Irrigation Efficiency Improvement for Sustainable Agriculture in Changing Climate: A Transboundary Watershed Between Iraq and Iran

Efficient water allocation for sustainable irrigated agriculture has become a growing concern, especially in transboundary river basins where the competition between upstream and downstream countries is substantially increasing. In this paper, the Diyala basin, one of the most water-stressed basins shared between Iraq and Iran, was used as an example case study. The water-stress situation is projected to get worse in the foreseeable future, as climate change adversely altered runoff at a time when demand for water is witnessing remarkable growth. Irrigated agriculture is the greatest consumer of the water supply, having a critical role for the efficiency of water use. The study aims at examining the sensitivity of irrigation demands to a set of potential improvements in irrigation efficiency (between 40 % and 60 %) in the riparian countries under different operational conditions. The investigation of the climate trends discloses that the area tends to be drier, with lower precipitation and higher rates of potential evapotranspiration. The possible impacts of climate change on water availability were examined through the simulation of various climatic scenarios with a rainfall-runoff model. Results show that the annual runoff may be reduced from 14 % to 30 %. It is estimated that such reduction can cause considerable water deficits, especially when there are small improvements in irrigation efficiency. This approach can support the development of a set of plausible scenarios to reduce irrigation water demand while maintaining a healthy agricultural sector.