A simple two-layer soil water balance model was used to calculate the actual and probable values of hydrological components, based on meteorological observed precipitation and temperature data. Meanwhile, the Possible Evapotranspiration (PET) was estimated using the Thornthwaite method based on the monthly average temperature. In addition, the PDSI was calculated by the adaptive algorithm proposed by Wells et al. (2004). Table 2 shows the classification of drought according to the Palmer's recommendation.
Classification of drought degree for SC-PDSI
| SC-PDSI value . | Categories . |
|---|---|
| −2 < value ≤ −1 | Mild dry |
| −3 < value ≤ −2 | Moderately dry |
| −4 < value ≤ −3 | Severely dry |
| value ≤ −4 | Extremely dry |
| SC-PDSI value . | Categories . |
|---|---|
| −2 < value ≤ −1 | Mild dry |
| −3 < value ≤ −2 | Moderately dry |
| −4 < value ≤ −3 | Severely dry |
| value ≤ −4 | Extremely dry |