[Acoustics] multi cell data

[Keith Ging]

Hank,

I use the multi cell option on most of LCRA's irrigation canal sites with
the Sontek SL (8 total sites).  I just started using it this year mainly for
QA purposes.  A couple of our sites have highly varying vegetation growth
along the banks which can affect our horizontal velocity profile.  I
purposefully setup the first and last cells very close to this vegetation in
order to be more sensitive to any changes in the long term trend (comparing
individual cells to index velocity cell).  From this data, we have been able
to get a rough estimate of when the vegetation caused a shift to our
index-velocity rating.  So it has been helpful in this regard.

In a separate instance (slightly embarrassing), we noticed during some
discharge measurements that two or three cells indicated a sudden drop in
velocities along the lines of 25%.  We found out from our technicians that
they were wading too close to the SL and crossing over one of the beams. 
Interestingly, the index cell velocity did not change much (about 4-5%)
which was not enough by itself to alarm us.  If we had not used the
multi-cell option, we would not have discovered this problem as easily in
order to correct it.  

I hope this gives you some idea of how we use the SL's multi-cell option.

Let me know if you have any other questions,


Keith Ging
Senior Hydrologist
Lower Colorado River Authority
Austin, TX
512-356-6009
1-800-776-5272 ext. 6009

>>> "Henry J Zajd Jr." <hzajd at usgs.gov> 8/5/2005 12:06:45 >>>
Greetings all
 
        It is time to shake the tree again.     I was wondering how many 
people are collecting velocity data using the multi cell option with 
either of the Sontek models   SL or XR???  Or with any other velocity 
sensor. 

        If you are using the multi cell option, can you explain how you 
are using this data and for what purposes? 

         Thanks in advance for your time on this request.

        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 
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