The Tennessee Valley Authority (TVA) operates hydroelectric dams along the Tennessee River as an integrated system to achieve its mission and satisfy numerous simultaneous water resource demands, including hydro power production. However, hydrogeneration operations inherently require scheduling unit outages for maintenance, which imposes costs due to foregone power generation. To address this challenge, we employed a RiverWare model to conduct baseline and alternative ensembles of rule-based simulations over a 3-month period to optimize unit outage scheduling for minimized costs. The RiverWare model encompasses the entire Tennessee River system, including 29 power reservoirs; and it simulates operational rules to move water through the system while satisfying multi-faceted demands. Baseline simulations represent current unit availability while an alternative represents an additional unit outage at a plant. Ensembles consist of simulating 110 different hydrologic inflow scenarios based on historic conditions. Therefore, 1 baseline and 29 alternatives were simulated, each with 110 ensembles for a total of 3300 model runs. Simulations were executed by running a RiverWare script that provides a time series of lost generation value due to a unit outage. The RiverWare model was scheduled to run on a daily frequency using the Delft FEWS system to provide internal stakeholders with regularly updated information reflecting changes in hydrology, seasonal operational rules, and price and demand forecasts. This application demonstrates the utility of RiverWare rule-based simulations to evaluate the effects of operational alternatives and minimizes the impacts of maintenance activities on business demands.