Water Diversion

Some sources erroneously quote that Niagara Falls has an average flow of about 12 million cubic feet per minute (200,000 cu ft/s) or even slightly more.   This figure is derived from the average rate of flow (202,000 cu ft/s) of the Niagara River.   This volume would pass over the falls if there were no hydroelectric water diversion upstream from the falls.   However, water is diverted continuously from Niagara and this figure is approximately three times the actual average flow volume over the falls. ^{Wiki n.p.}

The first treaty between Canada and the U.S.A. to limit water diversion was the "International Boundary Waters Treaty"of January 11, 1909, and the protocol of May 5, 1910.   Among other articles, the treaty stated that the United States may authorize and permit the diversion within the State of New York of the waters of the river above the Falls of Niagara for power purposes not exceeding in the aggregate a daily diversion at the rate of 20,000 cubic feet of water per second.   The United Kingdom, by the Dominion of Canada, or the Province of Ontario, may authorize and permit the diversion within the Province of Ontario of the waters of the river above the Falls of Niagara for power purposes not exceeding in the aggregate a daily diversion at the rate of 36,000 cubic feet of water per second.   The prohibitions do not apply to the diversion of water for sanitary or domestic purposes, or for the service of canals for the purposes of navigation.   The treaty also established an International Joint Commission (IJC) of the United States and Canada composed of six commissioners.   This commission has jurisdiction over all cases involving the use or obstruction or diversion of the waters. ^{Frontier n.p.}

The basis for determining the amount of water that can be diverted for power generation is contained in a treaty between the Governments of Canada and the United States concerning the "Diversion of the Niagara River", dated 1950, and generally referred to as the "1950 Niagara Treaty".   The treaty requires that during the daylight hours of the tourist season (0800 to 2200 hours local time, April 1st to September 15th and 0800 to 2000 hours local time September 16th to October 31st), the flow over Niagara Falls must not be less than 2832 cubic metres/second (cubic m/s) [100,000 cubic feet per second (cfs)].   At all other times, the flow must not be less than 1416 cu m/s (50,000 cfs).   The treaty also specifies that all water in excess of that required for domestic and sanitary purposes, navigation and the Falls flow may be diverted for power generation. ^{Park n.p.}

Remedial works were constructed in the 1950’s with the approval of the International Joint Commission (IJC) to maintain sufficient Falls flows as required by the treaty and to facilitate power diversions.   The remedial work consisted of excavation and fill on either flank of the Horseshoe Falls and a control structure extending about 0.8 kilometres (0.5 miles) out from the Canadian shore to the international boundary at the downstream end of the Chippawa-Grass Island Pool.   The original control structure had 13 gates with 5 more added in 1963.   The Chippawa-Grass Island Pool Control Structure is operated jointly by Ontario Power Generation (OPG) and the New York Power Authority (NYPA), also referred to as the Power Entities, and they regulate the water levels in the Chippawa-Grass Island Pool.   It also functions to adjust the Falls flow between tourist and non-tourist hours.   The operation of the structure is under the supervision of the International Joint Commission’s International Niagara Board of Control. ^{Park n.p.}