ABSTRACT

Precipitation deficit and its daily, seasonal and annual oscillations are inherent characteristics of Nigeria's climate. Droughts are generally characterized by a prolonged and abnormal moisture deficiency. In drought studies it is important to characterize the start and end of a drought as well as its intensity, duration, frequency and magnitude. The objective of this study was to apply the Standardized Precipitation Evapotranspiration index (SPEI) for drought assessment in the Benin- Owena River Basin, Nigeria. The SPEI was used in drought analysis based on the data from Climate Research Unit (CRU) for meteorological stations located inside the study area and three time scales including the 3-, 6- and 12-month SPEI were evaluated. After determining the dry and wet periods, drought durations, intensity, frequency and magnitudes were computed. Drought characteristics of the basin was detected and some moderate and severe droughts were captured. The result of relative frequencies show the mean relative frequencies of 47.62% for drought occurring in the basin at 12 month timescales. The observed Peak Intensities of SPEI values during 1980-2015 illustrate some severe droughts (-i.5/o-1.99) across the basin. These severe droughts are valuable tools for water resources managers interested in either short- or long- term or water supply.