This is a thorough, up-to-date guide to groundwater science and technology. Our understanding of the occurrence and movement of water under the Earth's surface is constantly advancing, with new models, improved drilling equipment, new research, and refined techniques for managing this vital resource. Responding to these tremendous changes, David Todd and new coauthor Larry Mays equip readers with a thorough and up-to-date grounding in the science and technology of groundwater hydrology. "Groundwater Hydrology, Third Edition" offers a unified presentation of the field, treating fundamental principles, methods, and problems as a whole. With this new edition, you'll be able to stay current with recent developments in groundwater hydrology, learn modern modeling methods, and apply what you've learned to realistic situations. Highlights of the Third Edition include: new example problems and case studies, as well as problem sets at the end of each chapter; a special focus on modern groundwater modeling methods, including a new chapter on modeling (Chapter 9), which describes the U. S. Geological Survey MODFLOW model; over 300 new figures and photos; both SI and U.S. customary units in the example problems; expanded coverage of groundwater contamination by chemicals; and new references at the end of each chapter, which provide sources for research and graduate study. Student and instructor resources for this text are available on the book's website.