaterNot all of California’s water supply is surface

water.About 40% of California’s population uses

groundwater.Groundwater is water under Earth’s surface

located in the spaces between rocks and soil.Not all the rain that falls on land runs off into

creeks and rivers. Some soaks in the soil and inside rocks.

GroundwaterAs water moves through these spaces, some

of it sticks to soil particles, but most of the water continues moving downward.It soon reaches an area that is filled with

water. This is called a water table.

GroundwaterYou can think of a water table as a line under

the ground.The ground above the line has air gaps in it.The ground below the line is totally filled with

water.The water table rises during wet season, and

drops during dry seasons.

GroundwaterGroundwater is can be found in rocks that have

pores, or small openings.The pores and spaces allow water to pass between

them.A rock layer can store a lot of water and let it flow

through. This is called an aquifer. Water can be obtained from them by drilling

wells.

GroundwaterA well is drilled from the surface to a spot

below the water table.A pump is used to bring the water to the

surface.A well can supply a house, neighborhood, or

even a city.If too much water is removed from a well, the

water table will drop. This will cause the well to become dry.

People should not use more well water than is replaced naturally by rainfall. Why?

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