These data were compiled for/to modeling efforts for U.S. Bureau of Reclamation National Environmental Policy Act (NEPA) analyses for the Colorado River in Grand Canyon, Arizona. Objective(s) of our study were to create revised monthly Lake Powell elevations and outflows from Bureau of Reclamation Colorado River Mid-term Modeling System (CRMMS) traces that incorporate the alternatives in the sEIS documents and indicate when potential actions may occur and how that changes water movement and storage. These data represent monthly hydrologies for Lake Powell: inflow, outflow, and elevation forecasts for 2024-2027, as well as volumes of water in outflows for different water mangement strategies in NEPA supplemental environmental impact statement (sEIS) documents from the U.S. Bureau of Reclamation (USBOR). These data were collected in 2023 and 2024. These data were collected from the USBOR CRMMS and used by U.S. Geological Survey-Southwest Biological Science Center-Grand Canyon Monitoring & Research Center modeling. These data can be used to evaluate different water management strategy potential impacts to storage in Lake Powell.