Underground Water

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Underground Water

• A family lives 50 km from the nearest stream or
  lake and gets water from a well.
• Where does the water in the well come from?

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Ground water

• Water located within the rocks below the Earths
  surface.
• Is an important resource
• Plays an important role in erosion and deposition

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Location of Ground Water

• Surface water seeps underground into the soil and
  rock
• 2 zones for underground water
• Zone of aeration
• Not completely filled with water
• Usually fills immediately after a rain
• Zone of saturation
• Further down
• Spaces between rock particles fills with water

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Water Table

• The underground boundary of where the two zones
  meet
• Rises during wet seasons
• Drops during dry seasons
• Climate determines where the water table is
  located
• Wet regions just beneath the soils surface
• Dry regions may be 100 of meters underground

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Falling Water Tables

• Sustainability ultimately depends on balancing
  withdrawals with rates of recharge.
• Major indicator that ground water withdrawals are
  exceeding recharge is a falling water table

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Aquifers

• A rock layer that stores and allows the flow of
  ground water.
• Some rocks hold more water than others
• Rock layers must be porous
• Porosity is the amount of space between
  individual rock particles
• Permeability is a rocks ability to let water
  pass through it (a rock that stops the flow of
  water is called impermeable)

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Aquifer Geology and Geography

• Best aquifers are formed of sandstone, limestone,
  or layers of sand and gravel
• Some cover large areas
• Some are important water supplies for cities and
  agriculture.

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Washington Aquifers
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Is That a fact!

• Geologists estimate that aquifers hold 50 million
  cubic kilometers of water worldwide. There is
  about 20 times more water underground than in all
  the rivers, lakes, and the atmosphere.

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How Much?
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How Much ??
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Recharge Zone

• The ground surface where water enters an aquifer
• Like rivers, aquifers, are dependant on the water
  cycle to maintain a constant flow of water.

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Tapping more ground water?

• More than 2 billion people already depend on
  ground water!
• Many areas groundwater use already exceeds
  aquifer recharge what then?
• Depleting groundwater is the single greatest
  threat to irrigated agriculture what then?

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Springs

• Ground water movement is determined by the slope
  of the water table
• A spring is when the water table reaches the
  Earths surface (are important sources of
  drinking water)

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Artesian Spring

• Are springs that form where cracks occur
  naturally in the cap rock and the pressurized
  water in the aquifer flows through the cracks to
  the surface

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Wells

• Is a human-made hole that is deeper than the
  level of the water table
• If the water table falls below the bottom of the
  well it will dry up

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Water in developing worlds

• In many villages and cities of the developing
  world, people withdraw water from rivers,
  streams, and ponds. These sources are often
  contaminated with pathogens (bacteria) and other
  pollutants.

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Cave Formations

• Forms when water dissolve and erodes certain
  types of rock under the ground
• Usually limestone (calcium carbonate)
• Dripstone are deposits calcium carbonate (a type
  of limestone) that drips from a crack in a caves
  ceiling

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Stalagmites
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Stalactites
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Environmental Connection

• Most bat species live in caves. These
  night-flying mammals navigate by sound and can
  reach speeds of 95 km/h. Today scientists know
  that bats play an extremely important role in the
  environment. Bats are great consumers of
  insects, and many bat species pollinate plants
  and distribute seeds.

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Sinkholes

• Occurs when the roof of a cave collapses
• When the water table is lower than the level of
  the cave, the cave is no longer supported by the
  water underneath

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Daily Assignment

• Review questions pg 284 1-4
• Explain how sink holes and caves form as a result
  of erosion.
• Concept map (zone of aeration, zone of
  saturation, water table, porosity, permeability,
  impermeable, confined aquifer, artesian spring,
  spring)

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Brain Food

• Much of Australias ground water is stored in
  artesian formations, such as those fed by a vast
  underground rock formation called the Great
  Artesian Basin. Unfortunately, most of the water
  is too salty for people to drink or use for
  irrigation.