Natural Lakes

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Lakes and Reservoirs
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Natural Lakes

• Lakes also formed when sediment that was
  deposited by glaciers dammed the flow of streams.

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Lakes and Reservoirs
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Crustal Movements

• Movement of Earths crust can create depressions
  that fill with water.

• These lakes often form along faults surfaces
  along which rocks break and move.

• Rock lying between two faults can sink to form a
  depression.

• If Earths crust continues to move along the
  faults, the lake will deepen.

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Lakes and Reservoirs
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Crustal Movements

• Lakes also can form after a volcanic eruption.

• Rainwater and runoff later fill the caldera.

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Lakes and Reservoirs
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Human-Made Lakes

• When a dam is built within a stream, a human-made
  lake forms.

• When water in a natural or artificially created
  lake is used for human consumption, the lake is
  called a reservoir.

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Lakes and Reservoirs
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Life in Lakes

• Many types of organisms can be found in different
  parts of lakes.

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Lakes and Reservoirs
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Life in Lakes
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Lakes and Reservoirs
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Life in Lakes

• As plants use sunlight to make food, they produce
  oxygen that other organisms need.

• Plants also provide many places for small
  organisms to hide from hungry predators.

• Organisms that use land and water, such as
  amphibians, also are found here.

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Lakes and Reservoirs
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Life in Lakes

• Because sunlight cannot penetrate to the bottom
  of a deep lake, rooted plants cannot survive
  there, so frogs and small fish have nowhere to
  hide.

• Wormlike organisms, bacteria and animal wastes
  that fall from higher layers of the lake are
  found on the lake bottom.

• Some fish species are found in deep waters of
  large lakes.

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Section Check
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Question 2
What is a lake called when the water is used for
human consumption?
Answer
When a dam is built a human-made lake, or
reservoir, forms. The reservoir is used to supply
drinking water to nearby communities.
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Wetlands
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Importance of Wetlands

• Today, wetlands are recognized as a valuable
  resource.

• Wetlands act as a natural sponge, soaking up
  excess water from rain, melting snow, and floods
  and then slowly releasing it.

• Wetlands near lakes and rivers help protect
  shorelines and stream banks against erosion
  because plant roots help hold soil in place and
  slow the speed of moving water.

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Wetlands
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Trapping Sediment

• Wetlands, such as those found on floodplains and
  deltas, are especially effective at trapping
  sediment because their vegetation slows the
  waters flow.

• Trapped sediment cannot enter the lake or stream,
  so the water remains clear.

• Fish, their eggs, and plant life all thrive in
  clear water.

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Wetlands
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Removing Nutrients

• Wetland plants also use nutrients for growth,
  slowing the rate of eutrophication.

• Lakes and streams that have large wetland areas
  generally have better water quality because
  wetlands remove nutrients from the water.

• Human wastewater, called sewage, contains high
  amounts of nutrients.

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Wetlands
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Removing Nutrients

• In most cities, the wastewater is treated at a
  sewage-treatment facility to remove pollutants.

• The water then is released into a river or other
  water body.

• Wetlands are so effective at removing nutrients
  that they sometimes are created at
  sewage-treatment facilities to treat sewage.

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Section Check
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Question 3
List some reasons why wetlands are an important
resource.
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Section Check
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Answer
Wetlands act as a natural sponge, soaking up
excess water from rain, melting snow, and floods
and then slowly releasing it. They help protect
shorelines and stream banks against erosion
because plant roots slow the speed of water.
Wetlands also slow the rate of eutrophication
because their plant roots take up excess
nutrients.
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Pollution of Freshwater
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Pollution Sources Point Source
Pollutants

• A pollutant is a substance that contaminates the
  environment.

• Water pollution occurs when substances are added
  to water that lower its quality.

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Pollution of Freshwater
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Pollution Sources Point Source
Pollutants

• Pollution that enters water from a specific
  location is called point source pollution.

• Point sources are fairly easy to control because
  the location of the pollution source is known.

