What is the cleanest lake in Cass County, Minnesota?

Rainy Lake in Cass County is the cleanest lake on the readings in Cass County, Minnesota with an EPA water-quality readings of — and 13.9 feet of water clarity.

How are these rankings calculated?

Nutrients and algae, total phosphorus, nitrogen, chlorophyll-a and turbidity, are read against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown; it is not the letter. Lakes without enough recent samples are UNRATED, not given an F. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in Cass County, Minnesota

Rainy Lake in Cass County leads the rankings on measured clarity and nutrients and 13.9 ft of clarity. Below are the top 50 cleanest monitored lakes in Cass County, Minnesota, ranked by EPA water quality score.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	Rainy Lake	Cass	—	13.9 ft	11.5 µg/L	1.8 µg/L
2	Deep Portage Lake	Cass	—	15.4 ft	9 µg/L	1.6 µg/L
3	Birch Lake	Cass	—	14 ft	12 µg/L	4 µg/L
4	Ada Lake	Cass	—	14 ft	10 µg/L	2.7 µg/L
5	Washburn Lake	Cass	—	14.1 ft	11 µg/L	3.7 µg/L
6	Long Lake	Cass	—	21.5 ft	9 µg/L	3 µg/L
7	Woman Lake	Cass	—	15 ft	11 µg/L	3.2 µg/L
8	Girl Lake	Cass	—	17.6 ft	12 µg/L	2.7 µg/L
9	Leech Lake	Cass	—	12.5 ft	12 µg/L	2.7 µg/L
10	Island Lake	Cass	—	17.5 ft	9 µg/L	2.7 µg/L
11	Island Lake	Cass	—	8.2 ft	20 µg/L	3.9 µg/L
12	Crooked Lake	Cass	—	12 ft	13 µg/L	4 µg/L
13	Portage Lake	Cass	—	7 ft	20 µg/L	5.9 µg/L
14	Upper Trelipe Lake	Cass	—	14 ft	12 µg/L	3.1 µg/L
15	Lawrence Lake	Cass	—	9.8 ft	17 µg/L	4.8 µg/L
16	Silver Lake	Cass	—	13 ft	14 µg/L	4.5 µg/L
17	Child Lake	Cass	—	12.1 ft	14 µg/L	3.7 µg/L
18	Baby Lake	Cass	—	12.5 ft	10 µg/L	2.9 µg/L
19	Inguadona Lake	Cass	—	12 ft	15 µg/L	4.5 µg/L
20	Pleasant Lake	Cass	—	15.5 ft	10 µg/L	3.1 µg/L
21	Roosevelt Lake	Cass	—	11.1 ft	12.5 µg/L	3.6 µg/L
22	Webb Lake	Cass	—	18 ft	9.5 µg/L	2.9 µg/L
23	Broadwater Bay Lake	Cass	—	14.4 ft	13.5 µg/L	3.6 µg/L
24	Blackwater Lake	Cass	—	14.1 ft	12 µg/L	4 µg/L
25	Man Lake	Cass	—	11 ft	10 µg/L	2.7 µg/L
26	Little Boy Lake	Cass	—	11 ft	14 µg/L	5.1 µg/L
27	Thunder Lake	Cass	—	16.5 ft	10 µg/L	2.4 µg/L
28	Little Portage Lake	Cass	—	16.4 ft	12 µg/L	2.7 µg/L
29	Pine Lake	Cass	—	16 ft	14 µg/L	3.2 µg/L
30	Ten Mile Lake	Cass	—	20.5 ft	8.5 µg/L	1.9 µg/L
31	Ponto Lake	Cass	—	19 ft	8 µg/L	2.1 µg/L
32	Wabedo Lake	Cass	—	10.5 ft	16 µg/L	4.9 µg/L
33	Little Sand Lake	Cass	—	7.5 ft	22.5 µg/L	5.6 µg/L
34	Loon Lake	Cass	—	12.1 ft	14 µg/L	3.5 µg/L
35	Sugar Lake	Cass	—	13.5 ft	18 µg/L	7 µg/L
36	Hattie Lake	Cass	—	10.3 ft	16.5 µg/L	4.5 µg/L
37	Lost Lake	Cass	—	14.8 ft	10.5 µg/L	2.3 µg/L
38	Boy Lake	Cass	—	10.5 ft	21 µg/L	6.3 µg/L
39	Stony Lake	Cass	—	23 ft	7 µg/L	2 µg/L
40	Steamboat Lake	Cass	—	12 ft	11 µg/L	3.4 µg/L
41	Leavitt Lake	Cass	—	7.9 ft	19 µg/L	5.3 µg/L
42	Barnum Lake	Cass	—	16.1 ft	9 µg/L	3 µg/L
43	Mule Lake	Cass	—	18 ft	10 µg/L	2.4 µg/L
44	Dade Lake	Cass	—	5.2 ft	12 µg/L	2 µg/L
45	Big Portage (W Bay Lake	Cass	—	8.5 ft	18.5 µg/L	5.6 µg/L
46	Cooper Lake	Cass	—	17.1 ft	13 µg/L	3.1 µg/L
47	Steamboat Bay Lake	Cass	—	9.8 ft	15 µg/L	3 µg/L
48	Mckeown Lake	Cass	—	16.1 ft	11 µg/L	2.7 µg/L
49	Kid Lake	Cass	—	15.5 ft	11.5 µg/L	3.3 µg/L
50	Boy Bay Lake	Cass	—	7.4 ft	13 µg/L	3.6 µg/L

Ranked List

More Answers for Cass County, Minnesota