The Impact of Climate Change on Dam Safety and Hydropower

Abstract

This PhD study focuses on the impact of climate change on hydropower systems and dam safety. The impact studies are based on hydrological and hydraulic models, and hydropower simulation model driven by scenarios from an Atmosphere-Ocean General Circulation Models (AOGCMs). High-resolution regional climate model (RCM) data for precipitation and temperature were used to generate climate input to the hydrological model. The study on the hydropower system provides a detailed analysis of a complex high-head system with multiple reservoirs and transfers. Results indicate that changes in the seasonality of runoff with a decrease in summer and an increase in autumn, winter, and spring. The seasonal change in runoff is strongly linked to changes in the snow cover. Projections based on the climate scenarios indicate an average increase in annual inflow to the system, and the hydropower simulation based on average climate conditions show an increase in energy generation under the current reservoir operation strategies. Conversely, the impact of climate change might come more from extreme weather events than the average conditions and thus the analysis has also considers whether the extreme conditions during the summer season in the form of prolonged droughts could potentially create a serious stress in the reservoirs and power production. The results show that the projected changes in drought duration and deficit volume will increase for the future climate. However, when compared with the total annual storage potential of the reservoirs, the increase in drought duration and deficit volume will not affect the power production or the reservoir operation.

The safety of the hydropower dams for climate change scenarios has also been thoroughly investigated in this PhD study. The dam safety evaluation has been based on both standards and risk based approaches. Results from the standard based safety evaluations are taken as a basis for the risk analysis study. Furthermore, a dam failure consequence analysis is conducted as a continuation of the risk analysis study. The standards based dam safety evaluation incorporates investigating changes in design floods due to climate change compared to the historical design flood values. The design flood is routed through the reservoir and the outflow flood and reservoir water level is determined. Then, the safety of the dams for the future climate is based on the evaluation of changes in design floods and the freeboard available to accommodate the increase in the flood levels. The results from the studies indicate that the design floods with the corresponding outflow floods and flood water levels will increase in the future, and this increase will affect the safety of the dams in the future. Then, the risk analysis approach is used to evaluate the most significant contributors to risk in addition to the increase in the design inflow flood as spillway blockage and waves due to landslide. The detailed risk based analysis is used to focus on how climate impacts influence dam safety. For the dams investigated in this study, the results from the risk analysis show that the total hydrological failure probability of the dam will increase in the future climate. The consequence analysis estimates the potential impact of climate change by simulating a dam break scenario for future extreme flooding conditions and evaluates the risk in the downstream area. The results for the study case dam indicate that the extent and depth of flood waters will increase by the future dam break scenario.