Water allocation sustainability assessment in climate change: amodeling approach using water footprint and just policy

Climate change has challenged water allocation for food production in water-scarce areas. This fact calls for water reallocation (RA) strategies in basins with dominant agriculture. This study develops a framework combining the SWAT model and water footprint (WF) to evaluate water resource sustainability and improve its indices by fair RA from agriculture. The Karkheh River Basin in Iran was chosen as a study area for verification. Deficit irrigation (DI) was a farm strategy to promote basin sustainability and maintain food security. DI was distributed according to the equality of resources, proposed by Ronald Dworkin, as a just allocation principle. It means irrigated water would be allocated based on an equal water ratio per hectare. Results showed that the basin is currently unsustainable regarding the groundwater (BkWS) and surface flow (BuWS). According to the SSP5-8.5 scenario, the BuWS in the basin increases from 1.12 to 1.22 (9%), and BkWS increases from 2 to 2.15 (7.5%), while GnWS remains relatively constant at 0.99. By Dworkin's principle, DI caused 21-48% reduction in water allocation among five provinces. RA improved the BuWS, GnWS, and BkWS and ensured environmental flow. Climate change reduces 3.5% of food production, with an extra 9% by RA. These reductions would not endanger food security.