[Acoustics] Fixed problem of High number of bad ensembles at Madeira river

[Pedro Moreira]

Hello, 

The high number of bad ensembles at Porto Velho was solved with a 300 kHz WH Monitor ADCP and a Novatel DGPS . With DGPS reference there were only 1 or 2 bad ensembles in each measurement. The only change in configuration wizard was the BP2 user command. 
I believe there will be no problem with the 600 kHz Rio Grande and DGPS. Local maximum depth even in higher discharges is 37 m. 

Report, photos, raw and configuration files can be found at CPRM (Brazilian Geological Survey) FTP area. For those interested on reprocessing the data and use:

1) Internet Explores or another browser: ftp://ftpcprm:ftpcprm@ftp.cprm.gov.br or
2) WS-FTP or similar software: Adress: ftp://ftp.cprm.gov.br   UserID: ftpcprm   Password: ftpcprm

I want to thank all of you that sent answers about this subject, in special to:
Jeff Conaway, Kevin Oberg, David Gaeuman and Randal Dinehart - USGS, Rod Kerr - NSW, Lennard Van der Hulst, and John Land - DRL (Sediview).

Pedro Moreira
CPRM - Brazilian Geologic Service
Hydrologist and System Analyst
Rio de Janeiro - Brazil
55 21 2546-0352


>>> "Pedro Moreira" <pneto at rj.cprm.gov.br> Friday, 9 December 2005 >>>

Hello,

I wonder if any one you have experienced ADCP river discharge measurements with exaggerated number of single ping bad ensembles (40% and even 60% of total ensembles) and identified the cause. 

Amazon basin is a challenge for river measurements with doppler effect based equipments. Madeira river has a high sediment concentration ( > 2.000 ppm) and mooving bottom at Porto Velho site. The measuments were made by ANA (Brazilian National Agency) and HIBAM (Hydrology of Amazon Basin) with a 300 and 600 kHz WorkHorse Monitor ADCP, Winriver wizard commands, maximum depth = 35 meters and averaged discharge between 23.000 and 31.000 m3/s . 
Even though range is improved by higher sediment concentration some colleagues think over mooving bottom as a probable cause. Others believe in bed rugosity and/or bed fractured rocks. No problem with bad bins (between 0 and 1%).
As a test, I suggested to field personnel to use once the user command WB1, trying to cross the bottom material obstacle. RD Instruments expert command description says that: sets profiling mode bandwidth (sampling rate).  Smaller bandwidths allow the ADCP to profile farther, but the standard deviation is increased by as much as 2.5 times., even knowing that 300 and 600 kHz maximum ranges are 60 and 130 meters, respctively. Standard deviation could be reduced increasing the depht cell size, averaging ensembles ou using multi pings ensembles. No improvment was achieved.

If requested I can upload raw and configuration files to a FTP folder for analysis.

Pedro Moreira
CPRM - Brazilian Geologic Service
Hydrologist and System Analyst
Rio de Janeiro - Brasil
55 21 2546-0352
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