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  1. #1
    Join Date
    Dec 2011

    Default Great Lake levels vs precipitation

    John -

    Why do we see the levels of the Great Lakes fluctuate over time yet precipitation measurements do not correlate to those cycles? Or do they and I'm just not using my data correctly?

    I would think that rain/snow amounts would directly impact water height of Superior or Huron, but that does not appear to be the case over time. Is this due to evaporation/sequestering that prevents that precipitation from reaching/impacts the lakes or?

    Water Level Data:

    Question 2
    What's a good site for historical precipitation data, for MI, say from 1900 to present? Sites like MSU seem to have incomplete data sets for historical info:

    PS - while doing some research, one of the "weather" sites had this to say about MI, clearly the authors were not sledders:
    The worst time to visit Michigan is the severely cold winter season from December to February. The northern highlands of the Upper Peninsula and areas near Lake Superior see snowfall in excess of 150" (3810mm). Snowstorms affect normal life and damage life and property.

  2. #2
    Join Date
    Jun 2001
    The Keweenaw Peninsula


    Hi 2TrakR

    That's an excellent question.

    You are certainly onto something when you mention evaporation. It is a pretty significant factor in the lake levels, but the #1 factor is the precipitation in the drainage basins for the Great Lakes. Which is not as big as many might think.

    There is also a bit of a lag in the precip that falls and that which makes it to the lakes. Also the water flows from Superior to MI/Huron, then Erie and finally Ontario. So the levels of the lakes upstream play a roll too, even though the US and Canadian governments can control a significant portion of what flows from lake to lake via locks and dams.

    With all that said, I have found a pretty close correlation between the lake levels and the precipitation in their basins, over a multi year period and to a smaller extent yearly and seasonal scale.

    As for precip data, your best bet is probably the National Climatic Data Center. It is a big site and ever changing, so you might have to do some digging around to find what you want.

    Good Luck!

  3. #3
    Join Date
    Dec 2009
    Green Bay, WI


    Great information. I follow the lake levels on a more micro basis due to flooding along the Fox River in Green Bay, WI. Since 2015 many facilities along the river began to flood and have required the installation of water remediation techniques. I also drive the tractor part-time at Cana Island, near Bailey's Harbor, WI. We take tourists to the Island lighthouse via tractor. Wagon Rides - Door County Maritime Museum ( Pre-2015 this was a walking path. This picture is a couple years old and the tractor has been upgraded (taller) due to lake levels.
    The Fox river level can vary significantly in a short period of time (I've seen 3' variances in a 5 Hr window). This is caused by minor tidal fluctuations and precipitation drainage; but a more prominent factor is a strong NE wind pushing water off Lake MI into Green Bay. USGS Current Conditions for USGS 040851385 FOX RIVER AT OIL TANK DEPOT AT GREEN BAY, WI Take a look at graph #3 for our fluctuations this week.

  4. #4
    Join Date
    Dec 2009
    Neenah, Wisconsin is about 40 miles south of Green Bay's Lambeau Field.


    I've been to Cana Island many times. I've seen the causeway vary from bone dry to up to our knees. I'll be sure to look for eyeman's tractor on our next visit. Here's a picture of the high water last summer in Fish Creek at one of the landings. Normally the water is off the far end of the pier on the right hand side.

    Fish Creek 2020.jpg

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