Acoustic Measurements for Reservoir Sedimentation Analysis

This study focuses on testing the capabilities of an acoustic Doppler current profiler ADCP to map sediment deposits in a hydropower reservoir exposed to a high sediment yield. The corrected backscatter signal of bottom tracking BT mode, for both 1.2 MHz and 0.6 MHz, was correlated with the dry bulk density of the collected bed samples and followed reasonable correlation with the particle sizes. The raw echoes from the water profiling WP mode for 1.2 MHz showed reasonable data until 10 - 15 m depth. In larger depths the signal emerged to a noise level of 20 dB. The echo profiles from the 0.6 MHz seemed to reach the noise level earlier but variations in the echoes were noticed up to 40 m. An analysis of the echo gradient revealed that there may be 3 different layers in the reservoir with different scattering characteristics. Mapping the results for both bed material and the echo of the surface layer demonstrated a good overview of the sedimentation pattern and hence the sedimentation processes in the reservoir and indicated the areas with different sediment masses, possible sedimentation paths, sediment inflows and changes in the sediment concentration related to weather conditions. Future research should focus on improving the correction of the BT backscatter signal and involve stratification and within the reservoir. The water profile backscatter should be further investigated and the reasons of stratification of the lake should be unraveled, including water quality, temperature, and influence of any organic material.