Principles of Hydrogeology Flashcards

1
Q

Base Flow

A

The amount of stream flow that can be attributed to groundwater inflow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Darcy

A

9.87 x 10-9 cm2 - Unit of intrinsic permeability

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Darcy’s Law

A

Q = KiA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

ne

A

Effective Porosity
Fraction of the total volume of an aquifer material that consists of interconnected pore space, = specific yield

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Field Capacity

A

amount of soil moisture or water content held in the soil after excess water has drained away and the rate of downward movement has decreased. It is time dependent.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

K

A

Hydraulic conductivity
Capacity of a porous medium to transmit water. Units (L/T)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

i

A

Hydraulic gradient,
Rate of change in total hydraulic head per unit distance, = (delta)h/L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

ki (or just k)

A

intrinsic permeability
property of the porous medium that measure the relative ease with which a fluid can be transmitted through it under a hydraulic gradient. Measured in darcys (units L2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Darcy’s law (permeability form)

A

Q = (A · k · ΔP)/(μ · Δx)
Q = flow rate (cm3/sec) (L3/T)
μ = fluid viscosity (centipoise, cp, 0.01g/cm · s) (M/L · T)
k = permeability (Darcys, cm2) (L2)
A = cross-section area (cm2) (L2)
ΔP = change in pressure (atm) (M/L2)
Δx = distance (cm) (L)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Matric Potential

A

The pressure (tension) exerted on the pore water due to the soi-water attraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Meinzer

A

Unit of hydraulic conductivity measured in gpd/ft^2.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

n

A

Porosity
Fraction of the bulk volume of a rock or soil that is occupied by void space (unitless)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Sr

A

Specific Retention
Ratio of volume of water a soil or rock can retain against gravity drainage to the total volume of soil or rock (unitless)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Ss

A

Specific Storage
Coefficient relating the amount of water stored/released per unit head change in a fully confined (fully saturated aquifer)

For such an aquifer, S = Ss x b
Amount of water per unit volume of a saturated formation that is store or expelled from storage due to compressibility of the mineral skeleton and pore water per change in unit head (units L-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Q

A

Volumetric flow rate. Units L3/T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

S

A

Storativity or Storage Coefficient
Volume of water that a permeable unit release from or takes into storage per unit surface area of the aquifer per unit change in head (unitless)
S = Vw / A · dh

S = Ss · b + Sy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Sy

A

Specific Yield
Ratio of the volume of water that drains from a saturated soil or rock by gravity to the total volume of the soil or rock (unitless)
In unconfined aquifer, Sy = S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Water table (pressure definition)

A

The surface within uncinfied groundwater at which the hydraulic pressure is equal to atmospheric pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Acres per square mile

A

640 acres/square mile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Basin Storage Equation

A

dS = P - E ± R ± U
dS = change in storage
P = Precipitation
E = Evapotranspiration
R = Runoff (net change in SW storage)
U = Underflow (net change in GW storage)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Permeability of confining layer

A

Less than approx. 10-2 darcy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

T

A

T = Transmissivity = K · b
T units gpd/ft (L3/T · L or L2/T)
where b = aquifer saturated thickness
Ability of an aquifer to transmit water

23
Q

K of clay

A

10-5 to 10-2 gpd/ft2

24
Q

K of clean sand

A

101 to 105 gpd/ft2

25
Q

K of silt

A

10-2 to 102 gpd/ft2

26
Q

K of glacial till

A

10-5 to 101 gpd/ft2

27
Q

K of gravel

A

104 to 107 gpd/ft2

28
Q

K of silty sand

A

100 to 104 gpd/ft2

29
Q

Transmissivity form of Darcys Law

A

Q = T · i · w
where
T = transmissivity
i = hydraulic gradient
w = average width of aquifer

30
Q

Dupuit’s Law - formula and what is it for?

A

Q = 1/2 · K · (H12 - H22)/l · w
where
H = height of water table at a well above an impermeable surface that serves as bottom of confined aquifer
l = distance between wells
w = aquifer width

For computing flow rate (Q) in unconfined aquifers

31
Q

Vd (with Darcy’s law formula)

A

Specific discharge or discharge velocity
Vd = K · i

32
Q

vs

A

Seepage velocity
The velocity at which water moves through pore spaces in an aquifer
vs = K i / ne

33
Q

Saltwater Intrusion equation

A

Z = 40h
where, at a given location
Z = depth below sea level where the freshwater-salt water interface exists
h = the height above sea level of the potentiometric surface

34
Q

Darcy’s Law for cross-sectional flow into a flow net

A

Q = K · H · (nf / nd) · w
where
Q = Discharge rate (L3/T)
K = hydraulic conductivity (L/T)
H = total head loss through the system
nf = number of flow tubes in the system
nd = number of equipotential lines (head drops) in system
w = width of the feature into the cross-section

35
Q

K of unfractured igneous and metamorphic rocks

A

10-7 to 10-3

36
Q

K of sandstone

A

10-3 to 101

37
Q

K of limestone and dolomite

A

10-2 to 101

38
Q

K of fractured igneous and metamorphic rocks

A

10-1 to 103

39
Q

K of permeable basalt

A

100 to 105

40
Q

K of karst limestone

A

101 to 105

41
Q

ne of gravel

A

0.1-0.35

42
Q

ne of clay

A

0.01 to 0.20

43
Q

ne of sand - coarse, medium, fine

A

coarse: 0.20 to 0.35
medium: 0.15 to 0.30
fine: 0.10 to 0.30

44
Q

ne of silt

A

0.01 to 0.30

45
Q

ne of sandstone

A

0.10 to 0.35

46
Q

ne of limestone

A

0.01 to 0.20

47
Q

ne of unfractured crystalline rock

A

0.00 to 0.05

48
Q

ne of fractured crystalline rock

A

0.00 to 0.10

49
Q
A
50
Q

Density of water (imperial)

A

62.4 lbs / ft3

51
Q

Darcy flux or specific discharge

A

q = Q/A = K · i
Units (L3/T) / L2 (cubic feet / square foot x day) or just L/T (feet/day)
Also referred to as Darcy velocity or apparent velocity, but really isn’t a velocity.

52
Q

Bulk density relative to porosity

A

n = 1-(ρbparticle)
where
ρb = bulk density
ρparticle = density of soil matrix material (for example, sand)

53
Q

Relationship between K (gpd/ft^2) and k (darcys = cm2)

A

Range of reasonable K (gpd/ft^2) is about 2 orders of magnitude higher than k (cm2 = darcy)