The manual provides a general overview of groundwater principles. Practical discussions are provided for planning groundwater investigations and modeling of groundwater flow. Additionally, a section on surface water and groundwater interaction is included. To enhance understanding of concepts, examples are provided throughout the manual. This manual initially presents an overview of the occurrence and movement of groundwater. Procedures for planning and managing a site characterization and modeling study are then presented. This is followed by chapters addressing the technical aspects of field investigative methods and computer modeling. A final chapter discussing the interaction of groundwater and surface water is then presented. Appendices are included that contain detailed references, definitions, and additional supporting information.