This document discusses the hydrogeology of Tennessee, detailing various types of aquifers, their properties, and the hydrologic cycle. It examines groundwater recharge, storage capacity, and the regional geology affecting water supply, including significant aquifer systems like the Mississippi Embayment and Central Basin aquifers. Additionally, it provides insights into trends in water withdrawal, public water supply sources, and specific characteristics of karst aquifers in the state.

1. The Hydrogeology of Tennessee
Thomas E. Ballard,PG, CHG
Taber Consultants
Murfreesboro,TN

2. BASIC
HYDROGEOLOGY

3. Hydrologic Cycle

4. Groundwater Recharge
— Recharge is the
processes involved in
the addition of water
to the saturated zone
— Naturally by
precipitation or runoff
— Artificially by
spreading or injection

5. Groundwater Recharge and
Discharge

6. Average Annual Precipitation 1951-80

7. Types of Aquifers
— Unconsolidated
— Sedimentary Bedrock
— Limestone/Karst
— Fractured Rock

8. Confined vs. Unconfined Aquifers
Unconfined Aquifer Confined Aquifer

9. Properties of Aquifers
— Porosity
— Effective Porosity
— Hydraulic
Conductivity
— SpecificYield
— Specific Retention
— Transmissivity
— Storativity

10. Porosity
The ratio of void space to the total volume of a soil or rock.

11. Examples of Porosity

12. Effective Porosity
The percent of the
total volume of a given
mass of soil or rock
that consists of
interconnected spaces.
Essentially equivalent to
permeability.

13. Primary vs. Secondary Porosity
The porosity that
represents the original
pore openings when a
rock or sediment
formed
The porosity
developed in a rock
after its deposition as
result of fracturing or
solution;usually not
uniformly distributed.
EXAMPLE: Karstic Limestone has relatively low primary porosity,
but can have high secondary porosity due to development of
solution cavities and channels.
Primary Porosity Secondary Porosity

14. The volume of water at the existing
kinematic viscosity that will move in a
porous medium in unit time under a unit
hydraulic gradient measured at right angles
to the direction of flow. Generally
designated as ‘K’ in most groundwater
equations.
Hydraulic Conductivity

15. Hydraulic Conductivity Illustration

17. SpecificYield/Specific Retention
That part of the water
in storage in the ground
that will drain under
the influence of gravity.
That part of water in
storage in the ground
that is retained as a film
on rock surfaces or in
very small openings.
Specific Yield Specific Retention

18. SpecificYield/Specific Retention

19. Head
ht = z + hp
ht = total head
Z = elevation head
hp = pressure head
As a practical matter, head
is really just the elevation
(above sea level) of the
standing water level in a
well.

20. Head and Gradient

21. Groundwater Gradient

22. — Darcy’s Law
— Groundwater Flow Rate (Velocity)
— Transmissivity
— Storativity
Principles of Groundwater Flow

23. Darcy’s Law
Groundwater Flow Rate
𝑽 = 𝑲
𝒅𝒉
𝒅𝒍
V = flow
K = hydraulic conductivity
dh = head difference
dl = distance between points
Groundwater FlowVolume
𝑸 = 𝑨 𝑲
𝒅𝒉
𝒅𝒍
Q = discharge
A = aquifer cross-section area
K = hydraulic conductivity
dh = head difference
dl = distance between points

24. 𝑽 𝒙 =
𝑸
𝒏 𝒆
𝑨
= −
𝑲 𝒅𝒉
𝒏 𝒆
𝒅𝒍
Where:
Vx = the average linear (seepage) velocity
ne = the effective porosity
Q = the discharge (flux)
A = the cross-sectional area of flow
K = the hydraulic conductivity
dh = difference in groundwater elevation between two
measurement points
dl = distance between the two measurement points used for dh
GroundwaterVelocity

25. Transmissivity
The capacity of an
aquifer to transmit
water at the prevailing
kinematic velocity.
T = Kb
T = transmissivity
K = hydraulic
conductivity
b = aquifer thickness

26. Volume of water that a permeable unit
releases from or takes into storage per unit
surface area per unit change in head.
Unconfined aquifer: storativity is virtually
equal to specific yield.
Confined aquifer: water is derived from
expansion of water and compression of the
aquifer – specific storage.
Storativity

