The International Control Dam, also known as the International Control Structure, operated by

Ontario Power Generation Ontario Power Generation Inc. (OPG) is a Crown corporations of Canada, Crown corporation and "government business enterprise" that is responsible for approximately half of the electricity generation in the province of Ontario, Canada. It is w ...

, is a

weir A weir or low-head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the water level. Weirs are also used to control the flow of water for outlets of l ...

that controls the water diversions from the

Niagara River The Niagara River ( ) flows north from Lake Erie to Lake Ontario, forming part of the border between Ontario, Canada, to the west, and New York, United States, to the east. The origin of the river's name is debated. Iroquoian scholar Bruce T ...

and dispatches the water between the

New York Power Authority The New York Power Authority (NYPA) is a public benefit corporation owned by the State of New York and is the largest state public power utility in the United States. It provides some of the lowest-cost electricity in the nation, operating 16 ge ...

and

in accordance with the terms of the 1950 Niagara Treaty. It was completed in 1954. To preserve

Niagara Falls Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorge, spanning the Canada–United States border, border between the Provinces and territories of Canada, province of Ontario in Canada and the state of New York (s ...

' natural beauty and to ensure an "unbroken curtain of water" is flowing over the falls, the 1950 treaty was signed by the U.S. and Canada to limit water usage by power plants. The treaty allows higher summertime diversion at night when tourists are fewer and during the winter months when there are even fewer tourists. The treaty states that during daylight time during the tourist season (April 1 to October 31), there must be of water flowing over the falls, and during the night and off-tourist season there must be of water flowing over the falls. This treaty is monitored by the International Niagara Board of Control, part of the International Joint Commission, using a

NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency charged with forecasting weather, monitoring oceanic and atmospheric conditions, charting the seas, conducting deep-sea exploratio ...

gauging station above the falls. This weir allows water from the upper river to be diverted into the intakes for the American and Canadian power stations. Two tunnels on the American side take water under the city of

Niagara Falls, New York Niagara Falls is a City (New York), city in Niagara County, New York, United States. As of the 2020 United States census, 2020 census, the city had a total population of 48,671. It is adjacent to the Niagara River, across from the city of Niagar ...

, and three tunnels on the Canadian side divert water under the city of

Niagara Falls, Ontario Niagara Falls is a city in Ontario, Canada, adjacent to, and named after, Niagara Falls. As of the Canada 2021 Census, 2021 census, the city had a population of 94,415. The city is located on the Niagara Peninsula along the western bank of the ...

. Once past these cities, the water flows into two canals and then into two large reservoirs. Behind the Canadian Sir Adam Beck Power Station is a reservoir covering and a similar reservoir on the US side behind the Robert Moses Power Plant. A trade-off exists between the two main industries of tourism and hydroelectric power. More water is diverted by the International Control Dam at night, between 10:00 pm and 7:00 am, filling the reservoirs overnight and allowing more water over Niagara Falls in the daytime hours for the tourists. As well, during the winter, from November 1 to March 31, when it is not the tourism season, more water is diverted for electrical power during the whole 24 hour period. The pool of water located immediately upstream of the International Water Control Dam is named the "Chippawa – Grass Island pool".

References

External links

{{Commons category, International Control Dam
International Niagara Board of Control
Dams in Canada Niagara River Dams completed in 1954 Ontario Power Generation Canada–United States relations Weirs