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