1. WATER IN SOILS

2. Water – A unique substance
A. Polar vs. Nonpolar Molecules

3. “water is a polar substance”
Strong Surface Tension
Strong Capillary Action

4. II. Soil Porosity
A. Varies with Texture
1. Approximately 50% for Undisturbed
Soils

6. III. Nature of Soil Water
A. Water Table
1. Zone of Aeration
2. Zone of Saturation

8. Nuclear
Gage
Resistance
Block
Potentiometer

9. A thought experiment……

10. A thought experiment……

11. B. How Water is Held in Soils 1. Cohesion
a. Forces Bonding Water to Itself
2. Adhesion
a. Bonds Water to Soil Grains
b. Measured in Bars
1 Bar = 1 Atmosphere
~15 psi
Positive end of the water molecule bonds with the negatively charged clay particle (hydrogen bonding)
ppt----cohesion-----adhesion

12. Hygroscopic
Water--
--water that is tightly bound to the soil particle and requires large expenditure of energy to remove it.

13. C. Water Available to Plants 1. Wilting Point: -15 Bars to
2. Field Capacity: -1/3 Bar
D. Hygroscopic Water
1. Held by Adhesion
a. Greater than -31 Bars
saturation
0 bar

15. E. Water Availability vs. Texture
1. Greatest in Loamy Soils
2. Least in Sandy and Clayey Soils

17. F. Water Use in USA
1. 83% Agriculture
2. Irrigation
a. Great Benefits – Great Problems
b. Mining Groundwater
ex: Ogallala Aquifer
c. Salinization
d. Waterlogging of Soil

19. G. Soil Drainage
1. Color
a. Oxidation State of Iron
Fe 2+ <> Fe e-
b. Organic Matter
Wet Soil Preserves Organics
c. Gleying
d. Mottling
2. Fragipan Soils
a. Can Cause Wetness

20. Well drained soil,
Ferric iron

21. High organic matter

22. Gleyed soil

23. Mottled soil

26. H. Vegetation
1. Hydrophilic Plants
a. Cyprus
b. Cattails
c. Willows
d. Reeds
2. Plants Requiring Good Drainage
a. Oak-Hickory Biome
b. Pines
c. Most Grasses

27. Part II

28. Water Movement in Soil and Rocks

29. Water Movement in Soil and Rocks
Two Principles to Remember:

30. Water Movement in Soil and Rocks
Two Principles to Remember:
1. Darcy’s Law

31. Water Movement in Soil and Rocks
Two Principles to Remember:
1. Darcy’s Law
Continuity Equation:
mass in = mass out + change in storage
“my name’s
Bubba!”

32. Water Movement in Soil and Rocks
I. Critical in Engineering and Environmental Geology
A. Dams, Reservoirs, Levees, etc.
“ Pore Pressure”

33. Water Movement in Soil and Rocks
I. Critical in Engineering and Environmental Geology
A. Dams, Reservoirs, Levees, etc.
B. Groundwater Contamination
Leaking Underground
Storage Tanks
Landfills
Surface
Spills

34. Water Movement in Soil and Rocks
I. Critical in Engineering and Environmental Geology
A. Dams, Reservoirs, Levees, etc.
B. Groundwater Contamination
C. Foundations
- Strength and Stability

35. I. Critical in Engineering and Environmental Geology
A. Dams, Reservoirs, Levees, etc.
B. Groundwater Contamination
C. Foundations
- Strength and Stability

36. II. Water Flow in a Porous Medium
A. Goal: Determine the permeability of the
engineering material

37. II. Water Flow in a Porous Medium
A. Goal: Determine the permeability of the
engineering material
Porosity Permeability

38. II. Water Flow in a Porous Medium
A. Goal: Determine the permeability of the
engineering material
Porosity Permeability
Porosity (def) % of
total rock that is
occupied by voids.
Permeability (def) the ease at
which water can move through
rock or soil

39. II. Water Flow in a Porous Medium B. Darcy‘s Law
Henri Darcy (1856)
Developed an empirical relationship of the
discharge of water through porous mediums.

