Introduction to Isotopes and Environmental Tracers as Indicators of Groundwater Flow

This book addresses the use of environmental tracers and environmental isotopes for identifying groundwater sources and quantifying rates of groundwater recharge, discharge, flow, and mixing. Its goal is to present the application of the techniques in a form that can be readily understood and appreciated by groundwater professionals who do not have a background in the use of isotopes or other environmental tracers. The aim is to raise awareness of the potential of these tools.

For most of the examples, the techniques were successfully applied. However, not all studies are so successful. Some of the limitations of the various tracers that contribute to failed studies are discussed toward the end of this book.

In this book, emphasis is given to techniques that provide information on groundwater residence times, as these facilitate estimation of groundwater flow rates. The focus is on the saturated zone and on water quantity rather than quality, so this book does not address use of compound-specific isotopic techniques to determine sources of anthropogenic contamination, geochemical reactions and pathways, soil evaporation or rates of plant water use. Although some of the examples demonstrate how residence time indicators have been used in conjunction with measurement of contaminant concentration to determine rates of plume movement or changes in contaminant concentrations over time.

Isotopes and environmental tracers are being used more widely in groundwater science, and this book aims to facilitate the continuation of this increased use.