Optimal Operation of Irrigation Canals with Conjunctive Use of Surface and Ground Water

The conjunctive use of surface and groundwater in irrigation networks influences the performance of canals. One condition of conjunctive use is to add the groundwater to the surface water via a canal to satisfy demand. Management and operation of the canal is a complex task that must consider demand variation and groundwater entering the canal. The variety of decision variables in conjunctive use requires the use of optimization techniques to determine optimal operation. Simulation models should be combinedwith optimization models for this purpose. In this research, an irrigation conveyance system simulation (ICSS) hydrodynamic model was used to simulate the flow in an irrigation canal. A combined optimization technique was used that considered the complex and implicit relations between the objective function anddecision variables. A model based on the shuffled complex evolution (SCE) optimization technique, a heuristic intelligent search technique, was used to develop an ICSS-SCE model. The proposed model was applied to the L8 canal of the Qazvin irrigation network, consisting of five conjunctive wells. Two options (25 and 40%) for demand increase provided by groundwater was considered. For each option, regular and optimum operations (four options in total) were taken into account. Optimal control settings (for water flow) were determined and canal performance for each option was calculated using the ICSS-SCE model.The results showed that setting controls according to optimal recommendations influenced by conjunctive use led to considerable performance improvement of the canal and intakes. The objective function of the canal was improved in two cases by 40-48%. In general, it was concluded that the proposed model was capable of determining optimal operation of the irrigation canals under conjunctive surface and groundwater use.