Overview

Dworshak Dam is a large concrete gravity dam on the North Fork of the Clearwater River in Clearwater County, Idaho. Operated by the U.S. Army Corps of Engineers, it was developed to provide hydroelectric power, reservoir storage and flood control for the lower Snake River drainage. The structure rises roughly 717 feet (about 219 meters) above the riverbed and produces around 400 megawatts of electrical capacity. For a technical summary and specifications see technical profile.

Characteristics and design

The dam is a conventional concrete gravity structure: its own weight resists the horizontal thrust of the impounded water. The site was selected to maximize storage and head for power generation; the resulting reservoir inundated steep river canyons and formed a deep, narrow impoundment. Mechanical installations include a powerhouse with turbines and generators sized to the available hydraulic head, spillways to pass floods, and outlet works for controlled releases. Further engineering details can be consulted via the engineering summary.

History and construction

Federal studies began in the 1950s to improve water-resource management in the Snake River system; the site on the North Fork Clearwater River was evaluated in 1953. Construction commenced in the mid-1960s and the project was completed in the early 1970s, with the dam brought into service to meet growing regional demands for power and storage. The facility is named for U.S. Senator Henry C. Dworshak Jr., who represented Idaho. Contemporary accounts and archival materials are available at construction history.

Uses, benefits and environmental context

Primary uses are hydroelectric generation, water storage for downstream needs, flood risk reduction and recreation such as boating and fishing on the reservoir. Releases from the dam are managed to meet power generation schedules and to provide cold-water flows that can benefit downstream aquatic environments, though the dam also blocked upstream fish migration and required regional mitigation efforts. For an overview of operational and environmental programs see management and mitigation.

Notable facts and distinctions

  • Dworshak is one of the tallest dams in the United States and among the prominent large concrete gravity dams worldwide.
  • Its size and storage create recreational opportunities and a notable reservoir ecology in what had been steep river canyon terrain.
  • Ongoing studies and operational adjustments continue to balance hydropower production with fisheries, ecosystem and regional water needs; additional resources are linked at further reading.

As a multi-purpose infrastructure asset, Dworshak Dam remains an important element of water and energy management in the Pacific Northwest. It illustrates mid-20th-century dam design and the long-term challenges of integrating large dams into riverine environments while addressing human and ecological requirements.