Long-Term Evaluation of Norris Reservoir Operation Under Climate Change

This study aimed to address the potential long-term effects of future climate change on the Tennessee Valley Authority’s (TVA’s) operation policy for Norris Reservoir. The Community Earth System Model 1.0 (CESM1.0), a general circulation model (GCM) accessible through the Intergovernmental Panel on Climate Change’s (IPCC’s) Coupled Model Intercomparison Project Phase 5 (CMIP5), with the Representative Concentration Pathway 4.5 (RCP4.5) was used to obtain projected precipitation and temperature data for three future climate scenarios, 2030’s, 2050’s, and 2070’s. Three hydrologic models were individually calibrated on 30 years of observed runoff data and combined utilizing linear programming to consider the strengths of each model. Inflow hydrographs were simulated for the future time spans using projected precipitation and temperature. Reservoir routing was then simulated using the inflow hydrographs via mass balance and the current operation policy to determine the storage elevation of the reservoir. Next, the routing simulations were utilized as input for a genetic algorithm forced optimization model, to minimize an elevation-based penalty value, optimizing Norris Reservoir’s operation policy. Finally, the operation performance of Norris Reservoir’s current operation policy versus the policies generated by the developed optimization model for each projected scenario were evaluated. The results suggested a 20.7, 23.8, and 24.3 percent increase in runoff for the 2030’s, 2050’s, and 2070’s, respectively. Although the current policy was able to support this increase in runoff, the optimization model decreased operation penalties by 23.3, 22.2, and 24.4 percent for the 2030’s, 2050’s and 2070’s, respectively. These results can provide substantial insight to TVA hydrologists and decision makers that their current policy may require re-evaluation, considering the potential impacts of climate change.