Illinois River At Marseilles Flow Report
As of July 20, 2026, Illinois River At Marseilles is flowing at 4,420 cfs with a gage height of 11.34 ft, receding 43% over the past 24 hours. Source: USGS gauge #05543500, refreshed throughout the day.
Historical Data
Illinois River At Marseilles at a glance
How Illinois River At Marseilles is running right now, where it sits on the map, and the key gauge stats.
Illinois River At Marseilles is flowing at 4,420 cfs, with the water sitting 11.34 ft at the gage. Flow is down 43% since yesterday as the gauge recedes.
This is USGS gauge #05543500 in Illinois. Over the past 10 days the average has been 8,689 cfs, peaking at 12,400 cfs.
For real-time updates and historical context, see the realtime view or the historical comparison. Browse other gauges in the Illinois flow report.
Engineering Data
Flow-duration statistics and observed peak-flow context computed from this gauge’s complete daily record (USGS #05543500).
Estimate flows at an ungauged site
Drainage-area ratio transfer from this gauge . Most reliable for hydrologically similar sites in the same watershed with area ratios between roughly 0.5 and 1.5.
Percentiles are flow-duration values computed from this gauge’s observed daily record as archived by Snoflo. Return periods are Weibull plotting-position estimates from observed annual maxima, provided as general reference context only. Always verify against official USGS NWIS records. Part of Snoflo for Engineering.
Streamflow Forecast
Over the next 5 days, Illinois River At Marseilles is expected to recede from today's 7890 cfs, toward roughly 6240 cfs by 2026-07-24 (likely range 2957-13168 cfs) -- drier than normal for the date.
Powered by PULSE — Snoflo’s forecast engine, trained on this gauge’s full record of storms, snowmelt, and dry spells.
| Date | Expected (p50) | Likely range (p25–p75) | vs normal | Projected stage |
|---|
How does this compare to past years?
Year-over-year overlay, annual peak discharge, the full distribution of daily flows on record, and the gauge's rating curve.
Weather Forecast
Next 5 days, hour by hour
Temperature line with weather symbols on top, snow + rain accumulation as columns, humidity as a dotted line.
5-day forecast table
Every 3 hours, broken out across temperature, snow, rain, humidity, and wind.
| Time | Condition | Temp (°F) | Snow (in) | Rain (in) | Humidity (%) | Wind (mps) | Wind dir |
|---|---|---|---|---|---|---|---|
| Loading detailed forecast… | |||||||
15-day forecast
Daily temperatures, snow, and rain projected over the next two weeks.
Illinois River At Marseilles
The Dresden Island and Marseilles Dams also impact the flow. Seasonally, the river experiences high flows in the spring due to snowmelt and precipitation, and low flows in the summer and fall. Interestingly, the river is home to several rare and endangered species, including the Hine's Emerald dragonfly and the Alligator Snapping Turtle. Additionally, the river was once a popular site for paddlewheel steamboats and was even featured in Mark Twain's book "Life on the Mississippi."
Nearby streamflow levels
Cross-check Illinois River At Marseilles's discharge against nearby gauges to spot whether the change here is local or regional.
| Gauge | Streamflow |
|---|---|
| Illinois River At Marseilles | 4,420 cfs |
| Fox River At Dayton | 1,190 cfs |
| Vermilion River Near Leonore | 288 cfs |
| Mazon River Near Coal City | 30 cfs |
| Kankakee River Near Wilmington | 2,600 cfs |
| Blackberry Creek Near Yorkville | 50 cfs |
Nearby snowpack data
Snowpack at SNOTEL stations near Illinois River At Marseilles. Spring snowmelt is the dominant driver of streamflow in mountain basins -- a deep snowpack upstream means more runoff later in the season.
| SNOTEL station | Snowpack |
|---|---|
| Earlville | 0 in |
| La Salle 0.1 W | 0 in |
| Peru 0.7 Ene | 2 in |
| Morris 6.4 Ese | 0 in |
| Carbon Hill 3.1 N | 0 in |
| Coal City | 0 in |
Plan a trip
Reservoirs, boat launches, river runs, and fishing spots within driving distance of Illinois River At Marseilles.
Boat launches
See all →
River levels & flood safety
- Read the level before you go
- A river that's runnable at one flow can be deadly at another. Check current discharge and gage height — like the values shown above — against the flood-stage thresholds, and remember levels can spike fast after rain or a dam release.
- Respect cold water
- Snowmelt rivers run cold even in summer. Sudden immersion triggers cold-water shock and saps strength within minutes. Wear a PFD, dress for the water temperature (not the air), and never wade or paddle alone.
- Watch for swiftwater hazards
- Strainers (downed trees), undercut rocks, and low-head dams are the deadliest features on moving water. High, fast, muddy water hides them. If in doubt, scout from shore and portage.
- Mind flash floods & releases
- Narrow canyons can flood from a storm miles upstream, and dam-controlled reaches can rise without warning. Know the forecast, the release schedule, and your exit before you launch.
Track Illinois River At Marseilles in the Snoflo app
Save this gauge as a favorite, set push alerts when streamflow crosses a threshold (e.g. "alert me when Illinois River At Marseilles crosses 5,000 cfs"), and Snoflo's iOS app will push the moment USGS reports the crossing.
About Illinois River At Marseilles
Where does the streamflow data for Illinois River At Marseilles come from?
Discharge, gage height, and water temperature come directly from the USGS streamflow gauge 05543500. Snoflo refreshes the time series throughout the day. Forecasts come from the NOAA / yr.no feed Snoflo's iOS app uses.
How often is the report updated?
USGS gauges report continuously (typically every 15 minutes). Snoflo pulls fresh values throughout the day — look for the "as of" timestamp on the streamflow hero card.
What's the difference between discharge and gage height?
Discharge (cubic feet per second, or cfs) is the volume of water flowing past the gauge each second. Gage height is how high the water sits at the gauge (feet). They're related by a rating curve specific to each gauge — higher water means more flow, but the exact ratio depends on channel shape.
How is "percent of median" calculated?
Today's discharge is compared to the historical median discharge on this calendar day across the gauge's full record. 100% = right on median; 200% = a very high year; 30% = a drought-level low.
What are flood stages, and is this river safe right now?
Flood stages are NWS-defined gage-height thresholds — Action, Minor, Moderate, Major — marking when nearby roads or floodplains start to be affected. "Safe" depends on your activity and skill: a level that's a fun paddle for an expert can be lethal for a wader. Always check the current level against the thresholds above and the safety links, and when in doubt, stay off the water.
Can I get alerts when Illinois River At Marseilles rises?
Yes — flow alerts are managed in the Snoflo iOS app. Favorite this gauge, set a streamflow threshold (e.g. "alert me when discharge crosses 5,000 cfs"), and you'll get a push the moment USGS reports the crossing.
Access the free Illinois River At Marseilles report
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