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An Evaluation of the Performance of Five Meteorological Drought Monitoring Indices Over an Arid and Semi-Arid Region of Gujarat (India)

Drought Monitoring plays an important role in drought risk assessment and management. Different meteorological drought indices are normally used to determine drought, which are essentially constant functions of rainfall and hydro-meteorological factors. A universal drought index cannot be used to evaluate the severity of drought in a specific region due to the essential difficulty of drought phenomena, hydro-climatic factors, and watershed characteristics. Classifying an appropriate drought index requires evaluating the performance of various drought indices. This study evaluated 5 meteorological drought indices for Gujarat, India utilizing a dataset from a total of 167 raingauge and climate stations having over 30 years (1986-2015 of the dataset). In various countries, several droughts indices have been introduced and utilized. This study evaluates the effectiveness of 5 meteorological drought monitoring indices in Gujarat. The following meteorological drought indexes were chosen based on data availability: Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Percent Departure from Normal (PDN), Effective Drought Index (EDI), and Reconnaissance Drought Index (RDI). The EDI is a time step independent drought indicator, with 1-, 3-, 6-, 9-, and 12-month time intervals defined for the four multi-time scale indices. This drought index was compared using several time scales of multi-time scale drought indices based on their association with the EDI. The evaluation of drought indices during the historic drought was assessed based on the occurrence and response of drought indices within the specific drought severity classes. In the present study area, the 9-month scale is suitable for comparisons of drought indices. The SPEI-9 had the highest relative occurrence in the 'severe dry' class, and it was subtle to 9-monthly rainfall in most districts. As a result of the study, SPEI-9 is considered the best drought index.