Turbidity observations in sediment flux studies: Examples from Russian rivers in cold environments

Turbidity is commonly used as a proxy to estimate suspended sediment content in streams, and for hydroecological purposes. The scope of this paper is to give an outlook to wider applications of nephelometric turbidimetry as a method. Uncalibrated turbidity records in conjunction with water chemistry data prove useful in detecting watershed reaction to single hydrological events during the spring flood in Arctic Russia. The turbidimetric survey technique was applied to study the spatial variability of sediment yield features on small rivers of the south-eastern part of Sakhalin Island. Suspended sediment concentration (SSC) vs. turbidity relation follows the geological features of the terrain and reflects the land-use intensity within the watersheds. For our Igarka key site, a logarithmic regression model was developed as an instrument of SSC calculation with turbidity data for each of the four studied watersheds. A regional regression model was developed for this site, and supplementary water optics data (filtered sample turbidity) was employed to increase the reliability of SSC calculations. Our results show that factors influencing turbidity, namely water colour and sediment grain size, have to be considered in multivariate models, to minimize errors and acquire an understanding of what kind of physical response is actually measured by nephelometry-based instruments.