An Apparatus and Method for Measuring Sand Content Based on Near-Infrared Shortwave Scattering

River suspended sediment content (sand content) is one of the most important hydrological parameters, and its measurement application in water resources is of great significance. In this paper, an online sand content measurement device is developed that is based on near-infrared short-wave scattering optical measurement at 850 nm wavelength to study the complex variation relationship between scattered light intensity and sand content. The sand content measurement method is obtained after several groups of experimental research, ensuring the sand content is in the range of 0–20 kg/m3, the relative error of measurement accuracy after calibration is less than 3.44%, and the uncertainty of $1.0148\pm 0.0174\ \text{kg}/\mathrm{m}^{3}$. The maximum relative error of field measurement accuracy is 9.84%, which meets the requirement of 10% set as a national standard. The research results have good application prospects in river and channel erosion control and automatic monitoring of water extraction for industry and agriculture.