Difference between revisions of "Acoustic Doppler current profiler (ADCP)"

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(Created page with "=Quick summary= file:bms_sensor.png|thumb|500px|Figure 1: (a) Geophone and accelerometer installed in a watertight housing mounted on an impact plate and exemplary (b) geoph...")
 
 
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=Quick summary=
 
=Quick summary=
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[[file:bms_sensor.png|thumb|500px|Figure 1: (a) Geophone and accelerometer installed in a watertight housing mounted on an impact plate and exemplary (b) geophone and (c) accelerometer signal of the identical single grain impact. SumIMP denotes the total number of peaks above the threshold amplitude Amin for the event shown. Amaxmax is the maximum amplitude registered during this event. Only positive amplitude values are considered.]]
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[[file:adcp_example_units.png|thumb|250px|Figure 1: Examples of ADCPs: (a) Teledyne RiverPro with 5 beams (source: http://www.teledynemarine.com) and (b) Sontek M9 with 9 beams and S5 with 5 beams (source: https://www.sontek.com).]]
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[[file:bms_vortex_tube.png|thumb|500px|Figure 2: (a) Conceptual sketch of the vortex tube functionality and (b) vortex tube outlet at HPP Schiffmühle (source: VAW).]]
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[[file:adcp_qboat.png|thumb|250px|Figure 2: Teledyne Marine Q-boat of VAW equipped with Riverpro ADCP and DGPS (source: VAW, ETH Zurich).]]
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[[file:bms_vortex_tube2.png|thumb|500px|Figure 3: (a) Vortex tube outlet with mounted sensors and (b) vortex tube running during the field calibration (source: VAW).]]
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[[file:adcp_wse.png|thumb|250px|Figure 3: Water surface elevation along the power canal of HPP Schiffmühle (black line: DGPS data and red line: total station data) (source: VAW, ETH Zurich).]]
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[[file:adcp_workflow.png|thumb|250px|Figure 4: Workflow used for post-processing of ADCP data (click to expand) (source: VAW, ETH Zurich)..]]
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[[file:adcp_output.png|thumb|250px|Figure 5: Depth averaged flow velocities upstream of the HPP Bannwil measured with the ADCP boat at a discharge of 402 m<sup>3</sup>/s (background image: © 2018 swisstopo (JD 100041)) (source: VAW, ETH Zurich).]]
  
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Developed by: VAW, ETH Zurich, Switzerland; Test Case partner: Limmatkraftwerke AG, Baden, Switzerland
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Developed by: Several Companies
  
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Date: February 2019
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Date: 2020
  
 
Type: [[:Category:Devices|Device]]
 
Type: [[:Category:Devices|Device]]
  
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Suitable for the following [[::Category:Measures|measures]]:
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=Introduction=
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Acoustic Doppler Current Profiler (ADCP) allows quick, easy and accurate measurements of 3D velocity time series and bathymetry, and computation of discharges in rivers, estuaries, lakes and reservoirs as well as oceans. ADCP data can be used for calibration of numerical models, hydraulic studies (for example, flow field around hydraulic structures), habitat quality assessment and modelling, hydro-morphologic surveys and sediment studies.
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The ADCP is equipped with multi-beams (three up to nine beams, Figure 1), which emit acoustic energy at a known frequency and record the frequency of the acoustic energy backscattered by the particles in the water column. The velocity of the water flow along each beam is computed based on the change in the frequency of the emitted and backscattered acoustic energy, i.e. the Doppler shift. Detailed information on the ADCP working principle and its limitations are described by Simpson (2002). The ADCP beams are positioned to 20 or 30 degree away from the vertical axis. By using a simple trigonometry, 3D velocity components are computed from the Doppler shifts measured with three or four sonar beams. In the latter, a redundant, fourth beam is used to compute error
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velocity, which is the difference between a velocity measured by one set of three beams and a velocity measured by another set of three beams at the same time (Simpson, 2002). The error velocity is used to evaluate the assumption of horizontal homogeneity. The frequency of the ultrasonic sound transmitted by commercially available ADCPs ranges from 30 kHz to 3000 KHz (Simpson, 2002). ADCP can be used at a fixed position, i.e. stationary, or mounted to a tethered boat, manned boat or a remote-controlled boat (Mueller et al., 2013). Non-stationary i.e. moving boat ADCP measurements yield the flow velocity and direction relative to the boat and hence the velocity of the boat should be accounted for by using either bottom tracking or global positioning system (GPS) to determine true flow velocity.
  
