There can be occasional equipment or database problems where erroneous data are reported for short periods of time until corrections can be made. This is why it is important to look at a record of streamflow (like the 7-day hydrograph plots) rather than a single point in time. However, most of the time the USGS has a high level of confidence in its real-time stage data.
During low streamflow conditions, aquatic grasses, debris, or rocks near the gage can produce artificial increases in water level readings. During extreme cold weather, ice can affect stage and discharge determinations at some stations. Adjustment of data for ice effects requires detailed analysis.