In 1969, Engineers Turned Off The Water Of Niagara Falls
And it may happen again: In 2016, the Niagara Frontier State Park Commission announced that it hoped to shut off the American Falls within the next few years. In response, Canada and the U.S. asked the International Joint Commission, the bilateral body that oversees U.S.-Canada border waters, and the U.S. Army Corps of Engineers to investigate and report on measures necessary to preserve or enhance the beauty of the American Falls, specifically with regard to the talus. The decision to leave the American Falls mostly alone was tied to the fact that the International Joint Commission wasn’t sure whether most tourists would really notice a major difference even if the talus was gone, plus the local interests that had initially pushed for the dewatering in hopes of stimulating tourism now thought that a dried waterfall would actually be bad for business.
Source: slate.com