great shots of my hometown! I think early spring is when it probably looks least attractive though!
to answer the above question, from Wikipedia:
Currently between 50% and 75% of the Niagara River's flow is diverted via four huge tunnels that arise far upstream from the waterfalls. The water then passes through hydroelectric turbines that supply power to nearby areas of the Canada and the USA before returning to the river well past the Falls.[11]
The most powerful hydroelectric stations on the Niagara River are Sir Adam Beck 1 and 2 on the Canadian side, and the Robert Moses Niagara Power Plant and the Lewiston Pump Generating Plant on the American side. All together, Niagara's generating stations can produce about 4.4 GW of power. The engineer credited with design of the system is Edward Dean Adams.[12]
In August 2005 Ontario Power Generation, which is responsible for the Sir Adam Beck stations, announced plans to build a new 6½ mile (10.4 km) tunnel to tap water from farther up the Niagara river than is possible with the existing arrangement. The project is expected to be completed in 2009, and will increase Sir Adam Beck's output by about 182 MW (4.2%).