Drought Dynamics: Enhanced Characterization Through Hyper-Temporal Satellite Observations

Abstract

Drought is a multifaceted hazard, influenced directly or indirectly by factors such as precipitation, evapo-transpiration, soil moisture content and groundwater levels. Drought dynamics is fundamentally linked to hydrological processes, as droughts directly impact water availability, soil moisture and overall hydrological balance. Given the global climate change and consequent increasing frequency of extreme events, assessing the vulnerability to drought stress in underprivileged areas has become highly relevant. In this context, drought characterization has become crucial for understanding the complex patterns of droughts and its impacts on agriculture, ecosystems and communities, thereby contributing to food security, environmental sustainability and disaster preparedness. The major goal of this study was to evaluate the onset, duration, frequency and extent of agricultural drought using satellite-based datasets. The hyper-temporal Système Pour l'Observation de la Terre (SPOT) VEGETATION (VGT) Normalized Difference Vegetation Index (NDVI) data were used in this study to quantify the drought related stress on vegetation cover. The spatial extent of drought and its pattern were estimated using the long-term Vegetation Condition Index (VCI) derived from hyper-temporal SPOT-VGT NDVI datasets. Notably, strong agreement was found between the estimations of onset and duration, particularly during severe drought years such as 2002 and 2008. The study reveals that more over 95% of the total area encountered severe crop stress before the second week of July in 1999, 2002 and 2008, which are identified as severe drought years in the region. The frequency maps effectively captured the occurrence of drought events over a sixteen-year span, highlighting distinct drought episodes in the study area and underscoring the significant prevalence of drought stress across a considerable area. The high r² (0.61) value indicates a significant level of shared variability between VCI and yield of major crops, demonstrating their consistent alignment in capturing vegetation health and crop yield anomalies. The comprehensive delineation of drought patterns in the Bundelkhand region revealed by this study is potential for future preparedness efforts, enabling strategic planning and facilitating the implementation of sustainable policy interventions.