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Hydrogeology > Properties of Aquifer > Flashcards

Properties of Aquifer Flashcards

1
Q

Capacity to do work

A

Energy

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2
Q

The product of the net force exerted and the distance through which the force moves.

A

Work

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3
Q

The product of mass of the body and its acceleration.

A

Force

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4
Q

The mass multiplied to the gravitational force (~9.8 m/s 2 )exerted to it by the

A

weight

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5
Q

A fluid or solid is its mass per unit volume.

A

density

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6
Q

A substance is its weight per unit volume.

A

specific weight

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7
Q

The force applied to a unit area perpendicular to the direction of the force

A

Pressure

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8
Q

Value of standard atmospheric pressure is?

A

1.013x10^5 Pa

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9
Q

Pressure is measured relative to _________ which varies with changing weather patterns

A

atmospheric pressure

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10
Q

Resistance to relative motion is proportional to a fluid property known as the dynamic viscosity

A

newtonian fluid

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11
Q

The proportionality constant for compressibility

A

bulk modulus

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12
Q

True or False. If pressure is applied, the same mass of fluid will be contained within a smaller volume because water is a compressible fluid

A

TRUE

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13
Q

the density is _______ to the change in pressure.

A

proportional

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14
Q

Assemblages of individual grains that were deposited by water, wind, ice, and gravity.

A

sediments

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15
Q

Openings between the sediment grains

A

pore spaces

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16
Q

Express mathematically the porosity of earth materials is the percentage of the rock or soil that is void of material

A

porosity (n) = 100Vv/V

Vv - volume of void space in a unit of earth materials
V - unit volume of earth material

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17
Q

what is pore throats?

A

passageway typically smaller than pores

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18
Q

Equation of total porosity

A

porosity (n) = 100 [1-(Pb/Pd)]

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19
Q

TRUE or FALSE. Effective porosity of a sediment is not a function of the size of the molecules that are being transported relative to the size of the passageways that connect the pores

A

FALSE. Function of the size of the molecules.

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20
Q

Percentage of cube packing of spheres

A

47.65%

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21
Q

Percentage of rhombohedral packing of spheres

A

25.95%

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22
Q

True or False. Does the diameter of the spheres influence the porosity

A

False. Does not influence the sphere

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23
Q

True or False. Porosity is also affected by the shape of grains and the fabric/orientation of the particles

A

True

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24
Q

True or False. If a sediment contains a mixture of grain sizes, the porosity will be lowered

A

True

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25
Q

Sediments are classified by the basis of ________________

A

diameter size

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26
Q

Enumerate types of geologic porosity

A

primary porosity
secondary porosity
fracture porosity
vuggy porosity

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27
Q

A type of porosity generated by the dissolution of large features.

A

Vuggy porosity

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28
Q

A type of porosity associated with fracture system or faulting.

A

Fracture porosity

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29
Q

A type of porosity system in a rock or unconfined alluvial deposit.

A

Primary porosity

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30
Q

A type of porosity that enhances the overall porosity of rock. It can co-exist or replace the porosity.

A

Secondary porosity

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31
Q

True or False. Can gypsum and salt can also be cavernous.

A

True

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32
Q

What are the range value of limestone and dolomites?

A

1 - 30%

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33
Q

What is the percent porosity of sedimentary rock?

A

3 - 30%

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34
Q

It measures how well or poorly sorted the grains are.

A

uniformity coefficient

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35
Q

Refers to a size corresponding to the 10% line of the grain size curve.

A

effective grain size

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36
Q

Ratio of grain size

A

Cu = d60/d10

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37
Q

True or False. Does compaction reduces pore volume by rearranging the grains and reshaping them.

A

True

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38
Q

Refers to the dissolved pore fluid with increasing porosity

A

dissolution material

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39
Q

True or False. Does deposition of cementing materials such as calcite, dolomite, or silica will not reduce porosity.

A

False. Will reduce

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40
Q

True or False. A sample with a Cu less than 4 is well sorted

A

TRUE

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41
Q

True or False. A sample with a Cu less than 6 is poorly sorted.

A

False. More than 6.

