Assessing Vulnerability and Adapting to Climate Change at Seattle City Light

Seattle City Light has been concerned about the effects of climate change on operations for several years. In 2013 the utility expanded its efforts to understand and manage climate change risk by initiating a new program for climate change research and adaptation as part of a 6-year strategic plan. SCL’s energy mix includes 90% hydropower, 50% of which is generated at hydropower projects owned and operated by SCL on the Skagit and Pend Oreille rivers. The Skagit and Pend Oreille basins are historically snow-dominated but are projected to shift to mixed-rain-and-snow basins with warming. Associated changes in the amount and timing of snowpack and streamflow, particularly in the Skagit basin, will challenge the utility’s ability to balance reservoir operations for the multiple objectives of power generation, flood control, recreation, and instream flows for fish protection. Initial vulnerability assessments indicate that less snow will reduce or delay reservoir refill in spring, which could cause a failure to reach the reservoir elevation required for recreation in summer and reduce the water that is available for fish protection and power generation in the following high-demand winter. Results of this initial vulnerability assessment were incorporated into the 20-year Integrated Resource Plan. With the new climate program, SCL is expanding its efforts to research climate impacts, assess vulnerability, and identify adaptation strategies. SCL is supporting research on glacier retreat in the North Cascades and modeling of associated impacts on streamflow and water temperatures in the Skagit basin. The utility is also expanding its efforts to assess the climate vulnerability of other aspects of operations. The transmission and distribution system in western Washington may be vulnerable to increases in climate-related disturbances such as heat waves, flooding, sea level rise, wildfires, and landslides. SCL has successfully reduced vulnerability to climatic variability by using the WindWatch tool to monitor forecasts of high winds and extreme wind events. The utility will explore other actions to increase resilience to longer term climate change risks to the system. SCL manages 12,000 acres of fish and wildlife habitat lands in the Skagit area. Assessing climate vulnerability of these lands will include evaluating restoration plans and objectives in the context of climate change and evaluating new land acquisitions for habitat viability in a changing climate. Information on vulnerability will be used to inform a utility-wide adaptation plan with the goal of “mainstreaming” climate adaptation into plans and operations