Comparative multi-index analysis of existing drought typology and environmental droughts in a climate-stressed region
Aman Srivastava, Anket Pandey, Rajib Maity
Abstract
Climate change is amplifying drought impacts globally, yet conventional drought typology (meteorological, agricultural, hydrological) systematically excludes environmental drought, a critical driver of ecosystem collapse, from multi-index comparative assessments. This omission persists despite evidence that anthropogenic warming exacerbates hydrological non-stationarity and ecological degradation. This study bridges this gap by analyzing meteorological (precipitation), agricultural (vegetation), hydrological (streamflow), and environmental (ecology) droughts. The comparative multi-index approach, developed by this study, employs four indices: the 3-month Standardised Precipitation Anomaly Index (SPAI-3 for meteorological drought), Vegetation Health Index (VHI for agricultural drought), 3-month Standardized Streamflow Index (SSI-3 for hydrological drought), and Environmental Drought Index (EDI for ecosystem water deficit). Drought severity is classified into four tiers (slight to extreme) across 1982-2023, with sub-period analysis (1982-2000 vs. 2001-2023) to isolate climate-change-driven shifts. Considering a rainfed-basin in India (Jaraikela gauging station in the Brahmani River basin), as the study site, results show 170 slight and 127 moderate drought events, spanning over 633 months-evidence of persistent mild-to-moderate water stress. Severe hydrological droughts nearly doubled in frequency and drought-months (10.5% → 21.7%), while severe environmental droughts surged by 65% (31.6% → 52.2%) and now constitute over a third (36.7%) of such events. Moderate meteorological droughts increased by 50% (57.9% → 87.0%), now spanning 100+ months, whereas moderate agricultural droughts halved (100% → 47.8%). Environmental droughts lasted 267 months over 49 events (average > 5 months/event). Severe and extreme droughts, though rarer (35 severe, 3 extreme), covered 153 months. These results underscore environmental drought as a critical but understudied dimension of climate change impacts, with ecological degradation accelerating faster than hydrological stress. Moreover, these findings demonstrate that climate-driven shifts in monsoon patterns disproportionately affect ecological water deficits compared to agricultural systems, where adaptive practices may buffer moderate droughts.