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Programs in the Great Lakes

The USGS provides maps, reports, and information to help others meet their needs to manage, 

develop, and protect America's water, energy, mineral, and land resources. We help find 

natural resources needed to build tomorrow, and supply scientific understanding needed to 

help minimize or mitigate the effects of natural hazards and environmental damage caused 

by human activities. The results of our efforts touch the daily lives of almost every American.

The Great Lakes System

The Great Lakes system comprises 

Lakes Superior, Michigan, Huron, Erie, 

and Ontario and their connecting waterways the St. Marys, the St. Clair, the 

Detroit, the Niagara, and the St. Lawrence Rivers; the Straits of Mackinac; 

Lake St. Clair; and the Welland Canal. 

The volume of water stored in the Great 

Lakes, which is about 6,020 trillion gallons, or 5,472 cubic miles, represents 20 

percent of the world's and 95 percent of 

North America's fresh surface water. 

These surface-water resources and their 

role in commerce, tourism, and recreation (fig. 1) have attracted 40 million 

people to live in the Great Lakes Basin 

about one-seventh of the total population 

of the United States and about one-third 

of the total population of Canada.

Contamination of the Great Lakes ecosystem limits recreation uses, threatens

Figure 1 . Sleeping Bear Dunes National Lakeshore, Leelanau County, Michigan.

productivity of commercial and sport 

fisheries, and increases the cost of watersupply treatment. The U.S. Geological 

Survey (USGS) conducts geologic and 

hydrologic investigations, the results of 

which will help planners understand and 

implement strategies to help reduce 

point- and nonpoint-source contamination that threatens water quality in the 

Great Lakes.

Toxic Substances

In 1983, the International Joint Commission an organization established by 

the Boundary Waters Treaty of 1909 

between the United States and Canada 

reported that 900 chemicals and heavy 

metals that are potentially dangerous to 

human health and biota had been identified in the Great Lakes. Concern about 

the potential effects of these chemicals 

and metals has increased as evidence of 

links between the presence of contaminants and carcinogenicity in fish, genetic 

defects in fish-eating birds, and reproductive disorders in biota has increased. Further possible links have been reported 

between developmental disorders in human infants and prenatal exposure to contaminants through consumption by their 

mothers of certain fish from the Great 

Lakes.

The Commission has identified 43 

Areas of Concern along the shoreline of 

the Great Lakes. Contamination by toxic 

substances, including polychlorinated 

biphenyls (PCB's), other synthetic 

organic compounds, trace elements in 

bottom sediments of rivers and harbors, 

and suspended-sediment inflow to the 

Great Lakes are specific water-quality 

problems in these areas. The USGS, in 

cooperation with numerous local, State, 

and other Federal agencies, is identifying 

the occurrence and distribution of these 

contaminants.

Iridfex of Subjects

The Great Lakes System 

Toxic Siibstances 

Selected Great Lakes Monitoring 

Information

Fluctuating Water evefe-Coasfal 

Erosfon and'Sirfj 

Coastal Wetlands

Specific studies on PCB contamination of the Great Lakes are being conducted by the USGS. For example, the 

USGS, in cooperation with the Wisconsin Department of Natural Resources, is 

estimating the total mass of PCB's present in the bottom sediments of the lower 

Fox River and computing the PCB load 

carried by the river to Green Bay in Lake 

Michigan. Accumulation of PCB's and 

other organochlorine pesticides in fish 

from Lake Michigan has resulted in fishconsumption advisories being issued by 

Wisconsin, Michigan, Illinois, and Indiana.

Additionally, the USGS, in cooperation with the Michigan and the Wisconsin Departments of Natural Resources, 

the Indiana Department of Environmental Management, and the U.S. Environmental Protection Agency, is estimating 

the total mass balance of pollutants entering the ecosystem of Lake Michigan. 

