Lake Ontario is primarily fed by the Niagara River, which flows from Lake Erie and passes over Niagara Falls before reaching Lake Ontario.

Lake Ontario is primarily fed by the Niagara River, which connects it to Lake Erie. The Niagara River flows northward from Lake Erie, passing over the famous Niagara Falls before entering Lake Ontario. This river serves as the natural outflow for water from Lake Erie, and its powerful current plays a significant role in shaping the lake’s water quality and ecosystem. The Niagara River is also a vital source of fresh water for the surrounding areas, contributing to the ecological balance of Lake Ontario. Additionally, the river serves as an important route for shipping and tourism.