Background

Regulating Water Levels

Low water levels on Lake Michigan and Lake Huron are a genuine concern for the International Joint Commission and were an important consideration in the International Upper Great Lakes Study Board’s report and recommendations for regulating the Lake Superior outflows.

The proposed regulation plan, Plan 2012, was tested under thirteen different water supply sequences, ranging from very dry to very wet, to ensure its robustness. An extreme and improbable climate change sequence that appears in an IJC presentation about Plan 2012 has raised concerns that Plan 2012 would cause the water levels of Lake Michigan, Lake Huron and the Georgian Bay to drop below current levels. This simulation demonstrates that under an extremely dry sequence, the current plan would result in Lake Superior becoming land-locked as water would no longer flow into the St. Mary’s River.

Plan 2012 reacts to this extreme decline in water supplies and prevents this hypothetical situation from occurring. In fact, under extremely dry stimulation, Plan 2012 fares better than existing plan (1977a). Based on historical water supplies, Plan 2012 would result in raising the water level of Lake Michigan and Lake Huron by four centimetres (from 175.38 m. to 175.42 m) compared to the current plan. Under almost all circumstances, there would be very little difference in the levels of Lake Michigan and Lake Huron under Plan 2012 when compared with the current plan.

While both plans provide some relief from extreme high and low water levels of Lake Michigan and Lake Huron, it is important to emphasize that the amount of water flowing out of Lake Superior that can be regulated is small in comparison to the amount of water from all the other unregulated supplies of water in the basin, such as other tributaries and rainfall.

Reviewing the existing plan

Changing water levels can have significant effects on the lives of the more than 25 million people who live in the upper Great Lakes basin. The people around the Great Lakes depend on these waters for a myriad of uses: their livelihoods; drinking water; fishing; recreational boating; and spiritual needs. The economic importance of this region cannot be understated and industries such as navigation, hydroelectricity and thermal power are dependent on water levels. Water levels are also important for maintaining healthy wetlands, fisheries and other ecosystems across the basin.

Water levels in the entire upper Great Lakes basin can be regulation at only one location upstream from Niagara Falls: at the outlet of Lake Superior on the St. Marys River. The International Joint Commission (IJC) approved hydropower development on the St. Marys River in 1914 and a regulation plan was implemented in 1921. Over the years, the IJC has incorporated new knowledge, data and modelling strategies to address the challenges of regulating water levels in the upper Great Lakes. The current Lake Superior regulation plan, 1977A, has been in effect since 1990. It represents the culmination of nearly 75 years of regulation experience responding to changing economic, environmental and social conditions.

The rationale for reviewing the existing plan is based on several important factors that have emerged over the past 20 years since the current plan was implemented:

  • First, there is considerable uncertainty about water supplies or net basin supplies (NBS) and corresponding water levels in the Great Lakes basin in the future as a result of natural climate variability and human-induced climate change.  Compounding uncertainty about NBS are the impacts of glacial isostatic adjustment (GIA), the differential adjustment of the earth’s crust that has the effect of gradually “tilting” the Great Lakes basin over time.
  • Second, there is better information available today than 20 years ago about the hydrology and hydraulics of the Great Lakes.  Researchers have more confidence in the newer models that describe how the system performs under a variety of conditions.  New knowledge has also been gained through recent investigations, such as the Study’s own analysis of the changes in the conveyance of the St. Clair River.
  • Finally, there is improved information about the different sectors and public interest concerns that any new regulation plan must address.  Under the Boundary Waters Treaty of 1909, the interests of domestic and sanitary water uses, navigation, and power[1] and irrigation are given order of precedence.  However, it is now recognized that in developing a new regulation plan, the needs of other interests, such as ecosystems, coastal zone uses, and recreational boating and tourism must be taken into account, as well.