Streamflow and Springflow at Comal and San Marcos Rivers

About the Springs

Comal Springs and Comal River

Comal Springs of Central Texas are the largest springs in the southwestern United States. The artesian springs emerge at the base of an escarpment formed by the Comal Springs fault. The Comal River is approximately 2 miles long and is a tributary of the Guadalupe River.

In addition to being an important economic resource of the region, the springs and associated river system are home to unique aquatic threatened native species, such as:

Modified from USGS Fact Sheet 099-97, Water Quality Assessment of the Comal Springs Riverine System, New Braunfels, Texas, 1993-94

Monitoring history

USGS 08169000, Comal River at New Braunfels

  • 1882 to Nov. 1927 (discharge measurements only)
  • Dec. 1927 to Sept. 1932 (daily mean discharges below base, and stage-discharge relation is not affected by backwater from Guadalupe River)
  • Oct. 1932 to current year

USGS 08168710, Comal Springs at New Braunfels

  • Dec. 1927 to Sept. 1932 (fragmentary daily springflow discharges)
  • Oct. 1932 to current year
Two of the main springs for Comal Springs
Two of the main orifices of Comal Springs. There are many other orifices where springs discharge from the Edwards aquifer, including several under Landa Lake.

San Marcos Springs and San Marcos River

San Marcos Springs is the second largest spring in Texas and is the headwaters for the San Marcos River in San Marcos.Spring Lake was built in 1848 at the site of a marsh formed by the springs to provide hydropower to a mill. The San Marcos River originates from the 15-acre lake and flows approximately 4 river miles (mi) south to its confluence with the Blanco River.

The water from San Marcos Springs is some of the most pristine in Texas. In addition to being a valued economic and recreational resource to the region, San Marcos Springs and the associated riverine system provide habitat to several unique threatened or endangered native species, such as:

Modified from USGS Fact Sheet 059-97, Water-Quality Summary of the San Marcos Springs Riverine System, San Marcos, Texas, July-August 1994

Monitoring history

USGS 08170500, San Marcos River at San Marcos

  • July 1915 to Sept. 1921 (daily mean discharges below base discharge)
  • May to Sept. 1956
  • Oct. 1994 to current year

USGS 08170000, San Marcos Springs at San Marcos

  • May 1956 to current year
Spring Lake in San Marcos
Spring Lake at San Marcos is entirely sourced from spring water. The San Marcos springs issue from the Edwards aquifer at the bottom of the lake.