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  Great Lakes-St. Lawrence Hydrology
What's New | Weekly Levels Forecast | Overview | Datums | Education
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Levels & Hydrology Section: Home | Levels | Hydrology | Flows

 
What's New
Water supply down, Lake Superior drops
Duluth News Tribune (4/3)
Lake Superior dropped two inches in March, a month it usually drops only a half-inch, the International Lake Superior Board of Control announced Tuesday.

Boaters lament low lake levels
The Windsor Star (3/12)
Recreational boaters are concerned given that lakes Huron and Michigan had record lows in January and lakes St. Clair and Erie are expected to see only modest rises over the next month.

Low water in Lake Michigan cause for concern
Superior Telegram (2/8)
Scientists say the record low water level of Lake Michigan could mean problems for wildlife. Other people who watch the lake for recreation say they're worried about the long-term health of the water body.

Great Lakes water levels reaching a low ebb
The Buffalo News (1/2)
Lakes Erie, Ontario and Superior are below historical averages for December, and Lakes Michigan and Huron are at record lows. The mild 2011-12 winter that carried over into a summer drought has created lower water levels throughout the Great Lakes system.

Flaws in pitch for regional diversion of Lake Michigan water
Milwaukee Journal Sentinel (12/5)
As a community completely outside the Great Lakes basin, the water diversion application from the City of Waukesha, Wis., needs the unanimous approval of all eight Great Lakes states for implementation.

Huge glacial aquifer under Ottawa County shrinking from overuse, water study finds
MLive (12/3)
A recent study conducted by the Institute of Water Research at Michigan State University reports that the glacial aquifer under the Ottawa County, Mich., region is shrinking.

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Weekly Water Levels Forecast
New! Update for Friday April 5, 2013 (includes data summary)

Weather conditions: Warm temperatures last weekend cooled off on Monday and Tuesday to below seasonal averages. Temperatures have risen in the middle of the week but are expected to drop again on Friday. Most areas will see near average temperatures through the weekend with chances of precipitation, although the precipitation forecasts are varied across the region over the next several days. Precipitation was well below average last month for the Great Lakes.

Water Level Conditions: The water level of Lake Superior is 3 inches below its level of one year ago, while Lake Michigan-Huron is 15 inches lower. Lakes St. Clair, Erie, and Ontario are 16, 17, and 14 inches, respectively, lower than their levels of a year ago. Over the next month, Lakes Superior and Michigan-Huron are forecasted to rise 2 and 4 inches, respectively. The water levels of Lakes St. Clair and Erie are each expected to increase 4 inches over the next thirty days while Lake Ontario is forecasted to rise 6 inches. See the Great Lakes Water Levels web page for more water level information.

Forecasted outflows / channel conditions: Lake Superior’s outflow through the St. Marys River is projected to be below average for the month of April. Lake Huron’s outflow into the St. Clair River and the outflow from Lake St. Clair into the Detroit River are also expected to be below average throughout the month of April. Lake Erie’s outflow through the Niagara River is predicted to be below average and the outflow of Lake Ontario into the St. Lawrence River is expected to be below average in April.

Alerts: Official records are based on monthly average water levels and not daily water levels. Lake Superior and Lake Michigan-Huron are below chart datum. 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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Updated: April 5, 2013
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