St. Marys River At Decatur flow report
As of July 14, 2026, St. Marys River At Decatur is flowing at 100 cfs with a gage height of 3.55 ft, rising 48% over the past 24 hours. Source: USGS gauge #04181500, refreshed throughout the day.
Historical Data
St. Marys River At Decatur at a glance
How St. Marys River At Decatur is running right now, where it sits on the map, and the key gauge stats.
St. Marys River At Decatur is flowing at 100 cfs, with the water sitting 3.55 ft at the gage. Flow is up 48% since yesterday — a rising hydrograph.
This is USGS gauge #04181500 in Indiana. Over the past 10 days the average has been 72 cfs, peaking at 100 cfs.
For real-time updates and historical context, see the realtime view or the historical comparison. Browse other gauges in the Indiana flow report.
Streamflow Forecast
Over the next 5 days, St. Marys River At Decatur is expected to recede from today's 100 cfs, toward roughly 68 cfs by 2026-07-19 (likely range 13-361 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.
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.
St. Marys River At Decatur
Marys River at Decatur, IN streamgauge measures water flow rate. The river is fed by several small creeks and tributaries, including the Little Wabash River. In the summer, flow rates tend to be lower due to decreased precipitation and higher evaporation rates. In the winter, the flow rate can increase due to snowmelt and rain. The river is known for its historic downtown area and has been a focal point for economic and recreational activities in the region. There are several dams along the river, including the Decatur Dam, which was built in the late 19th century to provide power to the city.
Nearby streamflow levels
Cross-check St. Marys River At Decatur's discharge against nearby gauges to spot whether the change here is local or regional.
| Gauge | Streamflow |
|---|---|
| St. Marys River At Decatur | 100 cfs |
| St Marys River At Walcot Street At Willshire Oh | 99 cfs |
| St. Marys River Near Fort Wayne | 91 cfs |
| Wabash River Near Bluffton Indiana | — |
| Wabash River At Linn Grove | 40 cfs |
| Wabash River At Bluffton | 109 cfs |
Nearby snowpack data
Snowpack at SNOTEL stations near St. Marys River At Decatur. 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 |
|---|---|
| Decatur 1n | 0 in |
| Ossian 2.4 W | 0 in |
| Fort Wayne International Airport | 0 in |
| Fort Wayne 2.6 Ne | 0 in |
| Fort Wayne 7.0 Ne | 0 in |
| Fort Wayne 4.1 Ne | 0 in |
Plan a trip
Reservoirs, boat launches, river runs, and fishing spots within driving distance of St. Marys River At Decatur.
Boat launches
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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 St. Marys River At Decatur in the Snoflo app
Save this gauge as a favorite, set push alerts when streamflow crosses a threshold (e.g. "alert me when St. Marys River At Decatur crosses 5,000 cfs"), and Snoflo's iOS app will push the moment USGS reports the crossing.
About St. Marys River At Decatur
Where does the streamflow data for St. Marys River At Decatur come from?
Discharge, gage height, and water temperature come directly from the USGS streamflow gauge 04181500. 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 St. Marys River At Decatur 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 St. Marys River At Decatur report
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