Salado MLT_Hydrogeology 101_Dr. Joe Yelderman
Transcript of Salado MLT_Hydrogeology 101_Dr. Joe Yelderman
Groundwater 101
Fundamentalsof
Hydrogeologyand
a few Texas aquifers
TAGD Training November 16
2017
Dr. Joe
Dr. Joe
Hydrogeologist
Baylor University
Texas land owner
wells (registered)
springs
rivers/streams
Grandparent
OutlineA. 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
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!
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%
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.
D. 2 Groundwater concepts
1. Aquifer– Material that can
store and transmit water easily
2. Flow system– Recharge to
discharge
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)
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.
Aquifer concept1. Unconfined (water table) aquifer –
an aquifer that has a free water surface (water table) on the top.
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.
2 Groundwater concepts
1. Aquifer– Material that can
store and transmit water easily
2. Flow system– Recharge to
discharge
E. GW – ABCs: terminology• Porosity
• Hydraulic conductivity Q=KIA– Similar to permeability
• Transmissivity T = K x b
Hydrogeological terminology
Homogeneous (Homogeneity)– The same everywhere
Heterogeneous (Heterogeneity)
Isotropic (Isotropy)– The same in all directions
Anisotropic (Anisotropy)
Electrical ConductanceCharged ionic species increase conductance therefore, Ec = TDS?
TDS = A x (Ec) where A = .55 to .75 or about .67
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
Northern Segment
Barton Springs Segment
San Antonio Segment
The Edwards BFZ aquifer
48
SALADO
SAN ANTONIO
AUSTIN
(I-35 CAC, 2011)
N
Linear features
52
• Lineation is directly in line with Big Boiling
• Desktop measurement: 213°
• Field measurement: 220°
UnderflowTCEQ’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.
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.
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.”