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Home , Lake Erie, Lake Ontario, Lake Superior, Niagara River, Welland Canal

TheWA GrTEReat Lak LEVELSes S

ne spring, Erie's Huron by way of the St. Marys River. L water levels rose to the Lake also drains into Lake point that when a storm Huron through the .

E hit, the waves pounding The straits are so wide and deep that the the shoreline caused $5 water levels in Michigan and Huron million in damage to cottages, homes and are the same. From , water V dikes. By the following spring, the water flows into via the St. Clair River, levels in Lake Erie had dropped 60 Lake St. Clair and the River. The

E centimetres. Marina owners were worried water then flows into Lake the water would not be deep enough for through the River and the

L some boats to dock. . , in turn,

empties into the St. Lawrence River. From Water levels in the rise and there, the water flows into the Gulf of St. fall all the time. They have been doing so Lawrence and the . In total,

R since the retreated about 10 000 water travels some 3 600 kilometres from years ago. Most changes in water levels the western end of to the are natural, but some are the result of

E Gulf of St. Lawrence. n human activities. The purpose of this fact

o sheet is to provide some background There is more to the Great Lakes than i T about the Great Lakes and St. Lawrence just the lakes. They are part of a com-

g River and to explain why plex system of lakes, rivers and streams e A their water levels rise which drains large tracts of the

r and fall. province of

Ontario as well as

o The Great Lakes and St. eight American i W Lawrence River form a chain of

r states. In total, the Great lakes with each one draining Lakes basin, on both sides a into the next. Lake Superior,

t Water travels some 3 600 kilometres of the , measures the largest of the five Great from the western end of Lake Superior to the Gulf of St. Lawrence 774 000 square kilometres. n Lakes, drains into Lake O

Environment Environnement Canada Natural Factors Short-term changes Seasonal changes from the water, followed a number of years of below-normal and Sometimes, water levels rise or fall In general, water levels in the Great rain fall. In contrast, heavy rains because of the wind. These are Lakes are lowest in the late fall and and snow in the early 1970s and considered to be short-term early winter. This is because water mid-1980s raised the water levels changes since they rarely last on the surface of the lake at this in the Great Lakes to heights longer than a day. For example, time of year is warmer than the air which were above average. when strong winds blow over a lake above. As a result, water in one direction for several hours, evaporates rapidly. With more water A quick look at the graph of water they may push the water levels up leaving the lakes — in this case in levels on pages four and five shows at one end making the levels drop the form of water vapour — than that water levels in the Great Lakes at the other end. This is called a entering, water levels decline. rise and fall regularly. wind set up or surge. This phenom- In spring, when the snow melts, The earth moves ena has caused the water levels in water runs into the lakes. The lakes Lake Erie, the shallowest of the The earth rises in however, at this time of year, are Great Lakes, to rise by as much as the Great Lakes cooler than the air above. As a two metres at its eastern end within basin by up to 50 result, less water evaporates now the span of just a few hours. centimetres every 100 years — this than in the fall and early winter. is a hangover from the ice ages. When the wind stops blowing or With more water entering the lakes When this area was covered by changes direction, the water than leaving them, their water levels glaciers, their tremendous weight oscillates or flows back and forth usually rise, ultimately reaching compressed the earth underneath. like a pendulum until it stabilizes. their peak in the summer. When the glaciers melted, the land, This is called a . The seasonal range between low now relieved of the weight, began An ice jam in a river which connects levels in the winter and high levels to rise. one of the lakes to another may in the summer runs between 30 It continues to do so today. The reduce the flow of water to a trickle. centimetres and 50 centimetres. land in the north and east rises This is what happened the day more rapidly than the land in the ran dry. On March 29, Long-term changes south and west. , for 1848, the residents of Niagara Falls example, rises more than 30 woke up to what was for them a Precipitation centimetres a century, while strange silence. Strong winds, Long-term changes does not move. The result currents and waves had jammed in water levels are is similar to tipping a bowl of water. hundreds of thousands of tonnes of usually the result of The water level on one side rises ice into the eastern end of Lake Erie heavier or lighter than normal and it falls on the other side. On between Fort Erie and Buffalo levels of precipitation. For Lake Superior, the water level at blocking the flow of water into the example, the low water levels in Duluth is rising 14 centimetres per and reducing Niagara the Great Lakes during the 1960s, century, and is falling 22 centi- Falls to drips— for nearly 30 hours. which left many docks a good walk metres per century at Michipicoten.

