Estimation the contribution of geological units as sources of suspended sediment yield using sediment fingerprinting approach (case study: The Toulbane watershed, Golestan Province)

In order to develop management plans for water and soil conservation and erosion control, it is necessary to identify the sources of sediment yield and the contribution of each source in watersheds. The aim of this study was to determine the contribution of different geological units to sediment yield of the Toulbane watershed in Golestan province. In view of this, samples were collected from different geological units. Collecting suspended sediment samples was carried out using Philips time-integrated sediment sampler over a one-year period (2017). Afterward, the concentration of 34 geochemical properties was examined for 41 source samples and 8 suspended sediment samples in the laboratory using the ICP device. Next, the optimal composite fingerprints were determined to discriminate sediment sources by using three statistical tests including mass conservation test, Kruskal-Wallis and stepwise discriminant function analysis. As a result, 15 tracers were selected as the optimal composite fingerprints and the contribution of different geological units to sediment yield was determined using the data derived from these tracers and implementing the multivariate mixing model. According to the results, the Qal and Jsl s.sh units had the highest contribution to sediment yield with the respective values of 68.22% and 28.75%. The Qal contains quaternary deposits and the Jsl s.sh (Shemshak formation) consists of sandstone and shale materials; both of which are highly sensitive to erosion. Hence it is necessary to carry out erosion control actions on erodible units to reduce sediment entrance to the river.