Niklas Ruf and Jana Spiller from Germany have been awarded the 2025 Stockholm Junior Water Prize for their development of a scalable flood warning system tailored 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 becoming an increasingly urgent global issue, with more frequent and severe events impacting communities worldwide. However, many small streams lack real-time monitoring infrastructure, making early warnings difficult. Over four years, Ruf and Spiller designed a network of low-cost sensors connected to a mobile app that delivers live flood alerts to both experts and the public. Their system is already being expanded across their region in collaboration with local authorities and organizations. The judging panel praised the project for addressing a critical global challenge. They highlighted that the students not only built a functional system and user-friendly app but are also actively working to scale their solution regionally with multiple partners. When asked about winning, Niklas Ruf said he was completely surprised, noting the high quality of other entries. Jana Spiller echoed the sentiment, expressing admiration for the diverse and impressive projects from around the world, many of which were in fields she didn’t fully understand. On the broader message they hope to convey, the duo emphasized the importance of tackling climate change at its root. “Of course, our project helps address the consequences of climate change, but the best solution would be if climate change didn’t exist in the first place,” they said. The Diploma of Excellence was awarded to Kagan Mehmet Ozkok from Türkiye for his innovative use of artificial intelligence to detect water leaks. By training AI models to recognize the sound of leaking water, Ozkok developed two working prototypes tested in real-world settings. The system has demonstrated measurable water savings and is now being refined for potential city-wide deployment with local government support. The jury commended the project for combining data, AI, and practical action to reduce urban water loss. The People’s Choice Award went to Divyasri Kothapalli from the United Kingdom for her solar-powered water distillation system. Her low-cost design uses a Fresnel lens to focus sunlight onto a metal pot, generating steam that condenses into clean drinking water through food-grade silicone tubing. The system operates without electricity, making it ideal for off-grid and rural communities. Testing under varying conditions showed consistent performance even in moderate climates like the UK. Claudia Toussaint, Chief People and Sustainability Officer at Xylem, praised the young innovators, calling them a powerful force in shaping a more water-secure future. She highlighted the importance of empowering the next generation of water problem-solvers through initiatives like the Stockholm Junior Water Prize. This year’s awards spotlighted flood resilience on multiple levels. While the Stockholm Junior Water Prize honored local innovation, the Stockholm Water Prize will be awarded to Austrian hydrologist Günter Blöschl, a leading expert in flood science. Together, their work reflects the global urgency of addressing flood risks through innovation and science. The Stockholm Junior Water Prize, established in 1997, is an international competition for students aged 15 to 20. It is organized by the Stockholm Water Foundation with Xylem as Founding Partner. Each year, thousands of young people from over 40 countries participate, with national winners advancing to the global final in Stockholm.