Investigating the Effect of Water Level of Chahnimeh Reservoirs on Sedimentation of Feeder 2 Canal

Intake canals of off-stream reservoirs, play a key role in achieving reservoir goals. Chahnimeh reservoirs have been constructed to store and use water optimally for drinking, agricultural development and play a complementary role to flood control. The Sistan plain in the southeast of Iran is highly dependent on surface water resources. The HEC RAS model is a well-known one-dimensional software for flow and sediment simulation. In this study, HEC RAS 6.0.0 was used to simulate sedimentation in feeder 2 canal under maximum conditions as well as minimum water level conditions of Chahnimeh reservoirs. Flow simulation in the model was performed quasi-unsteady using the standard step-by-step method by a flood hydrograph with a volume of one billion cubic meters. According to the simulation results, in maximum water level Conditions, Feeder 2 canal Sedimentation volume is equal to 54,200 m^3 which increases the bed level by 4.1m. Also, in minimum water level Conditions, sedimentation is equal to 52,700 m^3, which increases the bed level by 3.84 m. Comparison of the results in the two scenarios shows that in the case of maximum water level, volume of sediment per unit of length of Sistan River is equal to 6.5 m^3⁄L_River while in minimum water level volume of erosion is equal to 2.2m^3⁄L_River of Sistan River. Although feeder 2 canal in minimum water level conditions increases the inflow from the Hirmand river due to the decrease in the river bed level of sistan river but will act as a sedimentation canal in all conditions.