This book is focused on the use of isotope analysis of groundwater samples to better understand the origin, travel time, residence time (often referred to as ‘groundwater age’) and recharge of groundwater. Isotopes serve as indicators or inherent tracers that occur within all groundwater systems. The analyses are done on groundwater molecules or on dissolved constituents in the water. The methods for sampling wells and springs are not complicated and there are many commercial and other laboratories across the globe available for analysis of the most useful isotopes. Isotopes in the study of groundwater systems began in the 1950’s and there is now a large literature showing how they can be helpful. Given and relatively low cost per analysis and the many ways in which isotope data provide useful insights unobtainable in other ways, isotopes should be viewed as indispensable ‘tools’ for nearly all types of groundwater investigations. However, in standard practice, isotopes are not yet used to full advantage. An objective of the GW-Project is to correct this situation by providing education about isotopes in many books in various levels of detail. Peter Cook, the author of this book that provides a broad overview of as the starting point for this topic, is a leader in the field who has co-authored many of the seminal papers across a broad spectrum of isotope applications.

John Cherry, The Groundwater Project Leader
Guelph, Ontario, Canada, October 2020