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UNESCO-IHE Institute for Water Education, Delft (2016)

Climate change impacts on water resources in the Lake Tana Basin in Ethiopia

Abebe, A.G.

Titre : Climate change impacts on water resources in the Lake Tana Basin in Ethiopia

Auteur : Abebe, A.G.

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2016

Résumé partiel
Climate change has the potential to affect water resources availability in the Blue Nile Basin, Ethiopia. The Lake Tana and its catchments, located in the upper parts of Blue Nile, supports more than three millions of people and any impact on its ability to support livelihood of the communities in this basin is a major concern. Thus, the main objective of this study was to analyse the impact of climate change on hydrology and water resources in Tana Basin. The Soil and Water Assessment Tool (SWAT) was used to investigate the impact of climate change on streamflow of the study area. The climate change scenarios were based on daily bias-corrected GCMs with downscaled to 0.50 latitude and 0.50 longitude spatial resolution. The projected scenarios of A1B and A2 were obtained from CNRM_CM3 and MIROC3.2 models for two future horizons in 2055s (2046-2064) and 2090s (2081-2100). The SWAT model was calibrated and validated at four catchments (Gilgel Abay, Gummera, Ribb, and Megetch) and at the outlet of the Lake Tana. The hydrological model performance was evaluated using standard statistics, i.e. ENS, R2 and PBIAS. The results of calibration (ENS : 0.88 for Gilgel Abay, ENS : 0.87 for Gummera, ENS : 0.74 for Ribb, ENS : 0.68 for Megetch, and ENS : 0.81 for Lake Tana outlet) and validation (ENS : 0.93 for Gilgel Abay, ENS : 0.86 for Gummera, ENS : 0.79 for Ribb, and ENS : 0.78 for Megetch) on monthly time steps are satisfactory and then the model used for impact study. The climate change results showed that the mean annual precipitation increases for both scenarios and time horizons but with variations on monthly basis. The CNRM_CM3 model revealed that mean annual precipitation is projected to increase by 9-13% and 7-14% in 2055s and 2090s respectively overall the catchments in the Tana basin under A1B scenario. Under A2 scenario, the precipitation is projected to increase by 1-13% over Gilgel Abay, Gummera and Ribb. However, the model showed a slight decrease in the northern side of the basin at Megetch catchment by 1% in 2055s under A2 scenario. The MIROC3.2 model also depicted that increase of annual precipitation ranges from 18-22% and 28-34% in 2055s and 2090s respectively under A1B scenario whereas 34-42% and 51-59% in 2055s and 2090s respectively under A2 scenario. Hence, MIROC3.2 model projected precipitation higher than CNRM_CM3. On monthly basis, both GCM models showed the increment of mean daily precipitation during the beginning of dry season from October to December. According to the climate change scenarios, the temperature increases in all months in the basin.

Sujets  : climate change water resources hydrological modelling lake hydrology Ethiopia

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Page publiée le 21 décembre 2019