In Reply Refer To:† December 7, 2001
Mail Stop 415
OFFICE OF SURFACE WATER TECHNICAL MEMORANDUM NO. 2002.02
SUBJECT:† Policy and Technical Guidance on Discharge Measurements using Acoustic Doppler Current Profilers
The purpose of this memo is to provide policy and technical guidance for the measurement of discharge using acoustic Doppler current profilers (ADCP's).† The term ADCP is used here to describe acoustic Doppler profiler instruments used for making velocity-profile and discharge measurements from moving platforms and does not refer to any specific brand or model.† This memo supersedes Office of Surface Water (OSW) Technical Memorandum 96.02, Interim Policy and Technical Guidance on Broadband Acoustic Doppler Current Profilers.†
Policy and technical guidance described in this memo is based on knowledge and experience with ADCPís obtained by the USGS during the past 8 years, OSW training materials, and the report Quality Assurance Plan for Discharge Measurements Using Broadband Acoustic Doppler Current Profilers (Lipscomb, 1995).† Although this report still is mostly applicable, it currently is in revision.† Policies and guidance discussed in this memo supercedes information found in Lipscomb (1995).† The policies described in this memo have been reviewed by the OSW Hydroacoustics Work Group (OSW Memorandum).†
ADCP performance and operational characteristics are changing frequently as hardware and software continue to improve.† Frequent revisions of software, firmware, and documentation revisions are expected in the foreseeable future.† Thus, policy and technical guidance will be subject to change and revision, and some information may be specific to a particular system, version, or manufacturer.
The following policies apply to use of the ADCPís for making velocity-profile and streamflow measurements from moving vessels.
The following policies for measurements of streamflow using ADCPís are provided:
The vessel used to make the moving bed test should be held in a stationary position for about 10 minutes, provided that this can be done safely.† While in this stationary position, ADCP data should be recorded and examined for any apparent upstream movement of the boat relative to the channel bottom.† If apparent upstream boat movement is measured, then the water velocity measured by the ADCP will be less than the true water velocity and the discharge measured by the ADCP will be less than the true discharge.†
The DGPS must be capable of sub-meter accuracy.† When using a DGPS, it is necessary to properly calibrate the internal compass of the ADCP, and to measure or obtain an accurate estimate of the local magnetic variation.† For more information on compass calibrations and use of DPGS, users are directed to the OSW ADCP Web pages, manufacturer help files, and are encouraged to attend the Advanced ADCP Applications training class (http://hydroacoustics.usgs.gov/training/).
Personnel collecting and reviewing ADCP data for discharge measurements must have completed the USGS training class, Measurement of Streamflow using ADCPís.† For more advanced applications and measurement situations, including the use of DGPS; users are strongly encouraged to complete the USGS training class, Advanced ADCP Applications.† Information regarding USGS ADCP training classes may be found at http://hydroacoustics.usgs.gov/training/.
Users are responsible to keep current with policies, and recommended procedures and practices.† Attendance of a recent ADCP training classes or the USGS Hydroacoustics Workshop, subscription to the acoustics mailing list, and review of the OSW ADCP Web pages are all valid ways of keeping current.
Measurements made with the ADCP should be documented using the acoustic profiler discharge measurement note sheet (Attachment A--http://il.water.usgs.gov/adcp/memos/index.html).† When processing ADCP measurements, measurement data should be carefully reviewed.† Listed below are the most common problems found when reviewing ADCP data.
The Hydroacoustics Work Group currently is developing tutorials on finding and correcting some of these problems.† When they become available on the OSW ADCP Support World Wide Web pages (http://hydroacoustics.usgs.gov/), an announcement will be made to the acoustics mailing list (firstname.lastname@example.org).†
For additional information regarding these policies and guidance, please contact Kevin Oberg by phone (217-344-0037 ext 3004) or by email (email@example.com).†
Trimble Navigation Limited, 1999, AgGPS 124/132 Operation Manual: Trimble Navigation Limited, Sunnyvale, CA, USA, 170 p.
Lipscomb, S.W., 1995, Quality assurance plan for discharge measurements using Broadband acoustic Doppler current profilers:† U.S. Geological Survey Open File Report 95-701, 12 p.
Rantz, S.E., and others, 1982,† Measurement and computation of streamflow, Volume 1, Measurement of discharge:† U.S. Geological Survey Water-Supply Paper 2175, 631 p.
††††††††††††††††††††††† J. Michael Norris
††††††††††††††††††††††† Acting Chief, Office of Surface Water
WRD DISTRIBUTION:† A, B, FO, PO