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Niagara Falls (/naɪˈæɡrə/) is the collective name for three waterfalls that straddle the international border between Canada and the United States; more specifically, between the province of Ontario and the state of New York. They form the southern end of the Niagara Gorge. From largest to smallest, the three waterfalls are the Horseshoe Falls, the American Falls and the Bridal Veil Falls. The Horseshoe Falls lies on the border of the United States and Canada with the American Falls entirely on the United States’ side, separated by Goat Island. The smaller Bridal Veil Falls are also on the United States’ side, separated from the other waterfalls by Luna Island.
Located on the Niagara River, which drains Lake Erie into Lake Ontario, the combined falls form the highest flow rate of any waterfall in North America that has a vertical drop of more than 165 feet (50 m). During peak daytime tourist hours, more than six million cubic feet (168,000 m3) of water goes over the crest of the falls every minute. Horseshoe Falls is the most powerful waterfall in North America, as measured by flow rate.[The falls are 17 miles (27 km) north-northwest of Buffalo, New York, and 75 miles (121 km) south-southeast of Toronto, between the twin cities of Niagara Falls, Ontario, and Niagara Falls, New York. Niagara Falls was formed when glaciers receded at the end of the Wisconsin glaciation (the last ice age), and water from the newly formed Great Lakes carved a path through the Niagara Escarpment en route to the Atlantic Ocean. Niagara Falls is famed both for its beauty and as a valuable source of hydroelectric power. Balancing recreational, commercial, and industrial uses has been a challenge for the stewards of the falls since the 19th century.
The Horseshoe Falls drop about 188 feet (57 m), while the height of the American Falls varies between 70 and 100 feet (21 and 30 m) because of the presence of giant boulders at its base. The larger Horseshoe Falls are about 2,600 feet (790 m) wide, while the American Falls are 1,060 feet (320 m) wide. The distance between the American extremity of the Niagara Falls and the Canadian extremity is 3,409 feet (1,039 m).
The peak flow over Horseshoe Falls was recorded at 225,000 cubic feet (6,400 m3) per second. The average annual flow rate is 85,000 cubic feet (2,400 m3) per second. Since the flow is a direct function of the Lake Erie water elevation, it typically peaks in late spring or early summer. During the summer months, at least 100,000 cubic feet (2,800 m3) per second of water traverses the falls, some 90% of which goes over the Horseshoe Falls, while the balance is diverted to hydroelectric facilities. This is accomplished by employing a weir – the International Control Dam – with movable gates upstream from the Horseshoe Falls. The falls’ flow is further halved at night, and, during the low tourist season in the winter, remains a minimum of 50,000 cubic feet (1,400 m3) per second. Water diversion is regulated by the 1950 Niagara Treaty and is administered by the International Niagara Board of Control (IJC).
The verdant green colour of the water flowing over the Niagara Falls is a byproduct of the estimated 60 tonnes/minute of dissolved salts and “rock flour” (very finely ground rock) generated by the erosive force of the Niagara River itself