This book is the long-awaited successor to Owen M. Phillips's classic textbook, Flow and Reactions in Permeable Rocks, published in 1991. In the intervening eighteen years between the two, significant advances have been made to our understanding of subterranean flow, especially through the vast amount of research into underground storage of nuclear waste and aquifer pollution. This new book integrates and extends these modern ideas and techniques and applies them to the physics and chemistry of sub-surface flows in water-saturated, sandy and rocky media. It describes essential scientific concepts and tools for hydrologists and public health ecologists concerned with present day flow and transport, and also for geologists who interpret present day patterns of mineralization in terms of fluid flow in the distant past. The book is ideal for graduate students and professionals in hydrology, water resources, and aqueous geochemistry.