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ERTH3250 - Ellen's > Hyrdrogeology > Flashcards

Hyrdrogeology Flashcards

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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
What is the equation for hydraulic head?
h = trident + z where trident = pressure head
26
Are vertical or horizontal hydraulic gradients dominant over groundwater movements?
Veritcal
27
What do equipotential lines represent? And which way does groundwater flow in respect to them?
Equal head, and water flows perpendicular to them.
28
What is the potentiometric surface?
Unconfined water table level
29
What is piezometric head equivalent to in groundwater flow?
Hydraulic head
30
True or false: Flow is parallel to the water-table boundary
False. It is normally at an oblique angle.
31
What is refraction?
The change in direction of a flow path at the boundary between two layers of differing permeability.
32
What is the equation for refraction?
33
What type of drilling do you use for hard rock?
Rotary air drilling
34
What type of drilling is used for collapsing boreholes?
Rotary mud drilling
35
How does a percusion rig work and what types of soil is it used on?
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
What type of drilling is used for the implementation of shallow piezometers?
Auger drilling or hand drilling
37
What is a stilling tube used for?
To measure the water level in a turbulent discharging well.
38
What is the equation for the Hazen method?
K=C(d10)2 Where d10 is in [cm]
39
What are natural springs an indicator of?
Aquifer/aquitard contact
40
What equipment is used for spot measurements of groundwater depth?
Dip meters
41
What equipment is used for continuous monitoring of groundwater depth?
Pressure transducers
42
What equipment is used to gather water samples?
Bailers or pumps
43
What is bore purging and why is it used?
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
What are some other parameters that can be monitored to help conduct a full water balance? How can these be measured?
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
What type of flow occurs in the unsaturated zone?
Exponential
46
What are two features that are indicative of a steady state flow?
Recharge = discharge, head constant with time
47
What are some causes of transient flow?
Pumping, water injection, changing in land use, drought, seasonal rainfall changes
48
What is a groundwater mound and what causes it?
Caused by quarries and landfills, they are zones of increased recharge and locally raised water tables.
49
What is the transient response of an unconfined aquifer to pumping?
Formation of a cone of depression.
50
What is the transient response of a confined aquifer to pumping?
Changes in magnitude and direction of hydraulic gradients; piezometric surface gains a cone of depression.
51
What is transmissivity?
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
What is the transmissivity equation?
T=bK
53
What is storativity?
The volume of water in a confined aquifer that a unit will absorb or expel as head changes.
54
What is specific storage?
An aquifer's response to stress.
55
What is the equation for specific storage?
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
What is the equation for storativity?
S=Sy+bSs Where S = storativity
57
What is throughflow?
One of the two sources of water that is withdrawn during pumping (storage is the other source)
58
What are the three parameters that change the geometry of of the cone of depression?
Q, T, S
59
What is the process of a falling-head test?
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
What is the pump test?
Well is pumped at a constant rate and the rate of drawdown is observed in monitoring bores.
61
Which test is best to measure anisotropy?
Pump test
62
What is the equation for the slug test?
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
What is the pump test equation?
Q = (2πrb)Kdh/dr h0-h = Q/(4πT)\*W(u) u = r2S/(4Tt)
64
What is transient flow equation in words?
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
What is the transient flow equation in 1D?
d/dx\*(Kx\*dh/dx) = Ss\*dh/dt d2h/dx2+1/r\*dh/dr = S/T\*dh/dr
66
What is the calculation for recharge?
R = Sy\*dh/dt Where h = difference in peak and recession curve in recharge bore hydrograph
67
What is the Gibbs energy equation?
G = H-TS logKeq = -delta\*GR0/(2.303RT)
68
What is the saturation index equation?
SI = log(IAP/Keq)
69
What is a congruent reaction?
When all ions have high solubilities.
70
What is an incongruent reaction?
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
What are ion complexes?
Combinations of cations and anions in an ion, e.g. CaOH-. It reduces the activity of free ion in solution.
72
What are kinetics and what impacts it?
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
What affects affinity?
It increases with valency and ionic radius when ions are present in similar concentrations.
74
What is CEC?
Cation exchange capacity. It is higher in clays and organic matter due to higher surface areas and residual charges.
75
What is the equation for activity?
a = gamma\*m Where gamma = activity coefficient
76
What affects the activity coefficient?
It increases with valence and decreases with ion radius.
77
Is a monovalent or divalent ion preferentially sorbed in in a dilute and concentrated solutions?
Dilute - Divalet ion preferentially sorbed Concentrated - Sorption approximately equal because gamma(Ca2+) \<\< gamma(Na+)
78
True or false: redox reactions are often kinetically controlled
True
79
What is the equation for pE?
pE = -logae-
80
What is the charge balance equation?
Charge balance error = (Cat-An)/(Cat+An)\*100 In meq
81
Learn ion ratios!
!!!
82
What is net infiltration?
Also know as percolation, it is the water that percolates past the root zone.
83
What is the water balance equation?
P.ClPPT = ET.ClET+R.Clgw+Q.Clriv If Cl is only from precipitation ClET=0
84
What can tracers be used for?
To define age, age vs. depth or to calculate velocity.
85
What is Rn in R = Rnbn
Fraction of groundwater replaced in an aquifer annually
86
How can the rat of transport through the unsaturated zone be calculated?
Application of a conservative tracer
87
What is the equation for

ERTH3250 - Ellen's (1 decks)

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