Low-Power Underwater Acoustic Tracers for Long-Range River Bedload Monitoring

Understanding sediment transport (bedload) in rivers and streams is crucial for maintaining navigable waterways and ecological health. Unlike traditional localized sampling, tracers offer broader insights. This paper extends our efforts to overcome the limitations of RF tracers, which suffer from significant signal attenuation in water. We present a low-power underwater acoustic tracer utilizing an improved piezo driver with resonance-switching. The proposed tracers generate signals four times stronger than our previous prototype, enabling detection over distances up to 400 meters, a substantial improvement from the prior 200-meter limit. Simulation and real-world tests demonstrate robustness against Doppler shifts and moderate multipath propagation. Compact and costing only 15 € (including the transducer), the prototype promises year-long operation on a small battery. The technology also holds potential for diverse applications, including environmental monitoring, diver localization, or aquatic wildlife tracking.