Major Flood
30 ft
Current Water Level
Gage Height
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Streamflow
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Last Reading
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FLOOD STAGES
Know the flood categories.
Flood stages defined by the National Weather Service. Gage height data from USGS Water Resources.
Moderate Flood
24 ft
Minor Flood
18 ft
Action Stage
13 ft
What Floods at Each Level
43 ft
Water is several inches deep in the Walmart and CVS parking lots and other business in the region. Water surrounds the Balnco River Lodge apartments. Water into many homes and businesses along the river between I-35, SH 80 and River road. Water over teh Hwy 80 bridge at San Marcos
30 ft
Water begins to enter many homes and businesses begin to have water entering the structures. More secondary and even primary raods become impassable for vehicles
24 ft
Lowest homes are threatened. Water beings to cut off secondary roads near the river
18 ft
Roadways and low bridges along the river are flooded. Vehicles cannot pass. Livestock can be stranded.
13 ft
Overbank conditions may cut off livestock and low bridges near the river
Impact statements from the National Weather Service, describing what typically happens at each water level.
7-Day Water Level Chart
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Historic Crests
| Date | Stage | Flow |
|---|---|---|
| May 24, 2015 | 43.1 ft | 136,888 cfs |
| Oct 30, 2015 | 42.56 ft | 132,205 cfs |
| Oct 14, 2021 | 24.71 ft | 29,235 cfs |
About This Gauge
Get Flood Alerts for Blanco River
StormCast monitors this gauge and sends a push notification to your phone when the water level crosses into a new flood category — even at 3 AM.
Frequently Asked Questions
What is the current water level of Blanco River at San Marcos?
The Blanco River at San Marcos gauge is maintained by USGS (site 08171350) and reports water levels every 15 minutes. Visit this page to see the latest reading updated live, or download StormCast to get push alerts when levels rise.
What is flood stage for Blanco River at San Marcos?
The NWS-defined flood stage for Blanco River at San Marcos is 18 feet. Action stage begins at 13 feet. Moderate flooding starts at 24 feet, and major flooding at 30 feet.
How do I get alerts when Blanco River rises?
Download StormCast free on Google Play, go to River Gauges, and add Blanco River at San Marcos to your watchlist. StormCast will send a push notification to your phone whenever the water level crosses into a new NWS flood category.
Where is the Blanco River at San Marcos gauge located?
The gauge is located in Hays County, Texas at coordinates 29.8794°N, 97.9106°W. USGS site number: 08171350. Data is provided by the U.S. Geological Survey and the National Weather Service.
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Source & Notes
Data provided by: US Geological Survey, Observations courtesy of U.S. Geological Survey
- River forecasts for this location take into account past precipitation and the precipitation amounts expected approximately 24 hours into the future from the forecast issuance time.