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ERTH3250 - Ellen's > Hyrdrogeology > Flashcards

Hyrdrogeology Flashcards

1
Q

What is the equation for residence time?

A

Residence time = (water in storage)/(flux)

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2
Q

Where and why does interconnectivity of water occur with depth?

A

In saturated zone, because the pores become disconnected.

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3
Q

What is secondary porosity due to?

A

Chemical or physical processes.

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4
Q

What are some examples of anomalous porosity?

A

Lava tunnels, karst terranes and salt deposits

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5
Q

What are sedimentary aquifers made of?

A

Unconsolidated gravels, sands and other sedimentary deposits.

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6
Q

What are fractured rock aquifers made of?

A

Consolidated igneous, metamorphic or sedimentary rocks.

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7
Q

In fractured rock aquifers where can the water flow?

A

Usually through the secondary pore network, but in special cases it can be a dual porosity aquifer.

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8
Q

In what scenarios can salt water replace fresh water in aquifers near the sea?

A

If either over abstraction occurs or sea levels rise due to climate change.

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9
Q

What is an unconfined aquifer?

A

Where the water table occurs within the aquifer.

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10
Q

What is a confined aquifer?

A

The aquifer is saturated throughout.

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11
Q

What is an aquiclude?

A

Contains water but has no flow.

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12
Q

What type of hydrological unit has no water storage and no flow?

A

Aquifuge

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13
Q

For the letters in the image, enter the stages or processes in the hydrological cycle. Indicate which of them are flux processes and which are storage units.

A

A - Evaporation (flux)

B - Atmosphere (storage)

C - Precipitation (flux)

D - Ice caps (storage)

E - Evaporation (flux)

F - Evapotranspiration (flux)

G - Lakes (storage)

H - Groundwater flow (flux)

I - Runoff (flux) [I would say Rivers (storage)]

J - Oceans (storage)

K - Groundwater (storage)

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14
Q

Order the following storage types from lowest to highest total storage of water on Earth:

Lakes, rivers, soil moisture, grounwater, ice caps / glaciers, atmosphere, ocean

A

Rivers, atmosphere, soil moisture, lakes, groundwater, ice caps / glaciers, ocean

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15
Q

Does a well sorted aquifer have high or low effective porosity?

A

High

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16
Q

What is the grain size distribution like in a poorly sorted aquifer?

A

Both large and small grains present.

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17
Q

Does cementing increase of decrease effective porosity?

A

Decrease

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18
Q

What is Darcy’s Law?

A

Q=KA(-dh/dl)

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19
Q

What is the equation for the velocty of groundwater through an aquifer?

A

v=q/(ne)

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20
Q

What is the equation for hydraulic conductivity?

A

K=k*rhof*g/µ

where k = permeability [m2]

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21
Q

What does permeability dependent upon?

A

it is a rock property which depends on pore size and connection.

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22
Q

What is the equation for permeability?

A

k=Cd2

where d = mean grain diameter in unconsolidated sediments

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23
Q

Is Darcy’s law for micro- or macro-scopic calculations?

A

Macroscopic

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24
Q

What properties vary pressure head?

A

Fluid density and volume of fluid in bore

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25
Q

What is the equation for hydraulic head?

A

h = trident + z

where trident = pressure head

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26
Q

Are vertical or horizontal hydraulic gradients dominant over groundwater movements?

A

Veritcal

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27
Q

What do equipotential lines represent? And which way does groundwater flow in respect to them?

A

Equal head, and water flows perpendicular to them.

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28
Q

What is the potentiometric surface?

A

Unconfined water table level

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29
Q

What is piezometric head equivalent to in groundwater flow?

A

Hydraulic head

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30
Q

True or false: Flow is parallel to the water-table boundary

A

False. It is normally at an oblique angle.

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31
Q

What is refraction?

A

The change in direction of a flow path at the boundary between two layers of differing permeability.

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32
Q

What is the equation for refraction?

A
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33
Q

What type of drilling do you use for hard rock?

A

Rotary air drilling

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34
Q

What type of drilling is used for collapsing boreholes?

A

Rotary mud drilling

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35
Q

How does a percusion rig work and what types of soil is it used on?

A

It works similarly to pile driving. It can be used for any type of rock, but is particularly good for river gravels and boulders.

36
Q

What type of drilling is used for the implementation of shallow piezometers?

A

Auger drilling or hand drilling

37
Q

What is a stilling tube used for?

A

To measure the water level in a turbulent discharging well.

38
Q

What is the equation for the Hazen method?

A

K=C(d10)2

Where d10 is in [cm]

39
Q

What are natural springs an indicator of?

A

Aquifer/aquitard contact

40
Q

What equipment is used for spot measurements of groundwater depth?

A

Dip meters

41
Q

What equipment is used for continuous monitoring of groundwater depth?

A

Pressure transducers

42
Q

What equipment is used to gather water samples?

A

Bailers or pumps

43
Q

What is bore purging and why is it used?

A

Where water is pumped for a bore until physio-chemical parameters stabilise. This is to remove stratification which occurs in bores within low-flow aquifers, especially if they haven’t had water withdrawn for a long period of time.

44
Q

What are some other parameters that can be monitored to help conduct a full water balance? How can these be measured?

A

Precipitation - point measurements, rain radar for large scale indications

Evaporation - pan evaporation, lysimeter

Evapotranspiration - eddy covariance, sap flow

Stream discharge - current meter with cross-section, tracer tests

45
Q

What type of flow occurs in the unsaturated zone?

