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San Antonio River Basin

The San Antonio River Basin

The San Antonio River Basin is a dynamic ecosystem with rivers, creeks and streams that can quickly be impacted by rain events and other weather conditions. Human activities within the basin may also affect water conditions.

The San Antonio River Basin drains a land area of 4,180 square miles. The basin extends from Kerr and Medina counties in the Texas Hill Country southeast toward the Gulf of Mexico. It drains approximately half of Medina County to the far northwest; the majority of Bexar, Wilson and Karnes counties, which comprise the central portion of the basin; approximately one third of Goliad County to the southeast; and parts of Bandera, Kendall, Comal, Guadalupe, DeWitt, Kerr, Atascosa, Victoria and Refugio counties.

The basin’s major watersheds are:

  • Medina River Watershed
  • Leon Creek Watershed
  • Upper San Antonio River Watershed
  • Salado Creek Watershed
  • Cibolo Creek Watershed
  • Lower San Antonio River Watershed

The map below shows how these watersheds drain toward the Gulf of Mexico.

San Antonio River Basin Watershed map

The San Antonio River is the basin’s major river, flowing 240 miles from its headwaters in San Antonio, Bexar County, to its confluence with the Guadalupe River in Refugio County. Approximately 11 miles downriver of the confluence, the Guadalupe drains into the San Antonio Bay and the Gulf of Mexico.

Interesting San Antonio River Facts

  • Spring water from the Edwards Aquifer in Bexar County forms the humble origin of the San Antonio River, which has been home to indigenous peoples for over 12,000 years. There are numerous springs in the headwaters area, the largest and most well-known is the Blue Hole on the University of the Incarnate Word campus north of downtown San Antonio.
  • The Blue Hole is an artesian spring at approximately 670 feet above sea level fed by the Edwards Aquifer.
  • The San Antonio River flows 240 miles through Bexar, Wilson, Karnes, Goliad and Refugio counties, converging with the Guadalupe River before finally flowing into San Antonio Bay on the Gulf of Mexico.
  • Common mammals seen along the San Antonio River Basin riparian corridor include the common raccoon, Eastern Fox squirrels, Virginia opossums, White-tail deer, Nine-banded armadillos, Eastern Cottontail rabbits and feral hogs.
  • The San Antonio River carries surface water from 2,500-foot elevations within the Texas Hill Country of Bandera and Kerr counties to less than 100-foot elevations in Refugio County.
  • The San Antonio River watershed includes parts of Atascosa, Bandera, Bexar, Comal, Dewitt, Goliad, Guadalupe, Karnes, Kendall, Kerr, Medina, Refugio, Victoria and Wilson Counties.
  • The San Antonio River Basin is one of 23 major basins in Texas and drains over 4,194 square miles.
  • San Antonio River Basin contains over 8,800 miles of streams.