January 9, 2001

Peaking and Ponding in the St. Marys River

Three hydroelectric plants are allotted a major portion of the flow of the St. Marys River pursuant to the International Joint Commission's 1914 Orders of Approval, as ammended.   Outflows from Lake Superior into Lake Huron are are overseen by the Commission's International Lake Superior Board of Control.   Flows are set monthly by the Board according to Regulation Plan 1977-A.

The International Joint Commission (IJC) is an international organization established by the Boundary Waters Treaty of 1909 to prevent and resolve disputes over the use of waters shared by the United States and Canada. More information about the IJC is available on the IJC’s website at

Water levels in the upper Great Lakes have fallen sharply since 1998 and remain below average. There has been less flow available in the river for use by interests such as hydroelectric generation and commercial navigation.

The current low water situation, and recent inquiries on concerning the effects of water level fluctuations on navigation and the environment, have drawn the IJC’s attention to peaking and ponding operations in the St. Marys River. Peaking and ponding operations are carried out by the Edison Sault Electric Company and Great Lakes Power Limited to store water during times of off-peak demand and increase hydroelectric power generation during times of on-peak demand. Peaking (Fig. 1) is the variation of hourly flows within the daily average flow, while ponding (Fig. 2) is the variation of daily flows within the weekly average flow (i.e. higher weekday flows and lower weekend flows). An example of the actual water level variations just downstream of the Sault Ste. Marie locks, measured every six minutes, can be seen in Figure 3 . Water level fluctuations are also caused naturally by wind and a tmospheric pressure changes, a nd by seasonal changes in ice cover and aquatic vegetation.

The International Joint Commission recently advised the power entities that the IJC’s Orders of Approval do not authorize deviations from the monthly flow set under Regulation Plan 1977-A, and do not authorize peaking and ponding operations. It has, however, provided temporary authority to the power entities to conduct peaking and ponding operations until March 20, 2002, under the supervision of the International Lake Superior Board of Control.

The Commission has asked the Board to review the current situation and recommend whether peaking and ponding operations in the St. Marys River should continue, and if so, under what circumstances. Public hearings have been organized in Sault Ste. Marie, Michigan and Sault Ste. Marie, Ontario on January 28, 2002 in order to provide information from all interested parties that may be useful to the Board in preparing its report. Written comments will also be accepted until February 8, 2002.

The Board will report to the IJC by February 28 and, having considered the Board’s recommendations, the IJC will decide on further actions prior to March 20 expiration of temporary authority.


Frank Bevacqua Washington, D.C. (202) 736-9024
Fabien Lengellé Ottawa, Ontario (613) 995-0088