How to Read USGS Gauges Like a Fishing Local

The numbers a gauge gives you

The USGS defines stage, or gage height, as the height of the water surface in feet above a zero point that is arbitrary but often close to the streambed; its gauges record it, usually every 15 minutes, to the nearest 0.01 foot or 0.2% of stage, whichever is greater. Discharge, in cubic feet per second (cfs), is the volume of water passing the gauge. It is not measured continuously: USGS crews measure flow in the field every 6 to 8 weeks across a range of stages, build a rating curve for that site, and convert each stage reading into discharge. On reservoirs, the reading is the lake's elevation above a datum, which operators compare with set levels such as normal conservation pool and the top of the flood pool. Where one of our water pages has a gauge, it shows the latest value and a 30-day chart.

Rivers: compare with the river's own history

A flow means little without the river's own normal for that time of year. The USGS state maps in Water Data for the Nation compare each gauge's discharge with historical daily values for the date, expressed as percentiles, a job its older WaterWatch service used to do. Where our page has a matching river gauge, a panel places today's flow among the percentiles for the date; anything between the 25th and 75th percentile sits in the middle half of past years. The report line also says whether the flow is steady, rising or dropping against a week earlier. Many anglers wait for a river to fall back after a rise; in one Arkansas Game and Fish Commission report from the White River, a Calico Rock outfitter said the fishing picked up as the water dropped through the day.

Reservoirs: elevation against pool

Arkansas Game and Fish Commission fishing reports give each lake's elevation alongside its normal conservation pool and the top of its flood pool, which shows at a glance whether a lake is low, full or holding floodwater. Our lake pages print the level and how far it sits above or below conservation pool, plus the change over the past week. A lake well above pool is often releasing heavily downstream, which matters if you fish the tailwater below it.

What a gauge can get wrong

The USGS notes that the link between stage and flow shifts as channels change through erosion, deposition, seasonal vegetation growth, debris or ice, and that ratings are adjusted as new measurements come in. Recent data are provisional: improbable values are screened automatically, but instrument problems or changes at the site can lead to substantial revisions later, and the USGS asks users to consider this before decisions that affect personal safety. A gauge also describes the water where it sits, not a tributary miles away. Some USGS stations record water temperature too; our pages do not show it yet, so open the station page from the sources block if you need it.

How our reports work →

Building your own gauge habit

Note the gauge reading every time you fish your home water, alongside how the day went. After a season you will have your own record of which flows or levels suited you and which did not, and the USGS percentile for the date will tell you whether today is ordinary or unusual.

Trout rivers we track daily → · White River daily report →

A five-minute morning check

Open your water's page and read, in order: the level or flow and its weekly change; the pressure verdict; the wind against the banks you planned to fish; and the day's windows against your free hours. Then glance at the sources block to see when the gauge last reported.

Open your water →

Common questions