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Environment & Science
Tue February 5, 2013
What's impacting Great Lakes water levels?
The Great Lakes are experiencing low water levels.
One of our Facebook friends, Debbiedoe Nash, wrote this morning:
Over the last few years the waterline has dropped so far at our property on Huron that what once was the beach now has about two hundred feet of rocky swamp in front of it. Yikes.
So what are the causes behind these low lake levels?
We spoke with a few experts who gave us a run down of the factors, big and small, contributing to the extreme lows.
1. Mother Nature rules the day
Climate and weather patterns have the biggest and most influential effect on Great Lakes water levels.
It's a simple concept.
When there's more water going out than going in, water levels go down.
"The biggest impact on water levels is climate and weather patterns," said Jennifer McKay, Policy Specialist at the Tip of the Mitt Watershed Council in Northern Michigan. "Lake levels are determined by the hydrologic cycle, and when climate affects the system, you see changes in lake levels."
John Allis, Chief of Great Lakes Hydraulics and Hydrology with the U.S. Army Corp of Engineer's Detroit District agreed.
“We have had such a dry period and seen evaporation at higher-than-average rates. As long as those continue, water levels will continue to drop,” he said.
Water levels normally go up and down throughout the year. This year, the lake levels are expected to keep dropping as part of the normal seasonal decline throughout the fall and winter months.
2. Historical Dredging
Shoreline dredging, typically to expand marinas, has little to no impact on water levels, but historical channel dredging projects have altered water levels, according to the Army Corps' John Allis.
The U.S. Army Corps of Engineers dredged the St. Clair and Detroit Rivers for navigation. These projects deepened the channel by removing sand and gravel from the river bed. Allis says these historical dredging projects lowered water levels by an average of 10-16 inches in Lakes Michigan and Huron.
He points to a study by the Army Corp of Engineers that found these dredging projects significantly altered the river beds:
Major dredging efforts to facilitate commercial navigation throughout the St. Clair/Detroit River system occurred from 1910-1923 (the 22-foot project), from 1933-1936 (the 25-foot project) and from 1958-1962 (the 27-foot project).
Allis says once these projects were complete, there was no further lowering of water levels. The only dredging that has occurred since on these rivers has been maintenance dredging.
Low lake levels have caused marinas to spend a lot of money to keep their docks open to boaters. Now leaders in Lansing are calling for more money for dredging projects, as discussed in today's Environment Report.
3. Man-made water diversions
A diversion of water is a transfer of water across watershed boundaries through man-made infrastructure, such as a pipelines or canals.
The Great Lakes diversions transfer water in and out of the basin or between watersheds of lakes in the basin.
At present, more water is being diverted into the lakes than is being taken out, according to both Allis and McKay.
The Chicago Diversion is by far the largest and most well-known of the lake diversions. It moves water out of Lake Michigan at a rate of 3,200 cubic feet per second.
Water flows into Lake Superior from the Albany river system in northern Ontario at Long Lac and Ogoki at a rate of 5,000 cubic feet per second.
The University of Wisconsin's School of Freshwater Sciences has a map of all the existing diversions in and out of the lakes.
4. Regulating water flow through dams and locks
Water levels, inflows, and outflows are regulated by the International Joint Commission, an independent organization established by the United States and Canada.
The IJC's regulation plan is to keep lake levels as close to their long-term averages as possible, but they can only work with the water they have.
The Lake Ontario-St. Lawrence River basin is regulated at the Moses-Saunders Dam, the Soo Locks regulate the outflow from Lake Superior, and various canals, dams, channels and locks regulate diversions from Lake Ontario and Lake Erie.
Lake Michigan's diversion rate through Chicago is regulated by a U.S. Supreme Court decision in 1967.
“The overall point is to try to keep water levels similar and control for extremes,” said McKay.
Regulation can have an impact on controlling flows and balancing water levels, but in situations where all the lake levels are low, nature is the greater force.
“Considering the situation in the past 13 years, the lakes are all below their long-term averages, so there is not much you can do,” Allis said.
5. Consumptive Uses
Most water people use from the Great Lakes is returned to the basin, so the amount of water consumed is too tiny to consider when looking at the overall impact on Great Lakes water levels.
“We use a lot of water, but most of it is returned,” said McKay. “We estimate that the average consumption rate is about 5 percent, but since the '90s, there has been a decrease in withdrawals because of efficiency and conservation standards.”
The final verdict? Climate and weather patterns have the most profound effect on lake levels. Other factors play a role, but at the end of the day, Mother Nature has the final word.
-Rebecca Guerriero, Michigan Radio Newsroom
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