Spatio Temporal Agreement Between SPI and RAI for Drought Monitoring in Vadodara District, Gujarat

Abstract

Drought is among the most ruinous natural disasters, and its frequency and severity are likely to rise because of climate change, especially in susceptible areas like Gujarat, India. A precise assessment of drought is critical for early warning, mitigation planning, and sustainable management of water resources. This analysis assesses meteorological drought at Vadodara district for a 30-year period (1991–2021) with the help of two well-received indices: Standardized Precipitation Index (SPI) and Rainfall Anomaly Index (RAI). Eleven meteorological stations at the district level were used for the classification of drought, wet, and normal years according to the indices. Spatio-temporal concordance analysis was done to analyze the congruence of SPI and RAI in describing drought occurrence. Results indicated a moderate agreement among the indices with consistency of 30% at Kawat to 50% at Pilol and Rampura. Such differences mirror the effect of localized climatic and topographic factors along with methodological differences between RAI and SPI. Although both are useful for detecting drought, their partial agreement highlights the significance of a multi-index approach for increasing the reliability of drought monitoring. The results help improve knowledge of index performance and inform the construction of more reliable regional drought early warning systems and water resource management.