5 5 earths hydrosphere (earth sciences)

California Leveled Science Readers (Grade 5) Content leveled readers teach science concepts, vocabulary, and reading skills – at each student’s reading level – and allow students to read and explore the wonders of nonfiction. Leveled science readers deliver science content to help address the individual needs of all students. They reinforce reading skills and strategies while promoting science understanding. Each grade 5 science reader is a richly illustrated, selfcontained little book with 10 to 14 double pages. BELOW 5.1 Building Blocks of Matter (Physical Sciences) 5.2 Changes in Matter (Physical Sciences) 5.3 Basic Structures of Organisms (Life Sciences) 5.4 MISSING 5.5 Water on Earth (Earth Sciences) 5.6 Weather (Earth Sciences) 5.7 The Solar System (Earth Sciences) ON 5.1 Understanding Matter (Physical Sciences) 5.2 How Matter Changes (Physical Sciences) 5.3 The Building Blocks of Organisms (Life Sciences) 5.4 Systems of the Human Body (Life Sciences) 5.5 Earths Hydrosphere (Earth Sciences) 5.6 How Weather Works (Earth Sciences) 5.7 Earths Solar System (Earth Sciences) ADVANCED 5.1 Atoms (Physical Sciences) 5.2 Acids and Bases at Work (Physical Sciences) 5.3 MISSING 5.4 MISSING 5.5 MISSING 5.6 Hurricanes (Earth Sciences) 5.7 The Red Planet (Earth Sciences)

Genre Comprehension Skill Text Features Science Content

Nonfi ction Main Idea and Details • Captions

• Diagrams

• Glossary

Water on Earth

Scott Foresman Science 5.5

Standards Preview

Standard Set 3 Earth Sciences

3 Water on Earth moves between the

oceans and land through the processes

of evaporation and condensation As a

basis for understanding this concept:

3.a Students know most of Earth’s

water is present as salt water in the

oceans, which cover most of Earth’s

surface.

3.b Students know when liquid water

evaporates, it turns into water vapor

in the air and can reappear as a liquid

when cooled or as a solid if cooled

below the freezing point of water.

3.c Students know water vapor in the

air moves from one place to another and can form fog or clouds, which are tiny droplets of water or ice, and can fall to Earth as rain, hail, sleet,

or snow.

3.d Students know that the amount

of fresh water located in rivers, lakes, underground sources, and glaciers is limited and that its availability can be extended by recycling and decreasing the use of water.

3.e Students know the origin of water

used by their local communities.

ISBN 0-328-23465-6

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by Ann Cambal

Earth Sciences

aquifer

condensation

evaporation

precipitation

reservoir

salinity

sea level

sleet

water cycle

water table

watershed

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ISBN: 0-328-23465-6

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by Ann Cambal

Water on Earth

There could be no life on Earth without water It is a vital

resource We are used to having water easily available to us

We depend on it and sometimes even take it for granted Earth

is the only planet on which liquid water can be found The

hydrosphere includes all of the water on Earth

Three-quarters, or 75 percent, of Earth’s surface is covered

by water Think about what that means! The water from rivers,

ponds, swamps, streams, lakes, and oceans covers three times as

much of Earth as the land does You can also think about it this

way If you walked four blocks, three of those blocks would be

underwater!

San Francisco Bay

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Only about 3 percent of the water on Earth is in places other than the oceans This makes water a very limited resource

Communities have to develop ways to clean water and move it

to areas where there are large numbers of people The role of hydrologists is to understand Earth’s various forms of water and water systems Hydrologists also help plan for and educate us about water’s relation to the environment and to all forms of life

This is a big job In the end, we all must work together to make sure there is enough water to drink

Vernal Falls, Yosemite National Park Lake Michigan

Oceans of the World

The world’s oceans alone cover about 72 percent, or 100 72—,

of Earth The Pacifi c Ocean is the largest Next in size are the

Atlantic, Indian, Southern, and Arctic oceans The water in all of

the oceans is salty

The Pacifi c Ocean is the largest and deepest ocean in the

world Its depth averages about 4,000 meters At its deepest,

the Pacifi c is more than 11,000 meters deep That’s about 11

kilometers! Another measure used in talking about the oceans is

sea level This is the level of the ocean’s surface Like the other

properties of the oceans, sea level varies from ocean to ocean

Temperatures of the Oceans

Ocean surface temperature varies from place to place Near

the equator, ocean water is about 30°C But at Earth’s poles, the

ocean water can be -2°C

Ocean water near the mouth of the Nile River has less salinity than ocean water farther away.

