Report on  WMO Exploratory Meeting on CHy's Proposal for the Assessment of the Performance of Flow Measurements Instruments and Techniques, April 2007

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Report on
WMO Exploratory Meeting on CHy's Proposal for the Assessment of the Performance of Flow Measurements Instruments and Techniques
25th to 27th April 2007
Geneva, Switzerland

This report covers various items from the meeting considered of particular interest to the HMEI Membership and is not intended to be definitive.
Please see the presentations at the meeting and the WMO Final Report of the meeting from this link http://www.wmo.int/pages/prog/hwrp/FlowMeasurement.html

As a consequence of the meeting,  the original proposal has been revised, in particular the Expected Outputs of the initiative and the Work Plan. You can find this revised version (dated 6/6/2007) on the same link indicated above.

Attendees
For the full attendees list please see the Participants List here

HMEI was represented by:
Gerhard Pevny - LOGOTRONIC
Gayle Rominger - YSI (USA)
Ian Thompson - YSI (Europe)
Bruce Sumner - HMEI Executive Secretary
Christine Charstone - HMEI Administrator

Opening at 9.00
The meeting was opened and topic introduced by Dr Tyagi, who thanked the attending experts for participating in the meeting. Dr Tyagi stated his expectations for good planning to be achieved for this potential instrument assessment. Dr Tyagi proposed Dr Paul Pilon to chair the meeting. This was universally accepted.

Introduction by Dr PAul PILON and slide presentation
The Chairman welcomed the attendees and his pleasure in seeing a larger than anticipated participation and interest in the subject. He stressed the informal nature of the meeting and that this was a "brainstorming" meeting to decide the needs and possible future of an assessment of this instrumentation. He also introduced the Hydrology Commission, its work within WMO. He gave a presentation on the Thematic Area, within CHy, under which this assessment falls. This presentation included the CHy Terms of Reference (TORs) for that Theme. See these TORs here.

Proposal for the Assessment of the Performance of Flow Measurement Instruments and Techniques by Ms J Fulford et al.
This was presented by Janice Fulford. Some points introduced in this presentation:

  • Need for information on quality testing to be disseminated;

  • Need for new instrument techniques to be assessed;

  • Need for standardization for hydrometric measurements;

  • Need for participation of instrument manufacturers for support and loan of instruments in assessments and testing.

Objectives and outcomes expected:

  • Compile existing information for dissemination;

  • Creation of standards for Hydrometric measurements;

  • Provide a website for sharing and dissemination of information on this issue;

  • Testing of hydrometric instrumentation, both traditional and newer technologies;

  • Guidelines for testing of instrumentation and methodologies to known standards.

Examples of National Approaches to Assessment of Flow Measurement Instruments and Techniques Present Status of Streamflow

Measurement Techniques in Korea by Dr W Kim
 Dr Kim's presentation showed the meeting the interesting and extensive work Korea has completed on several newer technologies:

  • ADCP
  • Ultasonic Velocity Meter
  • Index Velocity Method
  • Use of Small Dam (Weir)
  • Large Scale Image Velocimetry
  • Image Level Maker
  • Pressure Water Level Senor
  • Ubiquitous River Boat

The presentation raised interest, questions and comments from the meeting. Korea's experience will obviously be useful to the proposal of the meeting. The methodologies, especially regarding "establishing system for providing real-time streamflow data", were especially of interest to the meeting.

Presentation from France by Mr Jérôme Le Coz
In this presentation the demand for accuracy in flow measurement was outlined, as were the technical difficulties and challenges involved.
His presentation covered:

1. River flow measurements in France:

  • Floods, rivers and uses;
  • Hydrometric services;
  • Needs for methodology and metrology.

2. Assessment of the instruments and techniques performance:
  • Uncertainties associated with various gauging methods;
  • Field tests and aDcp regattas;
  • Rating curves: uncertainty assessment and extension.

3. Research on innovating methods:
  • Acoustic Doppler current profilers (aDcp, Groupe Doppler);
  • Discharge monitoring systems;
  • Projects for video-based field measurements (LS-PIV)

France has done considerable work with testing during 2006 in the issues as noted above.

