The Indian Valley outlet works were retrofitted with a hydroelectric plant that was completed in 1982. At the time of the dam’s construction, it was uncommon for dams of Indian Valley’s size to include hydroelectric power generation in the original design. However, in response to the energy crisis in the late 1970’s, the federal government offered incentives to develop alternative energy supplies. The District partnered with Catalyst Energy Company to develop the Indian Valley hydroelectric plant. Catalyst Energy Company provided the engineering and construction of the plant, and the District provided the dam, water, and operation of the power project. In this way, the private company could take advantage of the federal tax credits, while using the District’s water, and would pay the District royalties from the sale of power. A problem arose later when energy prices dropped significantly and the hydroelectric plant didn’t generate enough revenue to operate the project, pay royalties, and pay taxes. The situation was resolved by the District acquiring the project in 1999.
The hydroelectric plant consists of two Francis-type turbines that have a maximum combined ability to generate 1,400 kilowatts of power, and a small 100 kilowatt turbine. Francis turbines are the most commonly used turbine used to generate hydroelectric power because they can be used in a wide range of head pressure and flows, and can achieve over 95% efficiency. The turbines consist of a spiral casing that wraps around the outside of the turbine’s rotating runner. Water enters the runner through a series of guide blades, or wicket gates, that direct the water into the runner evenly throughout the radius of the central runner. The runner is the inner wheel of blades that act like a highly engineered and sophisticated water wheel. The blades of the runner are constructed in a special shape to create higher pressure on the inlet and lower pressure on the outlet, and that pressure differential helps to maximize the forces needed to spin the runner. The runner is connected to a generator via a shaft, which produces the electricity.
The larger generators are used during the irrigation season and can also be used during the infrequent occasions when water needs to be released from the dam to maintain flood-dedicated storage. The small 100kW generator is used when water is released to maintain minimum habitat flows.
The hydroelectric power plant at Indian Valley creates an additional revenue stream for the District and contributes to the clean energy needed to meet California’s renewable energy goals. However, it also makes the District subject to increased regulatory requirements, which offsets some of the benefits afforded by the plant.