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Another thing that varies in the oceans is the level of

salinity, or the amount of salt in water Areas where rivers meet

oceans have very low salt levels Ocean water usually has a high salinity In warmer areas, ocean water evaporates, leaving behind salt, so water there has higher salt levels

If water has a high salinity and is cold, then it is heavier than the same amount of water that is warmer or less salty This helps explain how water is different in oceans across the world

Resources of the Oceans

If you’ve ever tasted salt water, you know it’s not good for you to drink Yet the ocean is a great source of many things we use and eat These include the fi sh and other seafood we eat and the salt we use on our food Although it is expensive to do, ocean water can become drinking water once the salt and other chemicals have been removed

Salt is left behind when ocean water in these shallow ponds evaporates.

Fresh Water

Only about 1003—, or 3 percent, of the hydrosphere is fresh water

Most of the water on Earth is in the oceans Earth has many

different sources of fresh water Fresh water still contains some salt,

but not nearly the amount that’s in seawater How far do you live

from the nearest fresh water? Where is fresh water found?

Almost all of the fresh water starts out as either rain or snow

Some of this water sinks into the soil Some collects in rivers,

ponds, lakes, swamps, or streams Not all of the water remains

in liquid form Some of it becomes frozen into sheets of ice and

glaciers More than half of Earth’s fresh water is frozen in ice

The ice and glaciers are too far from where it’s reasonable to try

and use them

7

Fresh water is not evenly spread all over Earth Some areas have more fresh water than other areas Some areas have more fresh water in some seasons than others But the amount of fresh water is limted everywhere The water supply can be used wisely

if it is recycled or less water is used

Scientists can help people use water wisely The scientists can give people information about the water’s quality They can also help reduce the amount of water a community needs through technology

This iceberg is fl oating in Disko Bay, Greenland Only — 1

10 of the iceberg fl oats above the water.

Groundwater

Groundwater is the melted snow or rainwater that ends

up sinking into the ground This water sinks until it reaches

something that it cannot move through Sand, for example, lets

water pass more freely through it than a dense layer of clay The

layer of rock and soil that groundwater moves through is called

an aquifer

The water table is the top level of the groundwater in an

aquifer Depending upon climate, rainfall, and other factors, the

level of any water table can change many times during a year

People need to use groundwater wisely so that the water table

doesn’t fall faster than the water is replaced

Surface water

Earth’s surface waters come from rainwater, groundwater,

and melting snow Rivers, lakes, and streams are

examples of surface water The water from small

creeks sometimes come together to

fl ow into larger rivers and streams

Groundwater can also seep into

rivers A watershed is the name for

an area whose waters drain into a

river This area can be very large

If there are chemicals on crops or

from industry in the area, they can

bring pollutants into the watershed

Some water falling

on the ground seeps into spaces in the rocks and soil.

9

Lakes are formed when water fl ows into a lower area that is

blocked by a natural or artifi cial dam A reservoir is much like

a lake It, too, is a body of water that collects in a low spot A reservoir, however, is usually an artifi cial lake formed behind a dam

The majority of fresh water on Earth is not in the lakes and rivers you’ve read about Seven-tenths of the Earth’s fresh water

is frozen in ice It is far from people and hard to use Most of the ice on Earth is in ice sheets on Greenland and Antarctica Ice sheets can be almost a mile thick in places The one at the North Pole fl oats on the ocean with no land underneath it

Glaciers are smaller areas of ice They form valleys near high mountains Glaciers and ice sheets form over time If more snow falls than melts, then the new snow pushes down the layers beneath it When glaciers and ice sheets come in contact with water, they can break off and form icebergs

The water table is lower

in places where people are using groundwater from an aquifer faster than it can

be refi lled.

Pollution from the surface can seep into the groundwater.

Getting Water Where

It Is Needed

How does water get to your faucet at school and at home?

How do you know whether it’s safe to drink?

In the United States, groundwater and surface water are two

sources of water that people use in their homes Water from

these sources, however, needs to be pumped, transported, and

“cleaned” before it is available for use at your home

Screens keep out large

objects Water and

chemicals are mixed

Heavy pollutants fall

to the bottom of the settling tank Water is

fi ltered through sand.

11

Water treatment plants are found across the United States

Indeed, they are found around the world In U.S plants, various chemicals and pollutants that have made their way into the water supply are removed Water is treated in order to create a supply of useable water that’s free from bacteria, looks sparkling clean, and has no unpleasant taste or odor Depending upon the water supply, the water may be processed through several treatments

Water is pumped with other chemicals to the water tower Water fl ows down from the tank It then fl ows through pipes

to homes and businesses.