The importance of sharing information was stressed and the importance of the dissemination of information. France is publishing information on aDPC methodologies which is currently in French but will soon be available also in English.

Canada - The assessment of the Performance of Measurement Instrumentation by Patrick J McCurry
Water Survey of Canada (WSC) has leveraged with other "Hydrological Services" on technology sharing and training issues at the provincial and governmental levels and with United States Geological Survey (USGS), universities and other research institutes.

WSC has worked closely with USGS on the development, evaluation, quality assurance and training in areas including:

  • Testing commercially available technologies;
  • Working with selected manufacturers and research scientists;
  • Investigation of flow disturbance around transducer heads;
  • Methods of dealing with moving bed situations for hydroacoustics;
  • Alternatives to GPS for hydroacoustics;
  • Measurement platforms.

WSC has also:

  • Done a comparison of hydroacoustic instruments against a Price AA meter. Instruments tested were: TRDI; ADCP; StreamPro; Sontek; Flowtracker;
  • Written operational specifications for (moving boat) acoustic Doppler technology;
  • Implemented a policy on use of acoustic Doppler data for final data production;
  • Produced ADCP procedural manuals;
  • Developed an ADCP accreditation process.

Some issues raised from his presentation were:

  • Some instruments have "black box" software which can cause problems with data integrity and Intercomparisons.
  • WSC provides a list of "Qualified Products" which meet their operational specifications  (therefore other products are not used operationally by them).

USGS Presentation - Assessing Flow Measurement Instruments by Janice Fulford
USGS has:

  • Several extensive Instrument testing facilities in the US; both Field and Laboratory testing;
  • However testing standards are not rigorous.

It was noted by one of the HMEI manufacturer representatives that this work is very valuable from the vendors viewpoint.

USGS have identified a demand for uncertainty analysis of measurements.

Information is disseminated through:

Uncertainty Analysis (UA) for Flow Measurements and Techniques using Standardized Methodology by Mr Marion Muste
Points in this presentation:

  • The best guide on this issue was identified as: ISO, 1993 - Guide to the Expression Uncertainty Measurement (ISO, 1993). This has been adapted by various scientific and research communities.
  • Mr Muste described in detail, for the meeting, UA using  Standardized Methodology.
  • The need was noted for coordination and extensive evaluation among  ADCP manufacturers, operators, data users and third party evaluators.

General Discussion
The group discussed the identification of errors. It was decided that there was a need to quantify error biases for different instruments. Standardized procedures need to be defined to minimize and regularize biases. Traceability to primary standards is not generally available for ADCP instruments. The group checked, added to and subtracted from the proposed tasks for the proposed assessment of flow measurement instruments. A Work Plan was established to progress the proposal and identify the tasks to be undertaken.

Governance
A discussion on governance, and who will be responsible for the various components of the Work Plan, was conducted. Also there was a discussion of the composition of the working group membership. It was decided to form a team of a small group of experts to form a Steering Group. The steering group would also be active members of the Expert Team. HMEI was nominated for, and accepted, a position on the Steering Group.

Website
WMO will host the website where all the data collected by the Work Plan will be made available. This will include links to manufacturer’s instrument specifications, establishing protocols and specifications and developing sample formats for reporting testing and verification results.

Summary
The participation of HMEI and their experts from the manufacturers was recognized and appreciated by the meeting. The HMEI manufacturers' representatives participated actively and their input was a valuable contribution to this preparatory meeting. Ian Thompson of YSI subsequently made available to the meeting participants documentation on Discharge Uncertainty that will be useful information for the group.

It was recognised by the meeting that the continued involvement of HMEI in this issue was important for the success of assessments arising from this meeting. This continuing involvement is ensured by the above mentioned position of HMEI on the Steering Group.

There is an International Association of Hydraulic Engineering and Research (IIHR) website database of hydrology instruments at http://www.iihr.uiowa.edu/ 

Closing of the conference
The meeting closed on Friday afternoon, 27 April 2007.