For upper-level undergraduate and graduate-level courses in Unsaturated Zone Hydrology for students in the fields of environmental science, geology, hydrology, engineering, soil science, soil mechanics, soil physics, and agricultural engineering. This text 1) presents A-to-Z coverage of unsaturated zone hydrology for those whose academic backgrounds and prerequisite classes may have not prepared them well for investigating phenomena in the unsaturated zone, and 2) offers systematic, integrated coverage of the state of the art for more prepared students. Multi-disciplinary in approach, it provides both a soil physics and an engineering approach to unsaturated zone hydrology. Coverage begins with the basic physical properties and the behavior of clays, and moves on to contaminant transport and parameters such as spatial variability, scaling, and fractals in the Earth sciences.