Rock Lake
Wright County, MinnesotaLimited DataMesotrophic
Rock Lake earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade.
A TSI near 48 places Rock Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake bottoms out at 37 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 183 acres, Rock Lake fits the Minnesota median for monitored lakes, with 3.0 miles of shoreline. Among the 64 graded lakes in Wright County, Rock Lake sits at rank 25, above the county median.
Eurasian watermilfoil is established at Rock Lake, which can dampen recreational access and pressure the native plant community. Walleye are documented at Rock Lake, one of 15 fish species on record for the lake. A documented public access point at Rock Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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 2020-06-26. Grade methodology: LakeGrade methodology.
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Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Moderate clarity, visible to about 7.5 ft. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.5 ft | C |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 37 ft |
| Average Depth | 13.6 ft |
| Surface Area | 183.12 acres |
| Shoreline Length | 3 mi |
| Littoral Zone | 54% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for Rock Lake (14-day solunar calendar)
→ Is it safe to eat fish from Rock Lake? (mercury & PFAS guide)
→ Rock Lake fishing regulations (limits, seasons, special rules)
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Ice Season
Historical ice data from Minnesota DNR (8 observations).
Estimated open water season: 245 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2003-03-30 (2003) | 2002-04-15 (2002) |
| Ice-In | 2003-11-22 (2003) | 2001-12-08 (2001) |
Most recent ice-out: 2005-04-06
Location
County Ranking
Ranked #25 of 64 lakes in Wright County
Nearby Lakes in Wright County
More Minnesota Lake Rankings
State Parks Near Rock Lake
Other Grade C Lakes in Minnesota
Mesotrophic Lakes in Minnesota
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2025-08-11 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 101.97 | 0.2 lb |
| Green Sunfish | 34.91 | 0.19 lb |
| Largemouth Bass | 17.91 | 0.83 lb |
| GOS | 14.27 | 0.09 lb |
| Black Crappie | 12.61 | 0.35 lb |
| Yellow Bass | 7.97 | 0.75 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Bluegill
Green Sunfish
Largemouth Bass
GOS
From the 2025-08-11 survey
A targeted survey of nearshore fish species in Rock Lake, was conducted on August 11th, 2025, by Area Fisheries staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and seining with a 50-foot or 15-foot seine, where possible. Backpack electrofishing was completed at…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Rock Lake. 4 reports on file.
- —Fisheries Lake Survey — RockFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Rock (2017)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — RockFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — RockPublic Water Access Sites · MN DNR LakeFinder
EPA Impairment Status
Rock Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN86-0182-00 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate
Most recent sample: 2020-06-26
Monitoring stations: 1