About site visits

There are two meanings to the term site visit within the USGS.

The first meaning is broad. A site visit occurs when a hydrologic technician visits a site in person to do some sort of work. Work may involve recalibrating instrumentation, replacing worn out hardware, taking a new rating of the stream so that discharge can be accurately calculated, or taking some sort of manual measurement. Manual measurements could include peak flow measurements during high water events, a water quality measurement such as a specific conductance measurement, a water quality sample that is sent to a laboratory for further analysis, or in the case of wells, a measurement of the depth of water in the well.

The second meaning is specific. For surface water sites, a site visit is an irregular manual surface water measurement, which exclude peak measurements. Peak measurements are of great interest because they are unusual, so those "site visits" are tracked separately. Site visits are selectable in the site web service using the hasDataTypeCd=sv filter or the outputDataTypeCd=sv key/value pair. Most surface water sites record measurements at regular intervals using automated equipment. Since site visits involve measurements by humans at irregular intervals, and since a human is making the measurement, and the accuracy of the measurement is assumed to be high, site visits are not considered provisional. In fact, they are often used to compare with automated measurements to see how accurate the automated measurement is.