The US national round of an international water science competition, coordinated by the Water Environment Federation since 1997 in partnership with its member associations. Open to students in grades 9 to 12 who are at least 15 years old by August 1 of the competition year, entering individually or in teams of two, with projects aimed at improving water quality, water resources management, or water and wastewater treatment at local, regional, national or global scale. Regional and self-nominated entrants compete at state level by mid-April, state winners are judged virtually in May, and the top finalists compete in person for the right to represent the United States at the international final during World Water Week in Stockholm.