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United States Department of Agriculture

Agricultural Research Service

Title: Use of Acoustic Doppler Current Profilers to Describe Velocity Distributions at the Reach Scale

Authors
item Shields Jr, Fletcher
item Knight, Scott
item Testa, Sam
item Cooper, Charles

Submitted to: Journal of the American Water Resources Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 1, 2003
Publication Date: December 31, 2003
Citation: Shields Jr., F.D., Knight, S.S., Testa III, S., Cooper, C.M. 2003. Use of acoustic doppler current profilers to describe velocity distributions at the reach scale. Journal of the American Water Resources Association. v. 39. pp. 1397-1408.

Interpretive Summary: In order to manage or restore river ecosystems, scientists need information about how damaged systems differ from more pristine conditions. One key factor in river habitats is the water velocity, which varies continuously in time and with location. Detailed velocity measurements are difficult to obtain with traditional methods, particularly in rivers too deep to wade. New devices called acoustic Doppler current profilers, which rely on echoes from sound waves striking small particles or bubbles suspended in the water, hold great promise for addressing this problem. Detailed data describing velocity conditions in three very different types of habitat found along the Little Tallahatchie River, Lafayette County, Mississippi were obtained using a Doppler profiler. Methods were developed to reduce the large amount of numerical data generated this way into meaningful statistics and indices. These descriptors were then compared with statistics that describe biological data sets representing samples of fish and insects obtained from the same places in the river. Evidently the Doppler data set allows scientists to rapidly and cheaply detect small patterns of fast and slow velocity that are important to various organisms. Additional work is needed to refine the method.

Technical Abstract: Detailed descriptions of riverine velocity fields are useful in characterizing and describing stream habitat. However, detailed velocity data are difficult to obtain, particularly in rivers too deep to wade. Acoustic Doppler current profilers (ADCP) may be used to rapidly collect detailed representations of river depth and velocity fields. Such data were collected from three types of habitat (naturally sinuous, channelized, and abandoned channel) along the Little Tallahatchie River, Mississippi in March 2000. Resulting data sets were used to compute frequency distributions for component velocities and vorticity, and vorticity values were used to compute an area-weighted mean vorticity (circulation). Computed vorticity and circulation values for naturally sinuous and channelized reaches were similar, but the sinuous reach displayed distinctive spatial patterns, with higher levels of vorticity consistently occurring near banks. Fish collections from the same habitats sampled by ADCP indicated closer similarity between the energetic, higher vorticity natural and channelized habitats than the more quiescent abandoned channel. Indices of ecological stress computed from fish collections indicated lower levels of stress in the natural channel, where vorticity patterns were temporally consistent. Benthic macroinvertebrate collections revealed distinct assemblages occupying the channelized and abandoned channel reaches. ADCP hold great potential as tools for the study of riverine ecosystems, but data reduction is difficult using existing software.

Last Modified: 11/22/2014
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