42
Q

__________ and ________ increases overall rock porosity.

A

weathering and fracturing

42
Q

According to Stewart 1964 __________ and ________ can have a porosity in the range of _______ to _______.

A

weathered plutonic and metamorphic rocks
30% - 60%

43
Q

True or False. Extrusive rocks cool and solidify quickly because they are formed in a surface environment this gives them radically different porosity characteristics

A

TRUE

44
Q

Lava cooling rapidly at the surface will trap degassing products, resulting in ____________ in the rock.

A

Vesicular texture

45
Q

According to Schoeller, 1962 porosity of basalt generally ranges from _______.

A

1 to 12%

46
Q

According to Davis, 1969 pumice can have a porosity as high as _______.

A

87%

47
Q

According to Keller, 1960, tuff has a porosity ranging from ______.

A

14% to 40%

48
Q

Volcanic ash may have a porosity of _________.

A

50%

49
Q

According to Davis, 1969, weathering of volcanic deposits can increase the porosity to values in excess of ______.

A

60%

50
Q

It is the volume of water that drains from saturated rock owing to the attraction of gravity to the total volume of the rock

A

Specific Yield (Sy)

51
Q

Water molecules cling to surfaces because of ___________.

A

surface tension

52
Q

True or False. If gravity exerts a force on a film of water surrounding a mineral grain, some of the films will pull away and drip downward.

A

False. Exerts a stress

53
Q

True or False. The remaining film will be thicker with a greater surface tension so that the stress of gravity will be exactly balanced by the surface tension.

A

False. Thinner

54
Q

Moisture clinging to the soil particles because of surface tension.

A

Pendular water

55
Q

The ratio of volume of water a rock can retain against gravity drainage to the total volume of rock.

A

Specific Retention (Sr)

56
Q

The formula use for calculating the porosity of a rock/material.

A

n=Sy + Sr

57
Q

It is the ability of a rock to transmit water that, together with its ability to hold water.

A

Hydraulic Conductivity

58
Q

Examples of rocks that exhibit porosity but lack interconnected voids

A

Vesicular basalt

59
Q

Example of rocks that have porosity but the pores are small that water flows through the rock with difficulty.

A

clay and shale

60
Q

A French Engineer, made the first systematic study of the movement of water through a porous medium.

A

Henry Darcy, 1856

61
Q

True or False. The discharge, Q is proportional to the difference in the height of the water, h (hydraulic head) between the ends and inversely proportional to the flow length, L.

A

TRUE

62
Q

True or False. The quantity of flow is inversely proportional to a coefficient, K, which is dependent upon the nature of the porous medium.

A

False. Proportional

63
Q

Formula for Darcy’s Law

A

Q = - KA [( hA - hB )/L] or Q = -KA (dh/dl)

Note: The negative sign indicates that flow is in the direction of decreasing hydraulic head

64
Q

Where dh/dl is known as the ______. The quantity _____ represents the change in head between two points that are very close together, and _____ is the distance between these points.

A

hydraulic gradient; dh; dl

65
Q

A measure of the quantity of any fluid flow over unit time. And it is directly proportional to the specific weight y.

A

discharge

66
Q

The force exerted by gravity on a unit volume of fluid

A

specific weight

67
Q

A function of the size of the openings through which the fluid moves.

A

Intrinsic Permeability

68
Q

True or False. Discharge is also proportional to the dynamic viscosity of the fluid, μ.

A

False. Inversely proportional

69
Q

True or False. For well-sorted sediments the intrinsic permeability is proportional to the grain size of the sediment.

A

True

70
Q

True or False. Unconsolidated coarse-grained sediments do not represent some of the most prolific producers of groundwater.

A

False. It represents

71
Q

Several factors relating to intrinsic permeability to grain size.

A
  1. As the median grain size increases, so does permeability.
  2. Permeability will decrease for a given median diameter as the standard deviation of particle size increases. The increase in S D indicates a more poorly sorted sample.
  3. Coarser samples show a greater decrease in permeability with an increase in standard deviation than fine samples.
  4. Unimodal (one dominant size) samples have a greater permeability than bimodal (two dominant size) samples
72
Q

The hydraulic conductivity of earth materials can be measured in the laboratory thru the use of _________.

