Overview of ADCP “Best Practices” Report

1. Overview of ADCP “Best Practices” Report Measuring Discharge with Acoustic Doppler Current Profilers from a Moving Boat Techniques and Methods Report Chapter 22 of Book3, Section A

2. Overview • Why a Techniques and Methods Report • Organization of the report • Highlight selected topics • Changes to existing policy • Quick-Reference guides and other forms • Availability of printed copies

3. Why and How • COE funded development of two guidance reports for ADCP use • Discharge • Velocity Mapping • Revised more general COE report to USGS specific T&M • USGS specific policy • StreamPro • Updated with latest guidance

4. Source of Material • Little “new” information • Consolidated information from: • QA/QC report • OSW Technical Memos • ADCP Training Classes • Hydroacoustic Updates • Added some changes to guidance based on latest experience • Published to allow additional updates without republishing entire report

5. Organization • Main Body contains guidance • Predeployment Preparation • Field Procedures • Office Procedures • Appendices contain details • Basic ADCP Operational Concepts • Collecting Data in Moving-Bed Conditions • Description of Water Modes • Beam-Alignment Tests • Forms and Quick-Reference Guides • Measurement Review Procedures

6. Predeployment • Understand basic limitations of ADCP • Apply ADCP limitations to site selection and expected performance in the field • Sediment • Unmeasured areas • Configuration • Compass B) Excessive Attenuation A) Excessive Backscatter

7. Predeployment – cont. • Instrument Quality Assurance • Beam Alignment Test • Recommended • 1st acquired • After factory repair • After firmware or hardware upgrades • Periodically • Detailed procedures in Appendix D • Typically for Rio Grandes and RiverSurveyors • Periodic Instrument Comparison

8. Predeployment – cont. • Ancillary Equipment • GPS • VTG and GGA • Echo Sounder • Deployments and Mounts • Other Equipment • Final Equip Preparation and Inspection • Verify all computer connections and communications before going to the field!!

9. Checklist in Appendix E

10. Field Procedures • Site Selection • Maybe the most important thing you do in the field. • Location, shape, velocity, other • Pre-Measurement Field Procedures • Set clock • Diagnostic tests • Speed of sound (temp and salinity) • Compass calibration • Instrument configuration • Use wizards • Moving-bed tests

11. Policy Change USGS policy (U.S. Geological Survey, 2002b; Oberg and others, 2005) requires that a moving-bed test be conducted prior to making a discharge measurement. In USGS training classes and in Oberg and others (2005), an exception to conducting a moving-bed test with every measurement was allowed if sufficient documentation was provided in the field folder to justify not conducting a moving-bed test. Field experience has shown that sediment transport characteristics can vary greatly for the same discharge, depending on the hydrograph shape, source of runoff, and season of the year. Thus, a moving bed may be detected at a location and discharge where one was not previously detected, or a moving bed may no longer exist at a location and discharge where one was previously detected. Moving-bed conditions also have been observed in low-velocity environments (less than 1 ft/s) and are likely caused by organic material transported by the water. Therefore, to ensure the quality of the data collected, every moving-boat measurement made with an ADCP must have a recorded moving-bed test. If a site routinely has a moving bed and GPS is always used with the ADCP, a moving-bed test is still required but need only be 5 minutes in length. This requirement supersedes Oberg and others (2005) and various USGS training materials.

12. Moving-Bed Test Requirements • Loop test preferred • Stationary tests • When • If compass calibration is not good • If bottom tracking cannot be maintained • StreamPro • How • 5-minutes in duration • With GPS • From a tagline or bridge or anchored • 10-minutes in duration • No GPS from manned or RC-boat These criteria supersede the guidance on stationary moving-bed tests that have been published previously in U.S. Geological Survey (2002b) and Oberg and others (2005).

13. Field Procedures – cont. • Discharge Measurement Procedures • No changes to existing guidance • Step by step quick-reference guides in Appendix E • Post-Measurement Field Procedures • An 8-pass measurement due to one or more transects being >5% from mean does not constitute a check measurement • Check measurements are required according to criteria in WSP 2175

14. Office Procedures • Preventive Maintenance • Saves time in the long term!!! • Data Storage • Follow office policy • Put data on server (usually within 72 hours) • Measurement Review • Data-Quality Indicators • Commonly Observed Problems

15. Measurement Review • Field forms complete, understandable, and legible. • Electronic files backup in field and archived in office. • Number of transects appropriate and in reciprocal pairs. • Configuration • Correct and appropriate • User input agrees with field form • Edge, top, and bottom extrapolations appropriate

16. Measurement Review – cont. • Independent temperature measurement recorded and checked. • Salinity measured and recorded. • Moving-bed test recorded and appropriate procedures used. • Slow smooth boat operation. • Edge distance measured, recorded, and consistent with electronic data. • Number and location of missing or invalid ensembles are acceptable.

17. Measurement Review – cont. • Number and location of invalid depth cells are acceptable. • Top and bottom extrapolation methods have been reviewed and are appropriate. • Measurement computations, including mean discharge and measurement gage height, are correct.

18. Missing and Invalid Data WinRiver II RiverSurveyor

19. Ambiguity Errors

20. Signal Attenuation

21. Beam Impinging on Wall

22. Smooth Boat Operation WinRiver II RiverSurveyor

23. Spikes in Streambed

24. Bad GPS

25. Appendix A – Basic Concepts • Doppler Concepts • Narrowband and Broadband • Computing Velocity in Orthogonal Coordinates • Measuring a Velocity Profile • Computing Discharge

26. Appendix B- Collecting Data in Moving-Bed Conditions • Cause and Effect of Moving-Bed • Methods to Indentify a Moving Bed • More detail than in main body of report • Stationary, no GPS • Stationary, with GPS • Loop • Methods to Account for Moving-Bed Effects • GPS • Loop method • Multiple moving-bed test method • Mid-section method • Azimuth method

27. Appendix C – Description of Water Modes • SonTek/YSI RiverSurveyor • TRDI • Rio Grande • 1 • 5/11 • 12 • StreamPro • 12 • 13, C, Low-Noise

28. Appendix D – Beam-Alignment Test • Detailed instructions and criteria for conducting a beam alignment test • Typically only applied to: • Rio Grande • RiverSurveyor

29. Appendix E – Forms andQuick-Reference Guides

30. Rio Grande Quick Sheet

31. RiverSurveyor Quick Sheet

32. Appendix F –Measurement Review Guides

33. Availability • PDF version available now • http://pubs.usgs.gov/tm/3a22/ • Linked from http://hydroacoustics.usgs.gov/ • Printed version • 3-hole punch, loose leaf • In printing now, available in a couple of months • Announcement memo will be accompany printed version.

34. Questions