Tuesday, June 4, 2013

Update about the Current Levels of the Great Lakes

Last fall I posted a blog update about the level of the Great Lakes.  At that time Lakes Huron and Michigan had the lowest level in recorded history and Lake Superior had the second lowest level. 

Charts showing the flow of Great Lakes water are below:

In general, the Great Lakes are in the midst of an extended low water period with all of the Great Lakes below their long-term average. Lakes Michigan and Huron (hydrologically connected at the Straits of Mackinac and, therefore, considered one lake) and Lake Superior have been below their long term average for the past 14 years. A new record low water level for Lake Michigan-Huron was set in January 2013. The new record low for January of 576.02 feet is the lowest monthly average ever recorded for any month over the official period of record for Great Lakes water levels, which extends back to 1918. The previous all-time low for Lake Michigan-Huron was 576.05 feet set in March of 1964.  Current forecasts predict all the Great Lakes will remain below average for at least the next 6 months, but do not call for record low levels for Lakes Superior, Erie, or Ontario.  However, the lake levels are so low that it is expected to take at least eight to ten years for them to recover, and perhaps as many as 30 years.

The photo below shows a stranded dock in the Georgian Bay taken in September 2012.  The low level of Lake Huron caused the shoreline to retreat several hundred feet.

Current Water Levels
The current levels of the Great Lakes have recovered several inches, thanks to a massive rain storm last year as well as due to an old fashioned snow pack this winter.  Last year when the Duluth, MN area received ten inches of rain, in only 24 hours, Lake Superior rose between three and four inches.  Melt water from the snow pack also slightly increased the lake level.

A similar level increase has taken place for Lakes Michigan and Huron.

Impact of Low Water Level
The Tip of the Mitt Watershed Council (dedicated to protecting the lakes, streams, wetlands, and groundwater of Northern Michigan) summarizes the positive and negative impact of low lake levels:  Low lake levels affect many interests including shipping, power generation, tourism, fishing, the ecology of the Great Lake ecosystem, shoreline property owners, and recreational boating. Periodic low water conditions can be beneficial for lake ecosystems. It consolidates sediments, allows new plants to colonize the lake bed and it provides habitat for rare plants and shorebirds. When water levels return, this expansion of plants becomes habitat for fish and wildlife, removes nutrients from water, and can increase water clarity.

At the same time, low water levels can adversely affect other interests such as commercial navigation, recreational boating, and marinas. During low level periods, lake carriers transporting iron ore, coal, grain, and other commodities are forced to carry fewer goods. Also, as water levels recede, marinas have fewer slips to sell to boaters and often dredge boat slips, channels, and harbor to accommodate boater needs costing millions.

Impact of Water Removal from the Great LakesI was curious how much water is being taken out of the Great Lakes.  For over a hundred years, we have been taking water out of Lake Michigan.  Currently water is being removed from three locations in south Lake Michigan:  Wilmette, Chicago, and Calumet.  In the late 1960s, Illinois pledged to take out no more than 3,200 cubic feet per second annually.  The chart below shows the amount of water removed over time.  As you can see, the amount removed has decreased significantly over the last several decades. 
 What impact would this have?   Mark Torregrossa (MLive.com) did the math:
The maximum outflow supposedly allowed is: 3,200 cubic feet per second.
  • Of that, 820 cubic feet per second is runoff back into the lake so the actual amount removed is 2,380 cubic feet per second.
  • Calculate the total: 2,380 X 60 seconds in a minute X 60 minutes in an hour X 24 hours in a day X 365 days in a year equals 75 billion cubic feet per year passing out of Lake Michigan.
  • There are 7.48 gallons of water in a cubic foot.
  • So 561 billion gallons of water are pulled out of Lake Michigan yearly along the Illinois shoreline (75000000000 * 7.48).
  • One inch of water over all of Lake Michigan and Lake Huron (which are connected) is 800 billion gallons of water.
  • So seven-tenths of an inch  of Lake Michigan - Lake Huron water is pulled out each year (561/800).
At first this small amount seems insignificant, but over time this amount can add up.  For example, over ten years a drop in level of seven-tenths of an inch per year would add up to an accumulated drop of  seven inches..
Is bottled water from the Great Lakes contributing to water level declines?
According to The Tip of the Mitt Watershed Council: Water is taken from the Great Lakes Basin for a variety of reasons – for drinking, bathing, laundry, agriculture, industry, and so much more. The majority of water withdrawn is returned to the Basin through runoff and discharge. However, some of the water withdrawn is made unavailable. The term consumptive use refers to any quantity of water that is withdrawn from the Great Lakes system and not returned. Examples of consumptive use include water that evaporates from irrigated fields, lawns, and golf courses and water incorporated into dairy products, canned foods, drinks, and chemicals. Approximately 5% of the water that is withdrawn from the Great Lakes watershed is consumed and is lost from the Basin. At this time, the 5% of water lost does not appear to be placing significant pressure on the Great Lakes.

Addition of Water into Lake Superior
At first I became concerned when I realized that over time the withdrawal of water in Illinois could have dramatic effect as well as a 5 percent loss per year from consumptive loss.  But then in the same article, and confirmed by other web sites, there is 25 percent more water being added to Lake Superior.  The Long Lac and Ogoki diversions redirect water into Lake Superior from the Albany River system in northern Ontario.   Combined, the flow of water in the Long Lac and Ogoki diversions averages 5,400 cubic feet per second.  The location of these diversions is shown below:

This means that the Long Lac and Ogoki diversions divert over 2,000 cubic feet per second greater than the amount of water diverted out of Chicago. This makes the Chicago and other smaller diversions of water from the Great Lakes currently negligible.

How is climate change affecting water levels of the Great Lakes?
So it appears that there is another reason why the levels of the Great Lakes are declining.  According to The Tip of the Mitt Watershed Council: While the primary reasoning for low lakes levels is natural weather conditions, it is also widely accepted that global climate change either will or is already dramatically altering what would otherwise be a natural occurrence. Scientists do anticipate that air and water temperatures, evaporation rates, ice cover, seasonal precipitation, and water levels will change. In the Great Lakes region we are already seeing shortened winters, decreased ice cover, and increased evaporation from the lake; the result being lower lake levels.

At least the scientists, natural resource managers, politicians, and others are measuring and keeping track of what is going on with the water levels of the Great Lakes.  Let's all hope that they make the right decisions to properly manage the lake levels.


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