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  Great Lakes-St. Lawrence Hydrology
What's New | Weekly Levels Forecast | Overview | Datums | Education
Laws | References | Related Resources

 
Levels & Hydrology Section: Home | Levels | Hydrology | Flows

 
What's New
Navigating the unknown
The Sault Star (8/10)
Hydrologists meddle with the question of how best to retain water in the Great Lakes.

What a wet summer
Collingwood Enterprise Bulletin (8/1)
It may not be the deluge that Toronto has received, but the local area is setting a new mark for rainfall this summer.

Grand Haven gets deadly rip current sensor
Muskegon Chronicle (7/25)
A device has been installed that monitors lake currents in front of the popular Grand Haven State Park. The device, called an Acoustic Doppler Profiler, uses sonar to measure the strength of currents along the beach and pier.

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Weekly Forecast
New! Update for Friday August 1, 2008 (includes data summary)

Weather conditions: Temperatures were moderate throughout the entire Great Lakes region this past week. In addition, most of the region experienced insignificant precipitation. Near average temperatures will continue throughout the weekend and into early next week. There is a chance of showers and thunderstorms on Friday and Saturday for most of the Great Lakes basin.

Lake Level Conditions: All of the Great Lakes were higher than they were at this time last year. Lake Superior is 17 inches above last year's level while lake Michigan-Huron is 8 inches higher than it was a year ago. Lakes St. Clair and Erie are 7 inches higher than they were last year while Lake Ontario is 13 inches above last year's level. Lake Superior is projected to rise 1 inch over the next 30 days, while Lake Michigan-Huron is predicted to fall 1 inch. Lakes St. Clair, Erie and Ontario are forecasted to fall 5 to 8 inches during the next month. All of the Great Lakes are expected to remain above their water levels of a year ago over the next few months. See the USACE Daily Levels web page for more water level information.

Current outflows / channel conditions: In July, outflow through the St. Mary's River was slightly below average, and outflows through the St. Clair and Detroit Rivers were also below average. The Niagara River's outflow was slightly above average, while outflow from the St. Lawrence River was also above average.

Alerts: Users of the Great Lakes, connecting channels and St. Lawrence River should keep informed of current conditions before undertaking any activities that could be affected by changing water levels. Mariners should utilize navigation charts and refer to current water level readings.

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Overview
Carved by glaciers, the Great Lakes-St. Lawrence River system is a series of steps that drains from Lake Superior in the west to the Atlantic Ocean in the east. Covering more than 94,000 square miles, the Great Lakes and their connecting channels form the largest fresh, surface water system on earth, holding about 18 percent of the world's supply.
 
Ever since the last glaciers retreated about 10,000 years ago, the system's water levels and outflows have been fluctuating, affecting the lakeshore environment and human activities. Unlike oceans, where ebbs and tides are constant and predictable, Great Lakes water level fluctuations are almost never regular, nor can their levels be predicted accurately in the long term. This is because the many factors affecting Great Lakes water levels and flows are never constant and likely can not be predicted accurately in the long term.
 
The major influences on Great Lakes hydrology are weather and climate, which affect the balance of water in the Great Lakes and their connecting channels. Water enters the system as precipitation, runoff (including snowmelt) from the surrounding land, and groundwater inflow. Water leaving the system consists of evaporation from the water's surface, groundwater outflow, consumptive uses and diversions.
 
The GLIN hydrology section discusses these factors and links to resources from many relevant agencies. We hope that an understanding of the Great Lakes system's dynamics will promote living in harmony with one of the most precious natural resources of this planet.
 
Coordinating Committee Co-chairs:
John Kangas
U.S. Army Corps of Engineers, Great Lakes and Ohio River Division
john.w.kangas@usace.army.mil
 
Peter Yee
Environment Canada, Great Lakes-St. Lawrence Regulation Office
peter_yee@pch.gc.ca

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Datums
Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data
 

Datums - explanation of datums used for water levels and navigational charts
Department of Fisheries and Oceans, Canadian Hydrographic Service

Establishment of International Great Lakes Datum 1985
Department of Fisheries and Oceans, Canadian Hydrographic Service

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Education
TEACH Great Lakes: Water Levels
Water levels are part of the ebb and flow of nature. Learn about the three types of water level fluctuations, how levels are measured on the Great Lakes, and what's causing the recent drop.

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Laws
Boundary Waters Treaty
United States and Canada, 1909

Great Lakes Charter

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References
Great Lakes Water Levels Home Page
U.S. Army Corps of Engineers (USACE), Detroit District
A regularly updated page of links to information on Great Lakes hydrology. Includes current conditions, recent water levels, forecasted levels, general news and information, multimedia, reference materials, and more!

Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data
 

Great Lakes Atlas
U.S. Environmental Protection Agency (EPA)
This Environmental Atlas and Resource Book is an excellent resource on the Great Lakes, including physical characteristics, natural processes, people, concerns, joint management and new directions (mirrored on Environment Canada's site).

Hydrologic Cycle Online Meteorology Guide
University of Illinois, Department of Atmospheric Sciences

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Related Resources
GLIN: Agencies and Organizations, Hydrology
GLIN: Environmental Research in the Great Lakes Region
GLIN: Great Lakes-St. Lawrence Water Flows
GLIN: Great Lakes-St. Lawrence Water Levels
GLIN: Weather and Climate in the Great Lakes Region

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CC Data This page was created under the guidance of the binational Coordinating Committee on Great Lakes Basic Hydraulic and Hydrologic Data. This symbol is used throughout the GLIN hydrology section to indicate data or references prepared under the auspices of the Coordinating Committee.

 

 
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Last Updated: November 1, 2006
Maintained by: Christine Manninen, manninen@glc.org
Selected Photos: Copyright ©John and Ann Mahan
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