Washington County Lake Quality
Minnesota, 31 lakes, average grade C (Fair)
Washington County's 31 graded lakes fall in the moderate-density bracket for Minnesota. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
A meaningful share of Washington's lakes break 50 feet of depth, which matters because deep lakes hold cooler water all summer and resist the resuspended-sediment problems that plague shallow basins. The county's best-graded lake is Square Lake (A).
Quick Answers for Washington County
Planning a trip? Check special fishing regulations for Square Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Minnesota regulations index.
DNR Reports (44)
Minnesota DNR LakeFinder resources for lakes in Washington County. Showing 12 most recent — browse all reports →
- —Fisheries Lake Survey — White BearFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — Big MarineFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — TannersFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — SquareFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — CloverdaleFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — LongFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — Little CarnelianFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — LilyFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — St. CroixFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — JaneFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — KeewahtinFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — ForestFisheries Lake Survey · MN DNR LakeFinder
All Lakes in Washington County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Square Lake | A | 17 ft | 68 ft | 8 µg/L |
| 2 | White Bear Lake | A | 15 ft | 83 ft | 15 µg/L |
| 3 | Big Carnelian Lake | A | 46.8 ft | 66 ft | - |
| 4 | Little Carnelian Lake | A | 21 ft | 68 ft | - |
| 5 | Jane Lake | A | 15 ft | 39 ft | - |
| 6 | Big Marine Lake | A | 11.5 ft | - | 14.5 µg/L |
| 7 | Big Carnelian Lake | B | 14.5 ft | 66 ft | - |
| 8 | Elmo Lake | B | 11.2 ft | 140 ft | - |
| 9 | Lake St. Croix | B | 5.2 ft | 78 ft | 18 µg/L |
| 10 | Long Lake | C | 8.5 ft | 25 ft | - |
| 11 | Battle Creek Lake | C | 7.4 ft | 15.3 ft | 49.5 µg/L |
| 12 | Mcdonald Lake | C | 5 ft | 28 ft | 21 µg/L |
| 13 | Legion Pond | C | 7 ft | - | - |
| 14 | Sunfish Lake | C | 8.5 ft | - | - |
| 15 | Forest Lake | C | 8 ft | 37 ft | - |
| 16 | Carver Lake | C | 8.5 ft | 36 ft | 31 µg/L |
| 17 | Tanners Lake | C | 6.6 ft | 46 ft | 28 µg/L |
| 18 | Lily Lake | C | 8.7 ft | 51 ft | - |
| 19 | St. Croix Lake | C | 8.7 ft | 78 ft | - |
| 20 | St. Croix 1.5 Mi. Upstream of Point Douglas Dr Lake | C | 9.4 ft | 78 ft | 30 µg/L |
| 21 | Clear Lake | C | 6.2 ft | 28 ft | 33 µg/L |
| 22 | Pool of Lake St. Croix | C | 4.3 ft | 78 ft | 39.2 µg/L |
| 23 | Pool on Lake St. Croix Downstream of I94 Bridge | C | 5 ft | 78 ft | 39.5 µg/L |
| 24 | Pool on Lake St. Croix | C | 5.9 ft | 78 ft | 32.9 µg/L |
| 25 | St. Croix 3.5 Mi. Downstream of E Chestnut St Lake | C | 5.9 ft | 78 ft | 38 µg/L |
| 26 | St. Croix 0.3 Mi. Downstream of I Lake | C | 6.1 ft | 78 ft | 34 µg/L |
| 27 | Unnamed Lake | D | 1.6 ft | 60 ft | 33 µg/L |
| 28 | Halfbreed Lake | D | 4.4 ft | 34 ft | - |
| 29 | Bone Lake | D | 5.5 ft | 30 ft | - |
| 30 | Oneka Lake | D | 4.4 ft | - | - |
| 31 | Grey Cloud Slough Lake | F | 3.3 ft | - | - |
Source: EPA National Aquatic Resource Surveys, 2026.