Weather conditions:
A large storm system made its way into the Great Lakes basin early this past week and brought cooler temperatures and rain along with it. Mid-week, overnight temperatures dipped to the freezing mark in many areas across the basin as high pressure and dry weather settled in. Looking ahead, a slow moving low pressure system is on its way to the basin and is expected to bring about an inch of rain to the region this weekend and early next week. Drier conditions and seasonal temperatures will return as this system moves out of the area.
Lake Level Conditions:
Lakes Ontario and Superior are presently 9 and 10 inches higher than they were at this time last year, respectively. Lakes Michigan-Huron and Erie are 1 inch lower than last year's level while Lake St. Clair is 3 inches lower than last year's level. Lakes Michigan Huron and Superior are predicted to rise 3 and 4 inches over the next month, respectively. Lakes Erie and Ontario are predicted to fall two inches, while Lake St. Clair is projected to stay the same over the next 30 days. Lakes Superior and Ontario are forecasted to stay above last year's water levels through October, while the remaining lakes are forecasted to remain at or below their levels of a year ago over the next several months.
See the USACE Daily Levels web page for more water level information.
Current outflows / channel conditions:
Outflows from the St. Marys, St. Clair and Detroit Rivers are expected to be below average for May while outflows from the Niagara and St. Lawrence Rivers are forecasted to be above average.
Alerts:
Lake Superior is currently below chart datum, but is forecasted to go above chart datum in June. Lake Michigan Huron is currently at chart datum and is expected to rise and remain a few inches above datum through October. 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.
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
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.
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!
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).