Chapter 11: Water

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Chapter 11 Water
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Section 1 Water Resources

• Some of the water we drink today has been around
  since water formed on Earth billions of years ago
• Water is essential to life on Earth
• Humans can only survive a for days without water

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The Water Cycle

• Earth has an abundance of water in all forms
  solid, liquid, and gas
• Water is renewable because it gets circulated
  through the water cycle where water molecules
  travel between the surface and atmosphere
• Water vapor (a gas) rises into the air
• Water vapor cools as it rises through the
  atmosphere and condenses into droplets forming
  clouds
• Water falls back down to Earth as precipitation
• Oceans are an important part because so much of
  water on Earth is in the ocean

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Global Water Distribution

• 71 of Earth's surface is covered with water, but
  97 of water on Earth is salt water
• Only a small percentage is liquid, fresh water
  that humans can use
• It is found in lakes, rivers, and beneath Earth's
  surface

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Surface Water

• Surface water is fresh water on Earth's land
  surface
• It's found in lakes, rivers, streams, and
  wetlands
• Throughout history, people have built cities near
  reliable sources of surface water
• Rivers, lakes, and streams provide drinking
  water, water to grow crops, food, power for
  industry, and transportation

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River Systems

• Streams form as water from falling rain and
  melting snow drains from mountains, hills,
  plateaus, and plains
• As streams flow downhill, they combine with other
  streams and form rivers
• As streams and rivers move across land, they form
  a flowing network of water called a river system
• The Mississippi, the Amazon, and the Nile are
  enormous river systems
• The Amazon is the largest river system in the
  world

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Watersheds

• The area of land drained by the river is called a
  watershed
• Pollution anywhere in a watershed may end up
  polluting a river
• The amount of water entering a watershed changes
  throughout the year
• Rapidly melting snow, spring and summer rains,
  etc. can dramatically increase the amount of
  water in a watershed
• Communities depending on these watersheds can be
  severely affected by changes in the river system

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Groundwater

• Most of the freshwater available to humans cannot
  be seen because it exists underground
• Water beneath Earth's surface in sediment and
  rock formations is called groundwater
• The point where rocks and soil are saturated with
  water is called the water table
• The water table can be at the surface or way
  below the surface

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Aquifers

• An aquifer is an underground formation that
  contains groundwater
• The water table forms the upper boundary of an
  aquifer
• Most aquifers are rock, sand, and gravel that
  have lots of space for water to accumulate
• Groundwater can dissolve limestone rock
  formations filling vast caves with water creating
  underground lakes
• Aquifers are an important water source for many
  cities and agriculture

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Porosity and Permeability

• Although rocks appear to be solid, many kinds of
  rocks contain small holes or pores
• Porosity is the percentage of the total volume of
  a rock that has pores
• The more porous a rock is, the more water it can
  hold
• The ability of a rock or soil to allow water to
  flow through it is called permeability
• Materials that allow water to flow through are
  permeable materials that do not let water flow
  through are impermeable

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Wells

• If you go anywhere on Earth and dig a hole deep
  enough, you will eventually find water.
• A hole that is dug or drilled to reach
  groundwater is called a well.
• People dig wells because groundwater may be a
  more reliable source of water than surface water
  in some areas and because water is filtered and
  purified as it travels underground.

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The Recharge Zone

• To reach an aquifer, surface water must travel
  down through permeable layers of soil and rock
• The area of the Earths surface from which water
  percolates down into an aquifer is called a
  recharge zone
• Recharge zones are environmentally sensitive
  areas because any pollution in a recharge zone
  can also enter the aquifer
• Size of recharge zone is affected by the
  permeability of the surface above the aquifer
• Structures such as buildings and parking lots can
  act as impermeable layers to reduce the amount
  of water entering an aquifer, so recharge zones
  must be managed carefully.

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Copy now, answer later

• Describe the distribution of water on Earth.
  Where is most of the fresh water located?
• Explain why fresh water is considered a limited
  resource.
• Explain why pollution in a watershed poses a
  potential threat to the river system that flows
  through it.
• Describe how water travels through rock.
• Why is an underground lake an aquifer?