Why are there sometimes differences between river stages as reported by the National Weather Service and by USGS?
At some USGS stream-gage installations, NWS maintains a separate stage sensor that is serviced by NWS technicians. Occasionally, calibration of any sensing device may drift from a “true” value, so there may be differences between USGS and NWS data reports. USGS personnel visit installations on an interval of 6 weeks or less to maintain equipment and make required adjustments. NWS technicians have a separate maintenance schedule. In either case, data retrieved from remote sensors is always considered provisional and subject to revision after quality control and analysis. Differences between remotely reported and field-measured data are usually small and within tolerances required for water resources management and control.
