CHPTR 16 Groundwater Flashcards

1
Q

what percentage of water is groundwater

A

1%

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2
Q

what percentage of fresh water (excluding ice) is groundwater

A

90%

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3
Q

phreatic zone

A

saturated zone; water in this zone is called ground water

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4
Q

soil moisture

A

some groundwater stays near the surface in the soil

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5
Q

water table

A

top of the saturated (phreatic) zone

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6
Q

vadose zone

A

zone of aeration

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7
Q

capillary fringe

A

random water in the ground outside of the phreatic zone

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8
Q

how can we see the water table

A
  • tops of rivers
  • bottoms of wells
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9
Q

porosity

A

fraction of rock volume that is voids (water or air + joints, faults, caves)

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10
Q

primary porosity

A

is in structures present when rock forms

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11
Q

secondary porosity

A

develops in structures after the rock has formed

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12
Q

permeability

A

measure of how easily fluid can flow through a rock

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13
Q

Specific yield

A

fraction of groundwater that will drain under influence of gravity

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14
Q

specific retention

A

fraction of groundwater that will remain under influence of gravity

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15
Q

Porosity equation

A

Porosity% = Specific Yield% + Specific Retention%

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16
Q

Aquitard

A

impermeable layer that hinders or prevents groundwater flow

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17
Q

Aquifer

A

permeable layer that holds enough groundwater to be a useful source

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18
Q

Porosity and permeability of crystalline igneous rock

A

low porosity
low permeability

19
Q

Porosity and permeability of shale (clay layers)

A

hi porosity
low permeability

20
Q

porosity and permeability of quartz sandstone

A

hi porosity
hi permeability

21
Q

porosity and permeability of glacial till

A

low porosity
low permeability

22
Q

Darcy’s Law + give it

A

equation for the calculation of groundwater velocity

V= (kh / pL)

k = constant
h = height
L = horizontal distance
p = porosity

23
Q

how can we increase the velocity of groundwater

A
  • increase height
24
Q

how can we decrease he velocity of groundwater

A
  • increase porosity
  • increase horizontal distance
25
perched water table
when an aquitard is situated above the main water table; producing a localized zone of saturation
26
geyser
produce regular "eruptions" of hot water
27
cone of depression
area of drawdown that forms around a well. occurs because groundwater flows relatively in response to extraction from aquifer. eventually the flow will level the water table
28
drawdown
lowering of water table due to withdrawl of water
29
confined aquifer
an inclined aquifer is surrounded by impermeable beds
30
unconfined aquifer
overlain by permeable rocks and soil. pressure increased by elevation changes
31
artesian well
water is in a confined aquifer and rises to a level above the aquifer due to pressure from changing elevations
32
subsidence
the grounds sinks because of how much and how quickly groundwater is being removed
33
saltwater intrusion
a natural barrier between salt and freshwater due to the density of seawater being higher than freshwater
34
brackish water
mixture of seawater and freshwater
35
acceptable tds in drinking water
500 mg / l
36
hard water
substantial amounts of dissolved calcium and magnesium
37
where do most caves form
at or just below the water table in the zone of saturation due to erosion
38
speleothems
features formed by deposition of chemical sediment ie. stalactites and stalagmites
39
stalactite
hangs from the cieling
40
stalagmite
upward growing mound
41
Karst topography
groundwater erosion forms distinct features on the surface of the Earth: - sinks and sinkholes form - lack of surface streams
42
most useful paramaters to finding water
electrical resistivity
43