Texas · Luling, TX
San Marcos River float season
Gauge 08172000 on the Lower San Marcos along the Zedler Mill Paddling Trail into Luling. The lower San Marcos slows into a shady canoe trail that finishes at the photogenic old Zedler Mill dam, with Luling barbecue waiting in town.
Right now at this gauge
loading CFS
Checking the live gauge…
Well above typical for this date
Live reading from the USGS gauge page for San Marcos River. Provisional data — subject to revision.
The year on this river
In a typical year at the Luling gauge, the San Marcos River runs fullest Apr–Jun and leanest Aug–Oct. Where today's reading falls inside that rhythm matters more than the raw number — the same flow that feels thin in spring can be the summer norm. Half of all past May days at this gauge ran above 271 CFS; the August median is 166 CFS.
| Month | Typical flow (CFS) | Relative volume |
|---|---|---|
| January | 231 | |
| February | 220 | |
| March | 230 | |
| April | 254 | |
| May | 271 | |
| June | 242 | |
| July | 199 | |
| August | 166 | |
| September | 178 | |
| October | 185 | |
| November | 198 | |
| December | 190 |
Record context
This gauge has measured daily flow since 1984 — 42 years of record. The largest daily average ever logged here was 90,500 CFS, in October 1999. Rivers do that sometimes; it's why the safety panel above isn't decoration.
Planning dates? The trip-window checker shows what flows have historically looked like on any week you pick for this river, or see what a CFS actually looks like.
More Texas float rivers
-
Blanco River
Wimberley through the cypress-lined bends toward Five Mile Dam near Kyle
Fullest: Mar–May
-
Brazos River
Below Morris Sheppard Dam at Possum Kingdom down to the Highway 180 bridge
Fullest: Jun–Aug
-
Colorado River
El Camino Real paddling trail from Bastrop toward Smithville
Fullest: May–Jul
-
Comal River
Prince Solms Park through the Tube Chute to the Guadalupe confluence
Fullest: Jan–Mar
-
Frio River
Garner State Park through the Concan crossings
Fullest: Mar–May
-
Guadalupe River
Canyon Dam tailrace from Sattler through the Horseshoe Loop toward New Braunfels
Fullest: Apr–Jun
Common questions
When is the San Marcos River usually at its fullest?
At the Luling gauge, the fullest stretch of a typical year is Apr–Jun, with the single highest monthly median in May (about 271 CFS). The leanest months are usually Aug–Oct.
What is a typical summer flow on the San Marcos River?
The July median at this gauge is about 199 CFS — half of past Julys ran higher, half lower. Late summer is this river's lean season, so expect readings to drift down as the season goes on.
Is the San Marcos River safe to float right now?
No flow number can answer that, and this site never labels a river safe. What the data can tell you is how today's reading compares with 42 years of this date's history — well above typical means pushier, colder, faster water. Pair that context with a PFD, a look at the river from the bank, and a call to a local outfitter before you commit.
Which USGS gauge does this page use?
USGS gauge 08172000 (San Marcos Rv at Luling, TX), chosen because it best represents the Lower San Marcos along the Zedler Mill Paddling Trail into Luling. Daily records here reach back to 1984.
Data: USGS gauge 08172000, approved daily records 1984–2026, retrieved 2026-08-07. Live readings are provisional and subject to revision. U.S. Geological Survey data is public domain.