Propagation of meteorological to streamflow flash droughts during summer monsoon season in India

Streamflow flash droughts (SFDs), characterized by a rapid decline in streamflow over a relatively short period, affect water availability, hydropower generation, and the ecosystem. However, the atmospheric and land processes that drive SFDs in the monsoonal climate of India remain unexplored. Using observations, reanalysis datasets, and model simulations, we examined the critical drivers of SFDs in 64 catchments in India during the 1971-2018 period. We identified meteorological flash droughts (MFDs) using precipitation and SFDs using in-situ observations and model simulations of streamflow. We show that precipitation deficit and anomalous high temperatures, driven mainly by summer monsoon breaks, lead to the development of MFDs. Antecedent baseflow conditions play a major role in the propagation of MFDs to SFDs. Favourable atmospheric conditions (driven by monsoon breaks) cause meteorological flash droughts, which translate to streamflow flash droughts. High and low baseflow conditions limit the rapid decline in streamflow, which controls the occurrence of streamflow flash drought. On the other hand, favourable atmospheric conditions combined with moderate baseflow can trigger streamflow flash droughts in India during the summer monsoon season. Moreover, humid catchments are more prone to propagation from meteorological to streamflow flash droughts during the monsoon season in India. Understanding the crucial role of atmospheric and land drivers can assist in examining the occurrence of streamflow flash drought with implications for water resources planning and management.