Drought assessment in the districts of Assam using standardized precipitation index

This study assessed the drought characteristics in various districts of Assam using a standardized precipitation index (SPI). Assam has been traditionally affected by floods; however, in the last few decades, droughts have occurred due to erratic rainfall patterns. In this study, gridded rainfall data provided by India Meteorological Department for 70 years (1951-2020) was used. The SPI was calculated at a 3-month time scale (SPI03) using accumulated rainfall of a 3-month sliding window to reflect seasonal or, to some extent, agricultural drought. In Assam, the percentage of drought in August and September that represented monsoonal drought was about 15% during the course of 70 years. Additionally, Assam's overall percentage of drought was at 14.5%, indicating that dryness will occur throughout the year regardless of the season. The most hit district in terms of the number of times was Bishwanath Chariali, and the least affected was Karbi Anglong. Furthermore, the Sivasagar district was found to be experiencing the highest number of droughts in the most intense category. The average drought in Assam lasted for roughly 5.2 months. Dhubri district, which had the lowest inter-arrival time (IAT) of drought, experienced drought spells more frequently. It is concluded that drought mitigation planning should be implemented in areas with a higher frequency of droughts, longer drought spells, and shorter IATs. The findings of this study will aid the efforts being made by various departments in proper planning, action, and management of multiple entities with regard to the state's drought.Research highlights3-month SPI can be very effective in detecting agricultural drought.The 3-month SPI for August and September month can be used to monitor drought conditions for Kharif crops.The average inter-arrival time of drought can be used to indicate how frequently a drought spell resurfaced.