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=Introduction=
 
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An indirect Bedload Monitoring System (BMS) is developed for bedload transport monitoring in the vortex tube system installed in the headwater channel of the FIThydro case study hydropower plant (HPP) Schiffmühle. The BMS allows the quantitative assessment of bedload transport in rivers, torrents and hydraulic sediment diversion structures. The measurements support the evaluation of bedload continuity across hydropower plants or other hydraulic structures.
 
  
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The BMS consists of two passive acoustic sensors, i.e. a geophone (GS-20DX manufactured by Geospace Technologies, Houston TX, USA) and an accelerometer (ICP352C03 manufactured by PCB Piezoelectronics, Depew NY, USA), mounted to an impact plate in a watertight housing (Figure 1a). These sensors do not directly measure bedload transport but register the vibration signals of the impact plate, i.e. oscillations induced by the impingement of passing bedload particles. In the case study HPP, the impact plate is the steel wall of the vortex tube (Figure 1a). The vibration signal output of both sensors is a voltage that is sampled at a frequency of fs = 51.2 kHz. The raw signals are then transmitted and further processed (Figure 1b, c).  
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=Application=
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Within the scope of FIThydro, high resolution 3D velocity, as well as bathymetry measurements, have been conducted using an ADCP mounted on a high speed remote-controlled boat at two hydropower plants (HPP) in Switzerland since the beginning of 2018. The models of the ADCP and the boat are River Pro 1200 kHz including piston style four-beam transducer with a 5th, independent 600 kHz vertical beam and Q-Boat purchased from Teledyne Marine, USA, respectively (Figure 2). An external Differential GPS (DGPS) system from A326 AtlasLink (Hemisphere) was used to accurately measure the positions of the ADCP. One set of the battery for the Q-boat allowed us to make measurements for 4 hours up to 10 hours depending on the flow velocity and field conditions i.e. temperature.
  
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The BMS presented here is similar to the Swiss Plate Geophone System (SPGS) (Rickenmann et al. 2012) but includes an additional accelerometer sensor to expand the range of frequencies and hence the potentially detectable particle sizes compared to the SPGS.
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Compass calibration and moving bed tests are conducted before each ADCP measurement at the case study HPPs. The Test Case study HPP Schiffmühle is located on the 35 km long river Limmat between in Untersiggenthal and Turgi near Baden in Switzerland (see the Test Case presentation file for HPP Schiffmühle). Two transects of ADCP at each densely spaced cross-section along the river were enough but high accuracy of altitude data was required for the bathymetry measurements at the HPP and in general. The present DGPS system resulted in ±1m of errors in altitude measurements (Figure 3, black line). Therefore, use of a total station, which is time consuming, or real-time kinematic (RTK) GPS is recommended to accurately determine water surface and hence bathymetry (Figure 3, red line from total station measurements).  
  
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The maximum amplitude recorded during a bedload transport event can be related to the maximum grain diameter. Additionally, the sum of impulse counts above a certain amplitude threshold can be related to the transported bedload volume. Both relations are BMS setup- and site-dependent and therefore, a calibration is required to correlate the recorded impact signals to known bedload transport rates, often obtained from traditional bedload sampling (Rickenmann et al. 2012). If possible, a calibration in a laboratory flume as well as in the field setting is recommended (Gray et al. 2010, Rickenmann et al. 2014, Wyss et al. 2016a, Wyss et al. 2016b, Albayrak et al. 2017).
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Furthermore, the test results from the HPP Bannwil located on River Aare in canton Bern indicated that averaging of at least 8 transects or even more at each cross-section is needed to obtain robust and smooth velocity field and accurate discharge data at highly turbulent and 3D flows occurring in rivers, turbine inlet and outlets or other hydraulic structures (see the Test Case presentation file for HPP Bannwil).
  
