Fractured rocks beneath Earth’s surface play a vital role in supplying clean water, extracting energy resources, and storing carbon dioxide and hydrogen. Water and other fluids move through these fractures where they react with the surrounding rock resulting in changes to the fluid chemistry in ways that influence engineered and natural Earth systems. This postdoctoral fellowship project will help advance the ability to predict the chemical reactions between water and rocks by analyzing data from a deep underground laboratory in South Dakota in conjunction with a new computer model approach. In addition to the scientific research, the project supports hands-on educational outreach to K–12 students, open-source educational tools, and professional development for the postdoctoral fellow, including fieldwork and mentoring experience. The project supports NSF’s mission by advancing geoscience, helping society address challenges like the energy transition, water sustainability, and environmental protection, and by facilitating student participation in geoscience and hydroscience. Fractured subsurface systems play a critical role in transporting reactive fluids and solutes but are notoriously complex to model accurately at the field scale. The postdoctoral fellowship work supported by this project will develop ways to move beyond that complexity with a reduced-order, bipartite graph-based framework that captures essential flow, transport, and geochemical interactions in fracture