The approach of this book is how-to-do and hands-on. Its purpose is to provide clear, step-by-step instruction in many of the fundamental methods of hydrogeologic investigation. These methods include both 1) the traditional techniques of data analysis, such as mathematical computation by electronic calculator and construction of graphs by hand-plotting, and 2) microcomputer techniques employing electronic spreadsheets, graphing and gridding and contouring software. The microcomputer methods employ commercial software such as Lotus 1-2-3. Microsoft Excel, Quattro-Pro, Golden Software's Grapher and Surfer, and Geraghty and Miller's AQTESOLV. Although familiarity with any of the applications is helpful, the instructions in this manual assume no prior experience with them. Basic Hydrogeologic Methods is divided into three sections: Groundwater Occurrence and Movement, Groundwater Investigations, and Well and Aquifer Hydraulics. Each section begins with a brief summary of relevant terminology and principles. This introductory chapter is followed by a case study, which may be employed to provide a practical context for the hydrogeological methods that are described in subsequent chapters. Most of the methodological exercises culminate in an analytical product, such as data table, graph, contour map, etc., which readily serve as a focus for problem-solving activities, classroom discussions, and investigative reports. Many of the exercises present at least two investigative methods for accomplishing a particular hydrogeologic task. For example, time-drawdown graphs may be produced by a hand-plotting method or by a microcomputer method. For the professional scientist, the choice of a particular method might depend on such factors as the time available to carry out the task, the degree of accuracy required, or the availability of assessory equipment and materials.