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

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

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

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

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

Specialty Tests Beam Alignment Test GPS vs BT discharges Compare GPS to BT distance made good Acceptable ratio: 1.003 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

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

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 `

Broadband Comparisons Morlock, S.E., 1996, Evaluation of acoustic Doppler current profiler measurements of river discharge, USGS WRIR 95-4218. 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

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

Initial Testing Results

More Field Data – Much More

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

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

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. 1421-1432 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

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

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)

Measurement Duration Analysis Duration = Total time spent sampling

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

Questions