We all are aware that climate change is evident and will cause adverse impacts on the social and natural systems of all nations; however, its impact will hit developing countries the worst and the hardest. This book focuses on the impact of climate change on the Lake Tana Basin - a source of the Blue Nile river. The Lake Tana has vital role for the livelihoods of the people residing in the region in particular and the downstream countries in general. In this work, GCM derived scenarios of climate change data are used for predicting the plausible future climate of the region. Statistical Downscaling Model (SDSM) is used to downscale the GCM data into a finer scale. A physically based hydrological model called SWAT (Soil and Water Assessment Tool) was setup, calibrated, validated and used for impact assessment. This book encompasses sound methodological approaches from climate change science to hydrological modeling, and can serve as an essential guide for practitioners and graduate students who are working on water resources and related disciplines. Yet, I remind the reader that the future is full of uncertainties, and so does climate change projections.