Monday, October 7, 2013

Apple #655: How Many Lakes are in Minnesota?

This weekend, I went with my dad and my brother to see the Minnesota-Michigan game.  Before the game, my brother lapsed into one of his behaviors that I remember all too well from growing up with him.  He started asking a whole lot of questions, on this occasion, about lakes in Minnesota.  I'll show you what I mean:

"There aren't really 10,000 lakes in Minnesota.  [I answered no, there aren't, there are more than 10,000.]  How do you know?  Who counts them?  Who decides what's a lake and what's a pond?  Why does the number change?  I've been to Minnesota, and I've flown over it too, and I haven't seen that many lakes.  I don't think they have 10,000 lakes in Minnesota.  Are they cheating and counting some Canadian lakes as theirs?" etc. etc.

Minnesota.  My brother would probably say to this, "I don't see 10,000 lakes.  Where are all the lakes?  Are you sure somebody didn't just make that up?"
(Map from Aquarium Pros)

Not having all my resources at my disposal, I could not adequately counter Mr. Annoying Question-Man.  (He didn't really want the answers anyway; he just wanted to be annoying.)  But now that I'm home with my laptop & the internet available, I am going to find the answers to his questions anyway.  So there.

  • As of 2013, the Minnesota DNR says there are 11,842 lakes in Minnesota.  These are lakes that cover 10+ acres.
  • The Minnesota Historical Society, meanwhile, says that Minnesota has 15,291 lakes of 10+ acres.  Their data is not dated, so I don't know if this is more or less current than the DNR.

This graphic gives you some idea of the number of lakes in Minnesota.  But I can just hear my brother asking about 25 more annoying questions in response to this.  So I'll see if I can find other visual evidence.
(Map from RMB Environmental Laboratories

Here's a little slice of Minnesota: the area around Detroit Lakes, Minnesota.  A ton of lakes just in this one area.  I'd like to say, you can extrapolate from this one place to the rest of the state, can't you?  But I know, I know, extrapolation works until it doesn't, as Simpsons fans will recall.
(Map from

I can't resist, though.  Here's another slice of Minnesota: area surrounding Pequot Lakes.  Dotted and sprinkled and pock-marked with lakes of all different sizes.
(Map from

This map shows the 1,029 lakes in Minnesota designated by the Nature Conservancy as priorities for conservation. Sure looks like a lot of lakes, doesn't it?  That's only 1/10 of the total number.
(Map from the Nature Conservancy Minnesota Science Sidebar)

  • OK, I'm not finding complete enough visual evidence, so let's go back to that number which seems to be the most reliable:  11,842 lakes of 10+ acres.  Maybe there are other things I can tell you to support that number.
  • I don't know who goes around counting the lakes in Minnesota, but people who work for the DNR seems to be the most likely ones, especially since the DNR is currently involved in a project to map all the watersheds for all the 100+ acre-lakes in the state.
  • Here are some other facts that indicate there are a crapton of lakes in Minnesota:
    • There are so many lakes in Minnesota, many are not named.  Still others have names that are the same as other lakes in the state.  The most commonly-used names of lakes are Long (115), Mud (92), Rice (78), Bass, Round, and Horseshoe.
    • The area covered by the 10 largest lakes entirely within Minnesota's borders totals 724,279 acres.  That's about 1,100 square miles.  The entire state is 86,938 square miles.  
    • In total, Minnesota has about 2.6 million acres' worth of lakes.
    • Only 4 counties in Minnesota have no natural lakes.  
    • Otter Tail County, conversely, contains 1,048 lakes, the most of any county in the United States.
  • That's a lotta lakes.
  • None of them are stolen from Canada. 

Why Does the Number of Lakes Change and Where did They all Come From?

  • Setting aside the very likely factor that different people count things according to different criteria, the reason the number of lakes might change over time is perhaps best explained by the State of Washington's Department of Ecology:
Lakes constantly undergo evolutionary change, reflecting the changes that occur in their watersheds. Most lakes will eventually fill in with remains of lake organisms and silt and soil washed in by floods and streams. These gradual changes in the physical and chemical components of a lake affect the development and succession of plant and animal communities. This natural process takes thousands of years. Human activities, however, can dramatically change lakes, for better or worse, in just a few years.
  • The human activity that can have the biggest effect on the appearance or disappearance of lakes is the building of dams. I suppose beavers could also have a pretty major effect on the number of lakes, too.
  • Minnesota's lakes were originally formed at the end of the Ice Age.  As the glaciers melted and retreated, they didn't do so in an organized fashion.  Big hunks of ice would get left behind, buried under silt and dirt and rock.  When the buried ice melted, the silt dropped down but there wouldn't be enough of it to fill in the hole, or kettle, left behind.  Then when it rained, the kettles filled up with water, and a lake was formed.
  • The same thing happened in Wisconsin and Canada, and pretty much all around the Great Lakes.

