Assessing the impacts of climate change on Hydrology of the Upper Awash River Basin using a conceptual rainfall-runoff Hydrological HBV model. The HBV model was calibrated and validated to simulate the streamflow using observed hydrometeorological data, GCMs and WFD outputs. Analysing the effect of old and new climate change scenarios in the Upper Awash River Basin.
Assessing the Impacts of Climate Change on Hydrology of the Upper Awash River Basin in Ethiopia, using a Conceptual Hydrological Model
GCMs output and a hydrological model have been used to infer information from available data and explore future hydrology in a basin. However, the large uncertainty that comes from many aspects, such as the hydrological model, and GCMs output are still a challenge to the researchers. The likely climate change impacts on hydrology of three subbasins in the Upper Awash River Basin have been evaluated using the semi-distributed HBV hydrological model, RCP and SRES climate scenarios. The streamflow difference analysis for the reference period (1971-2001) indicated that there was a noise, which makes it difficult to distinguish the climate change signal in some of the months in most of the GCMs, particularly in the intermediate future (2021-2050). However, in the far future period (2071-2100) there was a strong climate change signal in most of the months and scenarios relative to the noise. There was a significant increase in temperature in all GCMs in the three subbasins that leads to higher potential evapotranspiration. The temperature increase in new RCP scenarios was higher than for the old SRES scenarios in all the months and subbasins, excluding the IPSL A2 old scenario. The IPSL RCP scenarios showed increased precipitation and streamflow in three subbasins, for the intermediate and far future periods. The lowest streamflow percent change was in the CNCM3 A2 and ECHAM A2 scenario for the main rainy season (June-September) and in HADGEM RCP scenario for the dry and the small rainy season (February-May). There was a slight increase in streamflow similar than precipitation, though there was no such a clear general pattern in streamflow as that of temperature. The streamflow change was high in the new RCP scenarios as compared to the old SRES scenarios. The Hombole subbasin main rainy season, intermediate future streamflow change would be 1.31% (0.06 mm/day) and 56% (0.6 mm/day) for the ECHAM A2 and IPSL RCP8.5 scenarios, respectively, as compared to the reference period. However, the far future streamflow change would be -8.04% (0.06 mm/day) and 160% (2.13 mm/day) for the ECHAM A2 and IPSL RCP8.5 scenarios, respectively. The Hombole subbasin, which is the largest subbasin and the most downstream, showed the lowest percent change in streamflow as compared to the Bello and the Melka Kuntrie subbasins in most of the months and scenarios for the intermediate future and the far future periods. The Bello subbasin, which is the smallest and the most upstream showed the highest percent change in streamflow.