Global Water FP111 User Manual page 8

Global Water
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flow profile at the center of each subsection: zero the
averaging function and move the Flow Probe vertically
from the surface to the bottom, up and down, slowly and
smoothly for 20-40 seconds to obtain a good average.
The average velocity (obtained with the Flow Probe)
times the area of the subsection (use your graph paper
diagram) equals the flow for the subsection (Q = V x A).
Once the flow of each subsection is obtained, add all of
the subsection flows to obtain the total stream flow.
c. For the USGS "6 tens method", the Flow Probe is placed
at the center of the subsection at a depth from the surface
of 0.6 of the total depth. The Flow Probe is held in place
and the average velocity is obtained over a period of 40
seconds. The 0.6 depth is assumed to be the average
velocity point for the vertical profile. Therefore, this
average is similar to that obtained in technique 2 (above)
however; we feel that technique 2 is more accurate.
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