A special report by the Intergovernmental Panel on Climate Change that focuses on changes in the ocean and cryosphere—the frozen parts of the planet—includes a closer look at predicted impacts to hydropower around the globe.

While some parts of the world—such as India—are expected to see a loss of runoff and decline in hydropower generation as glaciers melt, modeling climate change impacts in British Columbia, northern Washington and California predicts more runoff in the winter and spring and less in the summer, the report said.

Approved by 195 member governments on Sept. 24, it notes that the global ocean covers about 71 percent of the Earth's surface and contains about 97 percent of its water, and that glaciers or ice sheets cover about 10 percent of the land area.

Scientists are "virtually certain" that the ocean has warmed since 1970, taking up more than 90 percent of the excess heat, the report noted. "Since 1993, the rate of ocean warming has more than doubled," it said.

It also stated, with "very high confidence," that marine heat waves are increasing in intensity, and have doubled in frequency since 1982.

Chapter 2, on High Mountain Areas, goes into detail on projected impacts to hydropower.

"There is robust evidence (medium agreement) [emphasis in original] that water input to hydropower facilities will change in the future due to cryosphere-related impacts on runoff," the report stated. "For example, in the Skagit river basin in British Columbia and Northern Washington and in California projections show more runoff in winter and less in summer, and in India snow and glacier runoff to hydropower plants is projected to decline in several basins."

In general, the report notes, periods of increased runoff will also increase the risk of nonproductive discharge, particularly during winter and spring melt, with the biggest impact expected for run-of-river facilities.

Several conclusions related to impacts in British Columbia and northern Washington reference a 2016 study published in Northwest Science that examined impacts of climate change in the Skagit River basin, including hydropower generation by Seattle City Light and Puget Sound Energy.

That study predicted small changes in the average annual generation, but substantial changes in seasonal generation, including a 19 percent increase in winter and spring, and 29 percent decrease in summer. These results were generally consistent with previous studies for the Columbia River basin and Washington, it said

K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.