Physical versus virtual water transfers to overcome local water shortages: A comparative analysis of impacts

Water shortages pose significant threats to local water security and food production around the world. Water managers have resorted to various water resources planning measures to overcome these challenges. For the first time and for a case study in Iran, we provide a comparative analysis of two such measures: physical and virtual inter-basin water transfers (IBWT). We evaluate green and blue water footprints (WF) associated with the production of 39 crops grown in humid Mazandaran and arid Semnan provinces, under (i) current production patterns and current local water availability; (ii) current production patterns and a planned physical IBWT scheme between Mazandaran (donor) and (receiving) Semnan province to provide water to water-intensive crops in the latter; (iii) modified cropping patterns, such that surplus production of water-intensive crops in Mazandaran abates production in Semnan province, coupled with interprovincial trade (i.e., a virtual IBWT scheme). We find that crops currently produced in Mazandaran have considerably lower blue WFs per unit of production (m ³ t ⁻¹) and a higher economic blue water productivity (EBWP, $ m ⁻¹) than in Semnan province. A physical IBWT would reduce blue water scarcity (BWS) in Semnan province by 34%, but at the cost of reduced EBWP by up to 46% of crops irrigated with the more costly transferred water. A virtual IBWT would reduce BWS in Semnan province to the same degree, while only modestly increasing BWS in Mazandaran province (from 0.15 to 0.21, indicating that Mazandaran water resources can sustainably support the proposed increase in production). Moreover, Mazandaran's provincial average EBWP is even raised (by 7%) in the virtual IBWT scenario.