Under the program, which was designed 

by the USGS, scientists are currently 

(1995) monitoring 11 tributaries that 

make up 50 percent of the drainage area 

of Lake Michigan and are assumed to 

contribute more than 90 percent of the 

tributary load of PCB's. Each of these 

tributaries, which carry drainage from 

four States, has complex flow and transport conditions near its mouth. Acoustic 

flow meters, data loggers, automatic 

water-quality samplers, and telecommunications equipment are required to 

obtain the necessary data from these 

sites. These data will be used along with
atmospheric and open-lake data to 

develop a mass-balance model for Lake 

Michigan that will be used to evaluate 

management options to reduce chemical 

concentrations and thus shorten the time 

that fish-consumption advisories will be 

needed.

Combined sewer overflows (CSO's) 

constitute another serious environmental 

concern to the Great Lakes. CSO's are 

structural devices on combined sewer 

systems that divert untreated sewage 

mixed with stormwater to tributary rivers 

or directly into the Great Lakes. In ongoing projects in Cleveland, Detroit, 

Houghton, Marquette, and Sault Ste. 

Marie, USGS scientists are measuring 

discharge, nutrients, metals, polyaromatic hydrocarbons, and eight organic 

bioaccumulative substances identified by 

a binational program. These investigations will characterize storm-related 

water quantity and quality from selected 

CSO's, thus allowing the USGS to make 

better estimates of annual pollutant loads 

from CSO's to the Great Lakes.

Selected Great Lakes 

Monitoring Information

Since the turn of the century, the 

USGS has maintained and operated a 

monitoring network of surface-watergaging stations on streams and rivers 

draining to the Great Lakes (fig. 2). Data 

from this multistate monitoring network 

provide the USGS and its many cooperators with information on surface-water

flows, quantity of available water, and 

water-quality characteristics. These data 

are critical for long-term management 

and daily administration of water 

resources.

Long-term data from the USGS 

stream-gaging network are used by Federal, State, and local agencies to design 

bridges and culverts that will convey 

peak flows and for flood-plain mapping 

to minimize flood damages. The National Weather Service and operators of 

hydroelectric power utilities and wastewater-treatment plants use stream-gaging 

data on a daily basis. Managers of fisheries and wildlife sanctuaries use USGS 

stream-gaging data during periods critical to the maintenance of suitable habitats for the fauna and flora they manage.

The USGS currently (1995) has two 

National Water-Quality Assessment 

(NAWQA) Program studies underway in 

the Great Lakes area the Western Lake 

Michigan Drainages and the Lake ErieLake St. Clair Basin. The long-term 

goals of the NAWQA Program are to 

describe the status and trends in the quality of a large representative part of the 

Nation's surface- and ground-water 

resources and to identify the natural and 

human factors that affect their quality. In 

particular, the USGS is measuring concentrations in surface and ground waters 

of pesticides used in agricultural and 

urban areas to determine their distribution and frequency of occurrence. The 

presence and distribution of nutrients

Figure 2. Surface-water-gaging stations on streams and lakes draining to the Great Lakes.

(nitrogen and phosphorous) also are 

being studied to determine if the major 

sources of these are agricultural practices, discharges from sewage-treatment 

plants, or combined-sewer overflows. 

The NAWQA Program will produce 

water-quality information that will be 

useful to policymakers and water managers at the local, State, and national levels 

of government.

Diversions of Water

Joint ownership of the Great Lakes by 

the United States and Canada has necessitated regulation of the diversion and 

use of water from the Lakes. Historically, the State of Illinois has diverted 

water down the Illinois River (by means 

of the Chicago River and associated 

waterways) to carry sanitary sewage 

away from Lake Michigan and to allow 

barge traffic on the Illinois River between the Mississippi River and Chicago. The U.S. Supreme Court decree 

(December 1, 1980) regulating the diversion and use of water from Lake Michigan limits diversion and use in Illinois to 

a 40-year average of 3,200 cubic feet per 

second. Accurate accounting of the water 

diversion is necessary to ensure compliance with the Court's decree.

The USGS is cooperating with the 

U.S. Army Corps of Engineers, the Illinois Department of TransportationDivision of Water Resources, and the 

Metropolitan Reclamation District of 

Greater Chicago to increase the accuracy 

of Lake Michigan diversion accounting. 

The USGS is using state-of-the-art techniques and technology, such as doppler 

acoustic flow profilers, acoustic velocity 

meters, and dye dilution to measure flow 

accurately in the Chicago River and the 

Chicago Sanitary and Ship Canal, as 

well as to monitor leakage through the 

lakefront diversion-control structures. 

