Two themes are carried through this book. The first is an introduction to the concept of materials and energy balance as a tool for understanding environmental processes and solving environmental engineering problems. The second theme of the book is the concept of sustainability, and deals with topics of water conservation, sludge minimization in water treatment, land treatment of waste water, protection of ozone layer.

Integrated watershed management has been receiving priority attention in the Eastern Nile Basin Countries because of serious natural resources degradation that also damaged the livelihood of the resident communities. It continues to be critical for rehabilitation of the natural resources not only for reducing environmental degradation, but also for tapping its full potential and improve the living condition of the communities in these areas. Accordingly, two pilot watershed management projects in Ethiopia and Sudan have been implemented. This report thus focuses on the impact assessment of the two-pilot watershed management projects in the two countries; Tana Belese Integrated Watershed Management Project (TBIWSMP) in Ethiopia and Community Watershed Management (CWM) Project in Sudan. The assessment of the pilot EN watershed management projects assembled number of facts that brought visible impacts in different dimensions that have the potential for scaling up adapted to the specific agroecological/environmental and socioeconomic framework. The impact assessment result is indicated for each of the three sections (biophysical, socioeconomic and institutional capacity impacts assessments) that will be discussed in the results section of this report.