Researchers at Pacific Northwest National Laboratory completed the most comprehensive study into the effects of drought on hydropower generation in the western United States this century. The study found that while drought raises concern for hydropower generation, the overall western hydropower fleet sustained 80% of its average expected generation—even during the most severe droughts over the past two decades. Furthermore, hydropower could still be relied upon to supply flexible power during periods of high energy demand.  

To conduct the study, researchers gathered data from eight climate sub-regions across 11 western states: Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming. That data indicated 2021 to be the second worst year for drought this century, with overall hydropower generation 16% lower than the average since 2001. However, the large sizes of western states and the wide range of weather across the West means drought rarely impairs hydroelectric power across all climate sub-regions simultaneously. Consequently, the overall hydropower fleet remains reliable even if certain plants or sub-regions produce less power.