Model My Watershed is a three-year project aimed at developing, testing, and disseminating a watershed-modeling toolset for secondary students. Designed to build on Google Earth, this tool provides a dynamic interface where students can add data, modify environmental conditions, work in a collaborative online learning environment, and be exposed to STEM careers. The design is based on the belief that students should have an authentic, exciting, intuitive, and interactive tool set that allows them to investigate their own neighborhoods. The investigations challenge students to make real-world decisions based on scientific knowledge and models. The project uses the complexity of environmental science to engage and excite students about the diverse STEM careers that are necessary to study and address environmental issues. Using existing scientific data in an authentic, hydrologic modeling toolset, students learn to predict how environmental changes to the ecosystem affect the hydrologic cycle in their local watersheds. In addition to being able to modify the underlying environmental conditions, students can modify their watershed by implementing best-management practices such as green roofs and porous pavement. A collaborative Web-based communication platform is used to network teams of students and schools to pose questions or challenges and communicate their findings. The project will directly impact 25 teachers and 1000 students in the Philadelphia area with plans for national dissemination.