Rainy and Namakan Lakes are located along the international boundary of the Ontario, Canada, and the Minnesota, USA, border. These lakes are part of a waterway that extends from the Sawtooth Mountains, which are located about 50 miles inland from Lake Superior, to the Arctic Ocean. The water levels of these lakes are controlled according to regulations set by the International Joint Commission (IJC), an independent international organization established under the Boundary Waters Treaty of 1909, to help prevent disputes regarding use of boundary waters.
A hydroelectric dam located on the Rainy River at Fort Frances, Ontario/International Falls, Minnesota and two water-control dams located at Kettle Falls, Ontario, the outlet of Namakan Lake, maintain lake levels. These structures are owned and operated by H2O Power LP on the Canadian side and by Boise Inc. on the United States side. The companies manage the water levels of Rainy and Namakan Lakes in accordance with the rule curves established by the International Joint Commission. The IJC has delegated the oversight of the rule curves to the International Rainy Lake Board of Control, which has both a U.S. and Canadian representative and technical staff. There is a similar group known as the Lake of the Woods Control Board for that area.
The first rule curves were introduced by the IJC in 1949 after detailed study and public hearings. The serious floods, which occurred in 1950 and 1954 led to a reevaluation and modification of the rule curves in 1957. The rule curves were modified again in 1970 due to high and low water events on Rainy and Namakan Lakes from 1957 to 1968. The latest revisions to the rule curves came on January 6, 2000 after a self appointed group known as the International Steering Committee advocated further changes to the rule curves on both lakes.
The IJC establishes minimum and maximum discharge requirements in order to avoid "emergency conditions" as much as possible. Emergency conditions are defined to exist when the levels of Rainy and Namakan Lakes are higher than 1108.1 feet above sea level (337.75 meters) and 1118.6 feet (340.95 meters) respectively and inflows exceed the discharge capacity of the dams. Emergency conditions also occur when Rainy Lake is below 1104.6 feet (336.68 meters) and Namakan Lake is below 1108.6 feet (337.90 meters) and minimum discharges are in effect.
The maximum discharges through the dams on both lakes can at times be exceeded by the inflows into the two lakes. On Rainy Lake, there is a natural flow constriction located at the outlet of Rainy Lake or otherwise known as the Ranier rapids. A greater volume of water can be discharged through the International Falls/Fort Frances dam than can come through this natural constriction. This can cause the level of the Rainy River to drop in elevation between the outlet of Rainy Lake and the dam.