Background, Challenges, and Deliverables for Downstream Fish Survival Study and Management Decisions
McNary Dam is a hydroelectric dam on the Columbia River in Washington state, completed in 1954. It is 185’ (56 m) in height and 1.4 miles (2.2 km) long. The dam provides power, irrigation, navigation, and flood control benefits, but also poses challenges for the downstream migration of salmon and steelhead smolts. These fish are an important ecological and economic resource, and their survival is affected by the dam operations and the environmental conditions. One of the challenges for the downstream migration of smolts is the safe passage over the spillways, which are the gates that release excess water from the reservoir. The spillways are designed to provide a safe and efficient route for the fish, but they are subject to wear and tear, and sometimes can get stuck or malfunction. This can reduce the available spillway capacity, increase the water pressure and turbulence, and expose the fish to predators, injuries, or mortality.
In a typical year, the spillway operations at McNary Dam are guided by the Fish Passage Plan, which specifies the optimal timing, duration, and volume of spill for the fish migration. The plan is based on the best available science and the coordination among multiple stakeholders, including federal, state, tribal, and private entities. The plan aims to balance the competing objectives of power generation, water management, and fish protection. However, in 2024, the spillway operations at McNary Dam will face a significant challenge, as some of the gates are not operating properly and the enormous gantry cranes on site are not rated to lift the gates when they are stuck. This is expected to limit the spillway capacity and flexibility, and potentially compromise fish passage and survival. Therefore, it was determined that there was an urgent need for a downstream balloon tag study before outmigration, to measure the effects of the suboptimal spill gate performance on the smolt survival, and to inform the fish managers on how to best manage the outmigration of the smolt in 2024.
Whooshh Innovations Inc. is a company that specializes in safe, timely, and effective fish passage systems, using best in class technology and designs to allow fish to pass over dams, barriers, or other obstacles. For McNary, the company designed and manufactured a custom-built fish delivery system for the study spillways at McNary Dam, as subcontractor to Hinchinbrook, the lead contractor for the downstream balloon tag study. The ballon tag study fish delivery system consists of a gravity feed water delivery unit, a vertical fish delivery unit capable of delivering fish up to 30’ deep with the flow, and a custom release fish release unit. The system needed to be stout enough to perform in waters flowing up to 8 meters per second. Hatchery fish were provided to Hinchinbrook for the survival study. The system is designed to deliver the tagged smolts safely and efficiently at predetermined depths within the water column just prior to the spillway, where their survival after passage can be monitored and compared with the control group after their retrieval. The study fish delivery system designed by Whooshh Innovations Inc. is now installed and operating at McNary Dam, for the duration of the in-field downstream balloon tag study. The system will help to address the challenges and uncertainties of the spillway operations in 2024, and to enhance the fish survival and management at McNary Dam this season. The fish delivery system was designed, manufactured, and installed by Whooshh in less than a month, demonstrating the company's experience and capabilities to another time critical situation. Whooshh hopes, along with everyone involved in the project, that the survival study, with the revised gate regime, proves to be equivalent to prior years' study results.
Whooshh Innovations would like to express its thanks to Hinchinbrook for inviting us to partner with them on this project. Further, we would like to thank the principal parties directly involved in the installation including the USACE’s McNary dam operations personnel, Whooshh Innovations manufacturers and subcontractors, and on-site staff who each completed their tasks on time and with precision fit. Without the dedication of all these parties, the study fish delivery system would not have been completed and installed in such a short time frame. We are pleased to be part of this effort to better understand the conditions and outcomes for the out-migrating salmon at McNary Dam in 2024.
