In recent years, the focus in hydrogeologic investigations has expanded to include aquifer sustainability as part of resource evaluations. Revised and updated, this second edition includes new coverage of aquifers, US federal regulations, groundwater quality, and history of hydrogeology, and offers new international case studies. Useful as a field guide and a textbook, it contains standard methods for planning and undertaking hydrogeologic investigations. Presenting ASTM standards and EPA and US Geological Survey field techniques, the book covers hydrogeologic fundamentals, conceptual models, planning, surface and subsurface investigations, field inventory, stream flow and water quality measurements, and report preparation. It also contains source information for additional study, as well as a glossary. Downloadable software allows readers to design their own aquifer tests.