The Deerfield and Pactola reservoirs in the upper Rapid Creek basin near Rapid City, South Dakota supply municipal water to a growing metropolitan area while supporting environmental flows, flood risk reduction, and water rights obligations shared among multiple stakeholders. Despite its complexity, only an excel spreadsheet model existed to guide operation of the system prior to this project. Building on a 2019 feasibility study suggesting that improved alignment with overall goals and expectations was achievable, West Dakota Water Development District secured WaterSMART funding through a Bureau of Reclamation cooperative agreement to develop a RiverWare model capable of evaluating alternative management strategies across a range of hydrologic conditions.

PWRE guided Barr Engineering Co. (Barr) through the model build, development of RPL logic, and RiverSMART implementation for this tandem reservoir system, and Barr led hydrology development, scenario analysis, and stakeholder coordination. This division of labor reflects a deliberate cooperative partnership bringing together deep RiverWare modeling experience with applied knowledge of how operations decisions get made and communicated in practice. The modeling team's background spans both the consulting side and federal reservoir operations, which shaped decisions about model structure, calibration targets to prioritize, and translation of operational concepts into RPL logic in a way that operators can recognize and trust. The expertise of the team's model build allows for the potential of the planning model developed for this project to easily transition to an operational model with minimal additional development.

Our presentation will describe the extension of RiverWare to a geography where the platform has not previously been applied, the technical challenges of representing water rights accounting and minimum release triggers for a tandem system, and the use of RiverSMART to execute and manage a factorial scenario sweep across hundreds of run combinations. We will also briefly show how AI-generated interactive dashboard tools can be used to help a diverse stakeholder group, including a federal agency, a municipal utility, and a regional water development district, engage directly with scenario tradeoffs and begin converging on preferred operational strategies.