Projecting the water poverty index under CMIP6 climate scenarios: a case study of the Birjand Plain, Iran

ABSTRACT

Population growth, increasing water demand, and climate change have significantly intensified water scarcity across arid and semi-arid regions, particularly in eastern Iran. This study presents an integrated assessment of water resource conditions in the Birjand Plain during 2005–2021 using the Water Poverty Index (WPI) as a multidimensional framework encompassing five components: resources, consumption, access, capacity, and environment, capturing both physical and socio-environmental dimensions of water stress. Future WPI values for 2024–2041 were projected under three climate scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) based on outputs from CMIP6. Component weights were determined using the Analytical Network Process (ANP) method based on expert judgment. The results indicate that the resources component, with a relative weight of 0.299, has the greatest influence on regional water poverty. Projections show a decline in WPI values of 16.64, 17.42, and 19.28% under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively, compared to the baseline period, highlighting the sensitivity of water resources to climate forcing. The findings reveal that climate change and resource limitations strongly influence water stress dynamics. Water poverty in the Birjand Plain is expected to intensify under future climatic and demand pressures, highlighting the need for adaptive, evidence-based water management strategies in arid regions.