What is the cleanest lake in Washington County, Minnesota?

Square Lake in Washington County is the highest-rated lake in Washington County, Minnesota with an EPA water quality grade of A and 17 feet of water clarity.

How are these rankings calculated?

Lakes are graded A through F on nutrients and algae — total phosphorus, nitrogen, chlorophyll-a, and turbidity — 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 Washington County, Minnesota

Square Lake in Washington County leads the rankings with a water quality grade of A and 17 ft of clarity. Below are the top 43 cleanest monitored lakes in Washington County, Minnesota, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Square Lake	Washington	A	17 ft	9 µg/L	2.9 µg/L
2	Big Marine Lake	Washington	A	12 ft	13 µg/L	4.6 µg/L
3	White Bear Lake	Washington	A	14.4 ft	15 µg/L	2.7 µg/L
4	Pool	Washington	B	5.9 ft	31.1 µg/L	-
5	Clear Lake	Washington	C	6.2 ft	33 µg/L	6.9 µg/L
6	Pool of Lake St Croix	Washington	C	4.3 ft	39.2 µg/L	-
7	Tanners Lake	Washington	C	6.6 ft	30 µg/L	13.1 µg/L
8	Unnamed Lake	Washington	D	3 ft	77 µg/L	28.5 µg/L
9	Battle Creek Lake	Washington	D	7.2 ft	52 µg/L	9.7 µg/L
10	Carver Lake	Washington	D	7.4 ft	43 µg/L	12.2 µg/L
11	Mooers Lake	Washington	NR	-	-	-
12	Baldwin Lake	Washington	NR	-	-	-
13	Conley Lake	Washington	NR	-	-	-
14	Sea Lake	Washington	NR	-	-	-
15	Clear Lake	Washington	NR	-	-	-
16	Long Lake	Washington	NR	-	-	-
17	Lake Alice	Washington	NR	-	-	-
18	Long Lake	Washington	NR	-	-	-
19	Mud Lake	Washington	NR	-	-	-
20	Barker Lake	Washington	NR	-	-	-
21	Maple Marsh Lake	Washington	NR	-	-	-
22	Turtle Lake	Washington	NR	-	-	-
23	Bass Lake	Washington	NR	-	-	-
24	Goggins Lake	Washington	NR	-	-	-
25	Lynch Lake	Washington	NR	-	-	-
26	Long Lake	Washington	NR	-	-	-
27	Round Lake	Washington	NR	-	-	-
28	Mann Lake	Washington	NR	-	-	-
29	Louise Lake	Washington	NR	-	-	-
30	Silver Lake	Washington	NR	-	-	-
31	Loon Lake	Washington	NR	-	-	-
32	Bailey Lake	Washington	NR	-	-	-
33	Goose Lake	Washington	NR	-	-	-
34	Clear Lake	Washington	NR	-	-	-
35	McDonald Lake	Washington	NR	-	-	-
36	Twin Lakes	Washington	NR	-	-	-
37	Long Lake	Washington	NR	-	-	-
38	Long Lake	Washington	NR	-	-	-
39	Long Lake	Washington	NR	-	-	-
40	Egg Lake	Washington	NR	-	-	-
41	Rice Lake	Washington	NR	-	-	-
42	Horseshoe Lake	Washington	NR	-	-	-
43	Mud Lake	Washington	NR	-	-	-

Ranked List

More Answers for Washington County, Minnesota