This manual has been prepared as a guide to field personnel in the more practical aspects and commonly encountered problems of ground-water investigations, development, and management. Information is presented concerning such aspects as ground-water occurrence and movement, well-aquifer relationships, ground-water investigations, aquifer test analyses, estimating aquifer yield, data collection, and geophysical investigations. In addition, permeability tests, well design, dewatering systems, well specifications and drilling, well sterilization, pumps, and other aspects have been discussed. An extensive bibliography has also been included. The manual has been developed over a period of years, and its many contributors have diversified technical backgrounds. Contributors include personnel from the Bureau of Reclamation Engineering and Research Center (now Technical Service Center) and field offices, other agencies, foreign governments, and many individual scientists and engineers.