27. Calculating Storativity
S =Vw A dh
Vw = volume of water
A = surface area of
aquifer
dh = change in head
Ranges from 0.01 to
0.30
S = b Ss
b = aquifer thickness
Ss = specific storage
Ranges from 0.001 to
0.00001
Confined StorativityUnconfined Storativity

28. Relative Storage Capacity vs. Depth
— Alluvium generally
has highest storage
capacity
— Related to sand and
gravel content
— Bedrock storage
capacity inTN is
highly dependent on
fractures
— Fewer fractures with
depth

29. Karst Hydrogeology
— Two thirds of Tennessee is underlain by
limestone.
— Karst is an important groundwater source
in those areas.
— Primary porosity is low in limestone.
— Secondary porosity i.e. solution cavities
and fractures are an important
groundwater source.
— Karst aquifers best developed near
surface and in relatively pure limestones.

30. Karst Aquifers
— Openings forming the karst aquifer may
be partly or completely water-filled.
— The elevation where all pores are filled
with water in an aquifer is the water
table.
— Water tables in karst areas can be highly
irregular in elevation, because water-
carrying conduits can develop at various
elevations.

31. Idealized Diagram of Karst
Development

32. Distribution of Limestone
inTennessee

33. Karst Regions of Tennessee

34. REGIONAL GEOLOGY

35. RegionalGeology

36. Generalized Geology Key

37. Regional Structural Setting

38. Tennessee Aquifer Systems

39. TENNESSEE
HYDROGEOLOGY
OVERVIEW

41. PRINCIPALAQUIFERSIN
TENNESSEE
Rate of water withdrawal by public water
systems in millions of gallons per day, 2000
Source:U.S. Geological Survey
0.48 Mgal/d3.74 Mgal/d
244 Mgal/d
10.9 Mgal/d
Cretaceous sand
aquifer
Ordovician carbonate
aquifer
Pennsylvanian sandstone
aquiferTertiary sand
aquifer
36°
89°
88° 87° 86° 85° 84° 83° 82°
Modified from Bradley and
Hollyday, 1985
35°
2.27 Mgal/d2.27 Mgal/d
4.09 Mgal/d
17.1 Mgal/d
Alluvial
aquifer
Alluvial aquifer
Cambrian-Ordovician
carbonate aquifer
Mississippian
carbonate aquifer
Crystalline rock aquifer
41.2 Mgal/d

42. TENNESSEE WATER
SUPPLY SOURCES
Source of water supply,in percent,for public
water supply withdrawals in Tennessee, 2000
Source:U.S. Geological Survey

43. PRINCIPAL TN PUBLIC
WATER SUPPLY SYSTEMS
THAT WITHDREW
GROUNDWATER IN 2000
88°
36°
89°
87° 86° 85° 84° 83° 82°
35° Base from U.S. Geological Survey digital data, 1972,
No withdrawals
Ground-water withdrawals
(million gallons per day)
Less than 1
1 to 10
Greater than 10 to 20
More than 150
EXPLANATION
Public water-supply system using more than
0.02 million gallons per day ground water
from wells. Number is system identifier
Public water-supply system using more than
0.02 million gallons per day ground water
from springs or from both wells and springs
Public water-supply system using less than
0.02 million gallons per day ground water

44. GROUNDWATER
WITHDRAWALSFROM
PRINCIPALAQUIFERS,
2000
Source:U.S. Geological Survey

45. TRENDS IN PUBLIC
WATER SUPPLY
WITHDRAWALS,1950-
2000
Source:U.S. Geological Survey

46. TOP 10 COUNTIES FOR
PUBLICWATER SUPPLY
WITHDRAWALS,2010
Source:U.S. Geological Survey
County Population Served Withdrawals (Mgd)
Shelby 924,861 173.07
Madison 86,464 13.23
Hamilton 333,606 10.7
Carter 44,302 7.46
Tipton 59,109 6.5
Obion 31,636 5.34
Gibson 39,774 5.25
Dyer 36,890 5.17
Jefferson 38,758 4.58
Montgomery 169,404 3.58

47. TOP 10 COUNTIES FOR
DOMESTIC WATER
SUPPLYWITHDRAWALS,
2010
Source:U.S. Geological Survey
County Population on Well Water Withdrawals (Mgd)
Rutherford 34,507 2.48
Sevier 31,317 2.25
Fayette 22,675 1.63
Robertson 20.752 1.49
Hawkins 17,885 1.29
Grainger 15,294 1.10
Blount 14,284 1.03
Carter 13,122 0.94
McMinn 13,104 0.94
Jefferson 12,649 0.91

