Changing Lake Levels

By Jennifer McKay

Despite their vastness and ageless beauty, we often forget that the Great Lakes are a living system, an ever-changing ecological process. Those fortunate enough to visit or reside along the shore of a Great Lake for any length of time are sure to recognize that the only constant associated with the shoreline is change. On any given day, the location of the water’s edge can change dramatically. Day-to-day fluctuations are caused by wind and wave action along the shore, while annual or seasonal fluctuations are based mainly on changes in precipitation and runoff. However, the Great Lakes also experience long-term cycles that correspond to long-term trends in precipitation and temperature.

Most boaters are fully aware that lakes Superior, Michigan and Huron are currently in the midst of low water period. While the water levels for the lakes have begun to rise due to the seasons changing, the lakes are still below the long-term average.

According to the U.S. Army Corps of Engineers’ April 2008 Great Lake Water Level Summary, the mean water level for Lake Superior for the month of April was 600.4 feet, which was six inches higher than it was in April of last year, but still 10 inches lower than its monthly long-term average. Lake Superior is projected to be between eight and 15 inches above last year’s levels, but that is still below the long-term average. Lakes Huron and Michigan, which are connected by the Straits of Mackinac and are, therefore, considered one lake, rose six inches in April. The water levels were four inches below its April 2007 level and 19 inches below the long-term average. While the forecast for lakes Michigan and Huron is to be between five and eight inches above last year’s level, this is still below the long-term average.

While theories on low (and high) lake levels abound in the Great Lakes, lake levels are largely determined by the weather. Very simply, water inflow (precipitation, run-off and water from streams and ground water) minus water outflow (evaporation and water flowing out of the system) equals a change in lake water levels. In particular, Great Lakes water levels are especially influenced by winters: a hard winter, with above normal snowfall and bitter cold temperatures that create vast ice cover, will cause lake levels to rise; mild winters with higher temperatures, less ice cover and more evaporation will decrease lake levels.

Low lake levels affect many interests, including shipping, power generation, tourism, fishing, ecology, shoreline property owners and recreational boating. With low lake levels, our boating season can be cut short by four to six weeks. Additionally, as lake levels drop, boaters may become increasingly concentrated in certain areas, which can lead to an increase in accidents and damage to boats as groundings become more common. As water levels recede, marinas have fewer slips to sell to boaters and the need to dredge boat slips, channels and harbors to accommodate boater needs will increase dramatically and cost millions.

The Great Lakes have always fluctuated, but the citizens of the Great Lakes Basin are growing more and more concerned as the lakes continue to remain in the midst of a low trend. From shoreline property owners and commercial freighters to recreational boaters and anglers, two resounding questions keep coming up: Where has all the water gone? What can be done to get it back and keep it?

There are some in the Great Lakes who are calling for greater manipulation of the lake levels to alter water levels. Currently, the United States and Canada are undergoing an intensive $17.5 million study to determine why water levels in the upper Great Lakes—lakes Superior, Michigan and Huron—have decreased to near-record lows and whether actions are needed to stabilize water levels. Public meetings have recently been held by the International Joint Commission (IJC) to discuss current and projected lake level conditions and regulation and to seek public input that will help develop potential alternative regulation plans for managing outflows from Lake Superior. But the question then arises, How much control does the International Joint Commission really have over the water levels of the lakes?

Under the Boundary Water Treaty of 1909, the IJC was established and charged with shaping policy for U.S. and Canadian waterways. Currently, the IJC regulates flows at two points in the Great Lakes, Lake Superior and Lake Ontario. Regulation of Lake Ontario has no impact on the upper lakes because of the difference in elevation at Niagara Falls, which acts as a control. The outflow from Lake Superior is regulated through three hydropower projects, five navigation locks, and a 16-gate control structure at the head of the rapids called the “compensating works” located at the two Sault Ste. Maries.

The “compensating works” were built to compensate for the increase in the size of the outlet of Lake Superior caused by diversion of water for power purposes. Flow from Lake Superior has been regulated through this collection of structures since the completion of the compensating works in 1921. The hydrologic conditions of the upper Great Lakes are monitored, and the International Lake Superior Board of Control determines the outflow level for each month. Most of the flow out of Lake Superior goes through the hydropower plants, and gate openings are adjusted each month to achieve the monthly Lake Superior outflow specified in a regulation plan.

