Environmental Systems Research

Table 2 Classification of the severity of drought events on the calculation of SPI/SPIE (McKee et al. 1993)

From: Spatiotemporal analysis of droughts characteristics and drivers in the Omo-Gibe River basin, Ethiopia

Categories	SPI/SPIE values
Extremely dry	≤ − 2.0
Severely dry	− 1. 5 to − 1. 99
Moderately dry	− 1. 0 to − 1. 49
Near normal	0.99 to − 0. 99
Moderately wet	1.0 to 1. 49
Severely wet	1.5 to1.99
Extremely wet	≥ 2.0

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