Optimizationof Irrigation Schedulingin Farm's Units atShaidChamran Irrigation and Drainage Network

The biggest consumer of water in the world is agricultural sector. So¡ optimization of agricultural water usage is considered of a great importance. In this research¡ optimization of irrigation scheduling in ShahidChamran irrigation and drainage network has been investigated at the scale of farm channels using a combined model including AquaCrop simulation model¡ a multi-objective classic optimization algorithm (weighted sum)¡ and genetic algorithm. Two types of irrigation scheduling methods of constant depth-interval and variable depth- interval proportionate with soil type in maize farm units (cropping pattern plant with high demand) were proposed. Objective functions were developed to optimize soil type 1 (coarse-textured) water productivity¡ leaching fraction¡ yield and the number of irrigation events while for soil type 2 (fine-textured) the objective functions were water productivity¡ soil saturated extract salinity¡ crop yield and the number of irrigation events. Each objective function component contains concepts of water resources sustainable development¡ control on drainage volume and environment¡ lands stability and utilization issues. For soil type 1¡ optimization results showed a reduction about 50% in water consumption¡ an increase up to 94 % in water productivity¡ a reduction of 62% in leaching fraction¡ three times reduction in irrigation events in constant depthinterval schedule. The results also showed a reduction of 50% in water consumption¡ 111% increase in water quantities efficiency¡ a reduction of 66% in leaching fraction¡ and three times reduction in irrigation events in variable depth-interval method in soil type 1. Furthermore¡ the results for soil type 2¡ were a reduction of 35% in water consumption¡ an increase of 63% in water productivity¡ 52% reduction in leaching fraction¡ reducing an irrigation event in constant depth-interval schedule. For variable depth-interval method¡ the results indicate a reduction of 35% in water concumption¡ an increase of 70% of water usage efficiency¡ 11% increase in crop yield and a reduction of an irrigation event¡ compared with the proposed irrigation scheduling.