Properties of aquifers Flashcards
1
Q
it is the capacity to do work
A
energy (J)
2
Q
is equal to the product of net force and the distance through which the force moves
A
work (J)
work = force x distance
3
Q
is equal to the product of mass and acceleration
A
Force
F=ma
4
Q
is equal to the mass multiplied to the gravitational force
A
weight
weight = mass x gravity
5
Q
it is the mass per unit volume
A
density
p = mass/volume
6
Q
weight per unit volume
A
specific weight
y = gravity x density
y = weight / volume
7
Q
is the force applied to a unit area perpendicular to a force
A
Pressure
P= F/Area
8
Q
In hydrogeology pressure is measured relative to ____
A
atmospheric pressure
9
Q
standard atm
A
1.013x10^5 Pa
10
Q
What is a newtonian fluid
A
it’s resistance to relative motion is directly proportional to its dynamic viscosity
11
Q
standard unit for dynamic viscosity
A
n.s/m^2
12
Q
poise unit
A
g/s.cm
13
Q
t or f: water is not a compressible fuid
A
F
14
Q
the change in density is directly proportional to ____
A
change in pressure
15
Q
proportionality constant for compressibility
A
bulk modulus n/m^2
16
Q
unit for specific weight
A
N/m^3
17
Q
unit for pressure
A
N/m^2
18
Q
assemblages of individual grains that were deposited by water, wind, ice, and gravity
A
sediments
19
Q
openings between individual grains
A
pore spaces
20
Q
____, ____, and ____ in earth materials are important in the study of hydrogeology
A
cracks, voids, and pore spaces
21
Q
it is the percentage of rock or soil that is void of material
A
porosity
22
Q
porosity is defined mathematically by the equation:
A
n = 100Vv / V
where; Vv is the volume of void per unit volume of earth material
and V is the unit volume of earth material including voids and solids
23
Q
explain immersion lab method
A
- known volume of sample is taken
- the sample will be dried under 105 degrees celsius until it reaches a constant weight
- sample is submerged into a known volume of water
- the volume of the porosity is equal to the difference in the initial volume of water and final volume
24
Q
porosity that excludes pores that are too small and not interconnected
A
effective porosity
25
according to peyton et. al (1986), effective porosity is a function of ____ and ____
the size of the molecule ; the size of the passageways that connect the pores
26
it is the term that refers to the passageways that connect the pores
pore throats
27
t or f: pore throats are typically smaller than the pores
T
28
if the molecule being transported is greater than the pore throats this would
limit the effective porosity with respect to that molecule
29
the formula for total porosity is :
n = 100 [1-(Pb/Pd)]
pb - bulk density of aquifer
pd - particle density of aquifer
30
porosity for cubic packing and rhombohedral packing
47.65
25.95
31
the diameter of the sphere ___ influence the porosity
DOES NOT
32
porosity of well rounded sediments is _______ to the particle size and ______ to the packing
independent ; dependent
33
range of porosity for well rounded sediments
26-48%
34
if a sediment contains a mixture of grains of different sizes, the porosity will be ___
lowered
35
porosity is also affected by the ___ and ____
shape of grains
fabric/orientation of the praticles
36
classification for roundness
very angular
angular
sub angular
sub rounded
rounded
well rounded
37
classification for sphericity
prismoidal
sub prismoidal
spherical
sub discoidal
discoidal
38
sediments are classified based on the basis of ___
grain size
39
t or f: the larger the phi scale, the smaller the grain size
t
40
phi scale for gravel sediments
< -1.00
41
phi scale for sand sized sediments
4 - -1.00
42
phi scale for silt sediments
8-4
43
phi scale for clay sediments
14-8
44
other term for gravel, sand, and mud sediments
rudite, arenite, lutite
45
sediment diameter for clay particles
< 1/256
46
sediment diameter for silt particles
1/256 - 1/16
47
sediment diameter for sand particles
1/16 - 2
48
sediment diameter for gravel size
2 - >256
49
two types of grain size scale
used by soil scientists
used by engineers
50
us standard sieve series by soil scientists
gravel - 75mm
very coarse sand - no. 10
coarse sand - no. 18
medium sand - no 35
fine sand - 60
very fine sand - no 140
silt - no. 270
clay - N/A
51
separates sand from fines
200-mesh screen with 0.075 mm openings
52
sediments <0.075 mm in size are classified by ____ or the rate at which sediments settle in water
hydrometer test
53
a measure of how poorly or well sorted sediments are
uniformity coefficient
54
formula for uniformity coefficient
Cu = d60/d10
55
what is an effective grain size?
