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101: Fundamentals of Hydrogeology and
review of Texas aquifers
Dr. Joe TAGD 2016
Who is Dr. Joe? Texan Land owner Well owner Grandparent
Outline What is Hydrogeology?
What is Groundwater?
How does groundwater flow?
Concepts
Terminology
How do wells work?
Texas Aquifers
Management challenges: Aquifers vs groundwater
Hydrogeology Complex and difficult Hydrology Hydrogeology Geohydrology etc.
Hydrogeology Complex and difficult Hydrology Hydrogeology Geohydrology etc.
Hydrogeology Complex and difficult Hydrology Hydrogeology Geohydrology etc.
What is Groundwater? the saturated zone
The Earth’s Water • Oceans and Inland Seas 97.208%
• Ice (mostly Greenland and Antarctica) 2.15 %
• Groundwater 0.62%
• Surface water 0.0091%
• Other 0.00604%
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%
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.
Darcy’s Law 1856
Q = KIA
Darcy’s Law
Darcy’s Law
Q = KIA Groundwater flows from higher to lower head
Groundwater contour maps and flow directions
Our activities affect our wells
Darcy’s Law 1856
Q = KIA
Groundwater concepts
• Aquifer – Material that can
store and transmit water easily
• 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 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 concept 1. 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.
Confined aquifer
Unconfined and Confined aquifers
Unconfined and Confined aquifers
Groundwater concepts
• Aquifer – Material that can
store and transmit water easily
• Flow system – Recharge to
discharge
Groundwater flow systems recharge to discharge
Groundwater divides
Local, Intermediate, and Regional flow systems
Hydrogeological terminology • Porosity
• Hydraulic conductivity Q=KIA – Similar to permeability
• Transmissivity T = Kxb
Hydrogeological terminology
• Storativity or Storage Coefficient S
• Specific Yield Sy
Groundwater and Wells
Flow to wells
Overlapping cones of depression
Hydrogeological terminology
• Homogeneous (Homogeneity) – The same everywhere
• Heterogeneous (Heterogeneity)
• Isotropic (Isotropy) – The same in all directions
• Anisotropic (Anisotropy)
Hydrogeological terminology
• Homogeneous (Homogeneity) – The same everywhere
• Heterogeneous (Heterogeneity)
• Isotropic (Isotropy) – The same in all directions
• Anisotropic (Anisotropy)
Water chemistry • H2O
– H180 O90
• Dipolar • The universal solvent
Water - the universal solvent
Aqifers Trinity
Groundwater Major aquifers Trinity (sand)
Aquifer
Groundwater Major aquifers Trinity (sand)
Aquifer
?
Aquifers Ogallala
Ogallala Aeolian Fluvial
Groundwater
The Brazos River Alluvium: regional
• 1 of 21 minor aquifers in Texas
Dallas
Waco
Austin
The Brazos River Alluvium: local
Brazos River
WACO
Lake Whitney
Brazos River Alluvium
Lithology
• Fining upward sequence • Sands and gravels • Heterogeneity
(after Epps, 1973)
Sandy pea gravel
Black Bell series soil
Water table
Sandy coarse gravel
Poorly sorted gravel
Blue clay (Taylor Fm.)
Red sandy clay
Sand
Edward Hay Ranch gravel deposit, near Marlin
Gaining and losing streams
The Brazos River is a gaining stream
Brazos River Alluvium aquifer
Unconfined aquifer
Saturated section
• Range: 0.25 – 60 ft • Average: 25 ft
Models
Models
Uncertainty
O,enquoted:“Allmodelsarewrong,butsomeareuseful”
BoxandDraper(1987)
Uncertainty
O,enquoted:“Allmodelsarewrong,butsomeareuseful”
BoxandDraper(1987)
Thesecondhalf:“...thepracHcalquesHonishowwrongdotheyhavetobetonotbeuseful.”
WellsacrossEagleFordShaleplay
Data Accessed April 2015
WellsacrossEagleFordShaleplay
Data Accessed April 2015
CLIMATE CHANGE ?
Questions?