*2.6.4 The seasonality index*

As explained previously, we quantified climate change impacts on the monthly concentration and seasonal variation of discharge volumes. **Table 5** presents the SI of the five GCMs median considering the reference period climate and farfuture climate under RCP4.5 and RCP8.5. As seen from the table, variations in SI between reference-period and end-century regimes are overall small. Over the Niger basin, the annual discharge volume under the RCP8.5 is seasonal compared with the reference period. For the Yobe and Jamaare rivers, the future annual river discharge volumes would be concentrated in less than three months. Annual SI over the HJKYRB river for the reference and Far-future period shows similar seasonal variability regimes of marked seasonality with a long dry period. The two basins generally receive most of the precipitation during the wet season; therefore, annual discharge occurs during the high-flow period.

#### *2.6.5 Climate change impacts on seasonal discharge variation*

Multi-model median monthly river discharge climatologies for the reference and far-future conditions under scenarios are presented in **Figure 6**.

#### **Figure 6.**

*Monthly streamflow climatologies projected for reference (1971–2000) and far-future (2070–2099) periods. The solid lines represent the ensemble median of all climate models combinations, while the colours represent the range from the 5th to 95th percentile.*
