Assessing the Effect of Future Climate Change on Drought Characteristics and Propagation from Meteorological to Hydrological Droughts—A Comparison of Three Indices

This study delves into the potential impacts of climate change on meteorological and hydrological droughts in the Western Ghats region of South India, a large and humid tropical region. Utilizing three drought indices—the Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), and Standardized Runoff Index (SRI), we assessed the historical drought patterns and projected future scenarios under different Representative Concentration Pathway (RCP) scenarios (4.5 and 8.5). This comprehensive analysis encompassed three future time segments (near: 2021–2040, mid: 2041–2070, far: 2071–2100) and compared results with a base period (1989–2018). The study demonstrated that drought propagation is notably faster (around 3 months) in wet, humid tropical regions, highlighting the urgency of understanding its dynamics. Furthermore, the findings indicate that droughts are expected to increase in count and severity (> 100%) in the Western Ghats in future, accompanied by an accelerated propagation rate (around 2 months), with recovery rates for hydrological droughts being notably swift in this region. The study emphasizes the significant influence of regional conditions on drought propagation, leading to variations in its characteristics. Additionally, it underscores the potential of Pearson correlation analysis in providing approximate results for estimating drought propagation periods in the wet, humid tropical regions. These findings are significant in formulating effective risk mitigation and adaptation strategies to address the mounting challenges posed by drought in this region.