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Water – The Great LakesThe issues and concerns faced by water resource managers in Canada are perceived not only in a national perspective (i.e., those problems common to all parts of the country), but also in a regional context (i.e., the interaction of a wide range of problems, many specific to a particular area, such as droughts on the Prairies, floods in the coastal provinces, and fluctuating water levels in the Great Lakes). The example of the Great Lakes presented here provides insight into one of the regions making up the Canadian mosaic. The Great Lakes basin, which straddles the Canada-United States border, contains 18% of the world's fresh surface water and is home to almost a third of the Canadian population.
How important are the Great Lakes to Canada and the United States?The Great Lakes basin (the lakes plus the area of land draining into the lakes) is home to 8.5 million Canadians and 30.7 million Americans. As well as providing drinking water, the lakes have played a major role in the development of both countries. They allow goods to be shipped to and from the heart of the continent; they are a source of hydroelectricity; and they are the site of industrial, commercial, agricultural, and urban development. The Great Lakes also provide an array of recreational opportunities. What are some of the problems and issues confronting the management of the Great Lakes system?The Great Lakes basin is a huge ecosystem. The specific problems in the Great Lakes have changed over time, but the broader issues have remained – those of deteriorating water quality through industrial and municipal uses, fluctuating water levels, flooding, and shoreline erosion. Other concerns are acid rain, airborne toxics, depletion of wetland areas, increased demands on the shoreline land base, the impacts associated with the unintentional introduction of exotic species, and climate change. How important are wetlands as part of the Great Lakes ecosystem?Great Lakes coastal wetlands are highly productive and diverse communities of plant and animal life. They are essential to the well-being of the Great Lakes ecosystem. Their unique vegetation provides cover and food for wildlife, helps protect shorelines from erosion, and helps improve water quality by filtering pollutants and trapping sediment. These wetlands are home to a wide variety of wildlife species – some of which are classified as rare, endangered, or threatened. Many fish species depend on Great Lakes wetlands for spawning, resting, and feeding. Wetlands are also critical for waterfowl as both nesting and migration habitat. In fact, it is estimated that 68 bird species are either totally or partially dependent on Great Lakes basin wetlands. About 20 species of mammals, 28 species of amphibians, and 27 species of reptiles have been associated with the marshes of Lake Erie. Wetlands are also important to humans. We use them for wildlife observation, water supplies, sportfishing, waterfowl hunting, trapping of furbearing animals, harvesting of trees, berries, and other vegetation, adult and public school education, and a variety of recreational pursuits. Unfortunately, humans also alter and fill in wetlands in order to use them for other purposes. About two thirds of the original wetlands in the lower Great Lakes basin have already been lost or severely degraded, while the health of those that remain continues to be threatened. As the area of Great Lakes wetlands shrinks, the importance of remaining wetlands becomes even greater. Is recreation an important use of the Great Lakes?Recreation is an increasingly important social and economic activity in the Great Lakes basin. Millions of people, from both within and outside the Great Lakes basin, use the lakes and their shorelines for a variety of recreational purposes. Among the major recreational activities around the Great Lakes are boating, sportfishing, hunting, bird-watching, camping, swimming, windsurfing, hiking, picnicking, and driving along the shoreline. These recreational uses supported the establishment of provincial and federal parks and led to a major service industry involving marinas, hotels, motels, resorts, campgrounds, and other nearby land-based recreational establishments. In addition, many people who use the Great Lakes for recreation have cottages or homes along the shoreline. What causes the levels of the Great Lakes to rise and fall?The Great Lakes receive their supplies of water from inflows from upper lakes in the chain and from precipitation that falls not only on the lakes themselves but also on their drainage basins and eventually flows into the lakes. They lose water through evaporation, outflows, and consumptive uses. The difference between the amount of water coming into the lakes and the amount going out determines whether lake levels remain steady, whether they rise, or whether they fall. Because the combined effects of precipitation, runoff, and evaporation vary from season to season and from year to year, the levels of the lakes also vary. Lake outflows also vary as a function of lake levels. For example, the lakes usually rise in the spring due to additional runoff and recede in late summer and early fall as runoff decreases.
