Which structure is key to controlling water levels and flows in Lake Ontario?

The Moses-Saunders Power Dam, located near the boundary of the U.S. and Canada between Cornwall, Ontario, and Massena, New York, plays a critical role in managing water levels and flows in Lake Ontario. This hydroelectric dam regulates the flow of water between Lake Ontario and the St. Lawrence River, which is vital for maintaining optimal water levels in the lake, especially during periods of high water or drought.

By adjusting the flow rate through the dam, operators can help manage flooding risks, support local ecosystems, and optimize hydropower generation. This function is essential for environmental stability and for the various industries and communities that rely on the water levels of Lake Ontario.

Other options may involve water management but serve different purposes. For instance, Niagara Falls Dam primarily manages the flow of water over Niagara Falls, affecting not only the falls but also impacting hydroelectric power generation. The Detroit River Lock is more focused on navigation and connecting waterways rather than regulating water levels in Lake Ontario. The Welland Canal facilitates shipping by bypassing Niagara Falls but does not directly control water levels in Lake Ontario itself.