Opposite the expedition's canoe camp on the Clearwater River, and nearly 2 miles above its confluence with the main Clearwater, is Dworshak Dam, which was built in 1966–1973. The dam and reservoir are named in honor of U.S. Senator Henry Dworshak (1894-1962), the leading proponent of the controversial project in Congress.
Whereas most large dams are curved against the pressure of deep reservoirs, the 717-foot-high Dworshak Dam is the tallest straight-axis concrete dam in the Western Hemisphere. It creates a reservoir—650 feet deep at the dam—which extends 54 miles up the North Fork.
Dworshak Dam's purposes were 1) to hold back and gradually release annual spring freshets on the 135-mile-long North Fork of the Clearwater, and 2) to generate hydroelectric power. However, simultaneous operation of all six of the power generators built into the dam would have required the construction of another dam some miles below the conflux of the two rivers. Therefore, with one generator producing only power for the dam itself, only three of its generators can be operated at one time.
Furthermore, the dam is too high to accommodate fish ladders, so two fish hatcheries are situated on the pointed upstream angle of the conflux, where three species of salmon are spawned—steelhead, chinook and coho salmon—and hauled up the North Fork canyon to finish their growth.
Whereas most large dams are curved against the pressure of deep reservoirs, the Dworshak is, at the height of 717 feet, the tallest straight-axis concrete dam in the Western Hemisphere. Its reservoir, 650 feet deep at the dam, extends 54 miles up the North Fork.