Salado MLT_Hydrogeology 101_Dr. Joe Yelderman

1. Groundwater 101
Fundamentals
of
Hydrogeology
and
a few Texas aquifers
TAGD Training
November 16
2017
Dr. Joe

2. Dr. Joe?
Hydrogeologist
Baylor University

3. Dr. Joe
Hydrogeologist
Baylor University
Texas land owner
wells (registered)

4. Dr. Joe
Hydrogeologist
Baylor University
Texas land owner
wells (registered)
springs

5. Dr. Joe
Hydrogeologist
Baylor University
Texas land owner
wells (registered)
springs
rivers/streams
Grandparent

6. Outline
A. What is Hydrogeology?
B. What is Groundwater?
C. How does GW flow?
D. Basic GW concepts
E. GW-ABCs (Terminology)
F. Affects of wells
G. Water Chemistry
H. A few Texas aquifers
I. Management challenges

7. A. What is Hydrogeology?
The study of groundwater
• Hydrology
– Surface water
• Geohydrology
– Engineer?
• Subsurface hydrology
– Engineer?
• Hydrogeology
– Geologist
Complex and Difficult
Rocks are different in places
Groundwater flow changes
And you can’t see it!

8. Hydrogeology
Complex and difficult
not secret and occult
Hydro and geology
The
study
of
Groundwater

9. B. What is Groundwater?
the saturated zone

10. The Earth’s Water
• Oceans and Inland Seas 97.208%
• Ice (mostly Greenland and Antarctica) 2.15 %
• Groundwater 0.62% 97.5%
• Surface water 0.0091%
– Lakes 0.009%
– Rivers and Streams 0.0001%
• Other 0.00604%
– Soil water 0.005%
– Atmosphere 0.001%
– Biosphere 0.00004%

11. C. How does groundwater flow?
• the Ohio Supreme Court in Frazier v. Brown:48 (1861)
• In the absence of express contract and a positive authorized
legislation, as between proprietors of adjoining land, the law
recognizes no correlative rights in respect to underground
waters percolating, oozing, or filtrating through the earth; and
this mainly from considerations of public policy: (1) Because
the existence, origin, movement, and course of such waters,
and the causes which govern and direct their movements, are
so secret, occult, and concealed that an attempt to administer
any set of legal rules in respect to them would be involved in
hopeless uncertainty, and would, therefore, be practically
impossible.

12. Darcy’s Law
1856
Q = KIA

13. Darcy’s Law

15. Darcy’s Law
Q = KIA
Groundwater flows from higher to lower head

16. Groundwater contour maps and
flow directions

17. Our activities affect our wells

18. Darcy’s Law
1856
Q = KIA

19. D. 2 Groundwater concepts
1. Aquifer
– Material that can
store and transmit
water easily
2. Flow system
– Recharge to
discharge

20. Aquifer concept
• Aquifer - material that can store and
transmit water easily
• Aquitard – material that retards
groundwater flow (also – Confining
Bed)
Aquifer (sand)
Confining bed (shale)

21. Aquifer concept
1. Unconfined (water table) aquifer –
an aquifer that has a free water
surface (water table) on the top.
2. Confined (artesian) aquifer – an
aquifer where the water rises above
the top of the aquifer or above the
bottom of the overlying confining
bed.

22. Aquifer concept
1. Unconfined (water table) aquifer –
an aquifer that has a free water
surface (water table) on the top.

23. Aquifer concept
2. Confined (artesian) aquifer – an aquifer
where the water rises above the top of the
aquifer or above the bottom of the
overlying confining bed.

24. Confined aquifer

25. Unconfined and Confined
aquifers

26. 2 Groundwater concepts
1. Aquifer
– Material that can
store and transmit
water easily
2. Flow system
– Recharge to
discharge

27. Groundwater flow systems
recharge to discharge

28. Local, Intermediate, and Regional flow
systems

29. E. GW – ABCs: terminology
• Porosity
• Hydraulic conductivity Q=KIA
– Similar to permeability
• Transmissivity T = K x b

30. Hydrogeological terminology
• Storativity or Storage Coefficient S
• Specific Yield Sy

31. Hydrogeological terminology
Homogeneous (Homogeneity)
– The same everywhere
Heterogeneous (Heterogeneity)
Isotropic (Isotropy)
– The same in all directions
Anisotropic (Anisotropy)

32. F. Groundwater and Wells

33. Flow to wells

34. Overlapping cones of depression

35. G. Water chemistry
• H2O
– H180 O90
• Dipolar
• The universal solvent

36. Water - the universal solvent

37. Electrical Conductance
Charged ionic species increase conductance therefore, Ec = TDS?
TDS = A x (Ec) where A = .55 to .75 or about .67

39. Chemistry changes with depth

40. H. A few Texas
aquifers
Ogallala

41. Ogallala
Aeolian
wind
Fluvial
water

42. A few Texas
aquifers
Trinity aquifer
Major aquifer
unconfined
outcrop
confined
downdip

43. Sand
clay and Ls

44. Discovery, Value, and Problem
– The first artesian well
drilled in Waco in 1889
• 1830 ft deep
•
• Flowed at the surface
• ~400,000 gal/d
– Waco advertized as “Geyser
City”
– by 1894, some wells ceased
flowing at the surface

45. ?

47. A few Texas
aquifers
Edwards BFZ

48. Northern Segment
Barton Springs Segment
San Antonio Segment
The Edwards BFZ aquifer
48
SALADO
SAN ANTONIO
AUSTIN
(I-35 CAC, 2011)

49. Northern Segment of the Edwards BFZ
aquifer, Central Texas
(Jones, 2003)

50. fractures
cave
losing stream
sink hole

51. Fractures and dye tracing

52. N
Linear features
52
• Lineation is directly in
line with Big Boiling
• Desktop measurement:
213°
• Field measurement: 220°

53. I. Management challenges

54. Underflow
TCEQ’s definition at 30 Tex. Admin. Code § 297.1(56)
• (56) Underflow of a stream--Water in sand,
soil, and gravel below the bed of the
watercourse, together with the water in the
lateral extensions of the water-bearing
material on each side of the surface channel,
such that the surface flows are in contact
with the subsurface flows, the latter flows
being confined within a space reasonably
defined and having a direction
corresponding to that of the surface flow.

55. Hyporheic Zone

56. Underflow
• (56) Underflow of a
stream--Water in sand,
soil, and gravel below the
bed of the watercourse,
together with the water in
the lateral extensions of
the water-bearing material
on each side of the surface
channel, such that the
surface flows are in
contact with the
subsurface flows, the latter
flows being confined
within a space reasonably
defined and having a
direction corresponding to
that of the surface flow.

57. Underflow

58. Underflow

59. Models

60. Uncertainty
Often quoted:
“All models are wrong, but some are useful”
Box and Draper (1987)

61. Uncertainty
Often quoted:
“All models are wrong, but some are useful”
Box and Draper (1987)
The second half:
“...the practical question is how wrong do
they have to be to not be useful.”

62. Questions?