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Hydrometric Rating Application (HydRA)

Last updated on June 5, 2026

Hydrometric work involves regular visits to a hydrometric gauging station across a range of streamflow conditions. A hydrometric gauging station typically consists of a stage sensor and benchmarks or reference gauge from which water level is referenced. Each field visit should collect three basic observations: reference of stage, measurement of discharge, and control observation. These observations are required to convert stage into discharge through the development of a hydrometric rating curve. (Note: Safety should be considered when collecting these observations, do not attempt any unsafe field work!).

The Hydrometric Rating Application (HydRA) is a publicly available tool for developing hydrometric rating curves based on observations of stage and discharge. HydRA is intended for use as an application for developing open channel rating equations only and may be used to supplement other available hydrometric tools or packages commonly used for data review. HydRA allows the user to upload observations of stage and discharge and automatically fits a rating curve. Users can adjust the fit according to onsite observations. It then generates a rating equation that can be used for converting stage datasets into discharge.