1. David S. Mueller U.S. Geological Survey Office of Surface Water
Comparison of Discharge Measurements Made Using the ADCP and Price Current Meters
David S. Mueller
U.S. Geological Survey
Office of Surface Water

2. Overview Purpose of Validation Instrument Check Field Validation
Laboratory Tests
Specialty Tests
Field Validation
Cup meter – ADCP method comparison
Collecting comparison measurements
Results to date
Ongoing Work
Summary and Conclusions

3. Purpose of Validation Assess accuracy Assess repeatability
Requires knowledge of the true value
What is the true discharge?
Assess repeatability
Measurements
Instruments
Data consistency and limitations
Instruments (Acoustic, Mechanical, etc.)
Users
Field conditions

4. Laboratory Tests Advantages Disadvantages Controlled conditions
Traceable to standards
Isolate specific conditions
Repeatable experiments
Disadvantages
Acoustic and magnetic interference
Tow tank tests lack turbulence
Backscatter material must be added
Backscatter uniformity
Flowing water – no traceable standard

5. Summary of Results Mean % Difference Mfgr Instrument BT WT TRDI
BB-WM 1
0.96
-0.87
BB-WM 5
0.99
-0.70
Rio Grande
-2.33
-0.78
SonTek
ADP
-1.50
-2.10

6. Specialty Tests Beam Alignment Test GPS vs BT discharges
Compare GPS to BT distance made good
Acceptable ratio: to 0.995
GPS vs BT discharges
Compared where no moving bed
Tests compass and bottom track
GPS vs BT ship tracks
Lag in GPS data

7. Field Validation Advantages Difficulties Real conditions
Turbulent flow
Irregular bed
Difficulties
Need variety of conditions
Time consuming
Repeatability / steady flow ???
What is the reference discharge?
Price meter or Rating

8. Difference in Methods AA meter ADCP Measures water speed
Direction assigned by user
Discrete point measurements
Velocity profile assumed
ADCP
Measures 3-D velocity
Profile measurements
Velocity profile extrapolated at top and bottom
Continuous measurement across stream
Large spatial sampling area `

9. Broadband Comparisons
Morlock, S.E., 1996, Evaluation of acoustic Doppler current profiler measurements of river discharge, USGS WRIR
12 gaging stations
9 states
31 ADCP measurements
Reference
Primarily stable ratings
Adjusted ratings
7 current-meter measurements to validate or adjust ratings
Characteristics
Width: 140 – 3,600 ft
Mean Depth: 5 – 25 ft
Mean Velocity: 0.7 – 3.8 ft/s
Discharge: 758 – 59,800 cfs
Results
26 within 5% of reference
All within 8% of reference

10. Initial Rio Grande Comparisons
Mueller, D.S., 2002, Field assessment of acoustic-Doppler based discharge measurements in ASCE Hydraulic Measurements and Experimental Methods 2002.

11. Initial Testing Results

12. More Field Data – Much More

13. Reference Discharge Simultaneous measurements
Sequential ADCP and reference measurement
Accurate gate, weir, or hydropower ratings
Stable accurate stage-discharge ratings

14. International Cooperation
U.S. Geological Survey
Environment Canada
Swedish Meterologic and Hydrologic Institute (SMHI)
Norwegian Water Resources and Energy Directorate (NVE)
Rijkswaterstaat Oost – Netherlands

15. Rio Grande Validation
Oberg, K.A., and Mueller, D.S., 2007, Validation of streamflow measurements made with acoustic Doppler current profilers, ASCE Journal of Hydraulic Engineering, Vol. 133, No. 12, December 2007, p
Water Mode
Number of Comps
Sites
Mean Depth (ft)
Mean Velocity (ft/s)
Discharge
(cfs)
Mean Percent
Diff.
Max. Percent Diff. 1 28 11
4.6 – 29.5
1.2 – 4.9
706 – 177,000
0.5
5.6
5/11 6
2.1 – 7.9
0.3 – 1.7
67 – 1,560
0.3
7.1 12 61 16
1.6 – 9.3
0.3 – 4.9
64 – 6,990
-0.1
-15.9
All
100 22
1.6 – 29.5
64 – 177,000

16. Plots of Reference Q vs ADCP Q
Mode 5/11
Mode 12
Mode 1
t-Test
p=0.41
t-Test
p=0.75
t-Test
p=0.85

17. Ongoing Comparison TRDI Rio Grande TRDI Streampro TRDI RiverRay (NEW!)
Mode 12 vs Mode 5/11
TRDI Streampro
Shallow water system
TRDI RiverRay (NEW!)
600 kHz phased array
SonTek/YSI RiverSurveyor (NEW!)
M9 – 3 frequencies (1, 3, 0.5 MHz)
M5 – 2 frequencies(1, 3 MHz)

18. Measurement Duration Analysis
Duration = Total time spent sampling

19. Summary and Conclusions
Comparison of discharge measurement instruments and methods is important to maintain data consistency
Laboratory test while valuable are limited
Field comparisons are important for instrument and methods comparisons
Field have shown that ADCP and Price AA methods:
Produce similar discharges
Display little to no bias
Continued field comparison are necessary
New instruments
Range of conditions

20. Questions