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.