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What are the cleanest & clearest lakes in Minnesota? We analyzed ALL the data.

cleanest clearest lakes in minnesota

What are the cleanest lakes in Minnesota?

It’s not an easy question to answer…

To start, there’s over 10,000 lakes in our state!

And our state, more than just about any other, is known for it’s beautiful waterways. “The Land of Sky Blue Waters” as our overlord, Hamm’s Brewery, liked to call it.

So, which lakes in Minnesota are the best of the best? Which lakes are the clearest, cleanest, and most swimmable in the entire state?

We dug into the data so you don’t have to. Here are all the cleanest lakes in Minnesota.

The Cleanest Lakes near Minneapolis, according to the data

Let’s start with the Twin Cities metro area.

If we want to go straight to the authority on this subject, we should check out the Metropolitan Council’s Study of Water Quality.

Each year, the 16-member council completes a massive monitoring effort of hundreds of lakes around the Twin Cities Metro area. With the help of 122 citizen-volunteers, the group measures water temperatures, collects water samples, and measures water clarity.

Specifically, they collect data on:

  • Total phosphorus: a key nutrient measure
  • Total Kjeldahl nitrogen: a common lake pollutant, usually from storm runoff
  • Chlorophyll-a: a measure of algae abundance (too much algae robs the lake of oxygen and stifles aquatic life)
  • Water clarity: In case you ever want to impress your friends, is technically known as “secchi depth,” named after the measuring tool used – the secchi disk

The team sends these samples to St. Paul for analysis, and after getting results, the council assigns each of the lakes a grade. 

Just like school, an “A” is best and an “F” is… an F. They also assign an overall cleanliness grade.

The Results

The Metropolitan Council’s 2020 Study reviewed an impressive 178 lakes. It covered from Stillwater to Apple Valley, Waconia to Forest Lake, and in general, all over the Twin Cities metro.

Of the 178 Lakes:

  • 42% of lakes received an overall grade of “A” or “B”, meaning good water quality
  • 35% of lakes received an overall grade of “C”, for average water quality
  • 23% of lakes received an overall grade of “D” or “F”, meaning, well, ya know…

Okay, okay… but what about the cleanest of the clean?

Well, the study is more interested in overall water health, so we had to do some digging. We poured through the results, read the attachments, and analyzed the details. (So you don’t have to…)

What did we find?

The 16 Cleanest Lakes around the Twin Cities

Of those 42% of lakes that got a good water quality rating, only 16 of them received straight “A” ratings across the board. (Meaning A ratings for the best phosphorus, nitrogen, chlorophyll, and water clarity levels.)

They were:

  1. Bass Lake (East) (Grant, MN)
  2. Bass Lake (West) (Grant, MN)
  3. Big Carnelian Lake (north of Stillwater, MN)
  4. Big Marine Lake (north of Maple Island, MN)
  5. Bush Lake (Bloomington, MN)
  6. Edith Lake (Afton, MN)
  7. Lake Elmo (Lake Elmo, MN)
  8. Jane Lake (Lake Elmo, MN)
  9. Keewahtin Lake (Forest Lake, MN)
  10. Lac Lavon Lake (Burnsville, MN)
  11. Little Carnelian Lake (north of Stillwater, MN)
  12. Olson Lake (Lake Elmo)
  13. Riley Lake (Eden Prairie / Chanhassan, MN)
  14. Square Lake (north of Stillwater, MN)
  15. Sunfish Lake (Sunfish Lake, MN)
  16. Woodpile Lake (east of White Bear Lake, MN)

Map of the Cleanest Lakes near Minneapolis

What is the most clear lake near Minneapolis?

So those previous 16 are the clearest on a chemical level, but what about pure water clarity?

If you’re looking to drop an anchor and see it at the bottom of the lake, three lakes were clearer than all the others in the study:

  1. Little Carnelian Lake, just north of Stillwater, MN, was the clearest lake in the Twin Cities. It had an average water clarity of 18.7 feet, with a maximum clarity over 26 feet deep!
  2. Lake Riley, which straddles the border between Chanhassan and Eden Praire, was the second clearest lake. Lake Riley’s average water clarity was 18.4 feet, with a maximum clarity of over 20 feet deep.
  3. Big Carnelian Lake, located just a few feet away from Little Carnelian, was the third clearest lake in the Twin Cities. Big Carnelian’s average clarity with 16.4 feet deep, with a maximum clarity over 20 feet deep.

So congratulations to Little Carnelian Lake near Stillwater. The clearest lake in the entire Twin Cities!

What about the rest of Minnesota?

Well, it seems the best data for that exists in a University of Minnesota database

From what we can gather, their database uses satellite data to monitor water clarity for 10,000+ lakes in our state.

They present the data in map format, meaning directly sorting the information isn’t possible. But if you’re patient enough, you can click around to see water clarify levels for all the lakes.

…And we were crazy (or obsessed) enough to do just that.

The Clearest (and cleanest) Lakes in all of Minnesota

Which lakes stood out in our search for the clearest water in all of Minnesota?

In order of depth of water clarity:

9. Knife Lake (Ely, MN) – 5.1 meters

8. Mountain (Boundary Waters) – 5.8 meters

7. Big Sand (Hubbard, MN) – 5.5 meters

6. East Twin (Nisswa, MN) – 5.5 meters

5. Eleventh Crow Wing (Hubbard, MN) – 5.7 meters

4. Ossawinnamakee (Ideal Corners, MN) – 6.1 meters

3. Deer Lake (Grand Rapids, MN) – 6.3 meters

2. Big Bass (Hubbard, MN) – 6.8 meters

Drumroll  please…

1. Trout Lake (Grand Rapids, MN) – 9.7 meters

With 31.8 feet of visibility, Trout Lake in Grand Rapids is the clearest, cleanest lake in all of Minnesota!

At least according to our haphazard analysis of the University of Minnesota’s satellite imagery data.

Surprised?

What about the cleanest BIG lake in Minnesota?

It’s worth noting that most of the above lakes are pretty small.

Cross referencing the University of Minnesota’s lake clarity levels database to our list of the biggest lakes in Minnesota, and we can find some interesting trends…

The first is that most of the big lakes aren’t all that clear. At least compared to the others on this list. This makes sense, considering many of the big lakes are also more trafficked.

Consider Lake Pepin. According to the data, it’s the least clear of the 15 largest lakes in the state, with an average visibility of just 0.51 meters. (Less than 2 feet.) Pepin also sits on the Mississippi River, meaning all that big shipping traffic tends to stir it up.

In any case, two big lakes stood out for their clarity levels:

2. Saganaga Lake – 3.31 meters

Located in Minnesota’s boundary waters, Saganaga is Minnesota’s 12th largest lake.

It’s also the state’s second clearest lake, with an impressive visible depth of nearly 11 feet!

1. Namakan Lake – 3.36 meters

Is it any surprise that a lake in Voyageurs National Park is one of our state’s cleanest?

Namakan Lake sits on the United States / Canadian border. It covers 24,000 acres, which is enough to make it the 10th largest lake in Minnesota.

But Namakan also has 11.02 feet of visibility, officially making it the clearest (big) lake in Minnesota!

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