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=Application=
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The ADCP data from both HPPs Schiffmühle and Bannwil are post-processed according to the workflow sketched in Figure 4 using the software WinRiver II (Teledyne software) and velocity mapping toolbox (VMT, Matlab based software for processing and visualizing ADCP data provided by U.S. Geological Survey). Figure 5 shows the depth-averaged velocities at the HPP Bannwil plotted with VMT. VMT can be used with the output files from Sontek ADCPs. For further data analysis and presentation on the maps like river bed changes, Q-GIS (free software) or ARC-GIS (Commercial software) are also recommended.
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Within the scope of FIThydro, a BMS consisting of a geophone and accelerometer was installed on the vortex tube at HPP Schiffmühle, which diverts bedload from the headwater channel to the residual flow reach. The vortex tube consists of a steel tube embedded in the side weir, connecting the two parallel channels (Figure 2). A gate valve is positioned in the side weir, which opens automatically when a predefined discharge is exceeded. The opening of the valve automatically triggers the BMS measurements.
 
  
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In contrast to the SPGS, the steel tube is used as an impact plate for the BMS and the sensors are mounted directly onto the outside of the steel tube (Figure 3). Therefore, laboratory calibration was not easily possible. Instead, the system was calibrated in the field by repeatedly dumping sediment samples of known grain size distribution and volume upstream of the vortex tube and subsequently flushing them to the residual flow reach. In addition, drop tests with single grains were performed when the vortex tube was not in operation. The single grain signals help to analyze the influence of grain size, grain form, drop height, and drop location on the amplitude and frequency signals.
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The present system based on the remote-controlled boat platform has advantages over the tethered boat ADCP application. These are less man-power needed, faster and more measurements in a shorter time, no flow disturbance and interference with beams and smoother movement of the boat.
  
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The first results of the presented BMS are promising, but the data analysis will be further refined and extended. Furthermore, a larger number of recorded flood events is necessary to check the plausibility of the results obtained so far. Overall, it is demonstrated that the measurement principle of the state-of-the-art SPGS can be extended to non-standardized impact plates like steel vortex tubes, and the use of an additional accelerometer sensor, given that appropriate calibration measures are taken.
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=Relevant mitigation measures and test cases=
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{{Suitable measures for Acoustic Doppler current profiler (ADCP)}}
  
 
=Other information=
 
=Other information=
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The total costs for the geophone and accelerometer sensors amount to approx. 885-1'330 €. The costs for the field computer, the analog-digital-converter, and the 3G modem are approx. 5'300-6'200 €. Additional costs for the installation, data transmission, and the calibration depending on the site conditions and set-up.
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The total costs for the Teledyne RiverPro 1200 kHz, Teledyne Q-boat and DGPS from Hemisphere Atlas link amount to approx. 22’000 €, 21’200 € and 3’340 € respectively. The costs of shipping, VAT, some mounting apparatus and long-range radio modem are excluded. For current costs of the equipment, we recommend to ask the corresponding supplier. Note that Q-boat can also house Sontek RiverSurveyor M9. Furthermore, a rugged laptop for field use is recommended.
  
 
=Relevant literature=
 
=Relevant literature=
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*Albayrak, I., Müller-Hagmann, M., Boes, R.M. (2017). Calibration of Swiss Plate Geophone System for bedload monitoring in a sediment bypass tunnel. In Proc. 2nd Intl. Workshop on Sediment Bypass Tunnels (Sumi, T., ed.), paper FP16, Kyoto University, Kyoto, Japan
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*Mueller, D.S., Wagner, C.R., Rehmel, M.S., Oberg, K.A., Rainville, F. (2013). Measuring discharge with acoustic Doppler current profilers from a moving boat (ver. 2.0, December 2013), U.S. Geological Survey Techniques and Methods, book 3, chap. http://dx.doi.org/10.3133/tm<sup>3</sup>A22.
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*Simpson, M.R. (2002). Discharge measurements using a broadband acoustic Doppler current profiler. Open-file Report 2001-1, https://doi.org/10.3133/ofr011.
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<b>Links to the suppliers of equipment:</b>
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*Teledyne Marine, ADCP RiverPro: http://www.teledynemarine.com/riverpro-adcp?ProductLineID=13
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*Teledyne Marine, Q-Boat: http://www.teledynemarine.com/Lists/Downloads/Q-Boat_1800_Datasheet.pdf
  
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*Gray, J.R., Laronne, J.B., Marr, J.D.G. (2010). Bedload-surrogate Monitoring Technologies, US Geological Survey Scientific Investigations Report 2010-5091. US Geological Survey: Reston VA.
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*Hemisphere Atlas DPS: https://hemispheregnss.com/Atlas/atlaslinke284a2-gnss-smart-antenna-1226
  
