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Index-Velocity

The USGS uses fixed hydroacoustic current meters in various deployment configurations (side-looking, upward and downward-looking) for many different applications. Perhaps the most common application is at streamflow-gaging stations to compute streamflow using index-velocity methods. The water velocity measured by a hydroacoustic current meter in a portion of a river can be used as a surrogate or "index" for the mean-channel velocity. Mean-channel velocities computed using index-velocity methods can be used to generate records of river streamflow. Upward and/or downward-looking fixed deployments have been used to measure tidal current patterns in bays, estuaries and harbors as well as wind-driven and density currents in lakes.


Index-Velocity Resources

Instrument Page: Descriptions of the types of hydroacoustic current meters commonly used for index velocity applications.

Guidance: Published guidance reports, technical memorandums, and recommended procedures.

Downloads: Downloads or links of software and firmware for commonly used acoustic Doppler velocity meters and acoustic profilers (access may be restricted to USGS and several other Government agencies); download AreaComp, a USGS program created for the development of stage-area ratings.

Deployments: A summary of mounts and deployments for side-looking and upward-looking applications.

Tech Tips: Quick reference sheets and other tips for deploying index velocity meters and computing discharge using the index velocity method.

References: Reports, including reports available online, with information about index-velocity applications.

Training: Class outlines and schedules for USGS hydroacoustic classes, including Streamflow Records Computation using Hydroacoustic Current Meters and Index-velocity Methods. This class includes site reconnaissance and selection; hydroacoustic current meter types, uses, and programming; index-velocity rating development, and data quality assurance/quality control.  Podcasts and webinars are also available.

Links: Useful links associated with index velocity and fixed deployment of ADCPs