Response of Sedimentgraphs and Sediment Rating Loops to Land Use Type and Spatial Pattern

Assessment of suspended sedimentgraph (SG) and rating loops are important tools for analyzing the behavior of watersheds and successful implementation of watershed management measures in reducing sediment. However، the development and analysis of SGs and rating loops and influencing factors need more attention in watershed-scale. Therefore، the present study aimed to conduct the analysis of 13 observed and simulated sedimentgraphs (SGs) during October 2011 and November 2012، in Galaz-Chai Watershed with an area of 103km2 located in West-Azarbaijan Province، Iran. Towards this attempt، the SG of observed events was derived using instantaneous unit sediment graph (IUSG) concept، and the effects of different land uses were investigated. Also، the variation and patterns of the simulated sedimentgraphs (SGs) and rating loops were plotted and interpreted with the respective land use types. Based on the results، anearly peak occurred in SGs with respect to the observed hydrograph peak rates and consequently had clock-wise pattern. Increase in falling limb of hydrograph could be attributed to the participation of sediment production from agricultural land inwatershed upstream. The model predicted SGs with good accuracy according to the Nash-Sutcliffe criterion (70%). Analysis of results indicated that the type and distribution pattern of different land uses had significant effect on the shape of SGs and sediment rating loops.