- *Intensity of drought sequences*

Intensity of drought can be defined as the magnitude and severity of the consequences for the rainfall deficit. It can be evaluated using the SPI values. In this study, the extreme value of the SPI was considered as a reference value for drought intensity.

#### 3.2.2. Time Series Change Detection

Rupture is defined as a sudden change in the properties of a random process [26]. Rupture tests are complementary to standard indices because the existence of sudden change in time series is a possible cause of the rupture of the homogeneity of these series [27]. In this study, the Cumulative Gap (CG) test was used to detect possible sudden changes in rainfall series. This non-parametric procedure, based on rank, analyzes whether the means of the two parts of the series are different for an unknown break date [28]. The statistic of this test is calculated from the cumulative sum of the "sign" function of the difference between the observed values and the median. This statistical processing is performed with Hydrospect 2.0 software. The test statistic is defined as follows (Equation (3)):

$$\left| \text{TS} \right| = \text{ (2\text{\textquotedblleft}n\text{\textquotedblright})} \max \left| \text{S}\_{\text{k}} \right| \text{ with } \text{S}\_{\text{k}} = \sum\_{i=1}^{k} \text{sign} \left( \mathbf{x}\_{i} - \mathbf{X}\_{\text{m}} \right) \text{ and } \left( \text{k} = \text{ 1, ..., n} \right) \tag{3}$$

where xi is the extreme hydrometric observation of rank *i* (*i* = 1 ... *n*); Xm is the median of the extreme hydrometric series; Sk is the statistic test; *n* is the number of value for the rank *i*.
