San Marcos River

The San Marcos River bursts forth from the Edwards Aquifer through 200 spring openings at the bottom of Spring Lake in the heart of San Marcos, Texas. The river provides a refreshing playground for swimming, canoeing, and tubing. The San Marcos River winds through over 130 acres of parkland. The upper 3.8 miles of the headwaters provides habitat to eight endangered and threatened aquatic species, including the San Marcos Fountain Darter, Texas Blind Salamander, the San Marcos Salamander, the San Marcos Gambusia and Texas Wild Rice. Archaeologists have discovered artifacts that indicate that the area around the Springs is one of the oldest continuously inhabited places in North America by human beings, dating back more than 12,000 years.

Map of San Marcos River (PDF)

Blanco River

The primary source for the Blanco is a series of springs in northern Kendall County. The river flows generally eastward for 87 miles (140 kilometers) through Kendall County, Blanco County and Hays County. Near San Marcos, it takes a southerly turn and joins with the San Marcos River. The upper reaches of the Blanco River are hilly, and the river’s slopes are frequently steep. As the river reaches the Balcones Escarpment near San Marcos, it widens and slopes moderately; this is typical of rivers in the central part of the state. The river is usually quite shallow, and it briefly dips below ground in some areas in the Hill Country. As with many of the rivers in the Texas Hill Country, there is great variability in the Blanco River’s flow. The mean flow is 93 feet³/s (3 m³/s), but heavy rains in the river’s watershed can cause flash flooding with little warning. The Blanco River winds through over 200 acres of parkland.

Map of Blanco River (PDF)


The Edwards Aquifer Habitat Conservation Plan protects the endangered species of the Edwards Aquifer while providing for the needs of agriculture, industry and cities that rely on the aquifer for fresh water. For more information, visit the Habitat Conservation Plan.