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

highest decline in surface runoff in both scenarios considered in the study forecasts. The pro- jected decline in surface runoff is greater in the intermediate term than in the far future, according to the RCP4.5 and RCP8.5 scenarios. Surface runoff is anticipated to decrease at the slowest rate in both scenarios over the far future and the intermediate term in the southwest, followed by the northeast. Reduced surface runoff in the catchment are all potential outcomes that could affect the catchment’s water resource availability and exacerbate water shortages (Fig 15). According to the result, climate change has caused a decline in the catchment’s groundwa- ter flow. The upstream of the catchment is frequently expected to have the biggest groundwa- ter decline in all scenarios that take into account study forecasts. Groundwater levels are declining faster in the southwest corner. Water stress downstream could be made worse by the potential for lower groundwater levels in the catchment, which would affect the availability of water resources in the catchment (Fig 16). The upstream of the catchment is expected to have the highest decrease in water yield under both scenarios considered in the study estimates. The projected loss in water yield is larger in the intermediate than in the far future, according to the RCP4.5 and RCP8.5 scenar- ios. The rate of water yield decline is greater in the southwest corner. The potential for a decreased total water yield in the catchment could affect the availability of water resources in

the catchment and worsen water stress downstream (Fig 17). In general, the increase in temperature and decline in annual and seasonal precipitation in both scenarios could be the cause of the catchment’s decreased average annual flow. The possi- bility of reduced surface water, groundwater, and total water yield in the catchment could have an impact on the availability of water resources in the catchment and exacerbate water stress downstream. The acceleration of the increasing water abstractions could also contribute to the further decline in water resources besides the climate change pressure. Reduced soil moisture, which is necessary for plant growth and groundwater storage, may result from the increase in PET (Fig 18) brought on by rising temperatures and a decline in precipitation. This may indicate decreased water availability for agricultural production, which will become a chronic problem for the farmers in the catchment whose only source of Fig 14. Impacts of climate change on water balance. https://doi.org/10.1371/journal.pone.0287314.g014 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 21 / 28