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*Rickenmann, D., Turowski, J.M., Fritschi, B., Klaiber, A., Ludwig, A. (2012). Bedload transport measurements at the Erlenbach stream with geophones and automated basket samplers. Earth Surface Processes and Landforms, 37, 1000-1011.
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*Sontek ADCP M9: https://www.sontek.com/riversurveyor-s5-m9
  
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*Rickenmann, D., Turowski, J.M., Fritschi, B., Wyss, C., Laronne, J., Barzilai, R., Reid, I., Kreisler, A., Aigner, J., Seitz, H., Habersack, H. (2014). Bedload transport measurements with impact plate geophones: comparison of sensor calibration in different gravel-bed streams. Earth Surface Processes and Landforms, 39, 928-942.
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<b>Software for ADCP data analysis:</b>
  
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*Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016a). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 1. Impulse counts and particle size identification. Water Resources Research, 52, 7744-7759.
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*Velocity Mapping Toolbox: https://hydroacoustics.usgs.gov/movingboat/VMT/VMT.shtml
  
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*Wyss, C.R., Rickenmann, D., Fritschi, B., Turowski, J.M, Weitbrecht, V., Boes, R.M. (2016b). Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 2. Application to field sites with direct bed load samples. Water Resources Research, 52, 7760-7778.
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*Q-GIS: https://qgis.org/en/site/
  
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*ARC-GIS: https://www.esri.com/en-us/arcgis/about-arcgis/overview
  
 
=Contact information=
 
=Contact information=

Latest revision as of 15:46, 2 October 2020

Quick summary

Figure 1: Examples of ADCPs: (a) Teledyne RiverPro with 5 beams (source: http://www.teledynemarine.com) and (b) Sontek M9 with 9 beams and S5 with 5 beams (source: https://www.sontek.com).
Figure 2: Teledyne Marine Q-boat of VAW equipped with Riverpro ADCP and DGPS (source: VAW, ETH Zurich).
Figure 3: Water surface elevation along the power canal of HPP Schiffmühle (black line: DGPS data and red line: total station data) (source: VAW, ETH Zurich).
Figure 4: Workflow used for post-processing of ADCP data (click to expand) (source: VAW, ETH Zurich)..
Figure 5: Depth averaged flow velocities upstream of the HPP Bannwil measured with the ADCP boat at a discharge of 402 m3/s (background image: © 2018 swisstopo (JD 100041)) (source: VAW, ETH Zurich).

Developed by: Several Companies

Date: 2020

Type: Device

Introduction

Acoustic Doppler Current Profiler (ADCP) allows quick, easy and accurate measurements of 3D velocity time series and bathymetry, and computation of discharges in rivers, estuaries, lakes and reservoirs as well as oceans. ADCP data can be used for calibration of numerical models, hydraulic studies (for example, flow field around hydraulic structures), habitat quality assessment and modelling, hydro-morphologic surveys and sediment studies.

The ADCP is equipped with multi-beams (three up to nine beams, Figure 1), which emit acoustic energy at a known frequency and record the frequency of the acoustic energy backscattered by the particles in the water column. The velocity of the water flow along each beam is computed based on the change in the frequency of the emitted and backscattered acoustic energy, i.e. the Doppler shift. Detailed information on the ADCP working principle and its limitations are described by Simpson (2002). The ADCP beams are positioned to 20 or 30 degree away from the vertical axis. By using a simple trigonometry, 3D velocity components are computed from the Doppler shifts measured with three or four sonar beams. In the latter, a redundant, fourth beam is used to compute error velocity, which is the difference between a velocity measured by one set of three beams and a velocity measured by another set of three beams at the same time (Simpson, 2002). The error velocity is used to evaluate the assumption of horizontal homogeneity. The frequency of the ultrasonic sound transmitted by commercially available ADCPs ranges from 30 kHz to 3000 KHz (Simpson, 2002). ADCP can be used at a fixed position, i.e. stationary, or mounted to a tethered boat, manned boat or a remote-controlled boat (Mueller et al., 2013). Non-stationary i.e. moving boat ADCP measurements yield the flow velocity and direction relative to the boat and hence the velocity of the boat should be accounted for by using either bottom tracking or global positioning system (GPS) to determine true flow velocity.


