Hydroelectric power is Alaska’s largest source of renewable energy, supplying 25% of the state’s electrical energy. Currently 45 hydro projects provide power to Alaska utility customers, ranging in size from the 105 kW Akutan hydro project to the 126 MW state-owned Bradley Lake project near Homer, which supplies 8% of the Railbelt’s electrical energy.

Lake Tap Systems

The 31 MW Crater Lake project, part of the state-owned Snettisham project that provides 80% of Juneau’s power, uses the natural impoundment of an existing lake and uses a “lake tap” 200 feet below the normal level of the lake t0 supply water to a powerhouse at sea level. The natural impoundment of Crater Lake creates kinetic energy potential (“head”) without the use of a dam, which can be costly to construct and have unintended environmental consequences. The 4.5 MW Black Bear Lake project on Prince of Wales Island and the 4 MW Goat Lake hydroelectric project near Skagway use the same method of natural impoundment and have both been certified as low-impact by the Low Impact Hydropower Institute. Certification as low-impact means the project has adhered to the Institute’s strict criteria on maintaining river flows, water quality, fish passage and protection, watershed health, endangered species protection, cultural resources, and recreation use and access.

Run of River Systems

While impoundment hydroelectric projects are one of the largest producing and cheapest forms of renewable energy, they can sometimes have detrimental environmental impacts that make low-impact hydro projects more desirable. “Run-of-the-river” projects use more modest structures to divert a portion of the natural river flow through turbines to make power before returning the water to the river downstream. Although run-of-the-river projects produce less electricity than impoundment projects, they maintain water levels downstream for salmon runs and avoid inundation of riparian valleys. This makes them ideal for many parts of Alaska, where energy demand is low and healthy rivers are important for the preservation of both the economy and wildlife