Through this new technology, previous 

estimated values of leakage through the 

diversion-control structures were found 

to be too low, and the water-budget 

accounting was adjusted accordingly.

Fluctuating Water Levels 

Coastal Erosion and 

Submergence

As the result of fluctuating water levels in the Great Lakes, hundreds of mil-
lions of dollars have been lost by the 

millions of people and many industries 

located near their shores. Record high 

water levels in the Great Lakes from 

1985 through 1987 resulted from aboveaverage rainfall. During this period, 

stormwaves superimposed on high water 

levels caused extensive and costly damage to the Illinois shore, particularly Chicago lakefront business, recreation 

beaches, parks, and private homes. The 

shore along western Lake Erie eroded 

rapidly, resulting in damage to public 

and private property. On steep shorelines 

with easily eroded soils, such as the 

unstable clay bluffs along parts of Lake 

Superior in northwestern Wisconsin, 

waves undercut the bluffs and caused 

them to slump. In these areas, the shore 

eroded as much as 15 to 20 feet in 1 day. 

Landslides along a 15-mile stretch of 

coastal bluffs on Lake Michigan north 

of Chicago resulted in erosion and retreat 

of the bluffs that averaged more than 9 

inches per year and locally exceeded 3 

feet per year.

The USGS, in cooperation with the 

Illinois State Geological Survey, the Indiana Geological Survey, and many universities, recently completed a coastal study 

of southern Lake Michigan in response 

to disastrous flooding in Chicago. The 5- 

year study documented the timing and 

magnitude of prehistoric lake-level fluctuations and assessed some of the important geologic processes responsible for 

severe erosion of the Illinois-Indiana 

shore. Seismic reflection data were collected to determine thickness and distribution of rock and sediments. These 

data, coupled with bathymetric data, 

were used to prepare a physiography 

map of the lake bottom. Maps of the 

areal distribution of bottom-sediment 

types also were prepared by using sidescan sonar, sample data, and observations by scuba divers. Sonar data also 

aided in assessment of the condition and 

extent of damage to shore-protection 

revetments along the Chicago waterfront. Profiles of sand thicknesses on 

beaches and the lake bottom based on 

700 sample locations along 50 transects 

off the Illinois Indiana shore resulted in 

the most complete characterization yet of 

sand distribution. Such information can 

be used to identify offshore sand for 

replacement of eroded beaches.

The USGS, in cooperation with the 

Ohio Department of Natural Resources, 

is documenting the historical erosion of 

Ohio's shoreline bluffs to determine the 

effects of natural processes and human 

activities on shore erosion. Understanding sand movement by mapping lakebottom physiography and sediment distribution could save millions of dollars in 

beach replenishment and maintenance 

costs. The results of this study of erosion 

potential will have wide applications because the Ohio shore is similar to other 

eroding areas throughout the Great Lakes 

area.

Scientists from the USGS and various 

universities are studying long-term waterlevel fluctuations of the Great Lakes 

(fig. 3). Observed water levels along the 

southern shore of Lake Michigan varied 

5.2 feet between low levels in 1964 and 

high levels from 1985 through 1987. 

However, recent USGS studies have 

shown that water levels along the southern shore varied by as much as 8.4 feet 

during the past 160 years. This new information on lake-level fluctuations pro6,000 4,000 2,000 

YEARS BEFORE 1990

Figure 3. Scales of lake-level change in the 

past. A, In the past 12,000 years, the lake has 

experienced dramatic change due to changing 

outlets and ground tilting; B, For the past 5,000 

years, climatically controlled fluctuations have 

been superimposed on a general falling trend; 

C, During the past 160 years, lake level has 

fluctuated a total of about 8 feet. Each peak in 

this century has been higher than the preceding peak.

vides planners with a long-term historical framework to use in protecting and 

managing lakeshore resources.

