Safety of Hydropower Dams in a Changing Climate

Global climate change is expected to lead to changes in precipitation patterns and increased frequency and intensity of extreme weather events, which may produce conditions outside current design criteria for dams. This study investigated climate change effects on future safety of the Aurland hydropower dams during extreme floods. The design inflow floods for present and future climate scenarios were calculated using two approaches. Flood frequency analysis was applied to the annual maximum series from the simulated daily flows for present and future periods. Analysis of extreme precipitation and floods was performed using a hydrological model to compute the corresponding extreme flood values for the present situation and future scenarios. The outflow flood with the associated water level was calculated using a reservoir routing model linking all the Aurland reservoirs. In this paper, the authors present current and future design floods for the Aurland case and the implications of the changes in flood levels on dam safety for single reservoirs and for the reservoir system as a whole. Results from this study show that there will be a change in seasonal shift in the peak inflow flood from summer to autumn for the future scenario; from the range of results of the climate models and emission scenarios, the design inflow flood and the probable maximum flood (PMF) in the autumn is projected to increase for the future scenario.