An Innovative Approach to Characterize Intensified Flash Drought Detection and its Impact on Terrestrial Ecosystem across Indian River Bains

Flash droughts have received widespread attention due to their abrupt onset or swift intensification, which makes it challenging to forecast and prepare for them, hence posing serious impacts on ecosystems, socioeconomic development, and agriculture. Most of the studies deal with conventional drought and lack knowledge of flash drought. To date, how the terrestrial ecosystem responds to flash over India has not been examined. As we know India is an agricultural-based economy, where a large fraction of the population relies on agriculture. In the present study, we have developed a novel method to quantitatively establish the definition of FD using the Aridity Index (AI). The spatiotemporal characteristics, including trends, and the causes of FDs in 25 significant river basins across India between 1981 and 2021 were then examined using this novel methodology. The hydrometeorological conditions were assessed extensively during the study at various flash drought stages. Also, we investigated flash drought's impact on the terrestrial ecosystem. The results show that FDs with rapid intensification are more common in humid areas compared to semi-arid and sub-humid areas. Furthermore, the study shows that in a substantial area of the research area, temperature and precipitation are both important major FD triggers. The differential effects of precipitation and soil moisture serve as FD triggers in some areas, such as the Western Ghats and northeast India. Furthermore, atmospheric aridity can create conditions that are favorable for the occurrence of FDs. It may accelerate the rapid onset of these flash droughts when combined with decreased soil moisture. The terrestrial ecosystem has been found to be extremely vulnerable to flash drought episodes, with the Ganga basin and Southern India exhibiting the most severe responses. Further, a serious decrease in Water Use Efficiency (WUE) and underlying WUE is also observed over some parts of Southern India and Ganga river basin, which indicates the non-resilient nature of the ecosystem towards flash drought conditions. The findings will provide policymakers with helpful information for developing appropriate effective regulations to reduce the effects of FDs on crop production, water scarcity, and allow them to develop proper water resource utilization methods in India.

Keywords: Aridity; Drivers, Flash drought; Drought intensification; Vapor pressure deficit.