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Pollution of Freshwater
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Nonpoint Source Pollutants

• Most water pollution doesnt enter a body of
  water from sources you can identify.

• When pollution comes from a wide area such as
  lawns, construction sites, and roads, it is
  called nonpoint source pollution.

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Pollution of Freshwater
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Reducing Water Pollution

• The key to clean water is to reduce the amount of
  pollutants that enter it.

• Controlling point source pollutants might seem
  easy-reduce the amount of pollutants at the
  source.

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Pollution of Freshwater
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Reducing Water Pollution

• Controlling nonpoint source pollution is more
  difficult.

• Fertilizers, herbicides, and insecticides are
  sprayed on crops and gardens over large land
  areas to encourage plant growth and reduce damage
  from weeds and insects.

• These substances can be carried into Earths
  surface freshwater.

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Pollution of Freshwater
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Reducing Water Pollution

• Controlling pollution requires difficult
  decisions about the types and amounts of
  pollutants that should be allowed in water.

• Laws that limit pollutants are written carefully
  to protect the water resource and the economy.

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Pollution of Freshwater
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Legislation

• The Rivers and Harbors Act of 1899 was the first
  attempt to use legislation to help regulate water
  pollution.

• This law required that when any work was done in
  water that ships use for navigation, like
  dredging the bottom, the wildlife resources of
  the water must be considered.

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Pollution of Freshwater
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Legislation

• By the late 1960s, water pollution became so bade
  in the United States that many beaches along the
  east and west coasts were unhealthy for swimming.

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Pollution of Freshwater
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Legislation

• In 1969, greasy debris floating on a large river
  in Cleveland, Ohio, caught on fire.

• In 1972, the U.S. Congress responded by passing
  the Federal Water Pollution Control Act.

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Pollution of Freshwater
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Legislation

• Amendments were added to this act in 1977 and
  1987, and it was renamed the Clean Water Act.

• These laws put limits on the types of pollution
  that can be discharged into streams and lakes.

• In 1970, Congress created the Environmental
  Protection Agency (EPA), to enforce water
  pollution limits.

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Pollution of Freshwater
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Legislation

• The Clean Water Act amendments also provided
  federal funds for communities and industries to
  limit their water pollution sources.

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Pollution of Freshwater
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Legislation

• Today, 55 percent of streams and rivers and 46
  percent of lakes that have been tested have good
  water quality.

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Pollution of Freshwater
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How can you help?

• You can do many things to reduce water pollution.
  Pay attention to how much water you use.

• Just turning off the faucet when you brush your
  teeth can save more than 19 L of water per day.

• Keep your yard and driveway free of pet wastes,
  oil, and other debris. When it rains, these
  pollutants run off to streams and lakes.

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Pollution of Freshwater
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How can you help?

• Learn alternate methods to care for your yard and
  garden, like composting grass clippings.

• Composting yard wastes reduces the amount of
  fertilizer and other chemicals needed for your
  yard.

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Pollution of Freshwater
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How can you help?

• Properly dispose of any hazardous substances,
  such as used oil, antifreeze, and paint.

• Learn about programs in your community for safe
  disposal of hazardous waste.

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Section Check
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Question 1
List some sources of nonpoint pollution.
Answer
Nonpoint source pollutants can come from lawns,
construction sites, roads, and farms.
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Section Check
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Question 2
Which of the following provides funds to
communities and industries to limit their water
pollution sources?
A. Clean Water Act B. Environmental Protection
Agency C. Federal Water Pollution Control Act D.
The Rivers and Harbors Act
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Section Check
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Answer
The answer is A. The Clean Water Act provides
federal funds to keep water sources free of
pollution.
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Section Check
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Question 3
Why is point source pollution easier to control
than nonpoint source pollution?
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Section Check
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Answer
Point source pollution enters water from a
specific location therefore, the location of the
pollution source is known. Nonpoint source
pollution can come from a wide area and the
source can be difficult to track down.