[Acoustics] Algae Growth Affecting Sontek SW Flow Calculations

[Winslow, Grant]

I have proposed to install a Sontek SW velocity meter on the floor of
one of our gunited canals.  However, there was some concern that the
actual flow within the canal would not be accurately measured during
periods when there might be heavy buildup of algae within the canal.

The reasoning was that the cross-sectional area that was originally
input into the Sontek SW software when the canal was clean, would be
effectively reduced during periods of heavy algae growth within the
canal at certain times of the year,  thereby, inaccurately calculating a
higher flow rate. 

It is my understanding that the "backwater effects" caused by heavy
algae growth on the sides of a gunited canal, would result in the meter
measuring lower velocities and, in turn, calculating lower flows at any
given stage versus when the canal was free of algae buildup on it's
sides.  I didn't think that the reduction in the cross-sectional area of
the canal with heavy algae buildup vs. the cross sectional area stored
in the Sontek SW software, when the canal was free of algae, would be of
significance.  Is this not the case?  Or would I need to enter a
correction factor for the cross sectional area to account for this algae
buildup in the canal certain times of the year.  Any feedback greatly
appreciated!

Regards,

Grant Winslow
PG&E Hydrographer

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