Tracing suspended and bed sediments during high and low water periods using geochemical characteristics - Case study: Vazrood watershed, northern Iran

Complete and comprehensive information about sediment dynamic and identification of hotspots of sediment production and transport are necessary for understanding the erosion processes and increasing the efficiency of soil and water conservation practices. Numerous studies used the sediment fingerprint techniques to investigate the contribution of different sources in suspended and bed sediment yield of the watersheds. However, the contribution of various land use/land covers in suspended and bed sediment yield for the great Caspian Sea basin is in an aura of ambiguity and the present study was conducted to gather information about an important part of this area in northern Iran, where rangelands are located upstream of Hyrcanian forests and dense agricultural lands are located downstream. The surface soil of different land use/land covers including forest, rangeland, agriculture and streambank lands were sampled in 30 points. Suspended and bed sediments were sampled in the watershed outlet in two high and low water periods. Geochemical characteristics of soil and sediment samples containing 59 elements were measured using ICP-OES GBC Integra. The reliable and suitable tracers from 59 elements were then selected using Range test, Kruskal-Wallis and Discriminant Function Analysis, respectively, in FingerPro package of R software. The results showed that for suspended sediment, streambank and rangeland had the highest contributions of 86.2% and 47.5%, respectively, in two high and low water periods. For bed sediment, in two high and low water periods, rangeland and streambank had the highest contributions of 73.8% and 84.4 %, respectively. Land use change and especially human activities such as agriculture, road construction and development of residential areas along the main river riparian zone has led to a significant increase in suspended and bed sediments.