2 to be getting warmer. Although Michigan and Huron may drop by opinions vary on the effect a 100 centimetres, while those in The earth's natural change in climate may have on the Lake St. Clair may fall by 90 climate system is Great Lakes, computer models centimetres, in Lake Erie by 80 never stable. It has suggest that supplies of water to centimetres and in lakes Ontario changed in the past the lakes may drop dramatically. and Superior by 40 centimetres and it appears to be The mean levels of water in lakes over the next 20 to 40 years. changing again. This time it seems

Water Cycle

TRANSPORT TRANSPORT (by wind) (by wind) TRANSPIRATION (evaporates CONDENSATION from plants) PRECIPITATION EVAPORATION (evaporates from lakes ) PRECIPITATION EVAPORATION (evaporates from land)

PERCOLATION (into the ground and becomes groundwater) RUN-OFF (returns to lakes) (some groundwater seeps into lakes and rivers)

The water levels of the Great Lakes are Not surprisingly, the affected by the amount of water rain or snow which falls directly flowing in and out of the lakes. The The processes which into the lakes increases the volume hydrologic or water cycle plays a make up the water cycle — of water in them, but so does some role in this process. evaporation, condensation, of the rain or snow which falls on precipitation and transpiration — The water cycle is the natural the ground. For example, when the are continuous but not consistent. recycling of water. It evaporates snow melts, some runs directly into They vary from season to season from oceans and lakes as well as the lakes and some percolates down and from year to year. from the land. Water vapour rises into the earth to become until it hits cooler air in the upper groundwater which may flow atmosphere, where it condenses to eventually into the Great Lakes. form clouds and returns to earth as Plants and trees take up some of the rain, snow, drizzle and other forms water in the ground and release it to of precipitation. the atmosphere through the process called transpiration.

3 Monthly Mean Water Levels ne important point about the graph: 184.0 Othe measurement on the left side of 183.8 183.6 the graph is the height of the lake's

s 183.4 e r surface and is expressed in metres above sea t

e 183.2 M level. For instance, in 1995 the level of water 183.0 in Lake Superior was about 183.3 metres 182.8 above sea level. 182.6 Lake Superior 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 5 5 5 5 5 5 5 5 5 5 5 5 1 1 6 2 2 4 4 0 0 0 6 6 7 7 3 3 7 7 8 8 9 9 8 8 9 9 5 5 8 0 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 177.6 177.4 177.2 177.0 176.8 176.6 176.4 176.2 176.0 Lakes Michigan-Huron 175.8 175.6

s 175.4 e r t

e 175.2 M 175.0 Lake St. Clair 174.8 174.6 174.4 174.2 174.0 173.8 173.6 173.4 Lake Erie 173.2 173.0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 5 5 5 5 5 5 5 5 5 5 5 5 5 1 1 2 2 4 4 0 0 0 6 6 6 7 7 3 3 7 7 8 8 9 9 8 8 9 9 5 5 0 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 9 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 2 75.8 75.6 75.4 75.2

