Major Surface and Groundwater Features
The map of the 19-county Alamo region outlines the region’s major rivers, aquifers and coastal bays. Generally, the major aquifers are found side-by-side in bands oriented from northeast (upper right on the map) to southwest (the lower left of the map). The region’s major rivers flow perpendicular to the aquifers; that is, from the northwest or upper left of the map, to the southeast, in the lower right of the map.
Beginning at the upper left of the map and moving to the lower right, the map shows the Edwards-Trinity Plateau aquifer under the Hill Country counties of Gillespie, Kerr, Kendall and Bandera. Next is the Edwards Balcones Fault Zone (BFZ) underlying parts of Comal, Bexar and Medina counties. After the Edwards BFZ is the Carrizo-Wilcox aquifer under Medina, Bexar, Guadalupe, Gonzales, Wilson, Atascosa, Frio, Karnes and Dewitt counties. Along the coast is the Gulf Coast aquifer, underlying Gonzales, Karnes, Dewitt, Lavaca, Jackson, Victoria, Goliad and Calhoun counties.
The major rivers on the map include the Colorado, Guadalupe, Nueces, San Antonio and Lavaca, all flowing in a general southeastward direction from the Hill Country to the Gulf of Mexico; that is, from the upper left of the map toward the lower right.
For more information on this exhibit, please contact the Comptroller’s Data Services Division at 512-463-4900 or at P.O. Box 13528, Austin, Texas 78711-3528.
Source: Texas Water Develoment Board.