Guadalupe River Basin

The Guadalupe River Basin begins in the Texas Hill country before crossing the Balcones Escarpment on its way to the Texas Coastal Plains and the Gulf of Mexico. Major tributaries to the Guadalupe River Basin include the San Marcos and Comal Rivers. The Guadalupe River Basin is relatively long and narrow, with a length of approximately 237 miles and a maximum width of about 50 miles. The basin has a drainage area of approximately 6,700 square miles (mi2).

Flash flooding is a frequent problem, especially in the northern part of the basin, as the steep topography produces rapidly rising river stages during storm periods, leaving residents with little warning time.

Although the climate over the Guadalupe River Basin is generally mild, the southern portion of the basin can be impacted from hurricanes that come through the Gulf of Mexico. The mean annual precipitation over the Guadalupe River Basin ranges from 26 to 40 inches, increasing from the west to southeast.

Available streamflow records show that major floods have occurred over nearly all sections of the Guadalupe River Basin. While there have been scattered floods throughout the basin’s nearly 150-year history, the last 20 years has shown an uptick in the frequency and magnitude of devastating floods, including major floods in 2002, 1998, and 2015.

For more information, refer to the Guadalupe River Basin Assessment Report

Interactive Basin Map

Analyzed locations are also shown on the WHAV map.

Analyzed Locations

Select the name to open detail pages for each location. For USGS streamgage locations, select the USGS streamgage number to open the real-time data page for that streamgage.

Name Site type USGS Site ID Drainage Area (mi2) Recommended Method (Method Descriptions)

Based on data published in the Watershed Hydrology Assessment for the Guadalupe River Basin report.

Site names and drainage areas displayed on the website are based on the Watershed Hydrology Assessment for the Guadalupe River Basin. For USGS streamgages, these may not exactly match the official USGS names or drainage areas for a given location. In addition, the drainage areas shown in this application are rounded to the nearest whole number. For locations downstream from Canyon Lake dam, drainage area values include only the uncontrolled area downstream from the reservoir.