At Bay Mills, Michigan, on the southern shore of Lake Superior a few miles 

west of Sault Ste. Marie, the USGS, in 

cooperation with the University of Michigan, is studying sediment core samples 

for their historical lake-level record. Submerged sand spits, which formed at Bay 

Mills during the past 2,000 years, indicate periods of extended low lake levels 

with mean levels that are 5 feet lower 

than the current mean level. Natural climatic changes during that time lowered 

Lake Superior for extended periods, perhaps centuries.

USGS scientists, in cooperation with 

the National Park Service and the University of Wisconsin, have documented 

approximately 15 feet of submergence 

over the past 2,000 years at the Apostle 

Islands National Lakeshore near Bayfield, Wisconsin. Studies have shown 

that the Lake Superior Basin is being progressively tilted from the northeast to the 

southwest as a result of residual uplift 

following glacier retreat about 10,000 

years ago. Lake level is controlled by the 

spillway to the St. Marys River at Sault 

Ste. Marie, but the outlet is rising more 

rapidly than most other points along the 

U.S. shore of the lake. As the outlet 

rises, the accompanying lake level submerges the shore at an increasing rate 

westward from Sault Ste. Marie to 

Duluth, Minnesota. Wetlands and forests 

are submerged below the present lake 

level. At Duluth, as much as 18 feet of 

submergence has taken place. The rates 

of lake-level rise in these areas are on the 

order of 1 inch per decade. Rising lake 

level attributable to uplift at the outlet 

will continue to inundate low-lying areas 

and river mouths, to expand wetlands, 

and to contribute to erosion of exposed 

and erodible shores. Engineering projects along shore and river mouth areas 

need to take such changes into account.

Coastal Wetlands

Coastal wetlands of Lakes Superior, 

Michigan, Huron, Erie, and Ontario protect the drinking water and shoreline 

communities of millions of Great Lakes 

residents. Coastal wetlands are an ecologically important but disappearing compo-
nent of the Great Lakes (fig. 4). These 

wetlands provide habitat for many species of plants and animals.

The USGS, in cooperation with 

numerous State Departments of Natural 

Resources, Native American Tribes, 

State universities, and other Federal 

agencies, is collecting and analyzing sediment cores to document the history of 

wetland changes in the Great Lake 

States. The analysis is delineating the 

high levels of the lakes, the timing of 

peat deposition, the changing climatic

regimes, the extent of former wetlands, 

the deterioration and regrowth of wetlands, and the history of early human 

impacts on the wetlands. Results of the 

analyses are being incorporated into digital mapping products that will provide 

land-use planners, policymakers, and scientists with a predictive tool that can be 

used to manage and protect wetlands. 

Such information will help water managers identify locations where wetland preservation and restoration can strike the 

best balance between ecological and economic imperatives.

EXPLANATION

 Present-day coastal wetlands

Area encompassing wetlands of recent geologic past

Figure 4. Great Lakes coastal wetlands.

Many processes have been interacting 

to cause the deterioration of Great Lakes 

wetlands since the glaciers melted. Fish 

and migratory bird populations are being 

adversely affected by a loss of food and 

habitat as a result of increased sediment 

loads in the water and shallowing of the 

aquatic habitats. The U.S. Environmental 

Protection Agency has sought USGS 

assistance to develop methods to estimate the contribution of sediment loads 

of several large rivers to the Great Lakes 

in areas of Illinois, Indiana, Michigan, 

Minnesota, and Wisconsin. Models are 

being developed to estimate the sediment 

loads of smaller streams that yield sediment to the Great Lakes.

Stephen J. Rheaume, S.J. Williams, and

C.E. Larsen

For more information contact any of the following:

For water information

Associate Regional Hydrologist for the

Great Lakes

6417 Normandy Lane

Madison, Wisconsin 53719-1133

(608)276-3811

For geologic information

Assistant Chief Geologist 

953 National Center 

Reston, Virginia 22092 

(703) 648-6660

Additional earth science information 

can be found by accessing the USGS 

"Home Page" on the World Wide Web at 

"http://www.usgs.gov," or by calling 

1-800-H2O-9000 (1-800-426-9000)

For more information on all USGS reports 

and products (including maps, images, and 

computerized data) call 

1-800-USA-MAPS.

& US. GOVERNMENT PRINTING OFFICE: 1995-647-831

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet FS-056-95