Niagara Falls without water is just a cliff

Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorgte, between the Canadian Province of Ontario and the US state of New York.  The largest is Horseshoe Falls, also known as Canadian Falls, which straddles the international border between Canada and the United States.[1] The smaller American Falls and Bridal Veil Falls lie entirely within the United States. Bridal Veil Falls are separated from Horseshoe Falls by Goat Island and from American Falls by Luna Island.

Located on the Niagara River,, which drains Lake Erie into Lake Ontario, the combined falls have the highest flow rate of any waterfall in North America that has a vertical drop of more than 50 metres. During peak more than 168,000 m3 of water goes over the crest of the falls every minute.[2] Horseshoe Falls is the most powerful waterfall in North America, as measured by flow rate.

Niagara Falls has seen plenty of dramatic stunts over the centuries, ever since a local hotel owner sent a condemned ship with a “cargo of ferocious animals” over the falls in 1827. (Only the goose survived the plunge.) But no feat has attracted more visitors than a scientific survey conducted in 1969. That year, the U.S. Army Corps of Engineers turned off American Falls. The engineers wanted to find a way to remove the unseemly boulders that had piled up at its base since 1931, cutting the height of the falls in half. But the study itself proved more appealing than any improvement they could recommend. The first weekend after the “dewatering,” about 100,000 people showed up to see this natural wonder without its liquid veil.

The performance will have an encore at some point in the coming years when New York State once again dewaters American Falls. The purpose this time is more pedestrian—to replace two bridges—but the process will be the same. Engineers will construct a dam between the American bank of the Niagara River and the eastern tip of Goat Island, stopping the flow of water—nearly 76,000 gallons every second—over the 11-story drop.

Will crowds show up this time? Photos from 1969 suggest the bedrock is nothing special to behold. Without water, American Falls is merely a cliff. And yet the spectacle fulfills a fantasy older than the American nation: human mastery over nature. To sap the falls completely would seem to be the ultimate triumph—but, in fact, Niagara Falls was long ago brought to heel.

The falls—American Falls, Horseshoe Falls and the small Bridal Veil Falls—formed some 12,000 years ago, when water from Lake Erie carved a channel to Lake Ontario. The name Niagara came from “Onguiaahra,” as the area was known in the language of the Iroquois people who settled there originally. After the French explorer Samuel de Champlain described the falls in 1604, word of the magnificent sight spread through Europe.

Reference: 

1) https://www.smithsonianmag.com/travel/when-niagara-falls-ran-dry-180972198/#BS5VKTbA0jWt9f2o.99

2) https://en.wikipedia.org/wiki/Niagara_Falls