Interim Policy and Technical Guidance on Broadband Acoustic Doppler Current Profilers

In Reply Refer To:                                  April 26, 1993
Mail Stop 415


SUBJECT:  Interim Policy and Technical Guidance on Broadband 
          Acoustic Doppler Current Profilers

Several Districts or Areas are acquiring broadband acoustic 
doppler current profilers (BB-ADCP) in fiscal year 1993.  
Technical information and guidance on using the BB-ADCPs are 
needed as we begin to collect basic data with them.  The Office of 
Surface Water (OSW) has initiated work to provide policy and 
technical guidance on use of BB-ADCP's for discharge measurements.  
This work includes:  (1) writing a discharge-measurement 
procedures manual; (2) developing and writing a quality-assurance 
plan; and (3) documenting and extending discharge-measurement 
verifications.  Information from these empirical verifications 
will be used to set initial policy on acceptable measurement 
environment for use of BB-ADCP's in discharge measurements.  These 
tasks are being done by a team of OSW and District personnel.

The purpose of this memorandum is to inform you that policy and 
technical guidance are being developed for the BB-ADCP, to provide 
interim policy on using BB-ADCP's for discharge measurements, and 
to request information that will contribute to the work outlined 

Much of the work needed to provide technical information and 
guidance on use of BB-ADCPs in the WRD has already been 
accomplished.  The vendor is providing training and the California 
District has led the WRD in promoting development of the BB-ADCP 
for river discharge measurements and in documenting it's usage.  
Several Districts have made current-meter measurements to verify 
the discharge measured by the BB-ADCP.  Please fill out the 
attached form if your District has made any such verification 
measurements which meet the criteria listed.  Send the form and 
measurement data to the Office of Surface Water, ATTN:  BB-ADCP 
Work Group.  A continuum has been set up on the QVARSA Prime to 
provide a forum for discussing BB-ADCP related topics.  The 
continuum name is ADCP.  You should use this continuum to air and 
answer questions, to discuss your experiences and problems with 
BB-ADCPs, and to describe ideas and needs for technical support.

System performance and operating characteristics of BB-ADCP's are 
changing as hardware and software continue to be developed.  
Software, firmware, and documentation revisions are expected to be 
issued frequently.  Policy and technical guidance will thus be 
subject to change and some information may be specific to a 
particular system (i.e. signal frequency), or version which may 
not be the most current.  Some general information, and especially 
the QA/QC guidance should be less transitory.  The interim policy 
provided here is for the 1200 kHz transducers using the transect 
software, release 2.62.


These policies apply to use of the BB-ADCP for making velocity 
profile and discharge measurements from moving boats, and are in 
effect until further technical information and more informed 
policies are provided.


The 1200 kHz BB-ADCP can measure discharge for a limited range of 
flow conditions.  Based on manufacturer recommendations and 
preliminary measurement verification information, the following 
conditions must be met for general use of the BB-ADCP to measure 
velocity profiles or discharge for basic data.  Measurements made 
at the limits of these conditions generally will not produce 
highly accurate results and will require specific error analysis.


6Vbar>0.4 fps                  10%

These and other measurement conditions (site characteristics and 
instrument operation) must be assessed to correctly set up the 
instrument/software, to determine appropriate measurement 
techniques, and to check the results for errors.  Some measurement 
conditions to be assessed are listed on the BB-ADCP Discharge 
Measurement Note form.  When a measurement condition appears 
problematic, measurement documentation should include:  (1) a 
brief description of the condition, (2) methods used to determine 
if the condition (i.e. mobile stream bed) is significant to the 
measurement, (3) how the effects of the conditions were accounted 
for (i.e. appropriate instrument operating modes, configuration 
file settings, tests, and error analyses).  Additional 
considerations on making discharge measurements are described in 
Rantz, 1982.  Measurement conditions to be assessed include the 

     Mobile stream bed
     Estimation of flow at channel edges
     Pitch and roll of boat platform
     Measurement starting and stopping procedures
     Side Lobe Interference
     Heading (compass) errors
     Shallow-depth-caused errors not covered elsewhere
     Vessel speed during measurement
     Vessel course during measurement
     Estimated velocity in unmeasured part of vertical

A minimum of two transects, one in each direction, is required for 
a discharge measurement.  The measured discharge will be the 
average of the transect discharges.  If the first two transect 
discharges vary by more than 5 percent, under steady flow 
conditions, then at least one more set will be obtained.  Transect 
measurements suspected to contain unusual errors should not be 
used to determine the discharge measurement, but should be saved 
and summarized on the ADCP Discharge Measurement Note form.  The 
top width of the unmeasured edge-flow area will be measured as the 
distance from the bank to the instrument (not to the stream-gager 
or another position on the boat).  