d10, size corresponding to the 10% line on the grain size curve
56
a sample with a Cu of less than 4 is
well sorted
57
a sample with a Cu of more than 6 is
poorly sorted
58
size corresponding to the 10% line on the grain size curve
d10, effective grain size
59
porosity ranges for sediments (davis)
well sorted sand or gravel - 25-50%
SAG mixed - 20-35%
glacial till - 10-20%
silt - 35-50%
clay - 33-60%
60
porosity of claystone (morris and johnson)
41-45%
61
porosity of sandstone (morris and johnson)
14-49%
62
porosity of shale (morris &johnson)
1-10%
63
porosity of crystalline rocks by morris and johnson
basalt - 3-35%
weathered granite - 34-57%
weathered gabbro - 42-45%
64
t or f: unconsolidated materials have higher porosity
T
65
cementing materials
silica, dolomite, calcite
66
compaction reduces pores by ____ and ____
rearranging mineral grains
reshaping them
67
t or f: dissolution of materials decreases porosity
F (increases)
68
t or f: the primary structures of the sediment may be preserved in the sedimentary rock
T
69
two main types of porosity
primary and secondary
70
four categories of porosity
primary
secondary
fracture
vuggy
71
the main or original porosity system in a rock or unconfined alluvial deposit
primary porosity
72
secondary porosity occurs either by _____ or ______
fracturing ; chemical leaching of mineral grains
73
subsequent or separate porosity system in a rock, either by fracturing or chemical leaching of minerals
secondary porosity
74
t or f: secondary porosity can replace or co-exist with primary porosity
T
75
porosity associated with fracture system or faulting
fracture porosity
76
t or f: hydrocarbons becomes a reservoir once it exhibits secondary porosity
T
77
this porosity was generated by dissolution of large features (macrofossils) leaving large holes, caves, or vugs
vuggy porosity
78
two well-known examples os sedimentary rocks of chemical/biochemical origin
limestone
dolomite
79
the materials that formed limestone and dolomites were originally part of an:
aqueous solution
80
example of a cavern that exemplify large openings
Carlsbad cavern in new mexico
81
may also be cavernous
gypsum and salt
82
as more water moves through the bedding plane, they are preferentially ____ and ____, causing rocks to become very porous
dissolved and enlarged
83
t or f: percent porosity of sedimentary rocks is highly variable
T
84
percent porosity of clastic sedimentary rocks
3-30%
85
porosity for limestones and dolomites
<1-30%
86
t or f: high ground resistivity means high porosity
F (low porosity)
87
_______ cools and solidify quickly because they are formed in a surface environment; this gives them radically _________
extrusive rocks ; different porosity characteristics
88
lava cooling rapidly at the surface will __________, resulting in holes in the rock or ______
trap degassing products ; vesicular texture
89
porosity of basalt
1-12%
90
porosity of tuff
14-40%
91
porosity of volcanic ash
50%
92
deep granite test hole in Northern Illinois, what percentage of porosity without, and with fractures
1.42 %
2.15 %
93
_______ and _____ increases overall rock porosity
weathering and fracturing
94
weathered plutonic and metamorphic rocks porosity
30-60%
95
porosity of pumice
less than or equal to 87%
96
weathered volcanic deposits porosity
>60%
97
dumoy aquifer is composed of what deposit
volcanic deposit
98
t or f: as depth increases, fractures decreases
T
99
it is the volume of water that gets drained from a saturated rock owing to gravitational attraction to the total volume of the rock
specific yield (sy)
100
water molecules cling to the surface because of
surface tension
101
what would happen if gravity exerts a force on a film of water surrounding a mineral grain?