Why do water levels sometimes seem to change from day to day?Water levels can change in a matter of hours. Sustained high winds from one direction can push the water level up at one end of the lake (this is known as "surge") and make the level go down by a corresponding amount at the opposite end. When the wind stops, the water will oscillate back and forth until it levels itself out, much as it would in a bathtub. This is known as "seiche". How often do extremes in lake levels occur?Since long-term lake level fluctuations are influenced by weather trends, we cannot predict when and how often extremes in levels will occur. Levels of some of the Great Lakes fell to record lows in the late 1920s, the mid-1930s, and the mid-1960s. Extremely high levels occurred in the early 1950s, the early 1970s, and the mid-1980s. The most recent record high lake levels period occurred between 1985 and 1987 when all of the lakes, except Lake Ontario, reached their highest levels recorded in the twentieth century. Over the following two years, lake levels dropped rapidly to their long-term averages. The 1990s were characterized by persistently high water levels and outflow throughout the Great Lakes-St. Lawrence system. How do water level fluctuations of the Great Lakes affect people living along their shores, and industrial and commercial operations?For people living on the shores of the Great Lakes, high water levels can increase the risks of shoreline flooding, erosion, and damage caused by waves during storms. Industries and commercial operations along the lake shores can face the same risks. While high water levels allow ships to carry heavier loads, extremely high levels and flows through the connecting channels can cause navigation problems. High levels can also be beneficial for hydroelectric plants, which can produce more electricity with the additional water. During extremely high water levels, however, the amount of water available to these plants can exceed their capacity and be spilled. Erosion of the shoreline at one point will supply the sand that helps build a beach farther down shore. This contributes to the constantly changing shorelines of the Great Lakes. Low water levels increase the size of lakeshore beaches, but extremely low levels can expose unsightly and, sometimes, hazardous rocks, mudflats, and other objects that can pose problems to both swimmers and boaters. As well, very low water levels can make some recreational docking facilities unfit for use. For industries depending on ships to transport their products and supplies, extremely low levels can interfere with loading and unloading. These ships may also have to carry lighter loads. Very low levels may cause reduced flows through connecting channels and thereby result in reduced hydropower production. Wetlands also depend on fluctuating water levels to maintain their ecological balance over the long term. This is true even though extremely high lake levels may flood marshes and lead to changes in their plant and animal populations, and very low levels may dry marshes out and cause other changes to plant and animal life. How have land use changes in the Great Lakes basin affected the lakes themselves?Since early in the twentieth century, significant changes in land use in the Great Lakes basin have occurred, including deforestation, urbanization, and drainage of wetlands. These activities have changed the runoff characteristics of the drainage basin. Although the extent to which these changes affect lake levels is difficult to define, research suggests that land use changes have increased water flows into the Great Lakes from some tributary streams. Do people also cause changes in lake levels?Several human activities have affected levels and flows of the Great Lakes. For example, structures have been built to regulate the outflows of Lakes Superior and Ontario. Lake Superior has been regulated since 1921 as a result of hydroelectric and navigation developments in the St. Marys River. Lake Ontario has been regulated since 1960 after completion of the St. Lawrence Seaway and Power Project. Besides assisting navigation and allowing for dependable hydropower, these regulation structures have helped, to some extent, to stabilize the range of lake level fluctuations. Diversions bring water into, and take water out of, the Great Lakes. The Long Lac and Ogoki diversions bring water into Lake Superior from sources that once flowed into James Bay. They were constructed for hydropower generation and logging. The Lake Michigan diversion at Chicago takes water out of Lake Michigan to the Mississippi River for domestic, navigation, hydroelectric, and sanitation purposes. The Welland Ship Canal, which was built to allow ships to bypass Niagara Falls and to provide water for power generation, routes additional water out of Lake Erie into Lake Ontario. In addition, the St. Clair and Detroit rivers have been dredged and modified. This has caused some drop in the levels of Lakes Michigan and Huron. Channel and shoreline modifications in connecting channels of the Great Lakes have affected lake levels and flows as well. For example, in the Niagara River, construction of bridges and infilling of shoreline areas have slightly reduced the flow carrying capacity of the river. Human effects on lake levels have been relatively small, however, compared to the changes caused