Projected intensification of drought in the Kızılırmak Basin, Türkiye, under CMIP6 climate scenarios: comparative evaluation of multi-model and multi-index approaches

Abstract

Drought is one of the most significant climatological hazards, exerting profound impacts on water resources, agriculture, and livelihoods. This study projects the future evolution of drought characteristics in the K & imath;z & imath;l & imath;rmak Basin, T & uuml;rkiye, under four CMIP6 Global Climate Models (ACCESS-CM2, EC-Earth3-Veg, GFDL-ESM4, HadGEM3-GC31-MM) for the SSP5-8.5 scenario. We employ three meteorological drought indices, the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and China Z Index (CZI) at monthly (1), seasonal (3), and annual (12) timescales. Historical (baseline) drought conditions from observed station data are compared to near-future (2025-2048), mid-future (2049-2074), and far-future (2075-2100) projections to assess changes in drought duration, frequency, and severity. Results indicate a progressive intensification of droughts, with a higher frequency of extreme drought events especially during the mid- and far-future periods. SPI-based analyses consistently project stronger drought severity compared to SPEI and CZI; however, increasing temperature and evapotranspiration also suggest that SPEI-based drought detection grows more critical toward the late 21st century. Our findings imply a pressing need for early warning strategies and adaptive water-resource management in the K & imath;z & imath;l & imath;rmak Basin. The study contributes a multi-model and multi-index perspective, serving as a basis for targeted drought mitigation under intensifying climate stress.