The basic goal of the regulation is to set the flow that will result in Lake Superior and lakes Michigan and Huron staying at nearly the same relative position within their natural range of fluctuation. The original regulation plan considered the interests of hydropower, navigation, and riparian owners on Lake Superior. Subsequent regulation plans consider other factors, including the levels of lakes Michigan and Huron and fishery concerns.

So how much control does the IJC really have over the lake levels? As it turns out, very little. Although the outflows for the lakes are controlled, the levels of the lakes are not controlled. So while the IJC has the ability to regulate lake levels, the commission’s ability to actually control lake levels is limited. The major influences on the hydrology of the lakes and their connecting channels are weather and climate. Precipitation, surface water runoff and ground water flows provide water to the Great Lakes system; evaporation and outflows take water away. The IJC cannot control most of those forces. The commission does have the ability to distribute water supplies provided by nature, but it cannot control those supplies.

“Any extended period of warm, dry weather will result in lower water levels, and any extended period of cool, wet weather will result in higher water levels, regardless of what actions are taken by the IJC,” said Frank Bevacqua, public information officer for the IJC.

The lakes respond to many natural factors. In the end, though, nature has the last word.

Controlling lake levels is also made difficult by the extensive surface area of the lakes. Their sheer size means that changes in water levels from controls require a significant amount of time to actually take effect. Therefore, regulations can alter and alleviate lake level extremes, but current regulations of lake levels do not affect long-term lake level trends and cannot influence levels significantly in the short term. The regulation of flows for Lake Superior are really just a drop in the bucket compared to the impact nature has.

While increasing the outflow from Lake Superior could increase the levels of Michigan and Huron, the increase would be limited and potentially detrimental to the lakes. It would take a very large increase in flows to raise lake levels for lakes Michigan and Huron. Together, they have a much larger surface area than Lake Superior. Therefore, according to Bevacqua, “any attempt to use Lake Superior as a reservoir exclusively to regulate water levels on the downstream lakes would greatly magnify the fluctuations on Lake Superior and cause negative impacts to Lake Superior interests.”

A U.S. Army Corps of Engineers computer model determined that the outflows from Lake Superior could be increased by 70 percent for three months and the water levels on lakes Michigan and Huron would increase less than three inches. The effect on Lake St. Clair and Lake Erie would be even more insignificant—less than two inches and less than a half-inch, respectively. These minute changes, however, would result in a drop in Lake Superior levels by five inches.

Furthermore, given that the Great Lakes system is so huge and takes so long to react, an attempt to raise one lake by lowering another during low water periods could actually result in additional damage. While raising lake levels in one part of the system through regulations could help recreational boaters, marinas, shippers and property owners, those same interests would be harmed in another part of the system.

“It would be physically possible (though not desirable) to raise the levels of lakes Michigan and Huron by one inch over the course of one month” said Bevacqua. However, “it would cause negative impacts on Lake Superior and could cause negative impacts on lakes Michigan and Huron, if there was a more critical need for this water supply on Michigan and Huron at some point in the future.”

The approach taken by the IJC is to regulate Lake Superior outflows for the benefit of the entire system. According to Bevacqua, “in the long run, this provides benefits to commercial navigation, recreational boating and shoreline property on all three lakes.”

Since the needs of the interests vary, designing a regulation plan that can satisfy all the interests all of the time poses a great challenge. The difficulty is compounded by the variability and unpredictability of water supplies. This will be further complicated with the unknown impacts on the Great Lakes ecosystem associated with climate change.

While it is recognized that low water levels can have a significant impact upon the environment and economy of the Great Lakes region, including millions of recreational boaters, it is important to remember that the Great Lakes are a dynamic, living, evolving system. The shapes and sizes of the Great Lakes are not what they were 10,000 years ago, nor will they remain how they are today centuries into the future. We choose to live and recreate on this magnificent resource and with that we must understand that the lakes undergo natural ecological processes beyond our control and even our understanding.

We cannot force the lakes to behave in a manner that is acceptable to our current uses or lifestyles. Not only is complete control of lake levels virtually impossible, by trying to manipulate the lakes to accommodate our needs, we would merely be creating more problems. Instead, we need to embrace the Great Lakes in their entirety. This includes accepting that at times the water will be high and at times the water will be low. Rather than trying to control the Great Lakes, we should instead enjoy them for all their glory.