Groundwater Flashcards

1
Q

Roughly _____% of Canada’s population is reliant on groundwater

A

25-40%

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2
Q

Define Groundwater

A

water that lies beneath the surface

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3
Q

Ground water makes up for __% of the hydrosphere’s fresh water, while glaciers make up for ___%

A

22% and 77%, respectively

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4
Q

___% of total precipitation infiltrates the ground and sends up as ground water

A

15%

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5
Q

True or False: ground water is static

A

False; it is slow moving

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6
Q

True or False: groundwater is found most commonly in underground lakes and rivers

A

True, but barely. It can occur, but is extremely rare

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7
Q

Where is groundwater most commonly found

A

pores of sediment and soil

fractures of bedrock

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8
Q

Porosity

A

percentage of voids or pore space (vs total volume)

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9
Q

What is porosity used to determine?

A

How much groundwater can be stored

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10
Q

How to measure porosity

A

Take a column with a toal volume of 1000 mL and fill it with dry sand (dry sand has a porosity filled with air). replace the air with water. The porosity=volume water/Volume total

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11
Q

Permeability or Conductivity

A

Capacity of rock or sediment to transmit a fluid

connected pores give a rock permeability

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12
Q

Specific yield

A

% that can drain by gravity

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13
Q

Specific retention

A

% that cannot drain by gravity

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14
Q

Distribution of ground water is found in what three places?

A

1) Unsaturated zone
2) Water Table
3) Zone of saturation

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15
Q

Unsaturated zone

A
  • above water table
  • voids filled by water and air
  • water is under suction (negative pressure) due to capillary forces (think TLC)
  • water cannot be pumped by wells
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16
Q

Water Table

A
  • Upper limit of zone of saturation
  • surface of water level in ground
  • depth varies seasonally
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17
Q

Zone of Saturation

A
  • below water table
  • all voids are filled with water
  • water is under positive pressure and can be sucked up by wells
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18
Q

Pressure distribution

A

unsat:
a) Patmos. P
b) water under (+) pressure

19
Q

What factors control infiltration?

A

1) precipitation
2) slope
3) geological material
3) vegetation

20
Q

In what three places is groundwater stored?

A

1) Aquifer
2) Acquitard
3) Aquiclude

21
Q

Aquifer

A

permeable rock layer or sediment that stores and transmits groundwater

22
Q

Acquitard

A

semi-permeable rock layer

23
Q

Aquiclude

A

impermeable rock layer (exCLUDEs water)

24
Q

Types of aquifers

A

Unconfined and confined

25
Q

Unconfined aquifer

A
  • no confining layer
  • groundwater is not under pressure
  • top of water table moves freely up and down
26
Q

Confined aquifer

A
  • sandwiched between 2 confining layers (usually inclined to allow recharge)
  • groundwater is under pressure
  • top of water table is above confined aquifer
27
Q

Types of wells

A

Non-flowing artesian well and flowing artisan well

28
Q

Non-flowing artesian well

A

water table (pressure surface) of a confined aquifer lies below ground level (pressure is not great enough to bring water to the surface)

29
Q

Flowing artesian well

A

Water table of a confined aquifer rests above ground level; water reaches ground surface using natural pressure of the confined aquifer

30
Q

What is the general pattern of movement?

A

recharge (high) –> discharge (low)

31
Q

True or False: velocity is highest nearest the surface

A

true

32
Q

Darcy’s Law states:

A

States that if permeability remains uniform, the velocity of groundwater will increase as the slope of the water table (hydraulic gradient) increases

33
Q

Darcy’s Law equation

A

v=-(K/fancy n)(i), where K = hydraulic conductivity, n = porosity, i=hydraulic gradient=driving force, v=velocity

34
Q

Ground water and stream interactions

A

1) gaining streams
- gain water from the inflow of groundwater through streambed
2) losing streams
- loss of water to the groundwater system by outflow through streambed

35
Q

The water table is ____ than the stream bed in the gaining streams interaction

A

higher

36
Q

The water table is ____ than the stream bed in the losing streams interaction

A

lower

-zone of aeration present

37
Q

Sources of groundwater contamination

A
  • road salt
  • fertilizers
  • pesticides
  • chemical and industrial materials
  • bacteria and viruses
38
Q

What are some problems associated with groundwater withdrawal?

A

Sewage contamination
-sewage often becomes purified as it passes through the aquifer composed of sand or permeable sandstone. However, in extremely permeable aquifers (ie. coarse gravel or fractured bedrock), the groudwater may travel long distances without being cleaned

Saltwater contamination
-excessive groundwater withdrawal causes saltwater to be drawn into wells

39
Q

What are the consequences of excessive pumping?

A

1) drawdown (lowering) of the W.T

2) cone of depression in the WT

40
Q

subsidence

A

Ground shrinks when water is pumped from wells faster than the recharge process can replace it

41
Q

Geysers

A

intermittent surface emission of hot water

occur when groundwater heats, changes to steam, and errupts

42
Q

Erosional features of groundwater

A
  • caves (underground cavity)

- Karst topography (typically form in limestone bedrock) (ie. caves and sinkholes)

43
Q

Depositional features

A
  • Groundwater is often mildly acidic, so it dissolves rocks (particularily limestone).
  • if rxn reverts and CO2 escapes, CaCO3 is deposited, creating stalactite (point down), stalagmite (point up), column/pillar etc