Preface

This book provides an overview of common tracer methods that can be used to estimate the age of young groundwater that has recharged since about 1960. The dating tracer methods include tritium ([latex]_{}^{3}{He}[/latex]), tritium/helium‑3 [latex]\left( \frac{_{}^{3}{He}}{_{}^{3}{He}} \right)[/latex], sulfur hexafluoride [latex]{(SF}_{6}),[/latex]and chlorofluorocarbons (CFCs). All of these methods except [latex]_{}^{3}H[/latex] involve the occurrence and transport of dissolved gases, and thus the basic concepts of dissolved gases are also included. The applications of tracers to address hydrogeologic problems are only mentioned briefly in this book because such problems are the topic of the Groundwater Project book Introduction to Isotopes and Environmental Tracers as Indicators of Groundwater Flow (Cook, 2020), which we encourage you to review.

This book is intended for knowledgeable practitioners and/or academics who desire to learn the details of how measured tracer concentrations can be converted to an apparent groundwater age. While we provide an overview of both the analytical methods and the systematics of age dating, the content is most useful for those who wish to implement groundwater age dating in their work.

As hydrogeologists, we are interested in solving both groundwater quality and quantity issues in a world where the availability of high-quality groundwater is diminishing. Our goal is to inform groundwater professionals and policy makers about the concepts and underlying assumptions involved in groundwater dating methods. The ultimate aim is to increase the application of these powerful methods while recognizing their inherent limitations.

By reading this book and completing the exercises, we aim to help readers achieve the following.