Polk County Lake Quality
Minnesota, 20 lakes, average grade C (Fair)
Polk County's 20 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. Polk County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Union Lake (A) is the cleanest in the county.
Quick Answers for Polk County
Planning a trip? Check special fishing regulations for Union Lake, and the best times to fish — or browse the full Minnesota regulations index.
DNR Reports (44)
Minnesota DNR LakeFinder resources for lakes in Polk County. Showing 12 most recent — browse all reports →
- —Fisheries Lake Survey — WhitefishFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — MoeFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — TurtleFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — StoreFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — SpringFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — SarahFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — Sand HillFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — PoplarFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — MapleFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — Hill RiverFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — CrossFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — CameronFisheries Lake Survey · MN DNR LakeFinder
All Lakes in Polk County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Union Lake | A | 14.5 ft | - | 14 µg/L |
| 2 | Cable Lake | B | 10.2 ft | 14 ft | 20 µg/L |
| 3 | Sand Hill Lake | B | 6.9 ft | 17 ft | 26 µg/L |
| 4 | Poplar Lake | B | 8.9 ft | 23 ft | 23 µg/L |
| 5 | Badger Lake | B | 6.7 ft | 19 ft | 27 µg/L |
| 6 | Sarah Lake | B | 7.9 ft | 27 ft | 29.5 µg/L |
| 7 | Kittleson Lake | B | 7.1 ft | - | 26 µg/L |
| 8 | Spring Lake | C | 4.9 ft | 35 ft | 27.5 µg/L |
| 9 | Whitefish Lake | C | 4.1 ft | 18 ft | 42.5 µg/L |
| 10 | Maple Lake | C | 3.4 ft | 14 ft | 38 µg/L |
| 11 | Turtle Lake | C | 3.6 ft | 12 ft | 56.5 µg/L |
| 12 | Uff Lake | C | 3.9 ft | - | 35 µg/L |
| 13 | Unnamed Lake | D | 2.6 ft | - | 52 µg/L |
| 14 | Unnamed Lake | D | 6.9 ft | 12 ft | 95 µg/L |
| 15 | Cross Lake | D | 3 ft | 19 ft | 57 µg/L |
| 16 | Store Lake | D | 6.9 ft | 19 ft | 193 µg/L |
| 17 | Halverson Lake | D | 3 ft | - | 51 µg/L |
| 18 | Hill River Lake | D | 4.6 ft | 60 ft | 95 µg/L |
| 19 | Oak Lake | F | 3 ft | - | 144 µg/L |
| 20 | Cameron Lake | F | 1 ft | 9 ft | 133 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.