The U.S. Geological Survey (USGS) established its first streamgage in 1889 on the Rio Grande River at Embudo, NM. As the need for stream-flow information increased, the USGS expanded its Streamgaging network, and continues to do so to this day.
Streamgaging generally involves obtaining continuous record of stage (height of water), obtaining periodic measurements of discharge, defining the relationship between the stage and the discharge, use the stage-discharge relationship to convert continuous record of stage into a record of discharge, and disseminating the streamflow information to Water Manages, Scientists, Engineers, and the General Public.
Streamflow information is used to predict floods, manage and allocate water resources, design engineering structures, compute water-quality loads, and operate water-control structures. The USGS has progressively improved the streamgaging program by incorporating new technologies and techniques that streamline data collection while increasing the quality of the streamflow data that are collected.
River Stage
The stage of a stream or lake is the height or elevation of the water surface above an arbitrary or predetermined datum. Though used interchangeably with stage, the term Gage Height refers to the stage at a monitored location. In streamgaging, gage heights are used as independent variables in the computation of stage-discharge relations.
River stage was traditionally measured from inside a stilling-well, but more recent advances have seen Gas-pressure sensors, and Radar stage recording being used as well.
Measurement of Discharge
A USGS hydrographer holds a wading rod that has a current meter attached to it. The current meter is used to measure water velocity at various vertical depths. The hydrographer makes these measurements at a number of locations horizontally across the stream and from these measurements can produce a value of streamflow in cubic feet per second.