*3.3. Projection Trends in SPI*

Projection trends in SPI for multiple timescales are considered with an emphasis of drought events under the RCP4.5 scenario. The purpose of this is to detect any trends or changes in drought events. In addition, as clarified in the previous section, just little, even no wet and drought events of extremely wet, extremely dry, very wet and severely dry are found out under the RCP8.5 scenarios. During 2021–2050, out of 14 stations, only five show significant upward trends in November for the SPI-1 index as presented in Figure 6b. There is a similar of upward trends for SPI-3 and SPI-6 in November. Importantly, no trends are detected in November for SPI-9, SPI-12 and SPI-24. Besides that, it is noteworthy that a poor signal of upward trends in SPI-9, SPI-12 and SPI-24 indices is illustrated for months in a year. It indicates an importance of short-term, plans more than long-term plans in related aspects such as water resources planning.

In February, insignificant downward trends are mostly observed over the whole basin (Figure 6a). In the months of March, May, July, October and December, more than half of total considered stations are defined with no trends in SPI-1 index. No trends in SPI-3 index are calculated for almost all the

months in a year, except for January, April and November. Downward trends in SPI-1 (in the months of February, April and June), SPI-3 (in April) and SPI-6 (in the months of July and August) indices are clearly observed. More importantly, the intensity of drought events in the north and east of the basin is generally stronger than that in other areas.

**Figure 6.** Spatial distribution of Sen's slope in February (**a**) and in November (**b**) for SPI-1 index.
