CFS is a volume passing a point over time
Cubic feet per second - written cfs, CFS, or ft3/s - is a unit of discharge or streamflow. One CFS means one cubic foot of water passes a specified point each second. A station reporting 1,000 CFS is estimating a rate, not the amount of water stored in the river and not its speed at every location.
Channel width, depth, gradient, constrictions, roughness, and downstream features determine what that discharge feels like on a run. A broad river at 1,000 CFS and a narrow creek at 1,000 CFS are completely different environments.
Gauge height is stage above a station datum
Gauge height, also called gage height or stage, is the elevation of the water surface above a reference datum established for that station. A reading of three feet generally does not mean the river is three feet deep. The riverbed may sit above or below the station's reference point, and depth varies across the channel.
Stage can be especially useful where paddlers have years of local experience tied to one established gauge, painted reference, bridge feature, or rapid. That meaning remains local to the station and section.
A rating curve connects stage to discharge
At many stations, hydrologists make physical discharge measurements across a range of stages and develop a stage-discharge relationship called a rating curve. Continuous stage observations can then be converted into estimated streamflow. The USGS explanation of rating curves describes this process.
The relationship can change when floods move the channel, sediment shifts, vegetation grows, ice forms, debris collects, or construction alters hydraulics. Agencies may mark recent values provisional while they review and correct the record.
A doubling of gauge height does not imply a doubling of CFS. Rating curves are site-specific and commonly nonlinear.
Why paddling ranges use different units
Some sections are traditionally discussed in CFS because a nearby discharge estimate correlates well with the run. Others use stage because local experience developed around a staff gauge or station height. Dam-release runs may be discussed by scheduled release, powerhouse output, or another operational signal.
A runnable range captures observed community experience with that relationship. It cannot account for every boat type, rapid change, hazard, access issue, temperature, weather event, or paddler. Treat it as a sorting and comparison tool.
Read the metadata around the number
Before using a value, confirm the station, unit, observation time, time zone, trend, provisional status, and relationship to the section. Ask whether the gauge is on the run, upstream, downstream, or on related water. Consider tributaries, travel time, diversions, and localized rainfall between the gauge and section.
River People presents configured gauge context with river sections where available. The app's condition labels and filters are most useful when paddlers still inspect those details and verify the originating source.
A practical reading sequence
- Confirm the exact river section.
- Open the associated station and source.
- Read the unit and observation timestamp.
- Review the trend, not only the latest value.
- Understand why that gauge relates to the run.
- Compare the value with a documented preferred range.
- Check weather, forecasts, releases, hazards, access, and local reports.
- Make an independent group decision.
For more background, see the official USGS streamgaging basics and the guide to runnable conditions.
