[Acoustics] RE: Algae Growth Affecting Sontek SW Flow Calculations

Thu Mar 10 09:09:43 CST 2005

Grant
      I would of thought that Sontek or someone who uses a SW velocity
meter would have responded back to you by now.

      So here is my 2 cents. I am using XR's on a river channel (same
general idea) that builds up weeds along the channel edges. I made a series
of measurements without any weeds in the channel and established an index
velocity rating. Then the summer months came and weeds grew in the
shallower section of the channel and my velocity rating was off. The
explanation of what happened to the rating seems to be a loss of effective
area, thereby concentrating the flows (velocity) into a narrow "alley way"
and making a shift to the rating. I had a sufficient number of measurements
during the "weed period" to make a new index velocity rating that was
significantly different from my original rating. I applied a velocity shift
to the base rating for the time period of weed growth. So yes large growth
of weeds in your channel will affect your ending discharges. Hope this
helps.

      Hank Zajd
------------------------------------------------------------------------
   Henry J. Zajd, Jr. (Hank)        Tel: (607)266-0217 ext. 3023
   U.S. Geological Survey           Cell phone (607) 227-3897
   30 Brown Road              Email: hzajd at usgs.gov
   Ithaca, NY  14850-1573           Fax: (607)266-0521
                              Web: http://ny.usgs.gov/

                      "Winslow, Grant"                                                                                                      
                      <GJW2 at pge.com>                  To:       <acoustics at simon.er.usgs.gov>                                               
                      Sent by:                        cc:                                                                                   
                      acoustics-bounces at simon.        Subject:  [Acoustics] RE: Algae Growth Affecting Sontek SW Flow Calculations          
                      er.usgs.gov                                                                                                           

                      03/09/2005 08:38 PM                                                                                                   

I'm resending this email out in hopes of getting a response back.  The
first time I sent out, I hadn't received any responses.

Look forward to any feedback!  Thanks in advance!

Regards,

Grant Winslow

_____________________________________________
From:   Winslow, Grant
Sent:   Monday, February 28, 2005 12:23 PM
To:     'acoustics at simon.er.usgs.gov'
Subject:        Algae Growth Affecting Sontek SW Flow Calculations

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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