An international research project coordinated by the International Atomic Energy Agency (IAEA) has shown that isotope-based techniques can help cities better protect and manage their drinking water supplies.
The five-year initiative, which ran from 2018 to 2023, brought together scientists and water experts from 10 countries to develop and apply high-resolution isotope tracing methods in urban environments. Using stable isotopes — natural variations in water molecules that act as unique identifiers — researchers can track water origins, detect evaporation losses, identify mixing between sources and pinpoint contamination faster than conventional methods.
The findings are already shaping water management in participating cities. In Costa Rica’s Central Valley, scientists traced seasonal shifts in water sources, improving supply planning.
“Understanding the seasonal shifts in our water sources has helped us better plan for dry periods and ensure consistent supply to our residents,” said German Esquivel-Hernandez from the Water Resources Management Laboratory at Universidad Nacional in Costa Rica.
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The international collaboration featured researchers from Argentina, Ecuador, Ethiopia, India, Morocco, Nepal, Romania, Slovenia and the U.S. Researchers adapted the techniques to local challenges, combining scientific precision with practical application.
In Kathmandu, Nepal, isotope data has already been incorporated into daily operations to trace where the water comes from and how it changes.
Other cities have used the research to improve water quality.
“The isotope data helped us identify blending zones in our network and optimize treatment processes,” said Klara Zagar of the Jozef Stefan Institute in Slovenia.
Ricardo Sanchez-Murillo, a senior researcher at the University of Texas at Arlington, called the approach “invaluable” for managing urban water supply systems, adding: “These techniques will play a crucial role in ensuring the sustainability of urban water supplies in the face of growing water demand and climate variability.”
The project also produced training programs, policy frameworks and peer-reviewed publications to build long-term capacity in isotope hydrology.
A Scientific Forum on Atoms for Water will be held September 16-17 at the IAEA Headquarters in Vienna during the agency’s 69th General Conference.