A

permeameters

73
Q

Let us recap the permeability of rocks!

A

Clastic sedimentary rocks have primary permeability characteristics similar to those of unconsolidated sediments. However, diagenesis can reduce the size of the throats that connect adjacent pores through cementation and compaction

Crystalline rocks typically have a low primary permeability

Volcanic rocks can have a high porosity and if the openings are large and well connected, then they may also become highly permeable

74
Q

Undulating surface at which pore water pressure is equal to atmospheric pressure.

A

Water table

75
Q

A _______ water table indicates the groundwater is flowing

A

sloping

76
Q

______________ are in topographical low spots

A

Groundwater discharge zones

77
Q

True or False. Groundwater generally flows away from topographical high spots toward topographical lows

A

true

78
Q

It is a geologic unit that can store and transmit water at rates fast enough to supply a reasonable amount to wells.

A

Aquifer

79
Q

Example of rock units of aquifer.

A

sand and gravels
sandstone
limestone
dolomites
basalt flows
fractured plutonic and metamorphic rocks

80
Q

__________ of aquifers would range about 10^-2 darcy upward.

A

Intrinsic permeability

81
Q

_______________ geologic unit having little or no intrinsic
permeability less than 10^-2 darcy.

A

Confining Layer

82
Q

Confining layers can be classified as:

A

Aquifuge, Aquitard, Aquiclude

83
Q

Absolutely impermeable unit that will not transmit any water.

A

Aquifuge

84
Q

A layer of low permeability that can store groundwater and also transmit it slowly from one aquifer to another (also called as leaky confining layer).

A

Aquitard

85
Q

A rock unit or geologic formation through which inappreciable quantity of water moves or is transmitted.

A

Aquiclude

86
Q

An aquifers that can be close to the land surface, with continuous layers of materials of high intrinsic permeability extending from the land surface to the base of the aquifer.

A

water table aquifer or unconfined aquifer

87
Q

________ (also called artesian aquifers) are overlain by confining layers.

A

Confined aquifers

88
Q

________ a confined aquifer is the surface representative of the level to which water will rise in a well cased to the aquifer.

A

Potentiometric surface

89
Q

A layer of saturated soil that forms above the main water table.

A

Perched aquifer

90
Q

The measure of the amount of water that can be transmitted horizontally through a unit width by the saturated thickness of the aquifer under a hydraulic gradient of 1.

It is also the product of the hydraulic conductivity and the saturated thickness of the aquifer.

A

Transmissivity

91
Q

The volume of water that a permeable unit will absorb or expel from storage per unit surface area per unit change in head

A

Storage Coefficient (Storativity)

92
Q

In the saturated zone, the head creates pressure, affecting the arrangement of mineral grains and the density of the water in the voids If the pressure increases, the mineral skeleton will expand if it drops, the mineral skeleton will contract.

A

Elasticity

93
Q

The amount of water per unit volume of a saturated formation that is stored or expelled from storage owing to the compressibility of the mineral skeleton and the pore water per unit change in head.

A

Specific Storage (Elastic Storage Coeffcient)

94
Q

At a given plane in a saturated aquifer, downward stress is placed on the aquifer skeleton by the weight of the overlying rock and water.

A

Total stress

95
Q

There is upward stress on the plane caused by the fluid pressure. The upward stress will, in part, counteract the total stress, so the resulting stress that is actually borne by the aquifer, called the ________________.

A

effective stress

96
Q

Unit is one that has the same properties at all locations

A

Homogenous

97
Q

__________ formations, hydraulic properties change spatially One example would be a change in thickness

A

Heterogeneous

98
Q

Units that have the same intrinsic permeability in all directions

A

Isotropic

99
Q

If the geometry of the voids is not uniform then there may be a direction in which intrinsic permeability is greater.

A

Anisotropic

100
Q

It exemplify massive porosity located in New Mexico

A

Carlsbad cavern

101
Q

Hydraulic conductivity of earth materials can be measured in the laboratory thru the use of ___________.

A

Permeameters

Hydrogeology (8 decks)

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