Drought hotspot analysis and risk assessment using probabilistic drought monitoring and severity-duration-frequency analysis

Drought hotspot identification requires continuous drought monitoring and spatial risk assessment. The present study analysed drought events in the agriculture-dominated mid-Mahanadi River Basin in Odisha, India, using crop water stress as a drought indicator. This drought index incorporated different factors that affect crop water deficit such as the cropping pattern, soil characteristics, and surface soil moisture. The drought monitoring framework utilized a relevance vector machine model-based classification that provided the uncertainty associated with drought categorization. Using the proposed framework, drought hotspots are identified in the study region and compared with indices based on precipitation and soil moisture. Further, a bivariate copula is employed to model the agricultural drought characteristics and develop the drought severity-duration-frequency (S-D-F) relationships. The drought hotspot maps and S-D-F curves are developed for different locations in the region. These provided useful information on the site-specific drought patterns and the characteristics of the devastating droughts of 2002 and 2012, characterized by an average drought duration of 7 months at several locations. The site-specific risk of short- and long-term agricultural droughts are then investigated using the conditional copula. The results suggest that the conditional return periods and the S-D-F curves are valuable tools to assess the spatial variability of drought risk in the region.