German students Niklas Ruf and Jana Spiller have been awarded the Stockholm Junior Water Prize 2025 for developing a scalable flood warning system for small streams. The award was presented by H.R.H. Crown Princess Victoria of Sweden during a ceremony at Stockholm City Hall as part of World Water Week.
Flooding is a growing concern worldwide, yet small streams often lack real-time monitoring. Over four years, Ruf and Spiller created a sensor network linked to a mobile app that delivers live flood alerts to experts and the public. The system is already being scaled up in their region with support from local partners.
The international 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.”
Reflecting on their win, Ruf said: “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.” 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.”
Divyasri Kothapalli from the UK receives the People’s Choice Award for her solar water distillation project.
Diploma of Excellence – Türkiye
Kagan Mehmet Ozkok from Türkiye received the Diploma of Excellence for work combining AI and water efficiency. By training artificial intelligence to recognise the sound of leaking water, Ozkok developed prototypes capable of detecting leaks in public spaces. Tested under real conditions, the devices demonstrated significant water savings and are being developed further with local government.
People’s Choice Award – United Kingdom
The People’s Choice Award went to Divyasri Kothapalli from the United Kingdom for her solar water distillation project. Using a Fresnel lens to concentrate sunlight onto a boiling pot, the system condenses steam into clean water without electricity. Tested in the UK, it consistently produced safe drinking water, demonstrating potential for off-grid and rural communities.
Claudia Toussaint, Chief People and Sustainability Officer at Xylem, which sponsors the Prize, commented: “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.”
Niklas Ruf and Jana Spiller of Germany receive the 2025 Stockholm Junior Water Prize from Crown Princess Victoria of Sweden.
A Year of Flood-Focused Excellence
Flooding is the theme of this year’s water prizes: the Stockholm Junior Water Prize recognising Ruf and Spiller’s innovation in Germany, and the Stockholm Water Prize honouring Austrian hydrologist Professor Günter Blöschl for his global leadership in flood science. Together, their work highlights the urgency of tackling flood risks locally and internationally.
