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This study aimed to assess trends of hydro-meteorological variables in the Upper Omo-Ghibe river basin, Ethiopia. Data records from eleven rainfall, eight air temperature, and five streamflow stations between 1981 to 2008 were investigated. The trends and change points were evaluated for different periods of time depending on data availability. Mann-Kendall and Pettit tests were used to identify trends and change points at a 5% significance level. The tests were applied to mean annual, monthly and seasonal time scales. Rainfall exhibited statistically decreasing trends at a mean annual time scale, while seasonal rainfall depicted heterogeneous results in both directions. For the majority of the stations, air temperature showed statistically significant increasing trends. The magnitude of change in temperature for mean annual, wet and dry season has increased about 0.48, 0.46, and 0.61 °C per decade for Jimma station. The Pettit test revealed that the late 1980s and 1990s were the change points. There is generally a decreasing trend in streamflow. The decline in annual rainfall and rise in temperature affected the streamflow negatively. Overall, the results indicate that trend sand change point times varied considerably across the stations and catchments. The identified significant trends can help to support planning decisions for water management.

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This paper discusses the response of climate change impact on future streamflow availability in Upper Awash River basin, Ethiopia. The change of climate was built using the CORDEX, RCM daily precipitation, maximum and minimum temperature under RCP4.5 and 8.5 scenarios. The climate model was examined in the historical period 1996–2015 for its ability to capture observed precipitation and temperature. Bias correction was performed on RCM temperature and precipitation to minimize the uncertainties that may occur from climate model projection. After the successful calibration and validation of the HBV hydrological model, streamflow was simulated for the periods of 2021–2040 and 2041–2060 and compared to streamflow of the baseline period 1996–2015 to investigate the changes. The results suggested that overall, following the precipitation increment, streamflow is expected to increase under both RCPs. The average monthly changes of streamflow are expected to increase by 40.1 and 29.4% under RCP4.5 and 16.9 and 18.5% under RCP8.5 scenarios for 2021–2040 and 2041–2060, respectively. Annual streamflow would increase by 28.5 and 23.95% under RCP4.5 and 8.5, respectively. The results of this work can help and inform the water resources planner and designer to frame an appropriate plan and management for the effective use of water in the future.

This paper was aimed to study the impact of climate change on the hydrology of Andasa watershed for the period 2013–2099. The soil and water assessment tool (SWAT) was calibrated and validated, and thereby used to study the impact of climate change on the water balance. The future climate change scenarios were developed using future climate outputs from the Hadley Center Climate Model version 3 (HadCM3) A2 (high) and B2 (low) emission scenarios and Canadian Earth System Model version 2 (CanESM2) Representative concentration pathways (RCP) 4.5 and 8.5 scenarios. The large-scale maximum/minimum temperature and rainfall data were downscaled to fine-scale resolution using the Statistical Downscaling Model (SDSM). The mean monthly temperature projection of the four scenarios indicated an increase by a range of 0.4–8.5 °C while the mean monthly rainfall showed both a decrease of up to 97% and an increase of up to 109%. The long-term mean of all the scenarios indicated an increasing temperature and decreasing rainfall trends. Simulations showed that climate change may cause substantial impacts in the hydrology of the watershed by increasing the potential evapotranspiration (PET) by 4.4–17.3% and decreasing streamflow and soil water by 48.8–95.6% and 12.7–76.8%, respectively. The findings suggested that climate change may cause moisture-constrained environments in the watershed, which may impact agricultural activities in the watershed. Appropriate agricultural water management interventions should be implemented to mitigate and adapt to the plausible impacts of climate change by conserving soil moisture and reducing evapotranspiration.