Edwards Aquifer

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Edwards Aquifer
08-10-26 - San Marcos River, San Marcos, TX, USA - downstream from the headwaters.jpg
Downstream from the headwaters of the San Marcos River
Country  United States
State  Texas
Region Texas Hill Country
District Edwards Plateau
Recharge zone 3,237 km2 (1,250 sq mi)
Geology Limestone karst[1]
Management Edwards Aquifer Authority
Website: Edwards Aquifer Website

The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of the Edwards Plateau in the U.S. state of Texas, it discharges about 900,000 acre feet (1.1 km3) of water a year and directly serves about two million people.[2] The Edwards Aquifer is also home to several unique and endangered species.


The aquifer's recharge zone,[3] where surface water enters the aquifer, follows the Balcones Fault line, from Brackettville (roughly along U.S. Highway 90), through San Antonio, and north to Austin along but a few miles west of Interstate 35. On certain stretches of highway in Austin and San Antonio, signs indicate that the driver is entering or leaving the recharge zone, as the zone's easternmost edge sits beneath heavy urban and suburban development.

Its contributing zone, where shed water is transported near the surface to the recharge zone, extends about 40 miles (64 km) north of the recharge zone at the west end, and tapers to end at a point in the east. The artesian zone,[4] where water springs from wells naturally due to the higher elevation of the recharge zone, extends 10–20 miles (16–32 km) south on the west end to only a few miles south on the east end. Across the eastern half of the aquifer, the recharge and artesian zones occupy common area.


The plentiful water provided by rivers fed from the Edwards Aquifer[5] is the primary reason Spanish missionaries were able to establish so many missions, like the Alamo Mission in San Antonio. Later, immigrants found the Texas Hill Country welcoming because of the food, energy, and water provided by these rivers. Without this supply in the arid plateau, early colonization would have been far more difficult. Cities[4] like San Antonio, New Braunfels, and San Marcos have been able to support large populations without the need to develop surface water resources. Farmers, ranchers, industrial and other downstream users benefit greatly from the underground water that flows out of natural springs into surface water sources (i.e. Guadalupe River) when the aquifer is full.


The Edwards Aquifer is home to several endemic cave-dwellers, including the widemouth blindcat (Satan eurystomus),[6] Texas blind salamander (Eurycea rathbuni),[7] Robber Baron cave harvestman (Texella cokendolpheri),[8] helotes mold beetle (Batrisodes venyivi),[8] and the Robber Baron cave meshweaver (Cicurina baronia).[9] These animals are underdeveloped and essentially eyeless. Springs fed by the aquifer are also home to many unique species, such as the Fountain darter (Etheostoma fonticola),[10] the possibly-extinct San Marcos gambusia (Gambusia georgei), the San Marcos salamander (Eurycea nana),[10] and the Barton Springs salamander (Eurycea sosorum).[11] Texas Wild Rice (Zizania texana)[12] is restricted to the upper San Marcos River.

Recharge zone[edit]

The Aquifer has a recharge zone[3] of 1,250 square miles (3,200 km2). Most of the water (75%-80%) that is in the Aquifer originated from some of the creeks and rivers flowing in the area. Two creeks that flow into the Aquifer are the Cibolo and Helotes Creeks.

See also[edit]


  1. ^ "The Edwards Aquifer". Environmental Science Institute. The University of Texas at Austin. Retrieved 2013-01-24. 
  2. ^ Eckhardt, G. (2010). "Numeric Data for Charts and Graphs". The Edwards Aquifer Website. 
  3. ^ a b "Edwards Aquifer Recharge Zone". Texas Commission on Environmental Quality. Retrieved 12 May 2010.  Texas Commission on Environmental Quality
  4. ^ a b "The Edwards Aquifer". San Antonio Water System. Retrieved 12 May 2010.  San Antonio Water System
  5. ^ Mitchell, Sarah Scott; Schmiedeskamp, Carl (2004). The Edwards Aquifer: Hidden Heart of Texas Map. Save Our Springs Alliance. ISBN 978-1-58611-238-7. 
  6. ^ Longley, Glenn: Widemouth Blindcat from the Handbook of Texas Online. Retrieved 12 May 2010. Texas State Historical Association
  7. ^ "Texas Blind Salamander". Texas Parks and Wildlife Department. Retrieved 12 May 2010.  Texas Parks and Wildlife Department
  8. ^ a b Quinn, Mike. "Texas Endangered Invertebrate Species". Texas Entomology. Retrieved 12 May 2010. 
  9. ^ Quinn, Mike. "Nine Bexar County Endangered Invertebrate Species". Texas Entomology. Retrieved 12 May 2010. 
  10. ^ a b "Endangered Species of the Edwards Aquifer". Edwards Aquifer. Retrieved 12 May 2010.  Edwards Aquifer
  11. ^ "Barton Springs Salamander". City of Austin, Texas. Retrieved 12 May 2010.  City of Austin, Texas
  12. ^ "Texas Wild Rice". Texas Parks and Wildlife Department. Retrieved 12 May 2010.  Texas Parks and Wildlife Department

External links[edit]