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Aquifers/Edwards Aquifer

Aquifers/Edwards Aquifer. What is an Aquifer ? A body of rock, sediment, or soil that contains drinkable water and can transmit this water to wells or springs. 3 Major Types of Aquifers. 1. Unconfined (most common) 2. Confined

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Aquifers/Edwards Aquifer

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  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.

  3. 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

  4. Unconfined Aquifer Water seeps through porous materials near the surface, but is trapped by impermeable rock below.

  5. 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

  6. 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

  7. Karst Aquifer 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

  8. Texas has 9 Major Aquifers

  9. Edwards Aquifer in Bexar County

  10. Edwards Aquifer Aquifer Region and Authority Boundaries Source: Edwards Aquifer Authority, 2002

  11. Edwards Aquifer Cross Section

  12. Geologic History About 17 million years ago, the aquifer rocks were uplifted and faulted, forming the Balcones Escarpment. They became subject to erosion and dissolution. http://www.watersheds.org/earth/karstmovie.htm

  13. Recharge Zone • Water enters the aquifer through faults, fractures, sinkholes, or percolation through the soil. This process is called recharge. • The recharge zoneis the area where water enters the aquifer.

  14. Caves Associated With the Edwards Aquifer Inner Space Cavern Austin, TX Devil’s Sinkhole State Natural Area Rocksprings, TX Natural Bridge Caverns Natural Bridge Caverns, TX Kickapoo Caverns State Park Brackettville, TX

  15. Flowpaths of the Edwards Aquifer Why does the water flow in the direction shown in the figure? Elevation

  16. How does the water come out & who uses it? Aquarina Springs San Marcos, TX 1 Million gallons of water released from the ground per day Wells & Springs

  17. Austin Barton (main) SpringAustin, TX

  18. San Marcos San Marcos SpringsSan Marcos, TX

  19. Del Rio San Felipe SpringsDel Rio, TX

  20. Water Supply Problems • Water Quantity – • Spring runoff is highly dependent on rainfall • Not enough recharge times between drought • Edwards aquifer holds a huge amount of water but: At less than 95% capacity, the springs run dry • Endemic fauna and flora inhabit springs and caves so these species are vulnerable to extinction if water levels get too low.

  21. Water Supply Problems • Water Quality - • Vulnerable because aquifer is relatively shallow • Little reaction time in case of a spill • Clean-up of local threats almost impossible • Aquifer has a low self-cleaning ability (natural remediation)

  22. Water Supply Problems Sources of Pollution - http://www.watersheds.org/earth/karstmovie.htm

  23. Environmental Impact 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. Endangered Comal Springs Dryopid Beetle Comal Springs Riffle Beetle Fountain Darter Peck’s Cave Amphipod San Marcos Gambusia Texas Blind Salamander Texas wild-rice Threatened San Marcos Salamander

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