.

The research was aimed at identifying suitable Standardized Precipitation Index (SPI) time scales for drought
analysis to prevent researchers from illogical SPI time scale application. The selection of the relevant time scales
for drought analysis is important in the context of climate change, which poses serious environmental degradation
challenges to mankind. SPI at different time scales of 1, 3, 6, 12 and 24 months were computed from 30 years of
rainfall data collected from seven meteorological stations in Sudano-Sahelian Region of Nigeria, and analyzed to
draw conclusion on the relevant SPI time scale suitable for the analysis of each drought categories: meteorological,
agricultural and hydrological droughts. The relevance of the different SPI time scales to various drought categories,
both at short-term and long-term, was established to determine the choice of SPI time scale for the respective
drought analysis. The findings showed that SPI at time scale of 1 month could be suitable for short term
investigation such as drought monitoring, real-time forecasting and few weeks’ meteorological drought analysis
while 3 months time scale could be suitable for few months’ meteorological drought and agricultural drought
analysis. SPI at 6 and 12 months time scales could be used for hydrological drought assessment in relation to surface
water and groundwater resources management respectively, while longer time scales showed unreliable results.
Conclusion drawn was that illogical application of SPI by drought analysts might yield confusing and poor results. It
is recommended that SPI time scales should be appropriately applied to the study of various drought categories and
water resources management as outlined in this study so that drought research efforts will yield outcomes of
significance.
Keywords: Drought, Standard Precipitation Index, Meteorological Drought, Agricultural Drought, Hydrological
Drought