water will pull away and drip downward, causing the film to thin, and increase in surface tension in order to balance gravity
102
material with highest specific yield
coarse sand (35-20)
103
material with lowest specific yield
clay (5-0)
104
moisture clinging to soil because of surface tension
pendular water
105
what materials generally have high specific yield?
sand and gravel
106
grain size distribution of sediments can be conveniently plotted in a
semilogarithmic paper
107
is the ratio of the water that is retained against the gravity to the total volume of the rock
specific retention (Sr)
108
formula for porosity as a function of specific yield and retention
n = Sy + Sr
109
the ability of rock to transmit water
hydraulic conductivity
110
constitute the most significant hyfrologic properties
ability to hold and transmit water
111
t or f: some rocks exhibit porosity but lack interconnectedness
T
112
example of a rock that exhibit porosity but lack interconnectedness
vesicular basalt
113
what percentage of vesicles does vesicular basalt have?
<50%
114
examples of sediments that have porosity but isn't large enough to allow transmit of water
clay and shales
115
french engineer who made the first systematic study of the movement of water through a porous medium
henry darcy
116
what did darcy study?
systematic study of the movement of water through a porous medium
117
darcy found that
the rate of water flow is directly proportional to the difference in water height in both ends of the filter beds and inversely proportional to the flow path
118
darcy determined that the quantity of flow is ____ to a coefficient, K, which is a function of ____
proportional
function of the nature of the porous medium
119
a thin vertical pipe used to measure pressure
piezometer
120
what is discharge according to darcy
discharge is directly proportional to the difference in the height of water, h (hydraulic head) and inversely proportional to the flow length (L)
121
t or f: flow is proportional to the cross-sectional area of the pipe
T
122
discharge formula
Q= -KA [(ha-hb)/L]
or
Q = -KA (dh/dl)
123
it is known as the hydraulic gradient
dh/dl
dh - change in head between two points
dl - distance between these points
124
the negative sign of a discharge indicates:
the flow is going in the direction of decreasing hydraulic head
125
specific discharge is also known as___
darcinian velocity (L/T)
126
formula for specific discharge
q = Q/A
127
why is darcinian velocity not considered as a true velocity
because the discharge is blocked by soil or rock material
128
measure of quantity of any fluid flow over time
discharge
129
dimensions of discharge
volume/time (L^3/T)
area (L^2)
gradient (L/L)
130
formula for K
K = -(L^3/T)/L^2 (L/L) = L/T
131
Hubbert (1956) pointed out that Darcy's K is a function of
the nature of the porous medium and the fluid passing through it (specific weight and viscosity)
132
t or f: discharge is directly proportional to specific weight
T
133
is the force exerted by gravity over a unit volume, basically a downward flow
specific weight
134
t or f: discharge is directly proportional to the dynamic viscosity of the fluid
F (inversely)
135
measure of the resistance of fluid to shearing
dynamic viscosity
136
it is the function of the size of the openings through which fluid pass through
intrinsic permeability
137
unit for intrinsic permeability
darcy
138
darcy can be described as
1 darcy = 1cp (1cm^3/s) / 1cm^2 / (1atm/ 1cm)
passing of one cubic meter of fluid (with a viscosity of 1 centipoise) per second through a one square centimeter cross sectional area under a pressure of 1 atm per cm thickness
139
represent some of the most profilic producers of groundwater
unconsolidated coarse-grained sediments
140
t or f: the smaller the size of the sediment grains, the larger the surface area the water contacts
T
141
for well sorted sediments, the intrinsic permeability is directly proportional to the
grain size
142
1 darcy is equal to
10^-8 cm^2
143
for sand sized alluvial deposits, what are the factors relating to intrinsic permeability
1. large median grain size = high intrinsic permeability
2. high SD = low intrinsic permeability
3. dako ang effect sa decrease sa permeability sa pagtaas sa SD sa coarse than fine
4. unimodal (one dominant size) has higher intrinsic permeability than bimodal
144
clastic sedimentary rocks have primary porosity similar to
unconsolidated sediments
145