Application

Within the scope of FIThydro, high resolution 3D velocity, as well as bathymetry measurements, have been conducted using an ADCP mounted on a high speed remote-controlled boat at two hydropower plants (HPP) in Switzerland since the beginning of 2018. The models of the ADCP and the boat are River Pro 1200 kHz including piston style four-beam transducer with a 5th, independent 600 kHz vertical beam and Q-Boat purchased from Teledyne Marine, USA, respectively (Figure 2). An external Differential GPS (DGPS) system from A326 AtlasLink (Hemisphere) was used to accurately measure the positions of the ADCP. One set of the battery for the Q-boat allowed us to make measurements for 4 hours up to 10 hours depending on the flow velocity and field conditions i.e. temperature.

Compass calibration and moving bed tests are conducted before each ADCP measurement at the case study HPPs. The Test Case study HPP Schiffmühle is located on the 35 km long river Limmat between in Untersiggenthal and Turgi near Baden in Switzerland (see the Test Case presentation file for HPP Schiffmühle). Two transects of ADCP at each densely spaced cross-section along the river were enough but high accuracy of altitude data was required for the bathymetry measurements at the HPP and in general. The present DGPS system resulted in ±1m of errors in altitude measurements (Figure 3, black line). Therefore, use of a total station, which is time consuming, or real-time kinematic (RTK) GPS is recommended to accurately determine water surface and hence bathymetry (Figure 3, red line from total station measurements).

Furthermore, the test results from the HPP Bannwil located on River Aare in canton Bern indicated that averaging of at least 8 transects or even more at each cross-section is needed to obtain robust and smooth velocity field and accurate discharge data at highly turbulent and 3D flows occurring in rivers, turbine inlet and outlets or other hydraulic structures (see the Test Case presentation file for HPP Bannwil).

The ADCP data from both HPPs Schiffmühle and Bannwil are post-processed according to the workflow sketched in Figure 4 using the software WinRiver II (Teledyne software) and velocity mapping toolbox (VMT, Matlab based software for processing and visualizing ADCP data provided by U.S. Geological Survey). Figure 5 shows the depth-averaged velocities at the HPP Bannwil plotted with VMT. VMT can be used with the output files from Sontek ADCPs. For further data analysis and presentation on the maps like river bed changes, Q-GIS (free software) or ARC-GIS (Commercial software) are also recommended.

The present system based on the remote-controlled boat platform has advantages over the tethered boat ADCP application. These are less man-power needed, faster and more measurements in a shorter time, no flow disturbance and interference with beams and smoother movement of the boat.

Relevant mitigation measures and test cases

Relevant measures
Bypass combined with other solutions
Complete or partial migration barrier removal
Construction of a 'river-in-the-river'
Drawdown reservoir flushing
Mitigating rapid, short-term variations in flow (hydro-peaking operations)
Mitigating reduced annual flow and low flow measures
Mitigating reduced flood peaks, magnitudes, and frequency
Operational measures (turbine operations, spillway passage)
Other types of fine screens
Removal of weirs
Sensory, behavioural barriers (electricity, light, sound, air-water curtains)
Skimming walls (fixed or floating)
Relevant test cases Applied in test case?
Altheim test case -
Altusried test case -
Anundsjö test case Yes
Bannwil test case Yes
Freudenau test case Yes
Gotein test case -
Guma and Vadocondes test cases Yes
Günz test case -
Ham test case Yes
Las Rives test case Yes
Schiffmühle test case Yes
Trois Villes test case Yes

Other information

The total costs for the Teledyne RiverPro 1200 kHz, Teledyne Q-boat and DGPS from Hemisphere Atlas link amount to approx. 22’000 €, 21’200 € and 3’340 € respectively. The costs of shipping, VAT, some mounting apparatus and long-range radio modem are excluded. For current costs of the equipment, we recommend to ask the corresponding supplier. Note that Q-boat can also house Sontek RiverSurveyor M9. Furthermore, a rugged laptop for field use is recommended.

Relevant literature

  • Mueller, D.S., Wagner, C.R., Rehmel, M.S., Oberg, K.A., Rainville, F. (2013). Measuring discharge with acoustic Doppler current profilers from a moving boat (ver. 2.0, December 2013), U.S. Geological Survey Techniques and Methods, book 3, chap. http://dx.doi.org/10.3133/tm3A22.
  • Simpson, M.R. (2002). Discharge measurements using a broadband acoustic Doppler current profiler. Open-file Report 2001-1, https://doi.org/10.3133/ofr011.

Links to the suppliers of equipment:

Software for ADCP data analysis:

Contact information

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