Continuous monitoring of suspended sediment in rivers by use of new methods

Abstract

Traditional sampling methods are restrictive for spatial and temporal monitoring of suspended sediment in river. Application of these methods is simple but labour intensive to collect and process. For this reason, the use of new technological methods has recently gained importance. These methods are commonly based on the scattering of sound or light in water. Acoustic methods involve propagating sound at around the Megahertz frequency range through the water column. Short bursts of high frequency sound are transmitted from a transducer and directed towards the measurement water sample. Sediment in suspension will scatter a part of this sound back to the transducer. Another method, laser scattering, directs a laser beam through the sample of water where particles in suspension will scatter, absorb and reflect the beam. The scattered laser beam is received by a ring detector that allows measurement of the scattering angle of the beam. Particle size and volumetric concentration can be calculated from knowledge of this angle. In addition to these methods, optical turbidimeters supply an estimate for suspended sediment concentration through measuring either the backscatter of the light or the attenuation of a light beam passing through a water sample. In this paper, these methods were presented and advantages and limitations of each were given for comparison.