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OSW Hydroacoustics

Known Issues

The Office of Surface Water has compiled a list of issues associated with hydroacoustic instruments in use in the Water Mission Area. The items listed below are the major issues that OSW is working to resolve. The intent of this list is to assist hydrographers using ADCPs, ADVs, and ADVMs by sharing these issues, the status of work on the issues, and any potential work-arounds. This list will be updated regularly.

SonTek iQ Plus

Issue Status Solutions
Bias in Computed Discharges
Testing by USGS HIF in the Hydraulics Lab and field comparisons by Colorado Division of Water Resources have indicated that computed discharges may be biased low in some channels and situations.
No additional testing is planned. The iQ Plus discharge computation feature is not used in the USGS. Additional tests by the HIF shown that a previously-detected velocity bias is much reduced with firmware 1.60. The iQ Plus should be suitable for application of the index velocity method (Levesque and Oberg, 2012) if firmware version 1.60 or later is installed.

Teledyne RD Instruments WinRiver II

Issue Status Solutions
Compass Evaluation Not Stored
Rio Grande compass evaluation is not stored if the "Close" button is pressed after total error reported but before the "Evaluate" and "Calibrate" buttons are re-enabled.
Present in WRII v. 2.10 and earlier Wait until the "evaluate" and "calibrate" buttons are re-enabled before closing.
"Negative" SMBT Results Not Used
When multiple stationary moving bed tests (SMBTs) are completed, checked, and some SMBTs indicate a moving bed correction is needed, any SMBT that has slightly negative (downstream) motion will not be used in determining the proportional correction.
Present in WRII v. 2.10 and later If multiple stationary MBTs are required for a correction, attempt to collect any tests where no moving bed is detected and the SMBT result is not negative and a near-zero moving-bed velocity will be used to determine the moving bed correction.
SMBT Application Not Recommended
When using the SMBA corrections, a correction will be applied if the moving bed test is checked, even if slight there is upstream boat motion for the SMBT.
Present in WRII v. 2.10 and later Uncheck all moving bed tests when no correction is warranted; ie. moving bed velocity is < 1% of mean flow speed.
RiverPro Will Not Start Pinging
The OSW has multiple reports from users saying that they are unable to get the RiverPro to ping. This occurs even after successfully completing the configuration wizard, compass calibration, and diagnositc tests. The problem seems to be related to the laptop or tablet in use and the way that WinRiver II communicates with ADCP.
Problem exists in 2.16 and prior versions. It seems that if any user command is entered, users can successfully initiate pinging. Most people experiencing this problem find that entering the CR1 command in the User Commands section of the configuration wizard solves the problem. Some users, but not all, have reported that the problem disappears when they switch to v. 2.16.

Teledyne RD Instruments RiverPro / RioPro

Issue Status Solutions
RioPro Blanking Distance
The default blanking distance for the RioPro is 10 cm. Given that the diameter of the RioPro is unchanged from the Rio Grande ADCP, the blanking distance probably ought to be 25 cm in order to minimize bias in measured velocity caused by flow disturbance (Mueller and others, 2007). RioPro (and RiverPro) firmware adjusts the blanking distance automatically to account for backscattering conditions and their effect on ringing.
Reported to TRDI. USGS evaluating this issue by reviewing comparison measurements. As a precaution, the OSW recommends an "Excluded Distance" of 0.82 ft be applied in QRev when processing data collected with a RioPro.
Depth Reference
For RiverPro ADCPs equipped with a vertical beam, discharges computed using the vertical beam as a reference tend to be less than discharges computed using the 4-beam average.
See entry for RiverRay ADCPs See entry for RiverRay ADCPs

Teledyne RD Instruments RiverRay

Issue Status Solutions
Low-backscatter Bias
Prior to firmware version 44.13, RiverRay discharges were biased low when the backscatter was low (< 70 dB).
Although firmware 44.13 seemed to eliminate the issue, there have been a few reports of the low bias issue occurring, but his may be caused by external interference. If the discharge measured using a RiverRay is unexpectedly less than the expected discharge during low backscatter conditions: (1) make a comparison measurement with another instrument, and (2) report results to OSW.
Depth Reference
For RiverRay and RiverPro ADCPs equipped with a vertical beam, discharges computed using the vertical beam as a reference tend to be less than discharges computed using the 4-beam average.
The cause(s) for depth differences is the subject of active research by USGS and TRDI. Modified firmware (44.16) reduced, but did not eliminate, differences. USGS research suggests that the firmware and transducer design may contribute to these differences, but these are preliminary conclusions at present. For RiverRay ADCPs equipped with a vertical beam, OSW recommends that the depth reference ("River Depth Source" in WinRiver II) be set to "BT Depth". However, if the depths from the 4-beam average are suspect for any reason, it may be desireable to switch to "Vertical Beam" or "Composite". This recommendation applies to RiverPro ADCPs also.

Teledyne RD Instruments StreamPro

Issue Status Solutions
Acoustic/Electromagnetic Interference
Some StreamPro measurements are susceptible to interference. Identified by examination of the PT3 test and by increases in correlation or vertical velocity with depth.
Exists in all firmware. Is site-dependent. OSW is preparing guidelines on how to detect the problem. No known solution. Use another instrument. Because the issue is site dependent and evidence suggests that it is constant in time, use of the StreamPro at these locations is not recommended.

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