Dr. Niko Wanders is recognized with the James B. Macelwane Medal for his seminal contributions to understanding and predicting hydrological extremes under climate change and human activities. In less than a decade since earning his Ph.D., Dr. Wanders has emerged as an international leader in hydrology, advancing both fundamental science and societal resilience to floods and droughts. Dr. Wanders’s pioneering research integrates large-scale hydrological modeling, remote sensing, and data assimilation to improve flood and drought forecasting. He was among the first to incorporate real satellite soil moisture products into data assimilation frameworks, significantly enhancing hydrological prediction skill. He also played a central role in building the first pan-European seasonal hydrological forecasting system. His methodological innovations in handling uncertainty have shaped the way satellite-based products are used to advance water science and practice. At the frontier of climate-hydrology interactions, Dr. Wanders has provided the first global assessments of river discharge predictability on decadal scales. By applying very large climate ensemble simulations, he demonstrated how conventional methods underestimate risks of compound flood and drought extremes. His work on human-water interactions further revealed how reservoirs and water management decisions can unintentionally amplify future drought risk. Equally impactful is his high-resolution global dataset of surface water temperature, downloaded thousands of times, which has become a critical resource for understanding the water-energy-ecosystem nexus. Dr. Wanders’s scientific productivity is remarkable, with over 100 peer-reviewed publications in leading disciplinary and interdisciplinary journals, including Water Resources Research and Nature Climate Change. His contributions have been recognized by multiple international honors, such as the AGU Hydrologic Sciences Early Career Award, the European Geosciences Union’s Arne Richter Award, and prestigious Dutch Academy prizes. He has also secured major grants from governmental agencies, nongovernmental organizations, and the National Geographic Society, enabling him to lead large, multipartner international consortia. Beyond research, Dr. Wanders exemplifies scientific leadership, outreach, and mentorship. He chairs the Dutch Expert Network on Drought and Freshwater, contributes to Intergovernmental Panel on Climate Change and World Meteorological Organization assessments, and frequently engages the public through media, education modules for schoolchildren, and open-source data and models. As a dedicated mentor, he leads a diverse, collaborative research team and fosters the next generation of water scientists. For his extraordinary scientific achievements, leadership in the hydrological sciences, and unwavering commitment to advancing science for society, Dr. Niko Wanders is most deserving of the James B. Macelwane Medal. —Amir AghaKouchak, University of California, Irvine, Irvine, California, Dennis Lettenmaier, University of California, Los Angeles, Los Angeles, California, Christa Peters-Lidard, Grasonville, Maryland , Alberto Montanari, University of Bologna, Bologna, Italy, Marc Bierkens, Utrecht University, Utrecht, Netherlands