San Marcos River level at Martindale
Texas · Tubing & floating
Measured at USGS 08171400 — San Marcos Rv nr Martindale, TX · NWS forecast point SMRT2
Reading taken · as of 43 min ago
Right around its normal summer float level
At 113 CFS, this gauge is inside the middle half of the 14 years USGS has recorded for this date (2011–2026), at 77% of the 146 CFS median.
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Flow history at Martindale
Daily values from USGS 08171400, updated every 15 to 60 minutes; NWS forecast for SMRT2 reissued through the day. Provisional.
Highest crests on record at Martindale
7 on record
| Stage | Flow | Date |
|---|---|---|
| 40.68 ft | 93,300 CFS | Oct 31, 2013 |
| 36.18 ft | — | Oct 30, 2015 |
| 26.23 ft | — | May 24, 2015 |
| 24.71 ft | 29,235 CFS | Oct 14, 2021 |
| 24.32 ft | 12,987 CFS | May 9, 2019 |
| 20.40 ft | 8,764 CFS | May 4, 2019 |
| 18.59 ft | — | May 18, 2015 |
Crests published by the National Weather Service.
About San Marcos River at Martindale
This gauge holds two records that seem to belong to different rivers. Its published monthly medians never leave the 150 to 180 CFS band at any point in the year. Its largest instantaneous peak is 93,300 CFS, reached twice: on 31 October 2013 at a stage of 40.68 feet, and again on 24 May 2015 at 40.39 feet.
That is a ratio of roughly 580 to one between the ordinary condition and the extreme, on a 547 square mile drainage. The flat baseline comes from spring flow; the peaks come from Texas storms landing on a basin that sheds them immediately. The published statistics cover 2011 to 2026, only about 15 years, so the median on this page is a shorter sample than most gauges here.
San Marcos River at Martindale — common questions
6 questions
How can a river with a 160 CFS median peak above 90,000?
Because the two numbers describe different regimes. The baseline is spring fed and remarkably constant, which is why the monthly medians sit between 150 and 180 CFS all year. The peaks are storm response on a basin that does not absorb much. The record shows 93,300 CFS on 31 October 2013 and again on 24 May 2015, and a daily mean of 18,000 CFS on the first of those dates.
How much history is behind the normal shown on this page?
About 15 years. USGS statistics for this station cover 2011 to 2026 and the daily series begins on 19 May 2011. That is a shorter window than most gauges on this site carry, so the percent of normal figure is drawn from a smaller sample. The record low daily mean in that window is 51.2 CFS, on 19 October 2022.
How does this reading compare with the San Marcos gauge upstream?
It is consistently a little larger and moves almost in step. Across 5,525 days of overlapping record since 2011 the two correlate at 0.859, and this gauge has carried a median of about 1.15 times the flow measured 6.8 miles upstream at San Marcos. The extra fifteen percent is what the reach between them contributes on an ordinary day.
Does rain upstream change San Marcos River at Martindale quickly?
Yes. It is free-flowing, so rain upstream moves it directly. Several feet in a few hours is normal after a heavy storm.
Is San Marcos River at Martindale high or low for this time of year?
The USGS median flow for late September here is 146 CFS, from 14 years of record (2011–2026). Today sits inside the middle half of those years, at 77% of the median. The comparison is what makes the raw number mean anything: the same reading is a drought on one river and a flood on another.
How often does this reading update?
USGS transmits from gauge 08171400 every 15 to 60 minutes, and the National Weather Service reissues the flood forecast for SMRT2 a few times a day — more often when the river is rising. This page refreshes from both when you open it. The timestamp is in the gauge's local time.