Little Rock Lake
Clearwater County, MinnesotaOligotrophic
On the LakeGrade rubric, Little Rock Lake pulls an A: clarity at 15.1 ft and 10 µg/L of phosphorus put it in the top bracket for Minnesota. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.
A TSI value of 37 puts Little Rock Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Within Clearwater County's 40 graded waters, Little Rock Lake sits at rank 7, near the top of the local distribution.
Little Rock Lake has no invasive species recorded in Minnesota state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Little Rock Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-04. Grade methodology: LakeGrade methodology.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 15.1 ft down. Phosphorus level: 9.5 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.1 ft | A |
| Phosphorus | 9.5 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Location
County Ranking
Ranked #7 of 40 lakes in Clearwater County
Nearby Lakes in Clearwater County
More Minnesota Lake Rankings
State Parks Near Little Rock Lake
Other Grade A Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-09-04
Monitoring stations: 2