A study on the estimating of sediment concentration with turbidity and acoustic backscatter signal for different sediment sizes

Abstract

Turbidity and acoustic measurement are alternative indirect methods to determine sediment concentration. Acoustic Doppler velocimetry can be used to estimate suspended sediment concentration (SSC) with the signal-to-noise ratio (SNR) in the water. In this study, particles size affecting turbidity and SNR values was investigated using four different sediment size groups (0-50, 50-100, 100-200, and 200-250 micron). The highest turbidity values were determined for small-sized sediment, and they decreased for bigger sediment size. Clay content decreased the relationship between sediment and turbidity and caused a reading error for high concentrations (>4 g.l(-1)). However, R-2 values greater than 0.900 were obtained for all treatments (R-2: 0.952, 0.992, 0.987, and 0.977, respectively, from small size to large size group). SNR values had good relationships with SSC values for less than 40 dB and 1 g.l(-1) sediment concentrations (R-2: 0.990, 0.998, 0.994, and 0.973, respectively, from small size to large size group). SNR values were strongly affected by small changes in sediment concentration but this property can be accepted as advantageous for sensitive measurement. As a result of this study, it could be concluded that turbidity and SNR values can be used for continuous sediment monitoring.