Due to the rapid growth of Egypt’s population and the very limited available water resources in Egypt, it becomes a must to reuse the drainage water in irrigation more than once and to develop more water resources such as desalinated water. Both reused water and desalinated water are called unconventional water resources. This volume deals with the unconventional water resources in Egypt. This volume consists of 18 chapters in 6 parts. Part I is an introduction and comprises two chapters. The chapter “The Evolution of Drainage Water in Egypt” presents the story of drainage in Egypt since irrigation converted from scattered basin irrigation to perennial irrigation system. The chapter titled “Management of the Integration Between Irrigation and Drainage Water in the Nile Delta” presents some of the management efforts made by the Egyptian Government to maximize the benefits of reusing the agricultural drainage water. Part II consists of three chapters dealing with the assessment of drainage system in Egypt. The chapter titled “The Assessment of Egypt’s Subsurface Drainage System” presents and assesses the various elements of the different types of drainage applied in Egypt and their impacts on agricultural productivity. In the chapter “Environmental Impact Assessment of Subsurface Drainage Projects,” the authors discuss and perform an environmental impact assessment (EIA) for the subsurface drainage projects considering the Mashtul Pilot Area (MPA) in Egypt as a real case study where the experimental fieldwork was carried out to obtain the data necessary to evaluate and assess the impact of subsurface drainage projects in the main categories of the environmental issues. They then develop an EIA matrix for subsurface drainage projects to qualify and quantify the baseline of environmental setting accompanied with their potential impacts. The third chapter of Part II is titled “New Design Criteria for Subsurface Drainage System Considering Heat Flow Within Soil” and introduces a new concept for the design of the subsurface drainage system via numerical simulation by considering the subsurface heat flow within the different kinds of soil including clay, clay loam, sandy clay loam, and loamy sand soils that are cultivated with maize crop.