by the natural factors described earlier. Who is responsible for flooding and shoreline erosion on properties along the St. Lawrence River and the Great Lakes?Planning for and managing the development of the Canadian shoreline is the responsibility of provincial and municipal governments. The protection of shore property is primarily the responsibility of the property owner. How do both countries share the Great Lakes?The Canada-United States border runs through four of the five Great Lakes and their interconnecting rivers, causing them to come under federal jurisdiction in both countries. Although the land on and under the shores of the lakes is provincial jurisdiction in Canada, the waters of the boundary lakes and rivers are under federal authority. Canada and the United States are party to the 1909 Boundary Waters Treaty The Great Lakes Water Quality Agreement (1972, 1978, 1987 Protocol) and the Niagara River Treaty (1950) are examples of arrangements between Canada and the United States that have followed the Boundary Waters Treaty. The federal governments of both countries provide considerable technical support to, and work closely with, the International Joint Commission, for example, on the management, wise use, and stewardship of the Great Lakes. For more information, contact:
Canadian Section Office of the What is being done to resolve concerns about fluctuating Great Lake water levels?The Governments of Canada and the United States provide the mandate and technical support to the International Joint Commission (IJC) for their international operational boards that monitor and decide on flow conditions in the St. Marys, Niagara, and St. Lawrence rivers. The IJC also carries out major reference studies on Great Lakes levels. The most recent investigation was completed in 1993 in response to a request by the Canadian and United States governments in 1986, when Great Lakes water levels were at record highs for the twentieth century. This IJC reference study examined all lake level interests in the basin, including owners of shoreline property, fishers, boaters, shippers, wildlife, and producers of hydroelectricity. Among the findings was the recommendation that federal governments should not undertake commitments to further regulate Great Lakes levels as a means of reducing shoreline flooding and erosion on the lakes. Instead, comprehensive shoreline land use and management programs should be undertaken to help adapt shoreline activities to fluctuations in water levels. The Government of Canada, through Environment Canada, also established the Great Lakes-St. Lawrence Water Levels Information Office in Burlington, Ontario to act as a focal point for material and public contact regarding fluctuating Great Lakes water levels What is being done to resolve concerns about Great Lakes water quality?The Canada-United States agreement provides the framework for resolving water quality concerns in the Great Lakes. The Great Lakes Water Quality Agreement (GLWQA) was first signed in 1972; it was revised in 1978. The 1978 agreement was amended by protocol in 1987. The 1972 GLWQA prescribed, among other things, targets for phosphorus loading reductions to control nutrient enrichment problems in the lakes. The 1978 agreement placed more emphasis on industrial pollutants and toxic substances and set water quality objectives for specific chemicals. The 1987 protocol advanced the cleanup of the Great Lakes by calling for the restoration of particularly degraded areas of concern and seeking the control of all sources of pollution, including airborne toxic substances. The protocol has also strengthened the public accountability of the governments of Canada and the United States, which must now report publicly to the International Joint Commission (IJC) on the progress of implementation of specific annexes to the agreement. As well, every two years the Great Lakes Water Quality and Science Advisory Boards of the IJC present their independent reports on progress (or lack thereof) toward achieving the objectives of the GLWQA. These reports are available from
Great Lakes Regional Office of the |
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Lake levels can change over periods of years for the same reasons. During periods of years in which precipitation and runoff in the Great Lakes basin are high and evaporation low, lake levels can gradually increase. In periods of low precipitation and high evaporation, lake levels can gradually lower. The resultant variation in lake outflows offsets a part of these water supply variations, but not all, hence the variations in lake levels. The length of time required for noticeable changes, and the degree of the changes, will depend on how wet or how dry the weather is and on ambient temperatures.
, which was designed to address and resolve disputes and issues regarding the Great Lakes and other boundary waters. This treaty established the International Joint Commission, a quasi-judicial body that may give or withhold approval for the use, obstruction, or diversion of boundary waters shared between Canada and the United States. When requested, it investigates matters of concern to one or both governments and, on mutual consent, it may decide matters of difference between both governments, although it has never been asked to do so.
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