School of Irrigation and drainage, Collage of Abouraihan, University of Tehran,Tehran,Iran
Measuring sensitivity of hydraulic structures is considered as an approach for evaluation of water projects performance, due to lower distribution efficiency in Irrigation and Drainage project schemes. Sensitivity analysis approach for irrigation structures is one of flow analysis methods which are developed in recent years in order to measure the behavior of flow in hydraulic structures in an irrigation network. This study examines the sensitivity of offtake structures in Varamin irrigation and drainage network project, which is one of the modern networks in Iran. The sensitivity measurement was carried out by the use of collected data from field in years of 2010, 2011 and 2012, and compared them with the water requirement for crop pattern calculated by CROPWAT model. Flow channel simulation was conducted in the project to identify the most sensitive offtake structures, due to inappropriate allocation of water particularly in downstream of network. Simulation and evaluation were carried out using SOBEK hydrodynamic model, and relationships introduced for sensitivity measures for offtake structures. Investigations and sensitive analysis on hydraulics structures in Varamin Irrigation network showed that Baffle modules have significant sensitivity. According to reviewed equations, sensitivity of Baffle modules is related to upstream depth, and opening of NEYRPIC module gates; which occurred more in terminal structures. The best way to have an optimal operation in this network is supply of required water depth in downstream of each canal. In these circumstances, the water depth in all offtakes is provided, and does not make any changes in the opening modules also.