San Antonio River
SAN ANTONIO RIVER. The San Antonio River rises in a cluster of springs in north central San Antonio (in central Bexar County) approximately four miles north of downtown (at 29° 28' N, 98° 29' W). Olmos Creek empties into the river just below its head, and other springs continue to join as the river flows through the city. From San Antonio, the river flows southeast 180 miles through Wilson, Karnes, and Goliad counties and then forms the county line between Victoria and Refugio counties. It empties into the Guadalupe River four miles north of Tivoli at the intersection of the Calhoun, Refugio, and Victoria county lines (at 28° 30' N, 96° 53' W). Along its course the river traverses flat to gently rolling terrain surfaced by clay and sandy loams that support mesquite, live oak, cacti, and grasses. The spring flow of the San Antonio and its principal tributaries, the Medina River and Cibolo Creek, makes the volume of the river steadier than that of most Texas streams. The San Antonio River is dammed to form two artificial reservoirs in the San Antonio area. One near the head of the stream, impounded by Olmos Dam, has a capacity of 15,500 acre-feet and is used solely for flood control. The other reservoir, Lake Blue Wing, ten miles south of San Antonio, has a capacity of 1,000 acre-feet and is used for irrigation.
Full article on the Texas State Historical Association's Handbook of Texas Online