Analysis of Changes in Precipitation and Drought in Aksu River Basin, Northwest China

Table 2

Drought classification of SPI.

Drought class	SPI value
Nondrought	SPI ≥ 0
Near normal	−1 < SPI < 0
Moderate	−1.5 < SPI ≤ −1
Severe/extreme	SPI ≤ −1.5