Determining the best irrigation water scheduling with the aim of maximum productivity in irrigation and drainage networks (Case study: Qazvin irrigation network)

In this study, a model was developed to determine the optimal irrigation schedule for the Qazvin Plain in such a way that economic productivity is maximized with the amount of water available and the area under cultivation. The AquaCrop plant growth model was used to determine crop performance in different irrigation programs. The plant growth model was connected to the MATLAB programming environment. Ants’ optimization algorithm was used to determine the optimal irrigation schedule. Products, the volume of different water, depth of irrigation water, and irrigation cycle were included as decision options. Finally, after determining the best parameters of ACO, the best irrigation program was determined by considering five different scenarios in terms of irrigation depth and frequency and crop cultivation priority. In order for the irrigation program to be generalizable in water deficit conditions, an irrigation deficit from 5% to 35% was considered in different stages of growth. If we want to have the same frequency and depth of water for all crops (scenario of constant irrigation frequency and constant irrigation depth) with the goal of maximum economic efficiency, the best irrigation schedule is frequency of 9 days with a depth of 86 mm. And if the goal is maximum water productivity, the best irrigation schedule is 8 days with a depth of 78 mm. In total, among all scenarios, the best irrigation program with the aim of maximum economic productivity was related to the second scenario with variable irrigation frequency of 7 and 8 days. The optimal water depth for autumn crops was 40 and 52 mm and for spring crops was 84 mm. In addition, the priority of planting was determined in the order of tomato, potato, fodder corn, beans, wheat, barley, rapeseed, seed corn, and sugar beet. In case of a decrease in the amount of available water, the best low-irrigation program for crops was determined in such a way as to create maximum economic productivity.