Fish Passage

Alden's engineering and biological staff include some of the world's experts on upstream and downstream fish passage.  

The experimental and developmental work over the last decade on the unique Alden Fish Friendly Turbine supplied accurate models of turbine mortality. Additional laboratory testing and development of fish entrance and bypass systems has enhanced Alden's expertise in conceptual design and feasibility of fish lift entrances, downstream passage systems, and fish ladders, optimized for site-specific features and challenges.

Alden Fish Friendly Turbine

With an increasing demand for renewable energy throughout the world, the ability to produce power while minimizing carbon dioxide emissions and other environmental impacts has become a driving force in the continued development of hydropower. 

A new hydropower technology that has the potential to meet power demands without impacting fish is the Alden turbine, which was developed through the U.S. Department of Energy’s (DOE) former Advanced Hydro Turbine Systems Program and with support from the Electric Power Research Institute (EPRI). The Alden turbine is designed to allow the safe passage of downstream migrating fish through an operating turbine. 

Given the high rates of turbine passage survival, the Alden turbine could be used to generate power using flows that are otherwise spilled over dams or through bypasses to meet fish passage or minimum flow criteria.

Alden Fish Friendly Turbine in the News

Fish-Friendly Turbine Making a Splash in Water Power -   Development Status of the Alden "Fish-Friendly" Turbine- HydroWorld

Alden Turbine Technology

The patented Alden Turbine is different from any existing turbine design and incorporates features to reduce fish injury and mortality associated with damaging shear and pressures as well as blade strike. 

Runner Features

•     Radial inlet from special flow distributor

•     Only three blades to reduce strike

•     An attached shroud to eliminate gaps


•     Efficiency: 94%

•     Fish survival: > 98% for fish less than 8 inches in length

•     Eel and sturgeon survival: > 99%


•     Head range: 20 ft to 120 ft 

•     Flow per unit: 500 cfs to 2500 cfs