Since the intakes outflow variations have an impact on network performance, it is necessary to evaluate the behavior of different types of intake structures in unsteady flow condition. In the present study, a computer model has been developed in which unsteady Saint–Venant flow equations have been discretized using finite difference and Crank–Nicolson method. Water surface elevation at junctions is calculated implicitly using matrix properties and influence line technique. After model verification, main channel of Miandarband irrigation network and its five branches were simulated. The result showed that without any operation instruction, a 10% decrease in the upstream flow discharge will reduce the slid gate, Neyrpic single orifice Module and double orifice Module intakes outflows for about 17.6%, 3.04% and 2.56%, respectively. With operation instruction, the maximum loss of flow volume is 707 m3 during the first 10 h of operation for intake with slid gate.