Koochiching County Lake Quality
Minnesota, 4 lakes, average grade C (Fair)
Koochiching County has 4 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. Koochiching 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.
A meaningful share of Koochiching'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 Battle Lake (C).
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Quick Answers for Koochiching County
Planning a trip? Check special fishing regulations for Battle Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Minnesota regulations index.
Fishing in Koochiching County
DNR Reports (6)
Minnesota DNR LakeFinder resources for lakes in Koochiching County. browse all reports →
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — RainyFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — BartlettFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Bartlett (1966)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — BartlettFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — BartlettPublic Water Access Sites · MN DNR LakeFinder
- —Public Water Access Sites — RainyPublic Water Access Sites · MN DNR LakeFinder
All Lakes in Koochiching County
4 lakes · 3 graded, 1 not rated3 graded lakes · 1 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Max Depth | Access |
|---|---|---|---|---|---|---|---|---|
| 1 | CBattle LakeKoochiching | C | 6 ft | 29 µg/L | 4.1 µg/L | No recent samples | 8.5 ft | Carry-in |
| 2 | CBartlett LakeKoochiching | C | 4.5 ft | 31.5 µg/L | 12.4 µg/L | No recent samples | 16 ft | ✓ Public |
| 3 | CDark LakeKoochiching | C | 6.4 ft | 139.5 µg/L | 5.8 µg/L | No recent samples | 50 ft | ✓ Public |
| NRRainy LakeKoochiching | NR | 7.5 ft | No recent samples | No recent samples | No recent samples | 161 ft | ✓ Public |
NR = not rated: the monitoring record does not meet the evidence bar for a grade. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of graded lakes that fit, with the water quality behind each one.
Other Counties in Minnesota
See how Koochiching County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 39 states and 2 Canadian provinces.
Source: EPA National Aquatic Resource Surveys, 2026.