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Hydrology > Midterm > Flashcards

Midterm Flashcards

1
Q

units of porosity

A

%

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2
Q

symbols of porosity

A

n

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3
Q

define porosity

A

space in a sediment or rock for the storage of fluids

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4
Q

types of porosity in rocks and consolidated sediments

A

1) primary
2) secondary
- solution
- fracture
3) vesicular

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5
Q

define primary/original/depositional porosity

A

on the surface
same time that the sediments were deposited
main type in clastic aquifers (intergranular)

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6
Q

define secondary/induced porosity

A

forms in the rock after lithification or crystallization

types: solution and fracture

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7
Q

define solution porosity

A

dissolution of a carbonate (limestone/dolomite)
from acidic solutions (H2CO3) migrating through sub surface
vuggy porosity is carbonates

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8
Q

define fracture porosity

A

breaking of the rock by stress (folding & faulting) or by differential cooling (columnar jointing) of volcanic rock

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9
Q

define vesicular porosity

A

forms in basalts

as gas escapes from lava

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10
Q

define hydrology

A

study of fresh water (surface and ground) in the environment

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11
Q

define hydrogeology

A

study of the flow of water through soils, sediments, and rocks

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12
Q

reasons to study groundwater

A

1) drinking water
2) commercial and industrial uses
3) groundwater maintains stream flow

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13
Q

driving force of the hydraulic cycle

A

sun/solar radiation

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14
Q

hydraulic cycle

A

1) evaporation/transpiration
2) condensation
3) precipitation
4) storage

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15
Q

define saturated zone

A

a subsurface zone where the pores are completely filled with water

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16
Q

define unsaturated zone

A

subsurface zone where the pores will contain both air and water

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17
Q

define permeability

A

measure of the ease with which a fluid can move through a rock

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18
Q

define water table

A

the surface which separates the zone of saturation from the zone of aeration (unsaturated zone)

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19
Q

define capillary fringe

A

a subsurface zone which is completely saturated with water but if above the water table, water moves upward in this zone because of surface tension

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20
Q

define flowing artesian aquifer

A

a location in a confined aquifer where the potentiometric surface is structurally above the ground surface

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21
Q

define transmissivity (T)

A

measure of the amount of water the can be transmitted horizontally through a saturated aquifer

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22
Q

define T with units

A

transmissivity

m2/s

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23
Q

define b with units

A

aquifer thickness

m

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24
Q

define K with units

A

hydraulic conductivity

m/s

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25
Q

define storativity (S)

A

volume of water absorbed or expelled after a change in head

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26
Q

define S with units

A

storativity

unitless

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27
Q

define Ss with units

A

specific storage

1/m

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28
Q

define specific storativity

A

volume of water of a saturated formation that is stored or expelled from storage

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29
Q

things that affect Ss in confined aquifers

A

a - the compressibility of mineral matrix

B - the compressibility of pore water

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30
Q

if the head decreases in a confined aquifer, the effects are

A

pressure
mineral grains will rearrange (and H2O is expelled)
pore water will expand (and H2O is expelled)

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31
Q

define pw with units

A

density of water

kg/m3

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32
Q

define g with units

A

gravity

m/s2

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33
Q

define a with units

A

compressibility of mineral matrix
1/Pa
1/N/m2

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34
Q

define B with units

A

compressibility of water
1/Pa
1/N/m2

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35
Q

S=Ss*b is storativity in what kind of aquifers

A

confined / artesian wells

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36
Q

how water is expelled or absorbed in an unconfined aquifer

A

a
B
fluctuations of the water table (Sy - specific yield)

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37
Q

S=Sy+Ss*b is storativity in what kind of aquifers

A

unconfined, watertable wells/aquifers

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38
Q

define specific yield

A

Sy is the volume of water absorbed or expelled from storage per change in water tale elevation

Sy has a bigger influence than Ss * b (except for very fine grained sediments)

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39
Q

define Sy with units

A

specific yield

unitless

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40
Q

define Vw with units

A

volume of water drained

m3

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41
Q

define A with units

A

surface area overlying the drained aquifer

m2

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42
Q

define Vh with units

A

average decline in the head

m

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43
Q

define homogeneous formations

A

hydraulic conductivity do not vary from one location to another in the formation
when modelling, K is the same throughout the aquifer

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44
Q

define heterogeneous formations

A

hydraulic conductivity vary from one location to another in the formation

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45
Q

geologic features that cause heterogeneity in aquifers

A

1) unit thickness
2) layering
3) faces changes (changes in depositional environments)
4) solution porosity
5) fractures

