Analysis of velocities along depths : complementarity of ADCP and LSPIV technologies for hydrometric studies

Introduction 

EDF (Électricité de France) is one of the world's largest electricity generators, with an installed capacity of about 130 GW. Streamflow velocity analysis plays a critical role within its hydroelectric and nuclear activities in ensuring the safety of facilities, optimizing the use of natural resources and meeting environmental requirements.

The ADCP (Acoustic Doppler Current Profiler) is a key technology for measuring flow rates and velocity profiles along depths. Based on the Doppler effect, this method detects frequency shifts generated by the movement of particles in the water. The collected data is then processed using specialized software such as VMT (Velocity Mapping Toolbox [1]) or the MAP tool integrated into the QRevInt software [2] to compute 3D streamflow velocity. However, the ADCP technology has significant limitations due to its "local" perspective, which focuses only on transects. To understand larger-scale flow patterns, such as recirculation zones and water pathways, a broader spatial coverage is required. The ADCP struggles to provide this coverage due to deployment time constraints and operational conditions related to stable flow rates. Generally, only a limited number of transects can be carried out.

To complement ADCP data, LSPIV (Large-Scale Particle Image Velocimetry) can be used. This method analyzes image sequences of the flow. By detecting visible tracers such as plant debris, bubbles, or turbulence patterns, it estimates the 2D surface velocity field. The Fudaa LSPIV software, developed by INRAE and EDF [3], is particularly well-suited for large-scale applications and easy to use, especially when combined with images from aerial drones. This makes it highly useful for rapid measurements over large areas, providing a comprehensive understanding of the steady-state flow patterns. It effectively addresses the limitations of ADCP technology, offering a complementary solution for more complete hydrodynamic analyses.

Practical example : study of Bazacle

• Context

A practical example of this complementarity is an operational study conducted at EDF's Bazacle hydroelectric plant on the Garonne River in Toulouse, France. By combining a Teledyne RDI RioPro 1200kHz ADCP mounted on a Pario2 aquatic drone from RiverDrone with LSPIV technologies using an aerial drone, a comprehensive analysis of velocity profiles was performed to design a solution focused on optimizing fish ecological continuity in the studied area.

• Results

For this study, about ten transects were conducted at varying distances from the intake of the turbine and the Bazacle weir. The observed surface velocities ranged between [0;140 cm/s]. They were higher on the right bank, immediately upstream of the water intake screen, and downstream the weir. Velocities at depth ranged between [0;60 cm/s] upstream of the weir and between [0; 120 cm/s] downstream.

References

[1] Parsons, D. R., Jackson, P. R., Czuba, J. A., Engel, F. L., Rhoads, B. L., Oberg, K. A., Best, J. L., Mueller, D. S., Johnson, K. K., & Riley, J. D. (2012). https://onlinelibrary.wiley.com/doi/abs/10.1002/esp.3367

[2] Lennermark, M., & Hauet, A. (2022). https://meetingorganizer.copernicus.org/EGU22/EGU22-9379.html

[3] Le Coz, J., Jodeau, M., Hauet, A., Marchand, B., Le Boursicaud, R. (2014) River Flow.