700-SDI-RADAR-300W-Man Rev 2 30 May 2022
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Part# 21370
In order to determine the discharge in a realistic channel, the area must be precisely measured by
measuring water depths at a series of points across the stream and multiplying by the width of the
stream within each segment represented by the depth measurement. The mean cross-section flow
velocity needs to be determined from measured surface flow velocity. Studies performed by USGS
reveal that, typically, the mean velocity is 80-95% of the surface velocity, the average being 85%.
Knowing the non-rectangular area of the stream cross-section, and knowing the surface flow
velocity, the following formula can be used:
𝑄𝑄
= 0,85
∗
𝑉𝑉
∗
𝐴𝐴
More details about water flow measurements can be found in the following technical note:
https://s3.amazonaws.com/Product_Sensors/701-Technotes3-Flow.pdf