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46
Q

spacial variability depend on

A

homogeneous and heterogeneous formations

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47
Q

directional variability depend on

A

isotropic and anisotropic formations

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48
Q

define isotropic formations

A

hydraulic conductivity is independent of the direction of measurement

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49
Q

define anisotropic formations

A

hydraulic conductivity vary depending on the direction of measurement

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50
Q

causes of anisotropic formations

A

1) imbrication of grains
2) clays
3) basalts

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51
Q

define Kb in parallel beds

A

weighted arithmetic average
influenced by the most permeable bed
m/s

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52
Q

define Kb in series beds

A

weighted harmonic average

m/s

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53
Q

porosity in unconsolidated sediments is controlled by

A

grain shape
grain size distribution (well vs poorly sorted)
particle arrangement (cubic vs face centered packing)

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54
Q

what does not affect the porosity in unconsolidated sediments

A

particle size

55
Q

define k with units

A

permeability

m2

56
Q

permeability (k) is affected by

A

pore throat diameter
sorting
fracturing

57
Q

how to estimate r average for well sorted ss

A

use the average radius of all the grains in the sediment

58
Q

how to estimate r average for poorly sorted ss

A

r pore = r smallest grains = D10 value

59
Q

why is the porosity of gravel and silt approx the same

A

grain size does not affect n

60
Q

what unconsolidated sediment has the greatest porosity

A

clay because of the platelet shape (compressibility)

61
Q

define karst limestone

A

limestone on the surface of the earth

62
Q

theory behind darcy’s law

A

volumetric flow rate of groundwater (Q) through an area (A) of a porous media

63
Q

Darcy’s law equation

A

Q=q*A

64
Q

define Q with units

A

volumetric groundwater flow

m3/s

65
Q

define q with units

A

specific discharge

m/s

66
Q

define A with units

A

cross sectional area

m2

67
Q

2 major driving forces to groundwater flow

A

gravitational force

pressure force

68
Q

define z with units

A

elevation head

m

69
Q

define trident thing with units

A

pressure head

m

70
Q

define h with units

A

head

m

71
Q

K is dependent on

A

intresnsic properties of the rock

properties of the fluids

72
Q

define i with units

A

hydraulic gradient

unitless

73
Q

flow through an open tube equation

A

q=vn where n=100%

74
Q

flow though a porous media (aquifer) equation

A

q=vn where n=whatever porosity %

75
Q

2mm diameter of grains differentiates between

A

gravel and sand

76
Q

field descriptions of soils include

A 
main sediment type (GRAVEL)
minor components (gravel)
color
moisture content
consistency (fine grained)
density (coarse grained)
geological origin
foreign materials
odour
presence of contaminants
77
Q

the 3 layers in a jar test are

A

mud
silt
sand

78
Q

classification of fine grained soils is based on

A

grain size

plasticity

79
Q

define cohesive

A

ability of a soil to be reshaped in the presence of some moisture without crumbling

80
Q

define plastic limit (PL)

A

the moisture content of a soil which will crumble when rolled into 1/8in d threads

81
Q

define liquid limit (LL)

A

the moisture content of a soil required to close a distance of 0.5in along the bottom of a groove after 25 blows

82
Q

what are flow nets

A

way to represent 2D ground water flow

83
Q

assumptions with flow nets

A

homogeneous and isotropic

in a steady state

84
Q

flow nets are drawn on what maps for unconfined aquifers

A

water table map

85
Q

flow nets are drawn on what maps for confined aquifers

A

potentiometric surface

86
Q

3 types of boundary conditions for flow nets

A

1) impermeable/no flow
2) constant head
3) water table

87
Q

adequate production of a household well

A

0.5 gallons per min

88
Q

no additional water storage capacity is needed over

A

5-10 gallons per min

89
Q

3 things in choosing a well location

A

1) max yield
2) min contamination
3) max safe operation

90
Q

preliminary info sources for choosing a well

A

1) alberta geologic survey
2) hydrogeologic maps and reports
3) alberta groundwater data base (drilling records are free but might not be reliable)
4) door to door surveys

91
Q

locating water wells

A 
geophysical surveys (\$\$$)
test drilling (log cuttings)
downhole geophysics (\$\$$ can use chips but lag time and cavings are problems)
pump tests
92
Q

considerations in choosing well locations

A

1) geology of area (yields)
2) contaminant sources
3) minimal distances
4) accessibility for cleaning/testing/monitoring (eg not close to buildings)
5) ground slope

