South Fork Snake River level at Irwin
Idaho · Fishing & wading
Measured at USGS 13032500 — SNAKE RIVER NR IRWIN ID · NWS forecast point PALI1
Reading taken · as of 58 min ago
Below normal — good wading, low and clear
At 4,050 CFS, this gauge is in the lowest quarter of the 80 years USGS has recorded for this date (1935–2026), at 74% of the 5,510 CFS median.
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Flood stages at Irwin
National Weather Service categories for gauge PALI1, WFO PIH. Impact wording is the NWS's own, verbatim.
-
Action 11.0 ft · 20,688 CFS
- 11.0 ft Fields aand low-lying areas near the river from Palisades Dam downstream to near Table Rock Canyon area may experience seep and ponding.
- Right now 6.19 ft
NWS forecast: 6.19 ft by .
Flow history at Irwin
Daily values from USGS 13032500, updated every 15 to 60 minutes; NWS forecast for PALI1 reissued through the day. Provisional.
Highest crests on record at Irwin
12 on record
| Stage | Flow | Date |
|---|---|---|
| 15.25 ft | 41,800 CFS | Jun 20, 1997 |
| 15.01 ft | 40,400 CFS | Jun 19, 1997 |
| 13.31 ft | 31,800 CFS | Jun 4, 1956 |
| 13.18 ft | 31,200 CFS | Jun 28, 1954 |
| 12.69 ft | 28,800 CFS | May 29, 1951 |
| 12.52 ft | 27,800 CFS | Jul 3, 1950 |
| 12.26 ft | 25,400 CFS | Jun 25, 1974 |
| 11.91 ft | 24,500 CFS | Jun 13, 2017 |
| 11.90 ft | 24,200 CFS | Jul 15, 2011 |
| 11.78 ft | 23,800 CFS | Jun 29, 2009 |
Crests published by the National Weather Service.
About South Fork Snake River at Irwin
This gauge runs high in summer and low in winter, which is backwards for a mountain river and is the clearest evidence of what controls it. Published monthly medians read 13,400 CFS in June, 12,900 in July and 8,940 in August, then fall to 3,010 in October and 1,450 by December. Below Palisades Dam the high water is held through the irrigation season rather than released with the snowmelt.
The record low says the same thing from the other end: 19 CFS on 8 November 1956, on a basin of 5,225 square miles. No drought produces that on a drainage that size. Daily statistics cover 1935 to 2026, about 79 years, and the record high is 40,300 CFS on 20 June 1997, the same event as the largest of the eighty-three annual peaks on file, 40,400 CFS at 15.25 feet.
South Fork Snake River at Irwin — common questions
6 questions
Why is the flow highest in June and July?
Because the station sits below Palisades Dam and the summer figure is a release rather than runoff. The published medians hold above 8,900 CFS from May through August and fall below 1,700 from November through March. On an unregulated river at this elevation you would expect the peak in late May or June and a steady decline after it, not a plateau into August.
How can a 5,225 square mile basin read 19 CFS?
It cannot, naturally. That daily mean, from 8 November 1956, is a management figure, and it is the lowest value in a 79-year record. It is worth keeping in mind when reading the record range on this page: the bottom of that range describes an operating decision rather than the driest the country above the gauge has ever been.
What are the flood categories here?
Only action stage, at 11 feet, with minor, moderate and major not published. The impact statement at 11 feet notes that fields and low-lying areas from Palisades Dam downstream toward Table Rock Canyon may see seep and ponding. Twelve crests are on file, topped by 15.25 and 15.01 feet on consecutive days in June 1997.
What makes the flow change on South Fork Snake River at Irwin?
Rain upstream, plus seasonal baseflow. The 12-month chart shows how it behaves through the year.
Is South Fork Snake River at Irwin high or low for this time of year?
The USGS median flow for late September here is 5,510 CFS, from 80 years of record (1935–2026). Today sits in the lowest quarter of those years, at 74% 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 13032500 every 15 to 60 minutes, and the National Weather Service reissues the flood forecast for PALI1 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.