Effective discharge for suspended sediment transportation in Ghohruod watershed

Soil erosion and sediment transport is a phenomenon that happens due to rainfall and water flow on the ground surface in different regions and scales. Different flow values have different effects on this process, so that any change in flow results in suspended sediment content change. Therefore, different flow performance and dominant flow determination (effective discharge) data are necessary for designation and implementation of proper soil erosion and sediment yield control projects along with watershed management. The main objective of present study was to estimate effective discharge for suspended sediment transportation in Ghohruod watershed in Iran with an area of 9091.34 ha. Suspended sediment and flow discharge data for a period of 20 years were applied. After preparing suitable sediment rating carves and data augmentation, the average daily discharge in each statistical year was calculated. Then, discharge values during the period were divided into same intervals. Discharge frequency and cumulative suspended sediment determined for each specific discharge class was plotted as histogram. Effective discharge and its frequency were determined by sediment- discharge histogram scrutinizing. Results demonstrated that effective discharge for the study station was in low flow class and equal to 0.125 m3/s with 46 days frequency and 21.8% flow duration.     Key words: Effective discharge, sediment transport, suspended sediment, sediment rating curve, Ghohruod watershed, Iran.