93
Q

4 basic types of water wells

A

dug (hand)
driven or jetted (hydraulically)
bored (auger wells)
drilled (rotary wells)

94
Q

common casing materials

A

steel (strong, corrodes)

plastic (popular, new no recycled)

95
Q

by alberta law, casings must

A

min of casing must be 10.61cm/4in
must extend more than 20cm above surface to prevent contamination
must extend more than 60cm above highest flood record in area if no water-tight cap
if non-metallic above ground, must be protected by steel casing

96
Q

intake purpose

A

allow water but not sediment to enter well during production (but not during development)

97
Q

intake types

A

screens

slotted/perforated casings/liners

98
Q

screens material and rx type

A

stainless steel mostly

unconsolidated sediments

99
Q

slotted/perforated casing/liners design and rx type

A 
irregular holes
consolidated formations (bed rx)
100
Q

size of openings in screens

A

easy entry of water preventing sediments

during development: D60

101
Q

2 types of annular fill

A

annular seal

filter/gravel pack

102
Q

annular fill

A

must be filled with impermeable inert material

materials: cement, bentonite, grout

103
Q

filter/gravel pack

A

gravel, clean quartz sand, glass beads

finergrained aquifers to improve yield

104
Q

surface considerations under law in alberta

A

water cannot enter the well
securely covered by the driller and owner
pump house can only have water well and the pump
water must not pool on the pump house floor

105
Q

well completion 3 steps

A

well development
well disinfection
yield test

106
Q

well development

A

remove fine sediments and water introduced to aquifer

107
Q

methods used to develop a well

A

overpumping
jetting (air or water)
surging (2 directions of flow)

108
Q

developed well types

A

naturally developed well (remove fine material, original aquifer material)
gravel-packed (sand/gravel filter is placed in the annulus, not created from og aquifer)

109
Q

well disinfection

A

cl 200mg/L for 12hrs

110
Q

yield test

A

min 2hr/until water level in well returns to min 90%

determine rate and depth

111
Q

safe pumping rate

A

extended period of time without lowering the level below pump intake

112
Q

pump must not lower the h2o level below

A

top of aquifer
top of perforations
top of pump intakes

113
Q

submissions to AEP

A

general stratigraphic log (geology)

well construction and design details (well license)

114
Q

geophysical surveys

A

indirect

115
Q

general processes of geophysical surveys

A

energy waves at or near surface
pass into subsurface
return to surface
processed and interpreted

116
Q

geophysical surveys give info on

A

statigraphy
structural features
groundwater
man made inclusions

117
Q

seismic waves

A 
p waves (primary, want to interpret)
s waves (secondary, can also penetrate subsurface)
surface waves (noise)
118
Q

seismic waves travel at

A

the speed of sound

119
Q

p waves

A

direct (across the surface)
reflected (bounces off subsurface interface)
refracted (travels along interface, must have differing subsurface densities)

120
Q

electrical conductivity/resistivity surveys

A

em-31/34/38

121
Q

ec surveys measure ability of a subsurface formation to

A

transmit (conduct)
or impede (resist)
…. the movement of an electrical current thru

122
Q

ability of a formation to conduct dependent on

A

porosity
v of water in pores
type of fluid

123
Q

ground penetrating radar

A

microwaves

speed of light

124
Q

source of GPR ground penetrating radar

A

transducer on a wagon or sled

125
Q

method of GPR

A 
max depth of 20m
bounce
conductivity
time
time to depth
126
Q

uses of GPR

A 
shallow disposal sites
water table
HC contamination
stratigraphy
caverns
127
Q

EM surveys

A

electric current thru transmitter coil
close to ground
electromagnetic field
colored map

128
Q

EM 31

A

long pole, fixed depth

salt water plumes, metals

129
Q

EM 34

A

2 separate units, 60m deep

deep and large salt water plumes, map bedrock topography

130
Q

EM 38

A

run at the same time as EM31
shallow depth less than 1.5m
agriculture

131
Q

ERI ERT electrical resistivity surveys

A

groundwater exploration
resistivity is inverse of conductivity
direct current
2 electrodes INTO ground

132
Q

resistivity surveys in 2 different fashions

A

electrical sounding

horizontal profiling

133
Q

electrical sounding

A

variations in depth
go to diff depths with each pass
wenner or schlumberger

134
Q

horizontal profiling

A

lateral variations
electrode spacing is not changed
recorded and contour mapped

Hydrology (1 decks)

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