In the last 40 years, environmental isotopes have become almost indispensable tools in different branches of hydrology and related environmental disciplines. Their numerous applications in hydrogeology include tracing the sources of ground water, estimation of recharge rates, and determination of groundwater ages. Environmental isotopes have gained the position of prominence in hydrogeology because they can be routinely measured with high sensitivity, thus allowing for improved accuracy and precision in quantitative description of hydrogeological processes. Environmental Isotopes in Hydrogeology brings together the different isotopic techniques commonly used in hydrogeology and includes numerous examples and problem sets for students.