Assessing Extreme Drought Using the Standardized Precipitation Index (SPI) in the Harohar-Punpun Basin, Bihar, India

By definition drought is a long period of deficient rainfall, especially one that badly affects growing or living conditions. Rainfall is believed to be a normal, wet and dry climate condition. It is one of the most important water-associated hazards. It greatly impacts on agricultural, hydrological, economic, environmental and social systems. Understanding these impacts is crucial for drought planning, mitigation, and response. It also helps decision-makers identify and reduce vulnerability to drought. A drought index value is a single number, far more valuable than raw numbers for result-making. The standardized precipitation index (SPI) has several characteristics that are upgrading over other indices, with its simplicity and flexibility.

The standardized precipitation index (SPI) method is used for observing and describing drought based on seventy (70) years of precipitation data from the Harohar-Punpun Basin, Bihar. Finding drought index with 3- month, 6-month, 12-month, time scale basis. Positive SPI values point to normal condition to wet condition and negative values indicate normal condition to dry condition. In this work, we computed years of intense drought between 1951 and 2021. We investigated how the effects of extreme drought varied across nine stations. At SPI-3, station-3 has a high extreme drought value, of -3.78 in 2008 and low extreme drought value of -2.63 in 2011 at station-9. Similar SPI-6 and SPI-12, station-3 has the highest extreme drought, which has found to be -4.20 in 2009, and station-2 has the lowest extreme drought, which was found to be -2.63 in 1966. Station-4 has the highest extreme drought, calculated as -3.39 in 1967, and station-6 has the lowest extreme drought value, which has -2.4 in 2018. Stations 8 and 9 in SPI-3 have a frequency of the same, which are 2.12. In comparison to other stations, they have the highest frequency. Station 4 in SPI-6 and SPI-12 has a high frequency of 3.09 and a low frequency of 0.87, while station 4 in SPI-12 has a high frequency of 3.37 and a low frequency of 0.36.