Kettles left behind after the glacier receded became today's lakes.
(Image from Wikimedia Commons, sourced from Reflections of a Travelinguist)

Minnesota vs. Wisconsin

  • Which leads me to another question that my brother didn't ask, but other people do when they talk about the number of lakes in Minnesota: is it true that Wisconsin actually has more lakes than Minnesota?
  • Most people from Wisconsin say their state has more, quoting a count of 15,074 lakes.
  • However, this number from Wisconsin's DNR includes lakes that "range in size from one- to two-acre spring ponds to [the] 137,708 acre Lake Winnebago."
  • In other words, Wisconsin includes in their count a lot of bodies of water that, according to Minnesota's definition of "lake," would not make the cut.
  • Wisconsin's DNR doesn't say how many of their lakes are 10+ acres, so it's hard to know how their count exactly compares.  They do say that about 3,620 of Wisconsin's lakes are 20+ acres.  
  • (If you want to go through Wisconsin DNR's PDF, copy the by-county lake data, convert it to a spreadsheet, sort by area, and count only those with an area of 10 acres or more, please be my guest and let us know the number you come up with.  And please also tell us how long it took you to do that.)
  • Perhaps the best method of comparison is in surface area:  
    • Wisconsin lakes: ~ 1 million acres' worth  (1,562.5 sq mi)
    • Wisconsin total state size: 65,497 square miles
    • Wisconsin lakes / square mile:  ~ 41.92
    • Minnesota lakes: ~ 2.6 million acres' worth (4,062.5 sq mi)
    • Minnesota total state size: 86,938 square miles
    • Minnesota lakes / square mile: ~ 21.40
  • According to my math, Minnesota seems to beat Wisconsin on the sheer number of lakes in its borders, and its lakes cover more ground than Wisconsin's do, though Wisconsin packs more water per inch in its smaller-sized state.
  • Maybe the conclusive factor is in the names.  "Minnesota" means "Sky-tinted water."  "Wisconsin" means "Grassy place." 
  • If your state name literally means water, I think you might win the water fight.

Ignoring the Great Lakes, the lakes in Minnesota look a little more visible.
(Map from Wikimedia)

What is a Lake, Anyway?

  • So who is right?  That is, has Wisconsin counted their lakes more correctly, or has Minnesota?  Well, there is no objective definition of "lake."  The distinctions between lake, pond, pool, puddle, etc. are pretty much arbitrary.  The terms date from when white people settled in the area, and they didn't really follow any mathematical formula, they just called 'em as they saw 'em.
  • Most people will designate a larger or deeper body of water a lake and a smaller waterbody a pond, but some things that have been called ponds are actually larger than some lakes.  
  • You might think that people who study lakes, ponds, pools, etc. might establish criteria to make them distinct from each other.  But because pools, ponds, lakes, and wetlands are in a slow but constant state of flux, one gradually filling becoming another, water-scientists have decided that there's really no point drawing a precise line between the categories.  Nature isn't fixed and numerical like that but is in a constant state of flux.
  • The World Health Organization defines a lake as "an enclosed body of water (usually freshwater) totally surrounded by land and with no direct access to the sea." Nothing about size or depth.  
  • The definition goes on to describe all the variations in types of lakes -- they may or may not have an observable input or output, they can be salty or not, and they may occur in a series linked by rivers so it can be hard to tell the river and the lake apart.  So the whole thing is kind of squishy.  Or muddy.  
The one thing that isn't muddy is that Minnesota does have a ton of lakes, there are more than 10,000 of them, and nobody's lying or cheating about that, they're just rounding off the number.  Geez.

As far as I'm concerned, though, no other lakes can compare to these.
(Image from The Nature Conservancy)

P.S. My brother is a water engineer.

P.P.S. Michigan won the football game.

Related entries: Rivers, Lake Michigan

Minnesota Department of Natural Resources, Lakes, Lakes, rivers, and wetlands facts
Minnesota Historical Society, Minnesota Facts, Symbols
RMB Environmental Laboratories, Inc. Minnesota lakes trivia, May 2, 2013
Minnesota Geological Survey, Why so many lakes?
State of Washington Department of Ecology, Lake information
FindTheData, Wisconsin vs. Minnesota
Wisconsin Department of Natural Resources, Wisconsin Lakes 2009
Actuality, Lakes of Minnesota and Wisconsin, August 25, 2010
University of Wisconsin-Eau Claire, The Spectator, Wisconsin vs. Minnesota - Lakes, March 4, 2010
Wisconsinology, Wisconsin... Land of 15,000 Lakes, February 2, 2008
New Hampshire Department of Environmental Services, Lake or Pond - What is the Difference?
World Health Organization, Water Quality Assessments, Chapter 7 - Lakes

No comments:

Post a Comment

If you're a spammer, there's no point posting a comment. It will automatically get filtered out or deleted. Comments from real people, however, are always very welcome!