California’s Water Needs

Before the California gold rush in 1848, few people lived

there, and so the need for water was met During and after the

gold rush, however, the population of California saw a steep

increase By the early 1900s, large cities—such as San Francisco

and Los Angeles–heavily increased the need for water resources

Because California has a very limited supply of fresh water,

the people there depend on aqueducts to bring them fresh water

An aqueduct is a system of pipes that carries water from a river

or lake to the area where it is needed Water fl ows through the

state in a network of aqueducts, tunnels, canals, and pipelines

The Los Angeles Aqueduct supplies some of the fresh water

used by the city of Los Angeles It carries water from the Owens

River of the Sierra Nevada to Los Angeles The fi rst part of the

system was built about 100 years ago Later, more pipes were

added to get water from some streams that fl owed into Mono

Lake In 1970, a second aqueduct was added to the system

The Colorado River Aqueduct supplies much of San Diego’s

fresh water This aqueduct begins at Lake Havasu at the border

of Arizona and California It carries water nearly 390 kilometers

to Lake Mathews in Riverside County before it heads south to

San Diego

The California Aqueduct carries fresh water from the

Sacramento River to people living more than 400 kilometers to

the south

13

Aqueduct systems like the California Aqueduct carry fresh water from rivers and lakes to people living many kilometers away.

California’s Water Sources

California has many natural water resources The northern

part of the state gets a large amount from rainfall and runoff

from mountain snow Most of the population of the state lives,

however, in Southern California The central region contains the

most farmland There are regional water projects, but even those

need additional water to meet the needs of the residents

California is the number one agricultural-producing state in

the country Some of its crops require a great quantity of water

Agriculture has become more effi cient in its use of water over

time Yet great quantities are still needed to support this

multi-billion dollar industry

15

Thinking about the different climates in California can help you understand the need for a system that can supply water from one region to another California has many climates They vary from snow-peaked mountains to hot, arid deserts From season to season and year to year, the amount of rainfall varies

Sometimes there are fl oods in the same years as droughts

Colorado River

San Joaquin River Sacramento River

San Francisco Bay

Tulare Lake

California Watersheds

The Water Cycle

The water cycle is a complex process It provides us with

the water that we drink, use to water our gardens, and bathe in

It also makes the different weather patterns around the world

In the hydrologic (water) cycle, Earth’s water mainly moves

through the air The steps of the water cycle are affected by

temperature and pressure

Some rain or melted

snow becomes

groundwater.

Water runs off the land and evaporates from plants.

Groundwater slowly moves through aquifers into rivers, lakes, and the ocean.

17

The Sun drives the water cycle It heats water, causing some

of it to evaporate Evaporation means that water changes

from a liquid into a vapor in the air Snow and ice can turn into water vapor by sublimation, or when ice changes to water vapor without fi rst melting into a lquid When air cools, condensation

can occur Condensation is the changing of water vapor back

into liquid When condensation occurs, clouds form

As water vapor rises, it may form a cloud.

Because salts are left behind when water evaporates, the oceans remain salty.

Cloud Formation

Clouds are an important part of the water cycle They form

when water vapor condenses onto dust or other particles When

this happens, tiny droplets or ice crystals form Precipitation

occurs when the water droplets or ice crystals grow large

enough to fall from clouds as rain, hail, sleet, or snow

Temperature and Pressure

The temperature determines what a cloud is made from

Clouds high in the sky often have a lower temperature than ones

near the surface of Earth

Air pressure affects the formation of clouds As air rises,

the pressure decreases With less air pressure, the air cools

and expands If the air cools enough, it can form ice crystals

This may be a surprise to you, but in the United States most

precipitation begins as snow The ice crystals that form in those

clouds may stick together and start to form snowfl akes If the

temperature of the air between the ground and the cloud is

below freezing, then it snows!

If the air is warm between the cloud and the ground,

then the crystals will melt to form rain As the rain falls, it

can refreeze and become sleet, or frozen raindrops You may

experience this when the temperature near the ground is cold

Hail Formation

Hailstones can form in clouds when strong winds blow

upward in them If raindrops blow up into freezing air, they will

freeze into ice and become heavier As they fall to Earth, winds

blow them up again where they gain another layer of ice

Freezing Rain Rain

Snow Sleet

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Kinds of Precipitation