IAEA’s Global Research Initiative Uses Isotopes to Strengthen Urban Water Resilience

From Costa Rica to Nepal, the initiative harnessed isotope hydrology—an advanced scientific technique—to provide cities with a deeper, more precise understanding of their water systems.

 

As urban populations expand and climate change tightens its grip on global water supplies, a groundbreaking five-year research project led by the International Atomic Energy Agency (IAEA) is reshaping how cities monitor, protect, and manage their water resources. From Costa Rica to Nepal, the initiative harnessed isotope hydrology—an advanced scientific technique—to provide cities with a deeper, more precise understanding of their water systems.

Running from 2018 to 2023, the project brought together researchers, utility managers, and policymakers from 10 countries: Argentina, Costa Rica, Ecuador, Ethiopia, India, Morocco, Nepal, Romania, Slovenia, and the United States. The result is a new generation of tools and strategies designed to help cities secure safe, sustainable drinking water amid rising urban demand and environmental pressures.

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Why Isotopes? A New Lens on Water Systems

Conventional water monitoring relies heavily on physical and chemical testing—important, but often limited in revealing the true origins and behavior of water sources. This IAEA-led initiative introduced the systematic application of stable isotope tracing—a method that identifies water's molecular fingerprints. These natural “labels” allow scientists to:

• Determine the source of water (groundwater, surface water, reservoirs)

• Track evaporation losses from storage and distribution systems

• Detect mixing zones between different water types

• Identify contamination pathways before they affect public health

For the first time, these methods were applied consistently across urban environments worldwide, demonstrating their utility in cities with vastly different geographies, climates, and infrastructure.

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Real-World Results from Cities in Crisis

Costa Rica: Adapting to Dry Seasons

In Costa Rica’s Central Valley, isotope data enabled scientists to understand seasonal variations in water sources. With this knowledge, city planners can now anticipate shortages during the dry season and adjust supply strategies accordingly.

“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, Universidad Nacional, Heredia.

Nepal: Daily Decision-Making Powered by Isotope Insights

In Kathmandu, Nepal’s rapidly growing capital, the project has revolutionized how officials manage water. Urban planners now incorporate isotope data into their daily operations, using it to track aquifer usage and monitor supply shifts.

“This project gave us the tools to trace where our water comes from and how it changes. That knowledge is now part of our daily decision-making,” said Bijay Man Shakya of the Center of Research for Environment, Energy and Water.

Ecuador and Morocco: Cleaner Water, Fewer Disruptions

In cities like Cuenca, Ecuador and Fes, Morocco, communities that once faced erratic and unclear water sources now benefit from cleaner and more reliable water supply, thanks to improved understanding of water mixing and flow patterns revealed by isotope studies.

Slovenia: Smarter Water Treatment

In Ljubljana, Slovenia, isotope techniques were used to identify blending zones in the municipal water network—areas where different water sources merge. This allowed for more targeted and efficient treatment processes.

“The isotope data helped us identify blending zones in our network and optimize treatment processes,” explained Klara Zagar of the Jozef Stefan Institute.

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A Global Collaboration, Locally Grounded

One of the project’s key strengths was its collaborative model. Researchers across all 10 countries shared findings, adapted techniques to suit local conditions, and built a network of interdisciplinary expertise. This ensured that the isotope solutions were not just scientifically rigorous—but also culturally and practically relevant.

The initiative also served as a capacity-building engine, offering training programs for young scientists, water managers, and policy professionals. Several participants have since incorporated isotope methods into national water strategies and university curricula.

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Scientific Breakthroughs and Policy Impact

Beyond field applications, the project also drove scientific innovation. The coordinated research led to:

• Publication of numerous peer-reviewed journal articles

• Development of practical toolkits for water utilities

• Establishment of policy guidelines for sustainable urban water use

• Training of hundreds of researchers and professionals in isotope techniques

“The development and application of novel isotope tracer techniques during this coordinated research project have provided us with invaluable tools for understanding and managing urban water supply systems,” said Ricardo Sanchez-Murillo of the University of Texas at Arlington. “These techniques will play a crucial role in ensuring sustainability in the face of growing water demand and climate variability.”

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Towards a Water-Secure Urban Future

With climate change accelerating and cities becoming denser, the challenge of securing drinking water for urban populations is greater than ever. The IAEA-coordinated project not only advanced science but also helped build resilient water infrastructure across continents.

Today, empowered by data from isotope tracing, cities are taking smarter, faster, and more equitable actions to ensure water access for all. They are proactively planning for droughts, minimizing contamination risks, and optimizing supply systems—creating a blueprint for climate-resilient urban living.

As this project shows, the path to sustainable water futures may lie hidden in the molecules themselves—and in our willingness to listen to the silent signatures of water.