Knowledge of trends and variations of current and historical hydro-climatological variables are pertinent to the future development and sustainable management of water resources of a given region. Rainfall is a principal element of the hydrological cycle, so that understanding its behavior may be of profound social and economic significance. The detection of trends and oscillations in precipitation time series yields important information for the understanding of climate. However, rainfall

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... es are particularly hard to gauge, because rainfall is not uniform and varies considerably from place to place and time to time, even on small scales. The Sitanadi basin has a tropical monsoon climate. The highland of the district experiences mainly orographic rainfall. Rainfall data for 42 years were considered for the study and SPI was calculated for the whole period. SPI values of the rain gauge stations of the Sitanadi basin were found to vary from +2.43 to -2.50. In all rain gauge stations higher abnormality is observed in pre monsoon season compared to post monsoon season. The validation based on station gauge rainfall data showed that the SPIs calculated were reliable for monitoring drought regions.