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OSW Hydroacoustics

Mid-Section Measurements

The mid-section method has been the primary method for measuring discharge within the USGS for decades. The mid-section method involves measuring the channel area and water velocities of a stream at a cross section. The channel is divided into a number of vertical subsections. Most natural channels must be divided into 20 or 30 sub-sections to adequately characterize their irregular geometry. The depth and average velocity are measured at each subsection and are applied to a sub-area whose width extends half way to the preceding and following observation points. The area of each subsection is determined by directly measuring width and depth. The average water velocity in each sub-section is estimated using the measured velocity at selected locations in the vertical. The total discharge within the stream is the sum of the individual subsection discharges.

Mid-Section Measurement Resources

Guidance: Published guidance reports, technical memorandums, and best practices.

Software: USGS utilities and post-processing programs, useful public domain software, manufacturers firmware and software (restricted), and links to other software.