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GEOLOGY > UNIT11 Groundwater > Flashcards

UNIT11 Groundwater Flashcards

1
Q

what is groundwater

A

the liquid water that resides in sediment or rock under the surface of the earth

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2
Q

what percent of water is saltwater in ocean

A

97.2%

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3
Q

what percent of of water is in ice caps and glaciers

A

2.14%

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4
Q

what percent of water is groundwater

A

0.61%

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5
Q

what percent of water is surface water (not salty)

A

0.009%

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6
Q

what is a pore

A

a pore is any open space within a volume of sediment or a body of rock

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7
Q

the total volume of open space in a body or rock or volume of sediment is termed

A

porosity %

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8
Q

What is the porosity of vesicular basalt

A

20%

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9
Q

what is the porosity of non vesicular basalt

A

<1%

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10
Q

What is the porosity of limestone

A

25%

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11
Q

What is the porosity of Shale

A

5%

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12
Q

What is the porosity of Well sorted elian sandstone

A

30%

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13
Q

What is the Porosity of Poorly sorted Sandstone

A

15%

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14
Q

What is the Porosity of conglomerate unconformity

A

30%

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15
Q

What is the porosity of granite and marble

A

<1%

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16
Q

What is primary porosity

A

Open space or porosity that originally formed with the rock

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17
Q

Primary porosity decreases with

A

burial compaction and cementation

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18
Q

crystalline rocks have ____ porosity

A

very little

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19
Q

What is secondary porosity

A

New pore space formed after the rock first formed

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20
Q

When rocks fracture what kind of porosity can occur

A

Secondary porosity

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21
Q

What is permeability

A

Permeability refers to the ease with which fluids can pass through a material via an interconnected network of pores

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22
Q

Is permeability the same as porosity

A

NO

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23
Q

Permeability depends on

A

The number of available conduits

The size of the conduits

The straightness of the Conduits

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24
Q

Can rocks with high porosity have low permeability

A

Yes, Vesicular basalt is an example

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25
Q

How might a rock have high porosity yet low permeability

A

Rock surrounds each pore meaning there are no conduits connecting the vesicles

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26
Q

What is an aquifer

A

An aquifer is a high-porosity, High permeability rock that transmits water easily

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27
Q

What is an aquitard

A

an aquitard is a low permeability rock that hinders water flow

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28
Q

what are the two types of aquifers

A

confined aquifers and unconfined aquifers

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29
Q

The Ogallala Formation is an example of

A

an Unconfined aquifer

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30
Q

The Dakota sandstone is an example of

A

a confined aquifer

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31
Q

What makes an unconfined aquifer

A

The aquifer reaches the ground surface

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32
Q

What makes a confined aquifer

A

A confined aquifer lies beneath an aquitard

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33
Q

What is the Water Table

A

The water table is the top of the groundwater reservoir in the subsurface

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34
Q

The water table separates….

A

the unsaturated zone from the saturated zone

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35
Q

The unsaturated zone of the subsurface is known as the _____, and is characterized by

A

The Vadose zone is above the water table

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36
Q

The saturated zone of the subsurface is known as the ____, and is characterized by

A

The phreatic zone lies below the water table

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37
Q

Why do ponds dry out in droughts

A

The water table falls below the Pond

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38
Q

The water table changes due to

A

Seasonal variations in rainfall and infiltration and can also rise and fall with the tides in coastal areas

39
Q

Topography can be used to estimate groundwater…..

A

Head and flow direction

40
Q

Groundwater flows ____ Hills

A

down

41
Q

A perched water table

A

Sits above a larger water table but cannot join it as it is “perched” on a small local aquitard

42
Q

The water table discharges by flowing into

A

Local or regional Discharge areas, which are surface water deposits

43
Q

The water table recharges via

A

rainfall via infiltration

44
Q

Local discharge areas are more specific than

A

Regional Discharge areas

45
Q

Deeper groundwater flow paths usually

A

Take longer to reach the discharge

46
Q

about how fast do ocean currents move

A

3km/h

47
Q

About how fast do steep river channels flow

A

30km/h

48
Q

About how fast does groundwater flow

A

0.00002km/h or 2cm/h

49
Q

Groundwater can be source of

A

Clean Water

50
Q

Describe Hydraulic Head

A

The potential energy in higher elevation water and pressure exerted by the weight of overlying water causes an energy balance in the system and causes flow