____ can reduce the size of the pore throats through compaction and _____
diagenesis ; cementation
146
t or f : crystalline rocks have typically low permeability
T
147
secondary permeability can develop through
fracturing, dissolution, and weathering
148
hydraulic conductivity of earth materials can be measure through a
permeameter
149
undulating surface, top most portion of aquifer
water table
150
in the water table the atmospheric pressure is equal to the ____
pore water pressure
151
in the absence of groundwater flow, water table will be
flat
152
a sloping water table indicates
presence of groundwater flow
153
groundwater discharge zones are in
topographical low spots
154
the position of the water table follows the ____
general shape of the topography
155
groundwater flows from
topographic highs to lows
156
a geologic unit that can hold and transmit water at rates fast enough to supply wells
aquifer
157
intrinsic permeability of an aquifer
10^-2 darcy upwards
158
examples of aquifers
unconsolidated sand and gravel, sandstone, limestone, dolomite, basalt flow, and fractured metamorphic and igneous rocks
159
geologic unit having little to no intrinsic permeability
confining layer
160
classification of confining layers
aquitard
aquiclude
aquifuge
161
an absolutely impermeable unit that will not transmit any water
aquifuge
162
also known as the leaky confining layer, can hold and transmit water but at very slow rates
aquitard
163
inappreciable amount of water moves or is transmitted
aquiclude
164
an aquifer close to land surface with high intrinsic permeability extending from land surface to the base of the aquifer
unconfined aquifer or water table aquifer
165
aquifers overlain by confining layers
confined aquifers or artesian aquifer
166
surface representative of the level at which groundwater will rise in a well cased to an aquifer
potentiometric surface
167
if the potentiometric surface is above the land, ____ may occur
flowing artesian well
168
is a saturated soil directly above the main water table
perched aquifer
169
where can we find perched aquifer in mindanao
bislig, surigao del sur
near former usep bislig campus
170
three ways in which confined aquifers can be formed
1. deposition of alternating layers of permeable sand and gravel and impermeable clay and silts deposited in intermontane basins
2. alternating layers of aquifers and confining units deposited on a regional dip
3. upwarping of beds by intrusion
171
maps showing construction of water table maps in areas with surface-water bodies
water table and potentiometric surface maps
172
characteristics of aquifer
transmissivity
storage coefficient
elasticity
specific storage
compressibility and effective stress
homogeneity and isotropy
173
the measure of the amount of water that can transmitted horizontally over a unit width by the saturated thickness of the aquifer under the hydraulic gradient of 1
transmissivity
174
formula for transmissivity
T = bK
b= thickness of aquifer
K= hydraulic conductivity
175
it is the volume of water that a permeable unit will absorb or expel from storage per unit surface area per unit change in head
storage coefficient (storativity)
176
in the saturated zone, the head creates pressure affecting the ___ and ___-
arrangement of mineral grains and density of the fluid
177
if the pressure in the head is high, mineral skeleton will ____
expand
178
the amount of water than can be absorbed or expelled owing to the compressibility of the mineral skeleton and the pore water per unit change in head
specific storage (elastic storage coefficient)
179
a downward stress placed on the aquifer skeleton by the weight of the overlying rock layer and water
total stress
180
the upward stress on the plane caused by the fluid pressure that counteracts the total stress
effective stress
181
t or f : effective stress is less than the total stress
t
182
formula for total stress
oT = oE + P
total = effective plus pressure
183
t or f : overextraction of groundwater decreases effective stress, causing subsidence
T
184
a unit that has the same properties in all locations
homogenous unit
185
a unit whose hydraulic property spatially change
heterogenous unit
186
units that have the same intrinsic permeability in all directions
isotropic
187
units that have non-uniform intrinsic permeability, geometry of the voids is not uniform
anisotropic
188
graphical method to see groundwater flow using three or four well situations
gradient of the potentiometric surface
