Identification of the most suitable meteorological drought index for a region: a case study of Raigarh district in Chhattisgarh

The drought is a prominent disaster the world is facing currently. The drought identification, its characterization, and monitoring are, thus, very important to mitigate this calamity. Many drought indices have been developed for this purpose in the past; however, their evaluation is necessary to select the best suited drought index for the specific area. This study aims to analyze the meteorological drought risk across the Raigarh district of Chhattisgarh state by evaluating five popular drought indices, namely, Reconnaissance drought index (RDI) rainfall anomaly index, standardized precipitation evapotranspiration index (SPEI), standardized precipitation index (SPI), and standardized anomaly index (SAI) considering all the tehsils of the district and proposes the methodology to select the best suited index for the region. The methodology has been selected in such a manner that it deals with all aspects of meteorological drought and the most suitable drought index for the region can be identified by comparing the drought indices based on the actual drought occurrence in the region which are identified by different agencies. These drought indices were computed for different assessment periods of 1, 3, 6, 9, and 12 months using the historical precipitation and temperature data derived from (NASA-POWER) for the period 1981-2021. The variation in severity in terms of extreme, severe, and moderate drought events has been observed with these drought indices in the district. Maximum correlation is observed between RAI and SAI across all assessment periods. Further, the SPI is seen to have fairly good agreement with all other drought indices and it rises with increasing assessment periods. Modified Mann-Kendall test shows a significant positive trend for all drought indices (except SPEI across all assessment periods, RDI-1 and RDI-3) across all assessment periods. The SPI performs exceptionally well in capturing the actual drought conditions reported by different agencies in the Raigarh region among all other indices considered in this study. It is also observed that although SPEI which comes out to be the second most suitable index for drought identification in the study region, it was not able to capture the drought events before 1990. However, SPEI identified most of the drought years post 1990 which shows the prevalent effect of temperature on the formulation of index driven by heavy industrialization in the region post 1990. Overall results suggest that the SPI is the best-suited meteorological drought index for the Raigarh region.