Field Investigation of Operational Management Effect on Water Losses and Sedimentation in Irrigation Channels

Management of irrigation networks can play a very important role in the hardware and software performance of these networks. In this research, by conducting field studies on suspended sediment transport and conveyance efficiency, the effect of operating conditions on sedimentation and water losses at Khouzestan province irrigation networks was analyzed. The inflow-outflow method and sediment flux continuity equation were used to determine the canal losses and sedimentation of suspended load in the studied reaches, respectively. The investigation was done on 4, 21 and 16 reaches of the main, secondary and tertiary channels, respectively. The ratio of free board of flow in canal as operation index was computed. The effects of this index on sedimentation rate and water losses relative to input discharge were studied in each kilometer of the canal. Results showed that 10% decreasing in the operational discharge relative to the designed discharge caused 0.23 and 0.26 kg s-1 km-1 increasing in sedimentation rates of the main and secondary channels, respectively. As the distance from the upstream of the main channel increased, the channel efficiency decreased. So that the increasing rate of the water losses in main channel of Karkheh irrigation network was 0.12 percent of the entrance discharge in each kilometer distance from the beginning of the channel. The increasing rate of water losses for the western and eastern channel of Dez irrigation network were 0.16% and 0.09%, respectively.