s 75.0 e r t

e 74.8 M 74.6 74.4 74.2 74.0 Lake Ontario 73.8 73.6

Graph source: U.S. Army Corps of Engineers 4 5 Human Factors

Dredging dredged many times in the second from Lake Erie. All of it, twentieth century. As a result, water however, is eventually sent into As on the Great Lakes grew levels on lakes Huron and Michigan Lake Ontario. larger, it became necessary to dropped by almost 40 centimetres. dredge the rivers and channels to The diversions have raised Lake meet their new depth requirements. Diversions Superior's water levels by two This affected water levels. For centimetres while they have example, the St. Clair and Detroit There are three main areas on the reduced 's and Lake River system which Great Lakes where water is Huron's by one centimetre. joins lakes Erie diverted. The first area is at the Similarly, the diversions have and Huron, Ogoki and Long Lac diversions, raised the long term water levels of was north of Lake Superior. Water is Lake Ontario by four centimetres, taken from the but have reduced Lake Erie's by watershed to drive hydro-electric nine centimetres. power plants on rivers feeding Lake Superior. Using water and not The result is an returning it increase in the amount of water which flows into Lake Superior of Consumptive about 160 cubic metres of water use is a per second. technical term which The second water diversion is in scientists use Chicago and is used for water to describe the supply, sewage disposal and practice of taking and using water commercial navigation purposes. from lakes or rivers, but not Water is removed from Lake returning it. Today more than 115 Michigan at a rate of 90 cubic cubic metres of water per second is metres per second. It is then sent lost from the through the Chicago Sanitary and due to consumptive use. The Canal and eventually to the amount will increase as the Mississippi River where it flows into population on the Canadian side of the Gulf of Mexico. the Great Lakes basin is expected to rise by about 20 per cent, The , which reaching an estimated 12 million connects lakes Erie and Ontario, is people by 2020. the third diversion. The water is used for shipping and generating electricity. The canal diverts up to 240 cubic metres of water per

6 Controlling the Flow

Controlling or regulating the flow of Ontario through the St. Lawrence balance when compared to their water from one lake to the next also River at Cornwall. long-term averages. For example, if affects the levels of water in the the water levels in Lake Superior Great Lakes. To regulate a lake Lake Superior are higher than average, and the means to adjust or change the water levels in lakes Michigan and amount of water which flows out of The flow of water out of Lake Huron are lower than average, then it and into the next lake. This is Superior is controlled by hydro- the amount of water flowing out of done according to rules set out by electric generating plants, Lake Superior is increased. the International Joint Commission navigation locks and a water-control (IJC). The rules were established structure with 16 gates. The IJC Lake Ontario and the by the Canadian and American manages the flow of water through St. Lawrence River governments and work toward the these structures through the fair, equitable and environmentally International Lake Superior Board During the 1950s the section of the sound management of the Great of Control. St. Lawrence from the point where Lakes and other . the river meets Lake Ontario The board adjusts the amount of downstream to Cornwall was The flow of water through the Great water which flows out of the lake modified so commercial shipping Lakes is controlled at two points: every month so that the water and hydro-electric plants could from Lake Superior to Lake Huron levels in lakes Superior, Huron and expand. These changes allow the at Sault Ste. Marie, and from Lake Michigan are kept in a rough IJC, through the International St. Lawrence River Board of Control, to control the volume of water flowing out of Lake Ontario.

These two organizations take into account the rights and needs of the owners of shoreline properties, shipping companies and the hydro-electric industry while keeping in mind that any actions taken to raise or lower Lake Ontario's levels s r

e will generally have the e n i g

n opposite effect on river E

f o

s levels downstream of the p r o C

y dam at Cornwall. m r A

. S . U

St. Marys River flow control structure

7 Information about Water Levels

For more information on water levels, please contact: Environment Canada Great Lakes-St. Lawrence Water Levels Information Office P.O. Box 5050 Burlington, Ontario L7R 4A6 Tel. (905) 336-4580 e-mail: [email protected] For more information on the Great Lakes and weather in Ontario, please see: http://www.on.ec.gc.ca/water/levels/intro-e.html http://www.great-lakes.net/ http://www.on.ec.gc.ca/water/greatlakes/intro-e.html

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