Edwards Aquifer

Edwards Aquifer
Texas
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
Map of Edwards-Trinity aquifer system
Website: Edwards Aquifer Website

The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of 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.

Geography

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.

Economy

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 and ranchers south of the aquifer benefit greatly or entirely from the irrigation possible from these rivers.

The community of Barnhart, in Irion County, has depleted the accessible aquifer due to heavy water extraction for fracking and agriculture.^[6]

Ecology

The Edwards Aquifer is home to several endemic cave-dwellers, including the widemouth blindcat (Satan eurystomus),^[7] Texas blind salamander (Eurycea rathbuni),^[8] Robber Baron cave harvestman (Texella cokendolpheri),^[9] helotes mold beetle (Batrisodes venyivi),^[9] and the Robber Baron cave meshweaver (Cicurina baronia).^[10] These animals are either completely without eyes or their eyes are so underdeveloped that they are essentially eyeless. Springs fed by the aquifer are also home to many unique species, such as the Fountain darter (Etheostoma fonticola),^[11] the possibly-extinct San Marcos gambusia (Gambusia georgei), the San Marcos salamander (Eurycea nana),^[11] and the Barton Springs salamander (Eurycea sosorum).^[12] Texas Wild Rice (Zizania texana)^[13] is restricted to the upper San Marcos River.

Recharge Zone

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

Notes

External links

• Edwards Aquifer Authority
• Handbook of Texas Online, s.v. "EDWARDS UNDERGROUND WATER DISTRICT,"
• Edwards Aquifer Home Page, Gregg Eckhardt
• Endangered Species of the Edwards Aquifer
• Save Our Springs Alliance - Edwards Aquifer Protection Plan
• Greater Edwards Aquifer Alliance
• Edwards Aquifer Guide University of Texas Library

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