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Empirical vs. analytical methods for modelling the uncertainty of ADCP discharge measurements
Published in Wim Uijttewaal, Mário J. Franca, Daniel Valero, Victor Chavarrias, Clàudia Ylla Arbós, Ralph Schielen, Alessandra Crosato, River Flow 2020, 2020
A. Despax, J. Le Coz, D.S. Mueller, G. Naudet, G. Pierrefeu, K. Delamarre, S.A. Moore, E.C. Jamieson
The Acoustic Doppler Current Profilers (ADCPs) are used to measure water discharge in rivers. The technology, terminology and general guidance for making ADCP discharge measurements are presented in various guides such as Mueller et al. (2013) or the WMO (2010) manual on streamgauging. The ADCP is commonly mounted on a boat or on a small float that transects a river cross-section. The ADCP uses sound propagation to measure both water velocity and depth. Due to physical limitations of the instrument (Mueller et al. 2013), velocities are measured throughout a limited portion of the cross-section. In the unmeasured areas, discharge has to be interpolated based on contiguous valid data or extrapolated near the riverbed (bottom discharge), near the water surface (top discharge) and near the banks (right and left discharges). An ADCP discharge measurement is then the average of elemental discharges based on a number of transects p, i.e. crossings of the stream, under approximately steady-flow conditions. Ideally, the average includes pairs of reciprocal transects.
Discharge
Published in Jochen Aberle, Colin D. Rennie, David M. Admiraal, Marian Muste, Experimental Hydraulics: Methods, Instrumentation, Data Processing and Management, 2017
Jochen Aberle, Colin D. Rennie, David M. Admiraal, Marian Muste
The Acoustic Doppler Current Profiler (ADCP) described in Section 3.3, Volume II was first used for measuring riverine discharge in the late 1980s. ADCP use for river-flow measurements has profoundly changed the way that velocities and discharge are collected in streams and man-made channels. One method for determining discharge with an ADCP is by individually collecting velocity profiles at fixed points across a section (the “section-by-section” method). The mid-section or mean section integration methods presented in Section 7.4.1 can be subsequently employed to estimate discharge. Most often, however, an ADCP is deployed from a moving boat or platform (the “moving-boat” method). In this approach, the ADCP collects velocities with high-spatial density that are subsequently converted to flow fluxes and integrated across the stream to estimate the discharge. Mueller et al. (2013) provide detailed guidance on procedures for conducting moving-boat ADCP measurements.
Morphodynamic modelling of a meandering sand bed river using Delft3D
Published in Silke Wieprecht, Stefan Haun, Karolin Weber, Markus Noack, Kristina Terheiden, River Sedimentation, 2016
M.S. Banda, A. Dittrich, J. Pervez
The acoustic Doppler current profiler (aDcp) data were used for the calibration of velocity data. In principle, the aDcp uses acoustic physics to measure the three-dimensional velocity of flowing water, and subsequently the data can be used to determine flow discharge (Parsons et al. 2013). We used a boat-mounted aDcp for repeated transects along a cross-section located about 4 km downstream of the upstream boundary. The location of the flow measurements is shown in Figure 1. The device used for this work was a Teledyne RDI RiverRay 600 kHz aDcp. The bottom tracking function of the aDcp was used. The aDcp was linked to a Global Positioning System (GPS) to provide both position and boat velocity. The aDcp was configured to measure velocities in 0.5 m bins. The instrument can not measure the first 1 m below the water surface and approximately 13% of the depth at the bottom of the channel but extrapolates the flow values for these unmeasured areas.
Acoustic sampling effects on bedload quantification using acoustic Doppler current profilers
Published in Journal of Hydraulic Research, 2020
Slaven Conevski, Massimo Guerrero, Axel Winterscheid, Colin D Rennie, Nils Ruther
ADCPs are active sonar systems that are typically used to measure the water velocity over varying ranges, producing a profile of velocity vectors along the three dimensions. The ADCP transmits an acoustic signal at an instrument-specific frequency and measures the change in frequency (e.g. Doppler shift) of the reflected signal from the particles in the water column. The general idea of the Doppler approach assumes that in the water there is a sufficient number of particles to reflect enough acoustic energy and to estimate the Doppler shift (RDInstruments, 2011). ADCPs are generally configured as an assembly of four transducers spaced at 90° azimuth intervals (i.e. Janus configuration). These transducers form acoustic beams with grazing angle of 70–60° that permit measurements of three velocity components under the assumption that the velocity is homogeneous in the plane defined by equal ranging distances from each of the transducers. This study focuses on the BT mode of ADCPs, which is a separate signal, used for detection of the riverbed and the vessel velocity, vBT. Compared with the water velocity profiling, the BT signal involves emitting longer acoustic pulses with lower sampling frequency to identify the riverbed, but it works with the same carrying frequency. For stationary deployment, the BT signal is affected by the riverbed mobility; in particular the so-called apparent bedload velocity results: va = vbt. This bias on the ADCP actual velocity is considered as a measure of the spatially-averaged bedload velocity (Rennie et al., 2002).
Tailor-made protocol for assessing water quality of irrigation canals: Case study of El-Nubaria canal, Egypt
Published in Water Science, 2018
Ahmed Sayed Hussein Hassanin Habash, Anas Mohamed El-Molla, Mohamed Shaban Mohamed Abusalama Shaban, Mustafa Ali Abdelall
The quantity of water was measured by the device of acoustic Doppler current profilers (ADCPs) that is known as a valuable tool for measuring stream flow. ADCP is a hydro-acoustic instrument or sonar device that is used to measure water velocities in discrete layers over a certain range that is defined by the acoustic frequency. Essentially, the ADCP emits a sound signal of a specific frequency and measures the return frequency that is received from backscatter via particles in the water column.