Evaluating the sustainability of new U.S. hydropower development will necessitate an approach that is comprehensive, transparent and consistent. We addressed this need by conducting a literature review to extract and analyze a swath of environmental metrics related to hydropower projects. The assessed documents included peer-reviewed journal articles, U.S. Federal Energy Regulatory Commission licensing documents, and two sets of certification documents from the Low Impact Hydropower Institute and the International Hydropower Association. Review of 117 documents led to creation of a database of > 3000 current environmental metrics related to hydropower projects in 285 locations worldwide. Information recorded for each environmental metric was used to map the comprehensiveness of environmental measurement types gathered across primary categories, dam life cycle stages, spatial scales and locations. A majority of metrics were related to water quantity and water quality, a large number of metrics were related to biota and biodiversity, and relatively few metrics were related to the categories of geomorphology, land cover, connectivity and fragmentation, and infrastructure and design. Forty-five subcategories of environmental metrics emerged from our analysis, thereby suggesting an envelope of measurements that are important for understanding the environmental effects of new hydropower projects. The categories and subcategories of environmental metrics represented in each type of literature varied, however. Our database will be used to inform stakeholder selection of appropriate environmental metrics for evaluating progress toward collective goals for new U.S. hydropower development.