Niklas Ruf and Jana Spiller from Germany received the prestigious Stockholm Junior Water Prize 2025 for their work on developing a scalable flood warning system for small streams. H.R.H. Crown Princess Victoria of Sweden presented the winners with their award during a ceremony at Stockholm City Hall as part of World Water Week in Stockholm.

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Niklas Ruf and Jana Spiller from Germany received the 2025 Stockholm Junior Water Prize for their scalable flood warning system for small streams. The award was presented by H.R.H. Crown Princess Victoria of Sweden at Stockholm City Hall during World Water Week. Image courtesy of Jonas Borg.

Flooding is an increasing concern worldwide, with more frequent and larger floods affecting communities. Yet on smaller streams, real-time data is often lacking, limiting the possibility of early warnings. Over four years of work, Ruf and Spiller created a network of sensors linked to an app that provides live alerts to both experts and the public. Their system is already being scaled up across their region in consultation with multiple partners.

The Jury noted that the project “addresses a critical challenge we are seeing around the globe: more frequent and bigger floods. Yet on smaller streams, we often lack the data needed to provide real-time warnings. The students have not only built a functioning system and an app that notifies experts and the public, they are already working to scale this system across their region in consultation with numerous partners.”

When asked how it felt to win, Niklas Ruf admitted: “I didn’t expect it at all. There were so many really good projects. I thought we were just here to have a good time and then go back home.”

Jana Spiller added: “Every project here is just amazing. Some were in areas like chemistry and biology that I didn’t even fully understand, but they were so impressive. That’s why it was such a big surprise for us.”

On what they hope decision-makers and industry leaders will take away from their work, the team reflected: “Of course, what we are doing is building something to tackle the consequences of climate change. But the ideal solution would be if there were no climate change to begin with.”

Diploma of Excellence – Türkiye

The Diploma of Excellence was awarded to Kagan Mehmet Ozkok from Türkiye for pioneering work that combines AI and water efficiency. By training artificial intelligence on the sound of leaking water, Ozkok built and deployed two prototypes to detect leaks in public spaces. Tested under real conditions, the prototypes demonstrated significant water savings and are now being developed further in collaboration with local government for possible city-wide implementation.

The Jury stated: “This year’s Diploma of Excellence recognizes how data, AI and action come together. Training AI based on the sound of leaking water, this student has demonstrated a powerful and practical approach to tackling urban water loss.”

People’s Choice Award – United Kingdom

The People’s Choice Award, voted on by the global public, went to Divyasri Kothapalli from the United Kingdom for her project Sun-based water distillation system.

This research project presents the development of a low-cost solar water distillation system designed to improve access to clean drinking water in off-grid and rural communities. Using a Fresnel lens to focus sunlight onto a metal boiling pot, the resulting steam passes through food-grade silicone tubing and condenses into clean water. The system operates without electricity, avoiding additional carbon emissions.

Kothapalli conducted three experiments where the independent variables included initial water volume, light intensity, and natural weather conditions. The system produced consistent yields even in moderate climates such as the UK, showing its promise for broader application.

“Innovation is paving the way to a more water-secure world, and the next generation is accelerating progress. The Stockholm Junior Water Prize competitors are an inspiring example of the ingenuity and passion young innovators bring to the table. On behalf of Xylem, I’d like to congratulate all those who took part in this year’s competition,” said Claudia Toussaint, Chief People and Sustainability Officer at Xylem.

“Xylem is proud to invest in the young innovators of the Stockholm Junior Water Prize. They are already shaping the future as the next generation of water problem-solvers. Together, we have the opportunity to empower communities everywhere to create a more water-secure world,” Toussaint added.

A year of flood-focused excellence

This year, both Water Prizes highlighted flooding: the Stockholm Junior Water Prize went to German students Niklas Ruf and Jana Spiller for their innovative flood warning system, while the Stockholm Water Prize will be awarded to Austrian professor Günter Blöschl, the world’s leading flood hydrologist. Together, their work underscores the urgency of addressing flood risks – from local innovations to global science.

Read more about the winning projects here:

• Stockholm Junior Water Prize 2025: Germany – Niklas Ruf and Jana Spiller
• Diploma of Excellence 2025: Türkiye – Kagan Mehmet Ozkok
• People’s Choice Award 2025: United Kingdom – Divyasri Kothapalli

About the Stockholm Junior Water Prize

The Stockholm Junior Water Prize is an international competition for students between the ages of 15 and 20, encouraging innovative solutions to major water challenges. Every year, thousands of young people from more than 40 countries take part, with the national winners competing in the global final in Stockholm.

The Stockholm Junior Water Prize has been organized annually since 1997. It is hosted by the Stockholm Water Foundation, with Xylem as Founding Partner.

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