From Concept to Comparison: Developing and Validating the Environmental Drought Index (EDI) for Holistic Drought Analysis

As a complex natural disaster, drought exerts wide-ranging impacts on environmental, hydrological, agricultural, and socioeconomic dimensions. Despite extensive studies on conventional drought types, understanding environmental droughts remains limited, hindering effective assessments. To address this, the present study introduces a novel Environmental Drought Index (EDI) to quantify environmental droughts (Srivastava & Maity, 2023). It evaluates its performance against established indices in India’s Brahmani River basin, specifically the Jaraikela catchment. The EDI was developed by integrating Minimum in-stream Flow Requirements (MFR), calculated by integrating Drought Duration Length (DDL), and Water Shortage Level (WSL). Historical and future streamflow rates (1980–2045) were simulated using the HydroClimatic Conceptual Streamflow (HCCS) model with outputs from three CMIP-6 General Circulation Models (EC-Earth3, MPI-ESM1-2-HR, and MRI-ESM2-0) under SSP245 and SSP585 scenarios. The results indicated a strong agreement between simulated and observed EDI values, particularly for MPI-ESM1-2-HR under SSP585. Severe droughts were found to dominate future scenarios (71–73% of all drought events during FP-2: 2023–2045), especially in non-monsoonal months, contrasting with moderate drought prevalence under SSP245 and the historical period. To further explore drought complexities, the study employed a comprehensive multi-index framework incorporating EDI alongside the 3-month Soil Moisture Anomaly Index (SPAI-3), Vegetation Health Index (VHI), and 3-month Standardized Streamflow Index (SSI-3). This comparative analysis revealed a pronounced upward trend in drought frequency and severity from the late 20th century (1982–2000) to the early 21st century (2001–2023). Severe hydrological droughts increased from 10.5% to 21.7%, while severe environmental droughts rose from 31.6% to 52.2%. Moderate agricultural droughts, in contrast, declined from 100% to 47.8%, and moderate meteorological droughts increased significantly from 57.9% to 87.0%. These findings highlight the evolving drought patterns in the Jaraikela catchment, characterized by more frequent and prolonged droughts. The results underscore the value of EDI in capturing environmental drought dynamics, validated through strong historical correspondence, and its integration within a broader multi-index framework to address gaps in traditional approaches. The study redefines conventional drought classifications by incorporating environmental dimensions and provides adaptive strategies to mitigate the impacts of increasing drought severity under changing climatic conditions.

Keywords: Climate Change Impacts; Water Resource Management; Adaptive Mitigation Strategies; Hydrological Modeling; Drought Vulnerability Assessment; Extreme Climatic Events

Reference: Srivastava, A., & Maity, R. (2023). Unveiling an Environmental Drought Index and its applicability in the perspective of drought recognition amidst climate change. Journal of Hydrology, 627, 130462. https://doi.org/10.1016/j.jhydrol.2023.130462