Question 1

Cleanest Lakes in Washington County, Minnesota?

Accepted Answer

Square Lake in Washington County leads the rankings with a water quality grade of A and 17 ft of clarity. Below are the top 16 cleanest monitored lakes in Washington County, Minnesota, ranked by EPA water quality score.

Question 2

What is the cleanest lake in Washington County, Minnesota?

Accepted Answer

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.

Question 3

How are these rankings calculated?

Accepted Answer

Lakes are graded A through F using the Metropolitan Council methodology, which combines Secchi depth (water clarity), total phosphorus, and chlorophyll-a (algae) into a single score. Source data comes from the EPA Water Quality Portal.

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Square Lake	Washington	A	17 ft	8 µg/L	-
2	White Bear Lake	Washington	A	15 ft	15 µg/L	-
3	Big Marine Lake	Washington	A	11.5 ft	14.5 µg/L	-
4	Lake St. Croix	Washington	B	5.2 ft	18 µg/L	-
5	Battle Creek Lake	Washington	C	7.4 ft	49.5 µg/L	-
6	Mcdonald Lake	Washington	C	5 ft	21 µg/L	-
7	Carver Lake	Washington	C	8.5 ft	31 µg/L	-
8	Tanners Lake	Washington	C	6.6 ft	28 µg/L	-
9	St. Croix 1.5 Mi. Upstream of Point Douglas Dr Lake	Washington	C	9.4 ft	30 µg/L	-
10	Clear Lake	Washington	C	6.2 ft	33 µg/L	-
11	Pool of Lake St. Croix	Washington	C	4.3 ft	39.2 µg/L	-
12	Pool on Lake St. Croix Downstream of I94 Bridge	Washington	C	5 ft	39.5 µg/L	-
13	Pool on Lake St. Croix	Washington	C	5.9 ft	32.9 µg/L	-
14	St. Croix 3.5 Mi. Downstream of E Chestnut St Lake	Washington	C	5.9 ft	38 µg/L	-
15	St. Croix 0.3 Mi. Downstream of I Lake	Washington	C	6.1 ft	34 µg/L	-
16	Unnamed Lake	Washington	D	1.6 ft	33 µg/L	-

Cleanest Lakes in Washington County, Minnesota

Ranked List

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