Downstream Fish Passages at Large-Scale and High-Head Hydroelectric Dams: A Columbia River Basin Review

Hydropower owners and regulators across regions face shared challenges related to fish passage and habitat connectivity while balancing the need to provide safe, efficient, and renewable energy. Recent literature highlights the importance of improved collaboration and information sharing across the fish passage community on both project successes and failures. The Pacific Northwest (PNW) of the United States and the Canadian province of British Columbia have a long history of hydropower development accompanied by substantial investment in fish passage research, design, and implementation. As a result, design criteria for Pacific salmonids (Oncorhynchus spp.), Bull Trout (Salvelinus confluentus), and other species have developed over time and are supported by comprehensive design guidelines while recognizing that species assemblages and management contexts differ among regions. This paper reviews downstream fish passage facilities at large-scale, high-head hydroelectric dams in the PNW to share transferable principles and practical insights that may inform fish passage planning in other geographic contexts. Downstream solutions can vary in size and cost, depending on fish species and dam operation. The objective is to generally limit entrainment through turbines or spillways and provide alternative passage for downstream migrants. By highlighting a range of implemented downstream passage systems, from surface collectors to trap-and-haul facilities, this paper emphasizes adaptable, species-specific approaches and lessons learned rather than prescriptive designs. These examples contribute to the broader international dialogue on fish passage and support context-sensitive decision-making in regions facing similar challenges.