Environmental and Economic Multi-Objective Model for Managing Irrigation and Drain Water

Abstract

To maximize total net benefits, farmers often tend to increase the area under cash crops production. Such crops may include water-intensive or salt sensitive crops. Restrictions on available water and drain water disposal conditions in the arid and semi-arid region could limit adoption of high value cropping pattern. Production of huge amounts of saline drainage waters threatens environmental sustainability of downstream water resources. A multi-objective model is presented for simultaneous management of crop yield, irrigation and drain water. The proposed model is an environmental economic model, at irrigation district-scale, that integrates agronomic, irrigation, drainage and economic aspects of irrigated agriculture. Source reduction strategies for irrigation water management are considered because they affect management of drainage water, crop yield and net profits. The recent MOPSO technique was applied to solve the multi-objective problem. Distributed soil-water-atmosphere-plant model (SWAP) was set up for regional simulation of soil salinity, crop yield and drain water. The developed model was applied to Voshmgir irrigation and drainage network in north eastern IRAN. It was found that using a multi-objective model makes feasible a flexible balance between environmental and economic benefits of irrigation and drainage scheme management. The proposed model obtained the optimized irrigation water allocation and cropping area to different crops which resulted in the reduction of drainage salt load to downstream while ensuring the net benefit function in the satisfactory level. The model results showed that variety in the physical and water allocation policy within different parts of irrigation and drainage network have a considerable impact on the cropping area and irrigation water of each crop and thus the net benefits as well as production of drain water for each crop and its salt load.