ABSTRACT
The present study is an attempt to analyze the nature of drought and prepare a 118-year comprehensive drought register detailing the frequency, duration, and severity of probable drought events till the end of the twenty-first century for a geographically diverse watershed in the eastern part of India. To take the effect of temperature, along with rainfall, into account, the Standardized Precipitation-Evapotranspiration Index (SPEI)–based drought categorization using the Hargreaves method for potential evapotranspiration (PET) calculation was used. In terms of input, gridded precipitation data from the Indian Meteorological Department (IMD), gridded temperature data from the National Oceanic and Atmospheric Administration-Physical Science Laboratory (NOAA-PSL), and multi-model ensemble (MME) of projected precipitation and temperature as predicted by The Coordinated Regional Climate Downscaling Experiment (CORDEX data) for RCP 4.5 were used (six driving models and r1i1p1 ensemble). It is observed that over 118 years, the nature of drought frequency, duration, magnitude, and intensity is showing a cyclical nature. While 1982–83 and 1988–90 were the most drought-prone periods in the twentieth century, post 2000, especially after 2010, drought frequency, duration, and severity have been on the rise. This is expected to continue into the 2050s, after which the next couple of decades will be relatively drought-free. The drought instances are expected to rise again by the end of the century, albeit with a smaller footprint than before 2060. But while the frequency and duration of droughts are higher during 2041–2060, the proportion of severe and extreme drought events is greater during 2021–2040. Drought is also predicted to have a very high progression rate, both temporally as well as spatially. It is observed that a short-term drought has a 66.67% chance of transitioning into a medium-term drought, while the chance for a medium-term drought to transition into a long-term drought is close to 80%. Furthermore, the magnitude and intensity of agricultural drought are much greater than for meteorological, hydrological, or even socio-economic drought, even though the effective duration of such droughts is quite low, indicating extreme water scarcity for a brief period. Except for a few monsoon months, almost every other month also exhibits a positive and statistically significant trend. Seasonal Mann Kendall and Sen’s slope tests also show a positive and statistically significant trend for annual drought events, indicating aggravation of the climatic conditions responsible for drought occurrences. The study relies upon open source software only, considering the impact of the work. Besides, the use of open source software guarantees the reproducibility of the study in various other areas with diverse geophysical settings.