40. II. Water Flow in a Porous Medium B. Darcy‘s Law 1. The experimentK

41. II. Water Flow in a Porous Medium
B. Darcy‘s Law
2. The results
unit discharge α permeability
unit discharge α head loss
unit discharge α hydraulic gradient

42. Also…..

43. II. Water Flow in a Porous Medium
B. Darcy‘s Law
2. The equation
v = Ki

44. II. Water Flow in a Porous Medium
B. Darcy‘s Law
2. The equation
v = Ki
where v = specific discharge (discharge per cross sectional area) (L/T)
* also called the Darcy Velocity
* function of the porous medium and
fluid

45. Darcy’s Law:
v = Ki
where v = specific discharge (discharge per unit area) (L/T)
K = hydraulic conductivity (L/T); also referred
to as coefficient of permeability
i = hydraulic gradient, where
i = dh/dl (unitless variable)

46. Darcy’s Law:
v = Ki
where v = specific discharge (discharge per unit area) (L/T)
K = hydraulic conductivity (L/T); also referred
to as coefficient of permeability
i = hydraulic gradient, where
i = dh/dl (unitless variable)

47. Darcy’s Law:
v = Ki
where v = specific discharge (discharge per unit area) (L/T)
K = hydraulic conductivity (L/T); also referred
to as coefficient of permeability
i = hydraulic gradient, where
i = dh/dl (unitless variable)
v = K dh dl

48. Darcy’s Law:
v = Ki
where v = specific discharge (discharge per unit area) (L/T)
K = hydraulic conductivity (L/T); also referred
to as coefficient of permeability
i = hydraulic gradient, where
i = dh/dl (unitless variable)
v = K dh dl
If Q = VA, then
Q = A K dh dl

49. B. Darcy‘s Law
4. Some Representative Values for Hydraulic Conductivity

50. The exposed truth: these are only APPARENT velocities and discharges
Darcy’s Law:
The exposed truth: these are only APPARENT velocities and discharges
Q = A K dh dl
v = K dh dl
Q = VA
Vs.

51. The exposed truth: these are only APPARENT velocities and discharges
Darcy’s Law:
The exposed truth: these are only APPARENT velocities and discharges
QL = A K dh
ne dl
vL = K dh
ne dl
Where ne effective porosity
VL = ave linear velocity (seepage velocity)
QL = ave linear discharge (seepage discharge)
Both of these variables
take into account that
not all of the area is
available for fluid flow
(porosity is less than 100%)

52. Find the specific discharge and average linear velocity of a pipe filled with sand with
the following measurements.
K = 1* 10-4 cm/s
dh = 1.0
dl = 100
Area = 75 cm2
Effective Porosity = 0.22

53. Find the specific discharge and average linear velocity of a pipe filled with sand with
the following measurements.
K = 1* 10-4 cm/s
dh = 1.0
dl = 100
Area = 75 cm2
Effective Porosity = 0.22
VL =-Kdh V =-Kdh
nedl dl
V = 1 * 10-6 cm/sec
VL = 4.55 * 10-6 cm/sec
How much would it move in one year?
4.55 * 10-6 cm * * 107 sec * 1 meter = 1.43 meters for VL
sec year cm
0.315 m for V

54. II. Water Flow in a Porous Medium B. Darcy‘s Law 3. The Limits
Equation assumes ‘Laminar Flow’; which is usually the case for flow
through soils.

55. II. Water Flow in a Porous Medium
C. Laboratory Determination of Permeability

56. II. Water Flow in a Porous Medium
C. Laboratory Determination of Permeability
1. Constant Head Permeameter
Q = A K dh dl
Q* dl= K
A dh

57. Example Problem: Q = A K dh Q* dl= K dl A dh = 0.0481 ft3/min Given:
Soil 6 inches diameter, 8 inches thick.
Hydraulic head = 16 inches
Flow of water = ft3 for 255 minutes
Find the hydraulic conductivity in units of ft per minute
Q = A K dh dl
Q* dl= K
A dh

