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 |
| 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.
Contents
Basin Characteristics[edit]
Geography[edit]
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.
Climate[edit]
The Edwards aquifer lies beneath part of the Edwards Plateau[5] and thus the climate of the Edwards Plateau can be used to describe the climate in the aquifer's region. The average annual temperature on the Edwards Plateau is 66 degrees Fahrenheit and the average annual precipitation amounts to 25.24 inches.[6] The temperatures vary by season with the lowest average temperature occurring in January, 50 degrees Fahrenheit, and the highest temperature occurring in July or August, nearing 85 degrees Fahrenheit for both months.[6] Conversely, January is the month with the lowest precipitation, averaging 1 inch, while May and September average the most, 3 inches.[6] The proximity of the Edwards Plateau to the Gulf of Mexico and its location in the middle latitudes creates variation in the weather patterns experienced between different years, seasons, and months.[6]
Economy[edit]
The plentiful water provided by rivers fed from the Edwards Aquifer[7] 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.
Ecology[edit]
The Edwards Aquifer is home to several endemic cave-dwellers, including the widemouth blindcat (Satan eurystomus),[8] Texas blind salamander (Eurycea rathbuni),[9] Robber Baron cave harvestman (Texella cokendolpheri),[10] helotes mold beetle (Batrisodes venyivi),[10] and the Robber Baron cave meshweaver (Cicurina baronia).[11] 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),[12] the possibly-extinct San Marcos gambusia (Gambusia georgei), the San Marcos salamander (Eurycea nana),[12] and the Barton Springs salamander (Eurycea sosorum).[13] Texas Wild Rice (Zizania texana)[14] 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.
Policy[edit]
Edwards Aquifer Authority regulates withdrawal permits, transfers, and groundwater conservation plans under authority granted by the Texas legislature. Groundwater law in the state of Texas is governed by the Rule of Capture, which gives landowners the right to pump groundwater beneath their land, with the exception of drilling a lateral well extending under a neighbor’s property, wasting water, or pumping with the intention of causing harm to a neighbor’s well.[15] In order to construct a well to withdraw water from the Edwards Aquifer, however, a user requires a permit that is granted by the Edwards Aquifer Authority. Permits for existing users are determined by maximum historical use, taking into consideration the overall availability of water in the aquifer.[16]
Wells that produce less than 25,000 gallons per day, wells that are solely for the purpose of watering livestock, and a few other exceptions are considered exempt wells that do not require a permit. Permits for withdrawal can be transferred to another user, provided that the new use is beneficial and occurs within the boundaries of the Authority, with a few geographical exceptions.
Groundwater conservation plans are required for permit holders who withdraw more than three acre feet per year (equivalent to 2,678 gallons per day), unless irrigators can prove more than 60 percent efficiency in their water use. Conservation plans require the use of Best Management Practices, as determined by the Edwards Aquifer Authority.[17]
In recharge zones of the aquifer permits are required to store regulated substances that could damage water quality. Additionally, The Texas Commission of Environmental Quality requires special permits for construction in the recharge zones of the aquifer.[18]
See also[edit]
Notes[edit]
- ^ "The Edwards Aquifer". Environmental Science Institute. The University of Texas at Austin. Retrieved 2013-01-24.
- ^ Eckhardt, G. (2010). "Numeric Data for Charts and Graphs". The Edwards Aquifer Website.
- ^ a b "Edwards Aquifer Recharge Zone". Texas Commission on Environmental Quality. Retrieved 12 May 2010. Texas Commission on Environmental Quality
- ^ a b "The Edwards Aquifer". San Antonio Water System. Retrieved 12 May 2010. San Antonio Water System
- ^ The Nature Conservancy of Texas (2008). "The Edwards Plateau Ecoregion: Extraordinary diversity of life amid hills and canyons in Central Texas" (PDF). Retrieved 2015.
- ^ a b c d South Central Climate Science Center (2013). "Drought History for the Edwards Plateau of Texas" (PDF). Retrieved 2015.
- ^ Mitchell, Sarah Scott; Schmiedeskamp, Carl (2004). The Edwards Aquifer: Hidden Heart of Texas Map. Save Our Springs Alliance. ISBN 978-1-58611-238-7.
- ^ Longley, Glenn: Widemouth Blindcat from the Handbook of Texas Online. Retrieved 12 May 2010. Texas State Historical Association
- ^ "Texas Blind Salamander". Texas Parks and Wildlife Department. Retrieved 12 May 2010. Texas Parks and Wildlife Department
- ^ a b Quinn, Mike. "Texas Endangered Invertebrate Species". Texas Entomology. Retrieved 12 May 2010.
- ^ Quinn, Mike. "Nine Bexar County Endangered Invertebrate Species". Texas Entomology. Retrieved 12 May 2010.
- ^ a b "Endangered Species of the Edwards Aquifer". Edwards Aquifer. Retrieved 12 May 2010. Edwards Aquifer
- ^ "Barton Springs Salamander". City of Austin, Texas. Retrieved 12 May 2010. City of Austin, Texas
- ^ "Texas Wild Rice". Texas Parks and Wildlife Department. Retrieved 12 May 2010. Texas Parks and Wildlife Department
- ^ "Texas water law". texaswater.tamu.edu. Retrieved 2015.
- ^ "Edwards Aquifer Authority". www.edwardsaquifer.org. Retrieved 2015.
- ^ "Rules and Statutes." Edwards Aquifer Authority. N.p., n.d. Web. 9 Oct. 2015.
- ^ "Texas Commission on Environmental Quality". Retrieved 2015.
External links[edit]
- 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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