Cheap dam power smelted the aluminum for Boeing's bombers and fed the plutonium works at Hanford. The episode follows the money: the 1939 Bonneville-Alcoa contract, the wartime arsenal, the Klamath Project's 225,000 irrigated acres, and the utility later called PacifiCorp that built the Klamath dams. Salmon and tribes subsidized all of it invisibly.
The popular figure that Grand Coulee power made aluminum for one-third of wartime aircraft is widely repeated but not audited. The exact split of Hanford's power between Grand Coulee and Bonneville is less documented, and how much of the salmon loss was foreseeable remains the series' open question.