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

Abstract

Abstract Climate change has challenged water allocation strategies for food production, particularly in water-scarce areas. This fact calls for re-evaluating water allocation in basins with dominant agricultural activities. This study develops a framework, combining the Soil and Water Assessment Tool (SWAT) model and water footprint (WF), to primarily evaluate water resource sustainability under climate change and improve its indices by just water reallocation (RA). The Karkheh River Basin, located in Iran, was chosen as a study area for verification. Here, the impacts of climate change on WF sustainability and food security were evaluated based on six main crops. Deficit irrigation (DI) was referred to as a farm strategy to simultaneously promote basin sustainability, maintain food security, and save water. DI was distributed according to the equality of resources, proposed by Ronald Dworkin, as a just allocation principle. It means that water for irrigation would be distributed based on an equal water ratio per hectare area. Results showed that the basin is currently unsustainable regarding the groundwater (BkWS) and blue water footprints (BuWS). According to the climate scenario of SSP5-8.5, the BuWS of the basin increases from 1.12 to 1.22 (9%), its BkWS increases from 2 to 2.15 (7.5%), while GnWS remains relatively constant at 0.99 <1. By Dworkin's principle, DI caused 21–48% reduction in water allocation among five provinces. RA improved the BuWS, GnWS, and BkWS of the whole basin to 0.99, 0.95, and 1.67 and ensured environmental flow. Climate change reduces 3.5% of overall food production, with an extra 9% by RA. However, these reductions would not significantly endanger food security.