About the Edwards Aquifer


Physical Address
Municipal Plaza Building
114 W. Commerce, 10th Floor
San Antonio, TX 78205

Mailing Address
P.O. Box 839966
San Antonio, TX 78283-3966

210.207.3003 (Phillip Covington)
210.207.2162 (Susan Courage)
210.207.2810 (David Bernal)
210.207.2815 (Grant Ellis)


The Edwards Aquifer provides San Antonio with an abundant source of groundwater vital to the livelihood of a growing population and an expanding economy. It stretches across thousands of acres over several counties in South Central Texas. Roughly 70 percent of the recharge zone is located west of Bexar County. Rainfall enters the aquifer through fractures, caves, sinkholes and other features and replenishes the aquifer. However, rapid growth and development continue to impact the aquifer, reducing the number of recharge features needed to maintain San Antonio's primary water resource. While rules are in place to regulate development and pollution, the best way to protect the aquifer is to conserve the sensitive and irreplaceable land located over its recharge and contributing zones. 

2000 Proposition 3
water hose

Voters first approved a 1/8-of-a-cent addition to the local sales tax in 2000 to collect $45 million to purchase sensitive properties located over the Edwards Aquifer. Before this election, there was no program designed to identify and protect sensitive land located over the aquifer. This was a parks and watershed program and, due to restrictions in state legislation, protection efforts under the Proposition 3 program were limited to Bexar County.

The majority of these funds (approximately $38 million) were used to acquire almost 6,500 acres of land. Many of the properties were former ranches and estates characterized by unique natural and man-made features and hilltops with long, scenic views. The properties range in size from 50 to 1,164 acres and are located primarily over north central and northwest Bexar County. Properties will be turned into natural areas for hiking and nature appreciation and will become distinctive pieces of San Antonio's municipal park system. Remaining funds were used for park operations and maintenance and for appropriate improvements designed for recreational and educational purposes. 

2005 Proposition 1

In 2005, voters again approved a 1/8-of-a-cent addition to the local sales tax, this time to collect $90 million for the purchase of sensitive properties located over the Edwards Aquifer. Due to changes in the state legislation, funds collected through the 2005 Edwards watershed protection initiative, titled Proposition 1, were used to acquire and preserve the most environmentally-sensitive properties located over the aquifer within Bexar County and beyond county lines.

Careful consideration was given to the selection of appropriate properties for acquisition as part of the Edwards Protection Program. A Scientific Evaluation Team (SET) consisting of aquifer experts convened to prioritize undeveloped properties based on their environmental characteristics in order to achieve maximum value for voter-approved dollars.   The SET is comprised of scientific experts representing various disciplines from an assortment of agencies and institutions, including the Edwards Aquifer Authority, the U.S. Fish and Wildlife Service, the U.S. Geological Survey and the San Antonio Water System.  The SET produced a GIS-based model to identify and rank sensitive properties for inclusion in the Edwards Aquifer Protection Program. The SET model serves as a decision-making tool for the the program's Conservation Advisory Board (CAB) and Land Acquisition Team (LAT) to assist in identifying properties that may be considered for the conservation easement program. The model uses a variety of indicators to identify properties that contain unique and desirable features that warrant long term protection based on attributes that are valuable to enhancing water quality and quantity over sensitive areas of the Edwards Aquifer. The model utilizes multiple datasets that reflect the most current information regarding items such as: permeability of the Edwards limestone below the surface; the streams and creeks flowing over the surface; the types of plants present; and the adjacency to existing preserved open spaces. 

Following acquisition, the environmental characteristics of each of the protected properties are monitored and evaluated on an annual basis to ensure compliance with aquifer protection program guidelines and restrictions.

2010 Proposition 1

In November 2010, voters approved the continuation of the 2005 sales tax (up to $90 million) for the Edwards Aquifer Protection Program.  Under Proposition 1, the City of San Antonio continued the watershed protection and preservation projects initiated in 2000 and continued in 2005 for preservation of sensitive land across strategic areas of the aquifer's recharge and contributing zones. 


In May 2015, voters approved the continuation of the 2005 sales tax (up to $100 million) for the Edwards Aquifer Protection Program. Under Proposition 1, the City of San Antonio will continue the watershed protection and preservation projects initiated in 2000 and continued through 2010. In addition to the $90 million set aside for watershed protection and preservation of sensitive land over the aquifer's recharge and contributing zones, $10 million will be used to create new protection zones within urban areas of Bexar County with the intention of safeguarding the city's drinking water.  By working with scientists, conservationists, landowners, and concerned citizens, the City of San Antonio looks forward to building on the success of the past aquifer protection initiatives.