Groundwater

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Groundwater
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BIG Idea

• Precipitation and
  infiltration
  contribute to groundwater,
  which is stored in underground reservoirs until
  it surfaces as a spring or is drawn from a well.

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Infiltration

• process of water moving into the soil/ground
• to penetrate, enter or gain access

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I. Water Beneath the Surface

• Groundwater underground water that fills almost
  all of the pores in rock and sediment

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Aquifer a body of rock that can store water and
also let water flow through
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Think of an AQUIFER as a

• large, horizontal sponge that absorbs and
  transports water along its length

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A. Rock Properties that Affect Groundwater

• Porosity
• Permeability

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1. Porosity percentage of open spaces in a rock
or sediment
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FACTORS THAT INFLUENCE POROSITY

• (a) SORTING amount of uniformity in
  particle size

HIGH pore space
LOW pore space
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• (b) SHAPE rounder particles more porous
• (c) PACKING loosely packed more porous

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2. Permeability how freely water flows through
open spaces in a rock (the pores must be
connected)
Impermeable water can NOT flow through
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Can something be porous but impermeable?

• The cork end is red because the grape juice went
  into it. Does this mean it is porous?
• If you turn the bottle upside down will it leak?
  Is the cork permeable?

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B. Zones of Groundwater

• 1. Zone of Saturation the layer of ground where
  all the pores are filled with water.

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• 2. Water Table upper surface of the zone of
  saturation

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• 3. Zone of Aeration upper region, where water is
  both in the soil and seeping down to the water
  table.

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Zone of Aeration
?
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• Capillary Action ability of water to rise UP the
  soil.
• Smaller particle size greater capillarity

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Capillary Fringe middle layer, between the water
table and the zone of aeration.
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C. MOVEMENT OF GROUNDWATER

• Depends on
• Permeability of the aquifer
• ? permeability ? velocity
• Gradient of the water table
• Gradient steepness of the slope
• ? gradient ? velocity

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II. Wells and Springs

• Water Table upper layer of rocks with all pores
  filled with water.

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• A. Ordinary Well A hole dug below the water
  table which fills up with water.

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Cone of Depression lowered area of the water
table due to pumping
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B. Artesian Wells water flows freely with no
pumping

• Underground water under pressure (between two
  impermeable rock layers) rises to the surface
• Water is naturally filtered as it passes through
  porous rock and seeps to surface

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III. Groundwater and Chemical Weathering

• Caverns rocks rich in calcite (limestone) slowly
  dissolved by carbonic acid.
• Hard water many dissolved minerals (Ca, Mg, Fe)
• Soft water few dissolved minerals

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Luray Caverns, VA
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• Formation of a Cave

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• 1. Stalactites water with dissolved calcite runs
  from a caves ceiling and solidifies downward.

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• 2. Stalagmites calcite rich water drips on the
  caves floor and builds upward.

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If the two connect, then it forms a column.
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3. Natural Bridge when the roof of a cavern
collapses in several places leaving an arch-
shaped rock.

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B. KARST TOPOGRAPHY

• regions where chemical weathering by groundwater
  is now visible at the surface
• regions where it is humid and there are limestone
  formations near the surface
• Virginia, Kentucky, Tennessee, Indiana, and
  Florida have Karst Topography

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1. Sinkholes (the main feature of Karst
Topography)
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How do sinkholes form?

• Rain seeps through soil and absorbs carbon
  dioxide and reacts with decaying vegetation
• Acidic water is created
• Water moves through spaces and cracks underground
• Limestone is slowly dissolved, creating network
  of cavities and voids
• Pores and cracks enlarge
• Land surface above collapses or sinks

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2. Streams that disappear in the ground

Like Lewis Creek in Staunton
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3. Caverns and Caves
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