48. WELL DRILLINGTRENDS
INTENNESSEE
Source:Tennessee Department of Environmental
and Conservation,Division ofWater Resources
Year Number of Wells Drilled
(approx)
2007 5000
2010 2400
2015 2150

49. REGIONAL AQUIFER
SYSTEMS

50. Mississippi EmbaymentAquifer System

51. Mississippi Embayment
Aquifer System

52. Mississippi Embayment Cross Section

53. Memphis Aquifers

54. Mississippi Embayment Stratigraphy

55. DetailedStratigraphy

56. DetailedStratigraphy

57. Upper Claiborne

58. Middle Claiborne (Memphis Sand)

59. Lower Claiborne – UpperWilcox

60. Middle Wilcox (Fort Pillow Sand)

61. LowerWilcox

62. Top of LowerWilcox Aquifer

63. McNairy-Nacatoch Aquifer

64. Pre-Pumping Groundwater Flow in
the LowerWilcox Aquifer

65. Water Quality
McNairy-NacatochAquifer

66. Aquifer Characteristics
— Cretaceous to
Quaternary
unconsolidated
sediments.
— Extremely productive
multiple sand
aquifers separated by
local and regional
confining beds.
— Aquifers thicken
from east to west
where they occur in
Tennessee.
— Greatest yields come
from the Memphis
Sand (Middle and
Lower Claiborne) –
generally 200 to
1,000 gpm but over
2,000 gpm locally.

67. Central Basin Aquifer System

68. Central Basin Aquifer System

69. Generalized Cross Section

70. CentralBasinStatigraphy

71. Detailed Stratigraphy

72. Detailed Stratigraphy

73. Detailed Stratigraphy

74. Detailed Stratigraphy

75. Conceptual Groundwater
Flow Model

76. Conceptual Groundwater Model
Inner Central Basin

77. Conceptual Groundwater Model
Outer Central Basin

78. Central BasinWellYields

79. Central BasinWater Quality

80. Aquifer Characteristics
— Carbonate rocks
(limestone and some
dolomite) are primary
aquifers.
— Intervening confining
units of shale and shaly
limestones
— Chattanooga Shale
separates Central
BasinAquifer System
from overlying
Mississippian rocks of
the Highland Rim
— Depth of freshwater
varies greatly.
— Wells are typically 50 –
200 feet deep.
— Depth to salt water is
generally greatest
where the limestone
and dolomite aquifers
crop out i.e. the apex
of the Nashville
Dome.
— Recharge rates affect
depth to salt water.

81. Highland Rim Aquifer System

82. Highland Rim Aquifer System

83. Generalized Cross Section

84. HighlandRimStratigraphy

85. HighlandRimDetailed
Stratigraphy

86. Conceptual Groundwater Model
Eastern Highland Rim

87. Highland RimWater Quality

88. Aquifer Characteristics
Most Productive
Mississippian Aquifers
— Ste. Genevieve
Limestone
— St. Louis Limestone
— Warsaw Limestone
— Fort Payne Formation
Fine-grained clastic rocks
are not generally
productive
— Mostly karst aquifers
— Groundwater moves
through fractures,
bedding planes, and
solution openings in
the limestone
— Hydraulic
characteristics (yield
and specific capacity)
vary greatly over short
distances

89. Knox Aquifer

90. Knox Aquifer

91. Cross Section of the Knox Aquifer

92. Knox Aquifer Stratigraphy

93. Conceptual Model of Groundwater
Flow in the Knox Aquifer

94. Water Quality of the
Upper Knox Aquifer

95. Aquifer Characteristics
— Regional aquifer.
— Distinct from Knox
Formation units inValley
and Ridge.
— Only exposed in
SequatchieValley.
— Recharge through
fractures that transect
the overlying confining
unit.
— Water yields in upper 50
feet.
— Dolomite typically has
the best yield
— Limestones yield little
water
— TDS < 1,000 mg/l at
center of Nashville
Dome and Sequatchie
Valley anticline
— Deeper zones have high
TDS
— Freshwater-saltwater
interface does not
coincide with shallower
aquifers

