Jordanelle Reservoir, a proposed component of the Bonneville Unit of the Central Utah Project, will be a major source of municipal and industrial water for the Salt Lake Valley. The final environmental impact statement identified the need to evaluate Jordanelle in terms of its downstream impact on Deer Creek Reservoir and the use of the water. To evaluate the impact, a combination of temperature and water quality simulation models, anaerobic simulation of the sediments, empirical nutrient loading models, and estimates of primary productivity were utilized. As a result of these efforts, Jordanelle Reservoir is expected to experience seasonal excesses of eutrophication with resulting low dissolved oxygen levels, potential mobilization of mine tailings, and seasonal recycling of nutrients from the sediments. To restrict the impact of these factors on downstream productivity and to allow efficient routing of nutrients and water through Deer Creek Reservoir, a multiple level withdrawal outlet structure and variable operation scenarios were designed for Jordanelle. The simulation period covered the entire stagnation period with the coefficients defined from previous Deer Creek simulations, the proposed Jordanelle operation plan, and empirical relationships. The procedures defined will be integrated with a watershed management plan to provide for efficient use of Jordanelle water with the resulting least impact to the downstream use of water. This analysis has applications to other impoundments and the determination of efficient operation plans.