Integrated Assessment of Drought and Vegetation Dynamics in an Arid Region of Southwest Iran.

Abstract

Drought, a pervasive natural hazard, poses serious threats to ecosystems, agriculture, and water resources, particularly in arid and semi-arid regions. This study provides a comprehensive long-term assessment of drought dynamics, vegetation health, and hydrological variations in Khuzestan Province, southwest Iran, during 2000–2023. Meteorological drought was carefully quantified using the Standardized Precipitation Index (SPI), while vegetation stress and temperature impacts were evaluated through the Vegetation Condition Index (VCI), Temperature Condition Index (TCI), and the integrated Vegetation Health Index (VHI) derived from MODIS satellite data processed in Google Earth Engine. Results revealed pronounced seasonal and interannual variability, with severe and recurrent summer droughts accompanied by occasional wet anomalies. Central and northern areas experienced the highest vegetation stress, whereas southern regions remained relatively stable and resilient throughout the study period. Hydrological analyses using GRACE and SMAP datasets indicated persistent and significant reductions in terrestrial water storage and soil moisture, strongly correlated with vegetation health indicators. Correlation analysis demonstrated that VHI was primarily influenced by VCI, with SPI and TCI exerting secondary but notable effects. Overall, the findings emphasize the crucial value of multi-index, satellite-based monitoring for understanding drought–vegetation interactions, improving early-warning capabilities, and supporting sustainable water, ecosystem, and agricultural management in semiarid environments.