58. Example Problem:
Q* dl= K
A dh
ft3/min

59. Example Problem:
Q* dl= K
A dh
ft3/min

60. II. Water Flow in a Porous Medium
C. Laboratory Determination of Permeability
2. Falling Head Permeameter
More common for fine grained soils

61. II. Water Flow in a Porous Medium
C. Laboratory Determination of Permeability
2. Falling Head Permeameter

65. D. Field Methods for Determining Permeability
In one locality: “Perk rates that are less than 15 minutes per inch or greater than 105 are unacceptable measurements. “

66. 1. Double Ring Infiltrometer
D. Field Methods for Determining Permeability
1. Double Ring Infiltrometer

67. D. Field Methods for Determining Permeability
2. Johnson Permeameter

68. 1. Slug Test (Bail Test) D. Field Methods for Determining Permeability
also referred to as the Hzorslev Method
K = r2 ln(L/R)
2LT0.37
Where:
r = radius of well
R = radius of bore hole
L = length of screened section
T0.37 = the time it take for the water
level to rise or fall to 37% of the
initial change

69. Example Problem: K = r2 ln(L/R) 2LT0.37 Where: r = radius of well
A slug test is performed by injecting water into a piezometer finished in coarse sand. The inside diameter of both the well screen and well casing is 2 inches. The well
screen is 10 feet in length. The data of the well recovery is shown below. Determine K from this test.
K = r2 ln(L/R)
2LT0.37
Where:
r = radius of well
R = radius of bore hole (well casing)
L = length of screened section
T0.37 = the time it take for the water
level to rise or fall to 37% of the
initial change

70. Hzorslev Method
Time since
Injection
(sec)
H (ft)
h/ho
0.88
1.000 1
0.6
0.682 2
0.38
0.432 3
0.21
0.239 4
0.12
0.136 5
0.06
0.068 6
0.04
0.045 7
0.02
0.023 8
0.01
0.011 9
0.000

71. Hzorslev Method

72. Example Problem: K = r2 ln(L/R) 2LT0.37 Where: r = radius of well
A slug test is performed by injecting water into a piezometer finished in coarse sand. The inside diameter of both the well screen and well casing is 2 inches. The well
screen is 10 feet in length. The data of the well recovery is shown below. Determine K from this test.
K = r2 ln(L/R)
2LT0.37
Where:
r = radius of well
R = radius of bore hole (well casing)
L = length of screened section
T0.37 = the time it take for the water
level to rise or fall to 37% of the
initial change

73. Example Problem: K = r2 ln(L/R) 2LT0.37
A slug test is performed by injecting water into a piezometer finished in coarse sand. The inside diameter of both the well screen and well casing is 2 inches. The well
screen is 10 feet in length. The data of the well recovery is shown below. Determine K from this test.
K = r2 ln(L/R)
2LT0.37
K = (0.083 ft)2 ln(10 ft/ (0.083 ft)
2(10ft)(2.3 sec)
Where:
r = radius of well
R = radius of bore hole (well casing)
L = length of screened section
T0.37 = the time it take for the water
level to rise or fall to 37% of the
initial change

74. Example Problem: K = r2 ln(L/R) 2LT0.37
A slug test is performed by injecting water into a piezometer finished in coarse sand. The inside diameter of both the well screen and well casing is 2 inches. The well
screen is 10 feet in length. The data of the well recovery is shown below. Determine K from this test.
K = r2 ln(L/R)
2LT0.37
K = (0.083 ft)2 ln(10 ft/ (0.083 ft)
2(10ft)(2.3 sec)
K = 7.18 * 10-4 ft/s
K = 62.0 ft/day
Where:
r = radius of well
R = radius of bore hole (well casing)
L = length of screened section
T0.37 = the time it take for the water
level to rise or fall to 37% of the
initial change

75. 4. Pump Test E. Field Methods for Determining Permeability
also referred to as the Thiem Method
K = Q* ln(r1/r2)
π(h12 – h22)

76. K = Q* ln(r1/r2)
π(h12 – h22)