A

Exponential

46
Q

What are two features that are indicative of a steady state flow?

A

Recharge = discharge, head constant with time

47
Q

What are some causes of transient flow?

A

Pumping, water injection, changing in land use, drought, seasonal rainfall changes

48
Q

What is a groundwater mound and what causes it?

A

Caused by quarries and landfills, they are zones of increased recharge and locally raised water tables.

49
Q

What is the transient response of an unconfined aquifer to pumping?

A

Formation of a cone of depression.

50
Q

What is the transient response of a confined aquifer to pumping?

A

Changes in magnitude and direction of hydraulic gradients; piezometric surface gains a cone of depression.

51
Q

What is transmissivity?

A

The volume of water that may be transmitted through a 1m wide section of the entire saturated thickness of the aquifer with a hydraulic gradient of 1.

52
Q

What is the transmissivity equation?

A

T=bK

53
Q

What is storativity?

A

The volume of water in a confined aquifer that a unit will absorb or expel as head changes.

54
Q

What is specific storage?

A

An aquifer’s response to stress.

55
Q

What is the equation for specific storage?

A

Ss = rhow*g(alpha+n*beta)

Ss [1/m]

alpha = compressibility of rock matrix [m2/m/s2]

beta = compressibility of water [m2/m/s2]

56
Q

What is the equation for storativity?

A

S=Sy+bSs

Where S = storativity

57
Q

What is throughflow?

A

One of the two sources of water that is withdrawn during pumping (storage is the other source)

58
Q

What are the three parameters that change the geometry of of the cone of depression?

A

Q, T, S

59
Q

What is the process of a falling-head test?

A
  1. Slug inserted
  2. Water level rises and induces head gradient between bore and aquifer
  3. Water level drop to remove head gradient is measured
60
Q

What is the pump test?

A

Well is pumped at a constant rate and the rate of drawdown is observed in monitoring bores.

61
Q

Which test is best to measure anisotropy?

A

Pump test

62
Q

What is the equation for the slug test?

A

K=r2ln(L/R)/(2LT0)

r = bore radius

L = screen length

R = screen radius (+ gravel perimeter)

T0 = time for H/H0 to reach 0.37

H = measured head

H0 = initial head

63
Q

What is the pump test equation?

A

Q = (2πrb)Kdh/dr

h0-h = Q/(4πT)*W(u)

u = r2S/(4Tt)

64
Q

What is transient flow equation in words?

A

The difference between the mass of recharge and discharge is equal to the change in storage and fluid density due to a change in hydraulic head.

65
Q

What is the transient flow equation in 1D?

A

d/dx*(Kx*dh/dx) = Ss*dh/dt

d2h/dx2+1/r*dh/dr = S/T*dh/dr

66
Q

What is the calculation for recharge?

A

R = Sy*dh/dt

Where h = difference in peak and recession curve in recharge bore hydrograph

67
Q

What is the Gibbs energy equation?

A

G = H-TS

logKeq = -delta*GR0/(2.303RT)

68
Q

What is the saturation index equation?

A

SI = log(IAP/Keq)

69
Q

What is a congruent reaction?

A

When all ions have high solubilities.

70
Q

What is an incongruent reaction?

A

When ions are in a solution in different ratios to the reactants due to the low solubility of some ions, e.g. Al, Si

71
Q

What are ion complexes?

A

Combinations of cations and anions in an ion, e.g. CaOH-. It reduces the activity of free ion in solution.

72
Q

What are kinetics and what impacts it?

A

Kinetics dictates the reaction rate and is affected by temperature, acidity, surface area to volume ratio and the presence of microbes. They may not always be reversible.

73
Q

What affects affinity?

A

It increases with valency and ionic radius when ions are present in similar concentrations.

74
Q

What is CEC?

A

Cation exchange capacity. It is higher in clays and organic matter due to higher surface areas and residual charges.

75
Q

What is the equation for activity?

A

a = gamma*m

Where gamma = activity coefficient

76
Q

What affects the activity coefficient?

A

It increases with valence and decreases with ion radius.

77
Q

Is a monovalent or divalent ion preferentially sorbed in in a dilute and concentrated solutions?

A

Dilute - Divalet ion preferentially sorbed

Concentrated - Sorption approximately equal because gamma(Ca2+) << gamma(Na+)

78
Q

True or false: redox reactions are often kinetically controlled

A

True

79
Q

What is the equation for pE?

A

pE = -logae-

80
Q

What is the charge balance equation?

A

Charge balance error = (Cat-An)/(Cat+An)*100

In meq

81
Q

Learn ion ratios!

A

!!!

82
Q

What is net infiltration?

A

Also know as percolation, it is the water that percolates past the root zone.

83
Q

What is the water balance equation?

A

P.ClPPT = ET.ClET+R.Clgw+Q.Clriv

If Cl is only from precipitation

ClET=0

84
Q

What can tracers be used for?

A

To define age, age vs. depth or to calculate velocity.

85
Q

What is Rn in R = Rnbn

A

Fraction of groundwater replaced in an aquifer annually

86
Q

How can the rat of transport through the unsaturated zone be calculated?

A

Application of a conservative tracer

87
Q

What is the equation for

A

ERTH3250 - Ellen's (1 decks)

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