Temporal Changes of Effective Discharge for Suspended Sediments Transport in Korkorsar Watershed

Suspended sediment transport by rivers is important in water quality of cities and villages fed by certain drainage basins. On the other hand, the effective discharge refers to discharge that transports the most sediment over long time and controls the shape of river bed. Therefore, determination of effective discharge for suspended sediment transport and analysis the variation of effective discharge at temporal scale is very important. The aim of this study is evaluating the effective discharge for sediment transport using flow discharge and sediment discharge for a thirty one year period (1983-2013) in Korkorsar watershed, Mazandaran Province. For this purpose at first, sediment rating curve was provided based on monthly, seasonally and total period time scale by using USBR and clusters average limit methods. Flow discharge was clustered into several equal clusters and mean flow discharge was calculated for each cluster. Then, for each mean flow discharge, amount of suspended sediment was determined based on flow discharge and sediment rating curves. Finally, the histogram of flow discharge and total sediment was plotted and effective discharge was determined. Results indicate monthly effective discharge and seasonally effective discharge vary from 0.24-25.42 m3 s-1 and 4.37-25, respectively. The effective discharge in whole studied period was equal to 24.36 with return period of 100-year. In addition, the comparison of effective discharge in different time scale demonstrated that effective discharge amount could have high variability in monthly and seasonal time scale. Determining the effective discharge and its temporal variation in watersheds plays the effective role on decreasing sediment transport via. appropriate rive reach and land management specially at the time of occurrence of effective discharge.