This International Standard specifies methods for determination of the concentrations and particle-size distributions of suspended sediment in streams and canals by surrogate techniques. Methods based on bulk-optical principle of water such as transmission and nephelometry are the most commonly used surrogates for determining suspended sediment concentrations (SSC). Instruments and techniques based on acoustic attenuation and/or acoustic backscatter principles are also in use for measurement of suspended sediment concentration. Instrumentation based on the laser diffraction principle is also used for the measurement of particle size distribution. This International Standard covers brief description of the operating principle of each method and details of some of the instruments available.

The detailed method and principle of optical and acoustical transmission, nephelometry, and optical back scatter (OBS), laser diffraction technique (LD) and acoustic back scatter technique (ABS) with their limitations are described in Annex A, Annex B and Annex C respectively.