1 aquifers/edwards aquifer. 2 what is an aquifer? a body of rock, sediment, or soil that contains...
TRANSCRIPT
1
Aquifers/Edwards Aquifer
2
What is an Aquifer?
A body of rock, sediment, or soil that contains drinkable water and can transmit this water to wells or springs in economically usable quantities
3 Major Types of Aquifers
1. Unconfined (most common)
2. Confined
3. Karst: a special type that occurs in
limestone rocks when a system of caves
is connected and water is flowing
through it. –Edwards Aquifer
Unconfined Aquifer
Water seeps through porous materials near the surface, but is trapped by impermeable rock below.
Confined Aquifer
Impermeable rock above and below. Rock strata must bend and outcrop at surface for rain to recharge porous material in between.
Water will pressurize if higher than well heads – artesian system
Karst Aquifer
Develops in thick limestone formations, usually in humid climates. Karst has both surface and subsurface features.
http://www.watersheds.org/earth/Sinkholes.html
Water naturally goes underground through sinkholes to caves (solution caverns).
Rainwater is slightly acidic and dissolves limestone rock to calcium carbonate & carries it away (dissolution).
Causes stalactite, stalagmite, & pillar formations in caverns
Karst Aquifer
8
Recharge Zone
Drainage Area
Artesian Zone
Source: Edwards Aquifer Authority, 2002
Edwards AquiferAquifer Region and Authority Boundaries
Edwards Aquifer in Bexar County
Geologic HistoryAbout 17 million years ago, the aquifer rockswere uplifted and faulted, forming the BalconesEscarpment. They became subject to erosion anddissolution.
http://www.watersheds.org/earth/karstmovie.htm
Edwards Aquifer Cross Section
Recharge Zone
• Water enters the aquifer through faults, fractures, sinkholes, or percolation through the soil. This process is called recharge.
• The recharge zone is the area where water enters the aquifer.
Caves Associated With the Edwards Aquifer
Devil’s Sinkhole State Natural Area
Rocksprings, TX
Natural Bridge CavernsNatural Bridge Caverns,
TX
Kickapoo Caverns State ParkBrackettville, TX
Inner Space CavernAustin, TX
Flowpaths of the Edwards Aquifer
Why does the water flow in the direction shown in the figure? Elevation
The aquifer contains severalflow systems – One occursnear Del Rio
Flowpaths of the Edwards Aquifer
Flowpaths of the Edwards Aquifer
The largest flow system runsfrom near Brackettville to nearKyle…
… and supplies the major springs at
San Marcos, New Braunfels, andSan Antonio.
Flowpaths of the Edwards Aquifer
Smaller flow systems include theBarton springs flow system…
Flowpaths of the Edwards Aquifer
Flowpaths of the Edwards Aquifer
…and areas north of the
Colorado River .
How does the water come out & who uses it?
Aquarina SpringsSan Marcos, TX
1 Million gallons of water released from the ground per day
Wells & Springs
Barton (main) Spring
Austin, TX
Austin
San Marcos Springs
San Marcos, TX
San Marcos
24
Del Rio
San Felipe
SpringsDel Rio,
TX
Water Supply Problems
Water Supply Problems
http://www.watersheds.org/earth/karstmovie.htm
EndangeredComal Springs Dryopid Beetle
Comal Springs Riffle Beetle
Fountain Darter
Peck’s Cave Amphipod
San Marcos Gambusia
Texas Blind Salamander
Texas wild-rice
ThreatenedSan Marcos Salamander
Eight species in the Edwards Aquifer, Comal Springs, and San Marcos Springs ecosystems are currently listed by the U.S. Department of Interior, Fish and Wildlife Service, as either
threatened or endangered species.
Environmental Impact