Presentation on theme: "Overview of ADCP “Best Practices” Report"— Presentation transcript:
1 Overview of ADCP “Best Practices” Report Measuring Discharge with Acoustic Doppler Current Profilers from a Moving BoatTechniques and Methods ReportChapter 22 of Book3, Section A
2 Overview Why a Techniques and Methods Report Organization of the reportHighlight selected topicsChanges to existing policyQuick-Reference guides and other formsAvailability of printed copies
3 Why and HowCOE funded development of two guidance reports for ADCP useDischargeVelocity MappingRevised more general COE report to USGS specific T&MUSGS specific policyStreamProUpdated with latest guidance
4 Source of Material Little “new” information Consolidated information from:QA/QC reportOSW Technical MemosADCP Training ClassesHydroacoustic UpdatesAdded some changes to guidance based on latest experiencePublished to allow additional updates without republishing entire report
5 Organization Main Body contains guidance Appendices contain details Predeployment PreparationField ProceduresOffice ProceduresAppendices contain detailsBasic ADCP Operational ConceptsCollecting Data in Moving-Bed ConditionsDescription of Water ModesBeam-Alignment TestsForms and Quick-Reference GuidesMeasurement Review Procedures
6 A) Excessive Backscatter B) Excessive Attenuation PredeploymentUnderstand basic limitations of ADCPApply ADCP limitations to site selection and expected performance in the fieldSedimentUnmeasured areasConfigurationCompassA) Excessive BackscatterB) Excessive Attenuation
7 Predeployment – cont. Instrument Quality Assurance Beam Alignment Test Recommended1st acquiredAfter factory repairAfter firmware or hardware upgradesPeriodicallyDetailed procedures in Appendix DTypically for Rio Grandes and RiverSurveyorsPeriodic Instrument Comparison
8 Predeployment – cont. Ancillary Equipment GPSVTG and GGAEcho SounderDeployments and MountsOther EquipmentFinal Equip Preparation and InspectionVerify all computer connections and communications before going to the field!!
10 Field Procedures Site Selection Pre-Measurement Field Procedures Maybe the most important thing you do in the field.Location, shape, velocity, otherPre-Measurement Field ProceduresSet clockDiagnostic testsSpeed of sound (temp and salinity)Compass calibrationInstrument configurationUse wizardsMoving-bed tests
11 Policy ChangeUSGS 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 providedin 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, everymoving-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 preferredStationary testsWhenIf compass calibration is not goodIf bottom tracking cannot be maintainedStreamProHow5-minutes in durationWith GPSFrom a tagline or bridge or anchored10-minutes in durationNo GPS from manned or RC-boatThese 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 ProceduresNo changes to existing guidanceStep by step quick-reference guides in Appendix EPost-Measurement Field ProceduresAn 8-pass measurement due to one or more transects being >5% from mean does not constitute a check measurementCheck measurements are required according to criteria in WSP 2175
14 Office Procedures Preventive Maintenance Data Storage Saves time in the long term!!!Data StorageFollow office policyPut data on server (usually within 72 hours)Measurement ReviewData-Quality IndicatorsCommonly 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.ConfigurationCorrect and appropriateUser input agrees with field formEdge, 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 IIRiverSurveyor
25 Appendix A – Basic Concepts Doppler ConceptsNarrowband and BroadbandComputing Velocity in Orthogonal CoordinatesMeasuring a Velocity ProfileComputing Discharge
26 Appendix B- Collecting Data in Moving-Bed Conditions Cause and Effect of Moving-BedMethods to Indentify a Moving BedMore detail than in main body of reportStationary, no GPSStationary, with GPSLoopMethods to Account for Moving-Bed EffectsGPSLoop methodMultiple moving-bed test methodMid-section methodAzimuth method
27 Appendix C – Description of Water Modes SonTek/YSI RiverSurveyorTRDIRio Grande15/1112StreamPro13, C, Low-Noise
28 Appendix D – Beam-Alignment Test Detailed instructions and criteria for conducting a beam alignment testTypically only applied to:Rio GrandeRiverSurveyor
33 Availability PDF version available now Printed version Linked fromPrinted version3-hole punch, loose leafIn printing now, available in a couple of monthsAnnouncement memo will be accompany printed version.