Table 2 Evaluation grades of drought severity.

From: The response of meteorological drought to extreme climate in the water-receiving area of the Tao river diversion project in China

Drought level

Drought type

SPEI range

1

No Drought

SPEI >  − 0.5

2

Mild Drought

 − 1.0 < SPEI ≤  − 0.5

3

Moderate Drought

 − 1.5 < SPEI ≤  − 1.0

4

Severe Drought

 − 2.0 < SPEI ≤  − 1.5

5

Extreme Drought

SPEI ≤  − 2.0

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