Isotope Hydrology: A Historical Perspective from the IAEA -- Isotopic and Nuclear Methodologies -- Isotopic Tracers for Obtaining Hydrologic Parameters -- Hydrologic Process Studies Using Radionuclides Produced by Cosmic Rays -- Stable Oxygen and Hydrogen Isotopes in Precipitation -- Tritium in the Hydrologic Cycle -- Assessing Sources and Transformations of Sulphate and Nitrate in the Hydrosphere Using Isotope Techniques -- Rare Gases -- U and Th Series Nuclides in Natural Waters -- Optical Isotope Ratio Measurements in Hydrology -- Hydrologic Process and Systems -- Some Classical Concepts Of Isotope Hydrology -- Isotopes in Lake Studies: A Historical Perspective -- A Review of Isotope Applications in Catchment Hydrology -- Contribution of Isotopic and Nuclear Tracers to Study of Groundwaters -- Dating of Young Groundwater -- Dating of Old Groundwater — History, Potential, Limits and Future -- Geothermal Systems -- Saline Waters -- Hydroclimatic Processes and Systems -- Isotopes in Atmospheric Moisture -- How Much Climatic Information Do Water Isotopes Contain? -- Stable Isotopes through the Holocene as Recorded in Low-Latitude, High-Altitude Ice Cores -- Groundwater as an Archive of Climatic and Environmental Change -- Isotopic Palaeolimnology.Environmental isotope and nuclear techniques provide unmatched insights into the processes governing the water cycle and its variability under past and present climates. This monograph is recommended to advanced students and specialists and presents historical perspective, state of the art applications and new developments of isotopes in hydrology, environmental disciplines and climate change studies. The spectrum of isotope applications addressed in this monograph ranges from the assessment of groundwater resources in terms of recharge and flow regime, identification of palaeogroundwater, water balance of river basins and lakes, to studies of the past and present global environmental and climate changes. The contributions are written by renowned specialists in the various application fields.