Table 2 Overview of drought types, indices used for assessment, and rationale for index selection.
Type of drought | Definition | Index used | Reason for using the index | Specific remarks |
|---|---|---|---|---|
Meteorological drought | A prolonged period of deficient precipitation relative to the statistical average leads to significant water shortages | Standardized Precipitation Anomaly Index (SPAI)17 | SPAI effectively quantifies precipitation anomalies and reflects deviations from long-term precipitation norms, making it ideal for assessing meteorological drought | SPAI-3 is used for its temporal relevance to short-term drought conditions |
Agricultural drought | A situation where soil moisture is insufficient to meet the needs of crops affects agricultural productivity | Vegetation Health Index (VHI)22 | VHI incorporates both vegetation indices and temperature data, providing a comprehensive assessment of agricultural drought conditions and their impact on crops | VHI offers timely insights into agricultural health, which is crucial for yield predictions |
Hydrological drought | A deficiency in water supply, characterized by low streamflow levels, affects water availability for human and ecological needs | Standardized Streamflow Index (SSI)25 | SSI is adept at assessing streamflow anomalies, offering a robust understanding of hydrological drought conditions over various time scales | SSI-3 is employed to capture short-term streamflow dynamics |
Environmental drought | A condition where streamflow levels fall below critical thresholds, impairing aquatic habitats and overall river ecosystem health | Environmental Drought Index (EDI)31 | EDI focuses on the ecological aspects of drought, providing an understanding of river ecosystems’ health and ability to support aquatic life | EDI is newly introduced and addresses the health of the riverine ecosystem |
