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Groundwater and Aquifers
Groundwater Hydraulics
Daene C. McKinney
Some Terminology
• Hydrology ()– - “water”; - “study of”– Study of Water: properties, distribution, and
effects on the Earth’s surface, soil, and atmosphere
• Water Management– Sustainable use of water resources– Manipulating the hydrologic cycle
• Hydraulic structures, water supply, water treatment, wastewater treatment & disposal, irrigation, hydropower generation, flood control, etc.
Some History
• Qanats – Subterranean tunnels used to tap and
transport groundwater– Originally in Persia– Kilometers in length– Up to 3000 years old– Many still operating
• Chinese Salt Wells– 1000 years ago: Drilled wells– Over 300 meters deep– Bamboo to retrieve cuttings– By year 1858: 1000 meters deep– Called “cable tool” drilling today
Ancient Persian Qanat
Ancient Chinese Salt Well
Old Theories
Homer (~1000 BC) “from whom all rivers are and the
entire sea and all springs and all deep wells have their waters”
Seneca (3 BC -65 AD) “You may be quite sure that it not mere
rainwater that is carried down into our greatest rivers.”
Da Vinci (1452-1519) accurate representation of the
hydrologic cycle
Descartes (1596-1650) Vapors are drawn up from the earth
and condensed…
Kircher (1615-1680) Water from the ocean is vaporized by
the hot earth, rises, and condenses inside mountains.
Old Theories (Cont.)
• Vitruvius (~80-20 BC) – 8th Book on Water and Aqueducts.
Rain and snow on land reappears as springs and rivers
• Palissy (1509-1590). – French scientist and potter - accurate
representation of the hydrologic cycle
• Perrault (1670): – Water balance on the Seine. River
flow explained by rainfall.
• Mariotte (1620-1684). – French physicist. First recharge
estimates. Leaky roof analogy.
• Vallisnieri (1723) – At lower altitudes in the Alps, artesian
wells are common. Higher altitudes in Alps, streams are losing water Groundwater originates from rain.
Modern Theories
• Henri Darcy (1856)– Relationship for the flow through
sand filters. Resistance of flow through aquifers. Solution for unsteady flow.
• King (1899)– Water table maps, groundwater
flow, cross-section
• Hazen, Slichter, O. E. Meinzer (1900s)
– Practical applications, basing on theoretical principles of French hydrogeology
• C.V. Theis (1930s)– Well Hydraulics
C.V. Theis
Henri Darcy
Global Water Resources
68.9% Glaciers & PermanentSnow Cover
29.9% FreshGround water
0.9% Other includingsoil moisture, swampwater and permafrost
97.5%Salt
Water
0.3% Freshwater Lakes &River Storage. Only this
portion is renewable
2.5% OF TOTAL GLOBAL (Freshwater)
TOTAL GLOBAL (Water)
Groundwater Management in IWRM: Training Manual, GW-MATE, 2010
Global Water Cycle
Principal sources of fresh water for
human activities(44,800 km3/yr)
Residence time:Average travel time for water through a subsystem of the hydrologic cycle
Tr = S/QStorage/flowrate
Atmospheric Moisture
Interception
Snowpack
Surface
Soil Moisture
Groundwater
Streams and Lakes
Runoff
RainSnow
Evaporation
Evapotranspiration
Evaporation
Throughfall and Stem Flow
Snowmelt
Infiltration
Overland Flow
Percolation
Groundwater Flow
Channel Flow
Pervious ImperviousWatershedBoundary
Energy
Hydrologic Cycle (Local view)
Our focus
Major Aquifers of Texas
Edwards
Ogallala
Edwards Aquifer
• Primary geologic unit is Edwards Limestone
• One of the most permeable and productive aquifers in the U.S.
• The aquifer occurs in 3 distinct segments:
• Contributing zone
• Recharge zone
• Artesian zone
Formation of Edwards Aquifer
Contributing Zone of Edwards Aquifer
• Located north and west of the aquifer in the region referred to as the Edwards Plateau or Texas Hill Country
• Largest part of the aquifer spanning 4400 sq. miles
• Water in this region travels to recharge zone
Recharge Zone of Edwards Aquifer
• Geologically known as the Balcones fault zone
• It consists of an abundance of Edwards Limestone that is exposed at the surface
-provides path for water to reach the artesian zone
Artesian Zone of Edwards Aquifer
• The artesian zone is a complex system of interconnected voids varying from microscopic pores to open caverns
• Located between two relatively less permeable layers that confine and pressurize the system
• Underlies 2100 square miles of land
The Edwards Group
Flowpaths of the Edwards Aquifer
The Ogallala Aquifer
• Approximately 170,000 wells draw water from the aquifer.
• Water level declines of 2-3 feet per year in some regions .
• Only 10% is restored by rainfall.
Example Ogallala Well Hydrograph
The Ogallala Aquifer
Water Level Change 1980 - 1994Water Level Change up to 1980
Summary
• Course Introduction and Housekeeping• Groundwater and Aqufiers
– Terminology– History
• Global Water Resources– Global Water Cycle
• Texas Aquifers– Edwards– Ogallala