The interdisciplinary field of geochemistry and hydrology, which deals with isotope utilization to estimate the age and origin of surface and groundwater is known as isotope hydrology. It also studies the circulation and movement of water with the hydrologic cycle. Water molecules carry unique isotope fingerprints located in parts of different proportions of oxygen and hydrogen isotopes which constitute the water molecule. It also helps in determining the age of ice or snow using stable isotopes. The techniques used are beneficial for conserving water supplies, controlling pollution and mapping aquifers. This field also has applications in ecohydrology. It is used to understand the impact of humans on the varied dimensions of the hydrological cycle and other ecosystem services. This book unravels the recent studies in the field of isotope hydrology. The ever-growing need of advanced technology is the reason that has fueled the research in this field in recent times. For all those who are interested in isotope hydrology, this book can prove to be an essential guide.