The impacts of climate change on hydrological processes of Gilgel Gibe catchment, southwest Ethiopia

Nile basin, however, reported varying changes in precipitation in the future periods. Accord- ing to [55], whose study considered 17 different GCMs, it was found that 10 out of the 17 GCMs reported a decrease in precipitation. However, when the ensemble of all 17 GCMs was analyzed, it revealed essentially no projected change in precipitation. On the other hand, [56] reported an increase in projected precipitation in the late 21st century using 11 GCMs. [57] have also reported significant RCM-GCM uncertainty on the signal of future precipitation in the upper Blue Nile (Abay) river basin. This may be due to the nature of precipitation and its dependence on topographical and physical elements. The results of precipitation projections in this study are consistent with those of studies on climate change [58, 59] Decreased precipitation was also noted in the study of [60] on the effects of climate change on the hydro-meteorological variables of the Finchaa sub-basin using the HadCM GCM. The study by [61] which also used CCLM downscaling, showed falling pre- cipitation by 6.6% and 6.4% over the upper Blue Nile basin for the periods 2041–2070 and 2071–2100. 3.2.2 Temperature. Tables 4 and 5 show the range in the predicted future maximum and minimum temperatures for each individual RCM and their ensemble mean, respectively. The result shows that maximum and minimum temperatures increase under both RCPs through- out the study years considered showing the warming trends in the catchment. However, com-

pared to RCP4.5, the magnitude of changes made by each individual RCM and their mean ensemble is greater for higher emission scenarios (RCP8.5). Under both emission scenarios, the change in temperature is also greater in the far future than the intermediate period. The magnitude of the temperature changes varies across all RCMs and the ensemble mean as well. Under both RCPs for the intermediate and far future, RCA4 has shown the greatest increase in maximum temperature. Concerning to the ensemble mean of the RCMs, under the medium emission scenario (RCP4.5), the maximum temperature would rise by an average of 1.69˚C and 2.49˚C, while the Table 4. Changes in temperature (˚C) across the four RCMs in RCP4.5 and RCP8.5 scenarios. No Tmax RCP4.5 RCP8.5 RCMs 2041–2070 2071–2099 2041–2070 2071–2099 1 CCLM4-8 1.61 2.36 1.89 3.54 2 HIRHAM5 1.54 2.42 1.66 3.55 3 RACMO22T 1.78 2.55 1.77 3.35 4 RCA4 1.84 2.65 2.06 3.82 5 CRCM5 1.64 2.44 1.77 3.48 6 REMO2009 1.72 2.54 1.83 3.57 Ensemble 1.69 2.49 1.83 3.55 https://doi.org/10.1371/journal.pone.0287314.t004 Table 5. Changes in temperature (˚C) across the four RCMs in RCP4.5 and RCP8.5 scenarios. No Tmin RCP4.5 RCP8.5 RCMs 2041–2070 2071–2099 2041–2070 2071–2099 1 CCLM4-8 1.98 3.31 2.45 5.21 2 HIRHAM5 1.74 2.91 1.89 4.44 3 RACMO22T 1.58 2.59 1.94 4.05 4 RCA4 1.52 2.38 1.93 3.73 5 CRCM5 1.77 2.94 2.09 4.57 6 REMO2009 1.61 2.63 1.92 4.07 Ensemble 1.70 2.79 2.04 4.35 https://doi.org/10.1371/journal.pone.0287314.t005 PLOS ONE

The impacts of climate change on hydrological processes of gilgel gibe catchment PLOS ONE | https://doi.org/10.1371/journal.pone.0287314 June 28, 2023 17 / 28