96. Cumberland Plateau Aquifer System

97. Cumberland Plateau Aquifer System

98. Generalized Cross Section
Northern Cumberland Plateau

99. Cross Sections - Mid and Southern
Cumberland Plateau inTennessee
Wilson, C.W., Jr. and Stearns, R.G., 1958,
Structure of the Cumberland Plateau,
Tennessee, State of Tennessee, Department of
Environment and Conservation, Division of
Geology, Report of Investigations No. 8

100. CumberlandPlateauStratigraphy

101. Groundwater Movement Model
Aquifers in consolidated rocks are directly recharged by precipitation where they
are exposed at the land surface. Water enters the aquifers primarily through
fractures. Fractures decrease in width and number with depth.In Pennsylvanian
rocks, underclay beneath coal beds creates perched water tables, which result in
springs that issue from valley walls.Water percolates slowly downward through
the underclay to reach the main water table.

102. Conceptual Groundwater Model
Cumberland Plateau
Groundwater moves primarily through fractures in clastic rocks and solution
openings in limestone. Fractures in shale confining units allow rapid downward
movement. Shallow near-surface fractures yield the most water to wells.

103. Cross Section and Recharge
Cumberland Plateau

104. GeneralWater Quality
Cumberland Plateau

105. Aquifer Characteristics
— Geology consists of
easterly dipping
Pennsylvanian and
Mississippian rocks.
— Pennsylvanian rocks are
primarily sandstone,
conglomerate and shale
with some coal beds.
— Mississippian rocks are
primarily shale and
limestones.
— Locally,excessive
concentrations of iron or
sulfate may be present.
— A complete, ideal cycle of
Pennsylvania rocks consists
of, from bottom to top:
underclay,coal, gray shale
or black platy shale,
freshwater limestone, and
sandstone or silty shale.
— Water from limestones
tends to be alkaline and
from coal/black shale more
acidic.
— Deeper water tends to be
more mineralized.

106. Valley and Ridge Aquifer System

107. Valley and Ridge Aquifer System

108. Valley and Ridge Province
Generalized Cross Section

109. Valley and Ridge Province
Conceptual Cross Section

110. Principal Aquifers inValley and Ridge
— Principal aquifers are
carbonate rocks of
Cambrian and
OrdovicianAge

111. ValleyandRidgeStratigraphy

112. ValleyandRidgeStratigraphy

113. Valley and Ridge Province
Conceptual Groundwater Model
Groundwater moves
downward through
interstitial pore spaces in
residuum and alluvium
into the consolidated
rocks, where it moves
along fractures, bedding
planes and solution
openings.The general
direction of flow is from
ridges to toward springs
and streams in the
valleys.

114. Conceptual Groundwater Model
Valley and Ridge

115. Conceptual Groundwater Model
WesternToe

116. Water Quality –Valley and Ridge

117. Aquifer Characteristics
— Geology is defined by
series of imbricate
faulting related to deep
detachment fault
system.
— Groundwater is
primary stored in
fractures, bedding
planes and solution
openings.
— Nature of the geology
dictates no regional
flow systems.
— Karst systems
generally have the best
yields.
— Fractures in clastic
rocks can yield water
locally.
— Some production from
alluvium and residuum.
— Groundwater type is
typically calcium-
magnesium-
bicarbonate.

118. Blue Ridge Aquifers

119. Blue Ridge Aquifer System

120. Generalized Geologic Cross Section
of EastTennessee

121. BlueRidgeStratigraphy

122. Blue Ridge Province
Conceptual Groundwater Model

123. Water Quality – Blue Ridge

124. Aquifer Characteristics
— Most available
groundwater is in
fractures within a
few hundred feet of
the ground surface.
— Production capacity
defined by number,
size and degree of
interconnected
fractures.
— Fractures close off at
depth.
— Regional
groundwater flow is
not significant
— Groundwater quality
is generally good
with lowTDS.
— Groundwater is
calcium-magnesium-
bicarbonate type.

125. Basal SandstoneAquifer

126. Basal Sandstone Aquifer System

127. Basal Sandstone Distribution

128. Basal Sandstone Stratigraphy

129. Conceptual Model of Basal Sandstone
Groundwater Occurrence

130. Aquifer Characteristics
— No surface
exposures
— Occurs at depths of
5,000 to 10,000 feet
— 200 to 400 feet thick
— Similar to other basal
units throughout the
world
— Limited data
— TDS exceeds 10,000
mg/l
— Not drinking water
quality
— Has been used for
deep injection wells

131. Questions?