Groundwater Depth as a Control on Flash-Drought Dissipation Versus Hydrological-Drought Development in India

Flash droughts (FDs) are characterized by their rapid onset, but their societal and agricultural impacts depend critically on the duration of anomalous moisture stress. While the land–atmosphere processes governing FD initiation have been widely studied, the role of subsurface water storage in regulating persistence and recovery remains poorly constrained. Groundwater depth serves as the primary regulator of drought propagation. Rather than treating groundwater as a passive reservoir, this research investigates its active role in the initiation and subsequent evolution of FDs. We investigate how groundwater storage either dampens flash-drought intensification via upward moisture flux or catalyzes the evolution of these events into major hydrological crises. Our approach determines the precise influence of the water table on the intensification and multi-seasonal persistence of FD events. We utilize groundwater-level observations from the Central Ground Water Board of India, spanning 1996 – 2023, to construct seasonal groundwater depth fields (0.25° resolution) for pre-monsoon, monsoon, and post-monsoon conditions. FD events are identified using a gridded catalog derived from the Standardized Evaporative Stress Ratio (SESR). Our analysis will employ contingency-based statistical tests (χ^²) and survival-type hazard analysis to quantify the probability of drought termination as a function of categorized water-table depths (shallow, intermediate, and deep). Spatial block-bootstrapping will be applied to account for regional spatial dependencies. We aim to identify critical groundwater depth thresholds beyond which the probability of flash-to-hydrological drought transition increases significantly. This work provides a new perspective on groundwater as a modulator of drought evolution in monsoon-dominated, groundwater-stressed environments.