This special issue of Isotopes in Environmental and Health Studies contains selected papers presented at the International Symposium on Isotope Hydrology convened by the International Atomic Energy Agency (IAEA) and held at IAEA Headquarters in Vienna, Austria, from 11 to 15 May 2015. The first symposium in this series was convened in 1963, and these quadrennial IAEA symposia have since provided a unique opportunity to review and advance the science and application of isotope hydrology worldwide. Building upon the discussions and exchange of information at the symposia, the IAEA has played a crucial role in promoting and expanding the use of isotopes in hydrology to gain unique insights into the functioning of terrestrial and atmospheric water cycles. After more than 50 years of development as a scientific discipline, isotope hydrology has widespread applications in water resources assessment and management, in the study of past and future changes in the Earth’s climate as well as of climate impacts on the water cycle, and in ‘forensics’ related to ecological, wildlife and food source traceability.
The 2015 IAEA symposium featured the theme of ‘Revisiting Foundations and Exploring Frontiers’ of isotope hydrology, with a review of the foundational concepts along with new developments and advances. The symposium attracted a record number of 347 participants from 77 countries and international organizations. The programme included 88 oral presentations and 239 posters, covering a diverse spectrum of hydrological, climatological and environmental disciplines relevant to the IAEA’s work, such as: (a) isotopes in precipitation, atmosphere–hydrosphere interactions, paleoclimate and paleo-hydrology, (b) studies on assessment of groundwater resources, age dating and noble gas isotope studies, (c) surface water isotopic and pollution studies, (d) advances in laser spectroscopy and other recently developed analytical methods, and (e) nutrient cycles and contamination.
A special session was devoted to commemorate 50 years of IAEA Technical Cooperation projects in isotope hydrology, water resources assessment and hydrological modelling. The final session was devoted to review cutting-edge developments in data interpretation and new fields where further isotope applications can contribute to the global water and climate agendas.
As availability of freshwater becomes more critical to the economic and social development of all nations, it has become evident that water often lies at the heart of global efforts to reduce poverty and achieve sustainable development. The recently adopted Sustainable Development Goals of the United Nations recognize this role, and accordingly include a separate and independent goal on water. Meeting this goal entails that society as a whole must change the way it develops, uses and manages water resources, guards against unsustainable overexploitation and widespread pollution of resources, and adapts to the impact of climate change on rainfall patterns. An accounting of the volume and flow rates of surface water courses and underground bodies alone is not sufficient for good water resources management. Instead, a comprehensive understanding of the origin, history and dynamics of each component of the water cycle is critical to the reliable assessment of hydrological systems as the sources of water supply in medium and long terms. These efforts will require the use of all available scientific tools, such as remote sensing, geophysics, hydrological monitoring and modelling. Recent advances in the understanding of parameters controlling the distribution of isotopes in the water cycle, as well as in measurement technologies for stable and radioactive isotopes, as demonstrated in some of the research papers at this Symposium, will allow a greater use of isotopes for efficient and reliable water resources assessment and management.
The next quadrennial IAEA Symposium on Isotope Hydrology will take place in Vienna, Austria, in 2019.