| Turbines & generators


The Ice Harbor Dam on the Snake River in Washington state, US.


A scientific framework for the future


Replacing turbine runners offers the opportunity to increase generating capacity and efficiency, as well as improving fish passage conditions. Recent US experience demonstrates how a scientific framework can be used for future turbine replacement at ageing hydropower facilities


THE US ARMY CORPS of Engineer’s (UASCE) Ice Harbor is the first dam on the Snake River in Washington state. It is one of four dams at the heart of a multi-decade debate about their impact on native salmon species. Operational since 1961 and standing at 30.5m high and 860m long, the dam has a six-unit powerhouse, a ten-bay spillway, two fish ladders, and a navigation lock. It generates around 1.7 TWh per year. As the Kaplan turbines in units 1-3 had been operational since commissioning, the turbine runner blades were cracking and the hubs leaking oil. Consequently, USACE initiated a design process for new state-of-the-art replacements. In 2019, over two decades of research came


to fruition when a one-of-a-kind stainless steel fixed-blade runner, optimised for both improved fish passage and power efficiency, was installed in Ice Harbor Dam’s Unit 2. And as recent research published in Renewable and Sustainable Energy Reviews shows, this will help pave the way for future turbine replacements at ageing hydropower projects.


Design process USACE based the new Ice Harbor improved fish


passage turbine designs on biological criteria obtained from laboratory experiments and other studies. Through the design process: The stay vanes and wicket gates were streamlined and better aligned to improve the hydraulics and minimise gaps to keep fish from passing between them and being injured. Gaps on the turbine blade periphery and near the hub were minimised to keep fish from passing through the gaps and being injured.


Blade shapes were optimised to reduce fish strikes on the leading edge, blade surface, and trailing edge, and to reduce fish exposure to potentially harmful shear and turbulence.


The design process was also a collaborative effort and stakeholders, including the US Army Corps of Engineers, Bonneville Power Administration, and NOAA Fisheries, worked directly with Voith Hydro. Computational fluid dynamics, scale performance model testing, and observational model testing were also carried out. Two separate turbine designs were selected for installation at Ice Harbor. An improved fish passage (IFP) Kaplan turbine design was selected for future installation in Units 1 and 3, and an IFP fixed-blade turbine unit was designed, installed in Unit 2, and began operating in 2019. The selection of two different types of turbine runners meant the benefits of each design could be utilised. Whereas the IFP fixed-blade was expected to have better fish passage and hydraulic performance, it was also expected to have a much lower range of operations. To validate the new IFP fixed-blade turbine instrumentation capable of measuring the hydraulic conditions fish are exposed to during passage through the turbine was required. And that’s where sensor fish (SF) came to the rescue. Described as being a small, neutrally buoyant, cylindrical device roughly the size of a juvenile salmonid smolt, the SF is not only useful to quantify hydraulic conditions, it can also be used to validate CFD models with experimental data to ensure those used during the design phase of a new turbine can accurately predict the hydraulic conditions fish will encounter.


SF were released directly into the intake at three


different elevations while the turbine was operated under three different routine operating conditions, with these measurements compared to a previous baseline study which investigated the original Kaplan turbine installed in the Unit 1 bay. As Martinez et al conclude in their research, the new IFP fixed-blade turbine successfully achieved the primary design objective of enhancing fish survival while improving power generation efficiency by approximately 4 %. They add that this scientific framework could


be expanded to help progress improvements in fish passage conditions at high-head dams. However, one key area to address for this expansion would be the SF device. The current commercially available SF is only designed to measure up to 1200 kPa. Although the pressure sensor in the SF is technically able to measure pressure up to 1400 kPa, with more advanced calibration, even this higher maximum pressure can be lower than the maximum pressures the SF would be exposed to during passage through a high-head dam.


References


A scientific framework for sustainable hydropower with improved fish passage Jayson Martinez, Tao Fu, Jingxian Wang, Jun Lu, Robert Mueller, Scott Titzler, Bradly A. Trumbo, Karl Anderson, Jon Renholds, John Skalski, Richard Townsend, Zhiqun Daniel Deng. Renewable and Sustainable Energy Reviews 211(2025)115355.


https://doi.org/10.1016/j.rser.2025.115355 www.waterpowermagazine.com | December 2025 | 25


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