Hydroacoustic Current Meters for the Measurement
of Discharge in Shallow Streams and Rivers
Mechanical Current Meters
The USGS traditionally has used mechanical, propeller-type current meters to measure water
velocities. Velocities are computed by the number of revolutions of the propeller per unit
of time.
Price type AA meter.
Photograph from Nolan and Shields, 2000. |
Pygmy meter.
Photograph from Nolan and Shields, 2000.
|
Limitations of mechanical current meters
Mechanical current meters have limitations, including the following:
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Shallow depth limit of 0.3 ft (pygmy meter)
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Low velocity threshold of 0.1 ft/s (foot per second) (pygmy meter)
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Extensive maintenance required to maintain meter accuracy
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Meter disturbance of the flow measured
These limitations can hamper the usefulness of mechanical meters, particularly at very low
flows when streams can be shallow and slow. It is during such low-flow periods that
accurate discharge data can become critical to government agencies, private firms, and the
general public. While mechanical current meters have served the USGS well, there is new
technology that could represent a major improvement in discharge-measurement
accuracy.
Indiana District Hydroacoustics Main
Page
Office of Surface Water Hydroacoustic Support
Pages
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The use of trade, product, or firm names is for descriptive purposes
only and does not imply endorsement by the United States Government.
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All information herein is provisional and subject to
revision.
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Emphasis on the instruments described in these pages does not imply that
these are the only instruments that can be used for this purpose. The instruments were
selected for the following reasons: the instruments are readily adaptable to this purpose,
the instruments are on Federal purchase schedules, and the instrument vendors have
voluntarily committed resources to this application. Other instruments will be
investigated within the limits of project funding and schedules.
U.S. Department of the Interior
U.S. Geological Survey
5957 Lakeside Boulevard
Indianapolis, Indiana
46278-1996
USA
Phone: (317)290-3333
Fax: (317)290-3313
URL: http://sunrise.er.usgs.gov/hydroacoustics/acoustic_wading_rod_mechanical.shtml
Last modified:Monday, 13-Aug-2007 15:58:47 EDT
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