Comparative Analysis of Multi-temporal Drought Indices Using Monthly Precipitation Data: A Study in the Southwestern Part of West Bengal, India

Abstract

Drought is considered as one of the most important natural hazards of regional character. Although drought has different dimensions, its effects vary across different sectors. Its immediate impact is felt in agricultural sector, and the countries which have less irrigation facility usually face acute problems due to this phenomenon. The southwestern part of West Bengal is also considered as one of the drought-prone regions of India due to its complex climatic and physiographical characteristics. Thus, in this study, an attempt has been initiated to examine the drought condition of the region using multi-temporal drought indices including Standardized Precipitation Index (SPI), Rainfall Anomaly Index (RAI), and Effective Drought Index (EDI), and to find out the best drought index. 113 years (1901–2013) of mean monthly precipitation data recorded by India Meteorological Department (IMD) has been used for the purpose. Correlation matrix (Karl Pearson) shows that EDI is the best drought index with the highest correlation value (R2 ≥ 0.72) among the drought indices with different time steps, while SPI3 is the best suited meteorological drought index, having a higher correlation value (R2 ≥ 0.95) with 3 months of the time steps, and medium correlation value (R2 ≥ 0.56) among all the time steps. Therefore, SPI3 has been used to analyze an individual drought event quantitatively in each district of the region, and on the basis of the parameters like Drought Duration (DD), Drought Magnitude (DM), and Drought Intensity (DI), three equal climatic periods have been classified (1901–1937, 1938–1975, and 1976–2013) to find out whether the drought events have increased or not. The highest drought frequency has been recorded in Purulia and Paschim Medinipur districts, while DD and DM are the highest in Birbhum district.