This book demonstrates, through concrete examples, the potential of isotope techniques in the development and management of water resources. It commences with a description of the characteristics of isotopes and their utility as tracers in studies pertaining to various stages of the hydrological cycle.

The book delves into the usage of both environmental isotopes and injected tracers in surface water and groundwater bodies, as well as the relationships between them. Special emphasis is placed on the application of isotopes in identifying groundwater recharge and the processes associated with it, given its significance. The role of isotopes in understanding groundwater contamination caused by natural pollutants such as inland salinity, arsenic, and nitrate is also discussed with the aid of examples.

1.Introduction. 2. Basis for applications of various isotopes in hydrology. 3. Isotope applications in surface water hydrology. 4. Isotope applications in groundwater hydrology. 5. Need for enhanced application of isotope hydrology and how to achieve it.