Defining stream flow and rainfall patterns over a period of different land cover changes together with understanding the community’s knowledge about natural resource dynamics of the Didessa sub-basin of the Blue Nile River are the main issues which this book investigates. Despite the fact that the Didessa sub basin study area provides the largest amount of the Blue Nile River flows and is comparatively well equipped with lengthy hydrological and meteorological data series, most studies related to the Blue Nile River have focused on its northern part. This makes the Didessa sub-basin one of less studied areas and a key to better understanding the overall hydrological regime of the Blue Nile. What is especially interesting about Didessa is that in some areas deforestation has not gone as far as in the northern part of the Blue Nile Sub-basins. There is more forest here now and the amount of forest cover is also changing during the analyzed observational records of rainfall and flow period, while much deforestation in the north occurred before the flow regime observations began.