Fresh WaterFresh Water

Chapter 7 Sections 1-4Chapter 7 Sections 1-4

SOL 6.7SOL 6.7

Earth is called the “water planet” Earth is called the “water planet” because nearly ¾ of Earth is made up because nearly ¾ of Earth is made up

of water. of water.

97% salt water97% salt water

3% fresh water3% fresh water

Less than 1% of the water on Earth is Less than 1% of the water on Earth is usable to humans. usable to humans.

Water is found in several forms on Earth, Water is found in several forms on Earth, including:including:OceansOceans

Ice (glaciers)Ice (glaciers)Rivers and lakesRivers and lakes

GroundwaterGroundwater

Far more fresh water is found Far more fresh water is found underground than in all of Earth's rivers underground than in all of Earth's rivers

and lakes. and lakes.

In addition to household purposes, In addition to household purposes, people use water for agriculture, people use water for agriculture,

industry, transportation and recreation. industry, transportation and recreation.

Water is also important for living things Water is also important for living things to grow, reproduce, and carry out other to grow, reproduce, and carry out other

important processes. important processes.

Example: Plants need water to carry out Example: Plants need water to carry out photosynthesis.photosynthesis.

A river and all its tributaries together A river and all its tributaries together make up a river system. make up a river system.

tributaries=the smaller streams and tributaries=the smaller streams and rivers that feed into a main river due to rivers that feed into a main river due to

the pull of gravity.the pull of gravity.

All the water in a river system drains into All the water in a river system drains into the main river. The land area that the main river. The land area that

supplies water to a river system is called supplies water to a river system is called a watershed (also called drainage a watershed (also called drainage

basins).basins).

Virginia has many watersheds. Virginia has many watersheds.

The largest watershed in VA is the James River The largest watershed in VA is the James River Watershed which stretches from Chesapeake Bay to Watershed which stretches from Chesapeake Bay to

the Virginia/West Virginia border. the Virginia/West Virginia border.

The smallest watershed in VA is the Yadkin The smallest watershed in VA is the Yadkin Watershed which stretches into North Carolina.Watershed which stretches into North Carolina.

One watershed is separated from another One watershed is separated from another by a ridge of land called a divide. by a ridge of land called a divide.

Streams on each side of the divide flow in Streams on each side of the divide flow in different directions. different directions.

The Continental Divide is the longest The Continental Divide is the longest divide in North America.divide in North America.

A flood occurs when the volume of water A flood occurs when the volume of water in a river increases so much that the in a river increases so much that the

river overflows its channel. Flood water river overflows its channel. Flood water has a lot of energy and can uproot trees has a lot of energy and can uproot trees

and wash away bridges and houses. and wash away bridges and houses.

Ponds and lakes form when water Ponds and lakes form when water collects in hollows and low-lying areas of collects in hollows and low-lying areas of

land. They are made up of still, or land. They are made up of still, or standing water. Ponds are generally standing water. Ponds are generally smaller and shallower than lakes. smaller and shallower than lakes.

Ponds have many plant species living in Ponds have many plant species living in them because of how shallow they are, them because of how shallow they are,

which allows sunlight to reach all the way which allows sunlight to reach all the way to the bottom. The bottom of a pond is to the bottom. The bottom of a pond is usually covered with mud and algae.usually covered with mud and algae.

Not all ponds exist-year round. Some dry Not all ponds exist-year round. Some dry up in the summer and reappear when up in the summer and reappear when runoff from spring rains and melting runoff from spring rains and melting

snow collects in low areas.snow collects in low areas.

Most lakes are deep enough that sun Most lakes are deep enough that sun does not reach all the way to the bottom. does not reach all the way to the bottom.

A lake bottom may usually consist of A lake bottom may usually consist of sand, pebbles or rock.sand, pebbles or rock.

People can create a lake by building a People can create a lake by building a dam across a river. The lake may be dam across a river. The lake may be

used for supplying drinking water, used for supplying drinking water, irrigating fields or for boating and fishing.irrigating fields or for boating and fishing.

A reservoir is a lake that stores water for A reservoir is a lake that stores water for human use.human use.

A lake environment can gradually change A lake environment can gradually change over time. over time.

When a glacier reaches the seacoast, When a glacier reaches the seacoast, icebergs form. About 90% of an iceberg icebergs form. About 90% of an iceberg lies below the surface. The underwater lies below the surface. The underwater part is a hazard to ships because it is part is a hazard to ships because it is

often much wider than the visible part. often much wider than the visible part.

Groundwater comes from precipitation Groundwater comes from precipitation that soaks into the ground instead of that soaks into the ground instead of

evaporating. Water underground trickles evaporating. Water underground trickles down between particles of soil and down between particles of soil and

through cracks and spaces in layers of through cracks and spaces in layers of rock.rock.

People can bring groundwater to the People can bring groundwater to the surface through the use of a well. surface through the use of a well.

A wetland is an area of land that is A wetland is an area of land that is covered with a shallow layer of water covered with a shallow layer of water

during some or all of the year. They form during some or all of the year. They form in places where water is trapped in low in places where water is trapped in low areas or where groundwater seeps onto areas or where groundwater seeps onto

the surface of the land.the surface of the land.

Examples: marshes, swamps and bogsExamples: marshes, swamps and bogs

Because of their sheltered waters and Because of their sheltered waters and rich supply of nutrients, wetlands provide rich supply of nutrients, wetlands provide

habitats for many living things.habitats for many living things.

Wetlands also naturally filter water and Wetlands also naturally filter water and help control floods by absorbing extra help control floods by absorbing extra

runoff from heavy rains. runoff from heavy rains.

The Florida Everglades and other The Florida Everglades and other wetlands are protected by laws to protect wetlands are protected by laws to protect many endangered species that live there.many endangered species that live there.