51
Q

Water deeper below the water table feels ___ pressure than at a lesser depth

A

More

52
Q

Darcy’s Law States

A

That discharge volume is proportional to the hydraulic gradient multiplied by the permeability K or k - hydraulic conductivity for water

53
Q

Darcy’s Law is

A

Q=K(h1-h2)/j)A

54
Q

What kind of unconsolidated deposit has particularly high hydraulic conductivity

A

Gravel

55
Q

High permeability will

A

increase flow rate

56
Q

Steeper Gradient will

A

Increase flow rate

57
Q

Low permeability will

A

Decrease flow rate

58
Q

Shallower Gradient will

A

Decrease flow rate

59
Q

Darcy’s Law is measured using a ____ or a _____

A

Piezometer or monitoring well

60
Q

Wells are

A

Hole that are excavated or drilled to obtain water

61
Q

Springs are

A

Natural Groundwater Outlet

62
Q

A spring develops where

A

The water table intersects the surface

63
Q

How do Wells work

A

The base of the well penetrates the aquifer below the water table

Water from the pore spaces migrate to the well and fill it to the depth of the water table

You need to monitor the rate of pumping and rate of recharge or drawdown might occur

64
Q

What is Drawdown

A

When the water table is lowered due to Well water collection

65
Q

What is a cone of depression

A

the cone shape of the water table created by the drawdown of wells

66
Q

How do Artesian Wells work

A

the well punctures an aquitard into an aquifer and water rises to the potentiometric surface

67
Q

What is the potentiometric surface

A

The imaginary water table that would occur if the aquifer was not contained by an aquitard

68
Q

What is groundwater depletion

A

When so much water is pumped away the water level drops significantly and can even dry out rivers and swamps

69
Q

A poorly planned septic tank and well can potentially result

A

in conical depressions causing a change in flow direction, and the release of contaminants into the groundwater

70
Q

Saltwater intrusion comes from

A

Pumping using a well along the coast until eventually the removal of fresh groundwater causes salty groundwater to be pulled into your well

71
Q

Vertical Saltwater Intrusion can be caused by ___ and causes ___

A

cause by breached dikes and flooding and causes root zone salinity,food scarcity, and water scarcity by contaminating aquifers

72
Q

In land subsidence

A

the removal of groundwater causes pores to collapse and causes fissures and scarps

73
Q

Natural contamination is when

A

Naturally occurring groundwater contains unwanted substances including iron ,manganese ,hydrogen ,, arsenic and other mineral deposits

74
Q

Natural Contamination makes water ____

A

Hard and can cause pipe and faucet damage

75
Q

Human cause contamination can come from

A

Septic tanks, Mines, salt, landfill, surface tanks, fertilizers, animal sewage, and injection wells

76
Q

A contaminant Plume is

A

when groundwater transports pollutants away from a source of input and creates a contaminant plume.

77
Q

Contaminant cleanup uses

A

Steam injection beneath the contaminated plume to drive the water upward in extraction wells

78
Q

Contaminant cleanup is

A

Very expensive

79
Q

Groundwater Overabundance is

A

An unwanted effect of a rising water table

80
Q

Groundwater Overabundance can cause

A

Basement flooding
Catastrophic slop failure (vajont dam)

81
Q

Why do caves form

A

Co2 reacts with water to form carbonic acid, this happens particularly to limestone. the more soluble beds are reacted away and form conduits or caves

82
Q

When caves form in limestone bedrock, the region is at risk of

A

Sinkholes

83
Q

The water table is important to monitor because it change the properties of

A

underlying rock and sediment

84
Q

the largest reservoir of fresh water on earth is

A

Groundwater

85
Q

Porosity and permeability determine…

A

how much groundwater there is and its ability to flow

86
Q

Two types if permeability

A

Primary and Secondary

87
Q

Water is stored underground in permeable ______ and unpermeable ____

A

Aquifers and Aquitards

88
Q

The water table is the point at which all underling rock is

A

saturated

89
Q

Groundwater flows along a similar path to

A

the overlying topography

90
Q

Wells and springs are locations where

A

Groundwater comes to the surface

91
Q

Sinkholes can form when

A

groundwater eats away underlying rock

92
Q

Some human issues regarding groundwater include

A

Groundwater depletion, groundwater polution, groundwater overabundance

93
Q
A

GEOLOGY (12 decks)

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