The terms and quirks of reading a river gauge, in plain language.
CFS stands for cubic feet per second: the volume of water passing a fixed point in the river every second. A cubic foot is about the size of a basketball. One cfs is one of those, passing a fixed point, every second. A small creek might run at 20 cfs; a major western river can run well over 10,000 cfs during spring runoff.
Gauge height, also spelled gage height and also called stage, is the water surface elevation at the gauge, measured in feet against a fixed reference point. It's the most direct measurement a gauge takes; discharge (cfs) is calculated from it using a rating curve specific to that site.
Compass direction has nothing to do with it.
Rivers flow downhill, following whatever path gravity and terrain gradient give them. Many rivers in the Lower 48 happen to trend south or east because of how the continent tilts, but plenty flow north, or any other direction, wherever that's the way the elevation drops. A river flowing north isn't unusual: it's just following the same rule every river follows, downhill, regardless of which way that happens to point on a map.
Each station's status badge compares today's reading to what's typical for that river on that day of year: high, low, or steady, plus an arrow showing whether it's currently rising or falling. It's a quick way to gauge conditions without parsing a raw number.
Most gauges report new readings every 15 to 60 minutes. The values on River Flow Co reflect the most recent reading available from the source network at the time the page loads.
The words you'll run into across every guide on this site.
Discharge is the formal name for the same thing cfs measures: the volume of water moving past a point per second. Gauges measure gauge height directly and calculate discharge from it.
Rating curve is the site specific relationship between gauge height and discharge, built from repeated manual measurements over time. Every gauge has its own rating curve, so a gauge height of three feet means something different on every river.
Hydrograph is a chart of discharge or gauge height over time. It's how you see whether a river is rising, falling, or holding steady, and how quickly.
Gauge datum is the fixed reference elevation a gauge height measurement is taken against. It's arbitrary to that station, so gauge heights aren't comparable between different rivers or even different gauges on the same river.
Flood stage is the gauge height at which a river leaves its banks and begins to cause flooding at that location, set by the National Weather Service for forecast points.
Wadeable describes a river low and slow enough to cross or fish on foot without a boat, typically true at lower flows.
Floatable describes enough water to float a tube, canoe, or raft without repeatedly dragging bottom. Floatable windows shrink or disappear during drought and open up during wetter periods.
Runnable is the whitewater version of floatable: enough flow, and the right kind of flow, for a rapid or section to be paddled at its intended difficulty rather than being too low to run or too high to be safe.
The International Scale of River Difficulty rates rapids from Class I, the easiest, to Class VI, extreme and exploratory, based on wave size, obstacles, and the consequences of a mistake.
Class I is fast moving water with small waves and few obstacles.
Class II has straightforward rapids with wide, clear channels.
Class III has moderate, irregular waves and may require maneuvering.
Class IV has intense, powerful rapids that need precise boat handling.
Class V has long, violent rapids with significant hazard if things go wrong. Exact difficulty and hazards vary by run, always check the specific river's guide.
Put-in is the access point where a trip starts and boats or tubes enter the water.
Take-out is the access point where a trip ends and boats or tubes come off the water.
Portage means carrying a boat around a hazard or obstacle on land rather than paddling through it.
Shuttle is the logistics of getting a vehicle from the put-in to the take-out, either by leaving a second car or using a shuttle service.
Strainer is a downed tree or debris pile that lets water through but can trap a person or boat. One of the most common causes of river fatalities.
Low-head dam is a small dam that creates a drowning hazard through its recirculating hydraulic just below it, often invisible or unremarkable looking from upstream.
Undercut describes a rock or bank that water flows beneath, creating a trap for a swimmer or boat.
Sieve is a gap between rocks or debris big enough for water to pass through but not a person or boat.