On the rarity of the 2015 drought in India: A country-wide drought atlas using the multivariate standardized drought index and copula-based severity-duration-frequency curves

Study region: The study is conducted over 30 meteorological sub-divisions of India. Study focus: The Multivariate Standardized Drought Index (MSDI) is employed to analyze the drought conditions caused by simultaneous precipitation and soil moisture deficiencies. The Severity-Duration-Frequency (SDF) relationships for the 30 sub-divisions are derived using copula-based conditional distribution for duration and severity; which are further used to prepare the country-wide drought atlas for different return periods. Subsequently, the developed atlas is used to assess the spatial extent and historical context of the impactful 2015 drought event. New hydrological insights for the region: This is the first study to present a country-wide drought atlas for India, considering concurrent deficits in precipitation and soil moisture, and using copula-based SDF relationships. In general, drought characteristics such as severity and duration are found to be significantly correlated, highlighting the importance of their joint modeling for probabilistic risk assessment of droughts in India. The drought atlas reveals regions that are severely affected by the drought variability. The drought atlas developed here shows that the impactful 2015 drought event was severely deficient both in terms of precipitation and soil moisture. In particular, West Uttar Pradesh, East Uttar Pradesh, Jharkhand, Marathwada, Telangana and North Interior Karnataka sub-divisions are found to be under a very rare drought (probability of exceedance less than 10 %).