The operation of the BB-ADCP uses technology which is highly 
complex when compared to use of our standard Price-AA meters.  
Several factors must be evaluated and understood in order to 
optimize the set-up of the BB-ADCP for a particular measurement, 
and to evaluate the quality of that measurement.  Districts using 
or planning to use BB-ADCPs are encouraged to develop expertise in 
the use of this device.   Parties making discharge measurements 
using the BB-ADCP must include a person who has (1) attended 
initial training in the use of the BB-ADCPs; (2) become familiar 
with the basic principals of operation of BB-ADCPs; (3) learned 
the principal BB-ADCP velocity and discharge measurement error 
sources and how to evaluate and minimize them; and (4) knows the 
operation and options of the Transect Software.  This information 
can be gained by experience, RDI manuals, other relevant 
literature, and training.  Initial training is currently defined 
as attendance of a workshop taught by RDI personnel or Mike 
Simpson of the California District, USGS.  A BB-ADCP course is 
being developed to address training needs.


Measurements made with the BB-ADCP should be documented on the 
standard 9-275 C or G, (all applicable information) and on the 
attached BB-ADCP Discharge Measurement Note form.  (This form is 
not an official government form and may be revised in a subsequent 
memorandum.  Your comments on how it may be improved are welcomed 
in the ADCP continuum.)  Each measurement should be checked.  The 
BB-ADCP configuration file and the raw data file for each of the 
transects making up the measurement should be saved on floppy 
diskette.  Districts may wish to archive additional files or data.  
We hope to have a software modification that will create a log-
form for each measurement that includes site measurement 
condition, instrument configuration, and measurement data. 

                                      Charles W. Boning




The Office of Surface Water (OSW) requests discharge measurement 
data from BB-ADCPs in conjunction with data from standard 
discharge determination procedures, for the purpose of making 
verifications of BB-ADCP collected discharge data.

In order for data to be used as a BB-ADCP discharge verification, 
the following criteria should be met:  The true discharge at the 
site of the BB-ADCP measurement must be known to an accuracy of 
5 percent or better.  The true discharge estimate should be based 
on a stage-discharge relation which is very stable for the part of 
the rating within which the measurement was made.  The stability 
of the rating must be well documented by standard current meter 
measurements which plot within 5 percent.  A concurrent discharge 
measurement using standard methods is always desirable but is not 
required where documentation of rating stability is very good.

To supply OSW with your data for this verification effort, please 
fill out this form and attach the items specified on page 3.

District or Field Office _________________________________________
Date ____________________
Contact Person ______________________ Telephone no. ______________

ADCP Measurements

Date(s) of measurements ____________________
Time period in which measurements were made ______________________
Number of transects used to determine discharge __________________
Was TRANSECT used?  Yes _____ No _____

Measurement Conditions

Flow (uniform, rapidly varying, etc.) ____________________________
Cross-section (sand, rock, mud, etc.) ____________________________
Stage (steady, fluctuating, steady rise, etc.) ___________________
Maximum measured cross-sectional depth ___________________________
Minimum measured cross-sectional depth ___________________________
Cross-sectional width ____________________________________________
Estimated mean channel velocity __________________________________
Was the appearance of unusually high suspended 
sediment concentrations observed or noted during 
the ADCP measurements? ___________________________________________
Was the water unusually clear? ___________________________________
Was substantial movement of the cross-sectional bottom 
material observed, noted, or suspected during the 
ADCP measurements? _______________________________________________
Remarks (unusual conditions, etc.) _______________________________

ADCP Deployment

Boat mounting location (bow, starboard side, etc.) _______________
Was any ferrous material present in the ADCP mount or other boat
equipment?  If yes, specify ______________________________________
Were the transects run near any large structures containing 
ferrous materials, such as bridges or high-tension towers?  If 
yes, specify distance type and approximate distance from transects 
Specify method used to determine transect edge distances (EDL, 
steel tape, estimate by eye, etc) ________________________________

Non-ADCP Determination of Discharge

Non-ADCP discharge determination for the period of ADCP 
measurements made from:
  1.  ______ gaging station rating curve
  2.  ______ Price AA or pygmy meter measurement(s)
  3.  ______ Neil Brown current meter measurements
  4.  ______ other (specify) _____________________________________

Description of Instrument

Instrument owner _________________________________________________
Instrument I.D. no. (i.e. serial no. or W no.) ___________________
Transducer frequency __________________________ kHz
Beam angle ___________ degrees
Type of transducer head:  Concave _____ Convex _____


Please attach the relevant items specified in the following 

  1. ______ ADCP CONFIG file (printout or on disk)
  2. ______ All ADCP raw data files on disk
  3. ______ Copies of the ADCP measurement note forms
  4. ______ Copies of the standard discharge measurement note 
            forms if standard current meter measurements were made
  5. ______ A copy of the current rating table
  6. ______ Copies of the last five discharge measurements made
            at the station to confirm the rating
  7. ______ Any miscellaneous field note forms
  8. ______ Other documentation which may be helpful

Please return this form plus the attachments to:

U.S. Geological Survey
Indiana District
5957 Lakeside Boulevard
Indianapolis, IN  46278
Attention:  Scott Morlock