Henrys Fork at Island Park
Idaho · Fishing & wading
Measured at USGS 13042500 — HENRYS FORK NR ISLAND PARK ID · NWS forecast point ISLI1
Reading taken Jul 28, 11:45 PM UTC
Below normal — good wading, low and clear
At 891 CFS, this gauge is running 69% of normal for late July — below the 1,290 CFS median USGS has recorded for this date across 93 years of record (1933–2026).
Data-derived guidance from USGS and NWS published values — not official advice, and not a safety assessment.
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12 months of flow at Island Park
Daily values from USGS gauge 13042500. Provisional data, subject to revision.
Highest crests on record at Island Park
| Stage | Flow | Date |
|---|---|---|
| 6.15 ft | 2,770 CFS | Apr 26, 1946 |
| 6.06 ft | 3,030 CFS | May 23, 1984 |
| 5.96 ft | 2,580 CFS | Jun 1, 1943 |
| 5.87 ft | 2,560 CFS | Jul 18, 1955 |
| 5.85 ft | 2,580 CFS | Aug 26, 1983 |
| 5.82 ft | 2,700 CFS | May 18, 1982 |
| 5.80 ft | 2,040 CFS | Jul 21, 2015 |
| 5.80 ft | 2,610 CFS | May 13, 1971 |
| 5.80 ft | 2,430 CFS | Jun 9, 1999 |
| 5.45 ft | 1,930 CFS | Jul 30, 2013 |
Historical crests published by the National Weather Service for this gauge.
About Henrys Fork at Island Park
This gauge measures Henrys Fork at Island Park, Idaho — the reading paddlers, anglers and outfitters on this stretch check before committing to a shuttle.
Box Canyon and Last Chance; world-famous dry-fly water.
Raw CFS means little on its own, so every reading on this page is shown against the USGS median for the same calendar day — 1,290 CFS for late July, from 93 years of record.
Henrys Fork at Island Park — common questions
What is the current flow on Henrys Fork at Island Park?
As of the last reading on this page, Henrys Fork at Island Park was running 891 CFS at a gage height of 4.36 ft, or 69% of the USGS median for this date. The number updates automatically from USGS gauge 13042500, which reports every 15 to 60 minutes.
Is that high or low for this time of year?
The USGS median flow for late July at this gauge is 1,290 CFS, calculated from 93 years of record (1933–2026). Comparing today's reading against that median is the only way a raw CFS number tells you anything — 200 CFS is a drought on one river and a flood on another.
How often does this reading update?
USGS transmits from this gauge every 15 to 60 minutes. This page bakes in the most recent reading when it is rebuilt, then refreshes live from USGS when you open it. Readings are provisional and subject to revision by USGS.
Is Henrys Fork at Island Park wadeable right now?
That depends on the reach and on your own judgement — riverlvl will not tell you the water is safe to stand in. What it will tell you is whether today's flow is unusually high or low for the date, against a seasonal median of 1,290 CFS, which is the single most useful input to that decision.
What makes the flow change on this stretch?
Rain in the basin upstream, plus seasonal baseflow. The 12-month chart shows the past year of daily values, which is the clearest picture of how this gauge behaves through the seasons.
Where does this data come from?
Flow and gage height are public-domain USGS data from gauge 13042500. Flood categories, impact statements and the forecast come from the NOAA / National Weather Service National Water Prediction Service, gauge ISLI1. riverlvl adds the seasonal comparison and plain-English summary; it is not an official source and does not issue warnings.