Potential Impacts of Climate Change on Water Resources and Water Quality of Norris Lake, Tennessee

This study assessed the potential impacts of climate change on hydrology, water resources operation, and water quality of the Norris Lake area in Tennessee. To project future climate conditions, the simulation outputs for 2030s, 2050s, and 2070s from six general circulation models (GCMs) were extracted under two Intergovernmental Panel on Climate Change (IPCC) greenhouse gases emissions scenarios (A2 and B1 for high and low emissions, respectively) to consider the range of uncertainty. The outputs of the six GCMs were weighted by considering their accuracy to simulate the climate conditions observed from 1961 to 1990 to suggest an ensemble average. A water balance model was calibrated to the observed hydrologic monitoring data and this calibrated model was used to simulate the runoff for different climate conditions. Flow duration curves in lieu of hydrologic regime were constructed from the generated runoff hydrographs and the percent changes of flow statistics representing drought, flood, and normal seasons were suggested for the future. Finally, the operational performance of Norris Dam under the projected climate conditions was evaluated by the quantitative indices, reliability, resilience, and vulnerability (RRV). The results suggest that future temperature and precipitation for the 2050s are expected to increase about 1.3ºC and 5.7%, respectively, based on the weighted GCMs. The probability of flood and drought is likely to increase in the presence of uncertainty of runoff generated using multi-GCMs and emissions scenarios. The weighted results suggest the improved RRV in the 2050s, implying the future inflows to Norris Dam meet the future dam operation requirement. However, based on the weighted scenario for the 2050s, the future stream temperature shows a slight increase (annually about +1^oC) and the concentration of dissolved oxygen shows an about 1 mg/L drop for the summer seasons. This minor deterioration of water quality is mainly due to the expected increase of air temperature in the future. The major findings and results of this study provide decision-makers and engineers with guidelines for evaluating the potential impacts of climate change on water resources systems of the Norris Lake area.