Todays Plan: Groundwater

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Todays Plan Groundwater

• Groundwater in the news
• Aquifer / aquitard
• Water table
• Groundwater flow
• Wells springs
• Groundwater contamination
• Note many figures here are from Jim Meyers, U
  Wyoming

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Groundwater in the News

• Russian mine flooded by underground lake
  (groundwater) (10/23)
• 46 miners trapped 44 rescued, one dead, one
  missing

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The Hydrologic Cycle
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Groundwater aquifers

• What is an aquifer?
• Any geologic unit through which water can move
  easily (i.e. its permeable)( high
  permeability)
• Porosity how much water a geologic material can
  hold

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Opposite of an aquifer?

• Aquitard / aquiclude
• retards the flow of groundwater (its almost
  never really zero)

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Groundwater aquifers

• What would be the properties (porosity/permeabilit
  y) of conglomerate?
• High porosity, high permeability

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Groundwater aquifers

• What would be the properties (porosity/permeabilit
  y) of unfractured granite?
• Low porosity, low permeability

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Groundwater aquifers

• Can you think of a rock/sediment with high
  porosity and low permeability?

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Groundwater aquifers

• Can you think of a rock/sediment with low
  porosity and high permeability?

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The Water Table
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Water Table Topography
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The Water Table
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The Water Table
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Groundwater Flow

• Groundwater velocity
• Depends on permeability and hydraulic gradient
  (slope of water table)
• Ranges from 100 m/day to mm/day
• A good round number 1 ft/day

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How is this possible?
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Gaining Stream
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Losing Stream
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Unconfined Aquifer
recharge area pollutable area!
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Confined Aquifer
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Potentiometric (Pressure) surface
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Artesian Well
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Artesian Well

• Well water rises above water table
• Flowing artesian well rises to surface of earth

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Pumping Animation

• Go to animation at http//almandine.geol.wwu.edu/
  dave/courses/2003/spring/101/lectures/water_level
  .swf

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Your WarmUp AnswersPart B Pumping wells

• That was a really cool animation but I just dont
  understand what is happening.
• Lets look at the situation again go!

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Your WarmUp AnswersPart B Pumping wells

• In the low permeability case the water is pumped
  primarily from the area directly around the well,
  whereas with the higher permeability the water
  seems to be drawn from a more broad area
  surrounding the well "hole". Since permeability
  refers to the ability of a material to let a
  fluid move through it, the low permeability
  doesn't allow the water to venture far from the
  path of pressure change (the "hole" of the well).

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• What happens when this well is heavily pumped?

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• What happens when a new well here is heavily
  pumped?

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Flow direction can change