Candlewood Lake in western CT is an 11-mile long man-made lake, built in 1924 for hydroelectric.
Excess power is used to pump water up hill from the nearby Housatonic River into the lake, then allowed to flow back into the river through pipes and turbines when power is needed. An interesting engineering idea.
Turbines, of course, are not healthy for anadromous fish, but Candlewood Lake is good for bass fishing, water-skiing, and swimming.