Rock River Lake
Rock County, WisconsinLimited DataOligotrophic
Rock River Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. 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 16 puts Rock River 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. Rock River Lake ranks 1 of 4 in Rock County, putting it in the upper tier of locally monitored lakes.
No invasive species are currently listed at Rock River Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Rock River 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, Wisconsin DNR Surface Water, last sampled 2021-07-06. 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 68.9 ft down. Trophic State Index: 16.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 68.9 ft | A |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 16 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Location
County Ranking
Ranked #1 of 4 lakes in Rock County
Nearby Lakes in Rock County
More Wisconsin Lake Rankings
State Parks Near Rock River Lake
Other Grade A Lakes in Wisconsin
Waukesha County · Clarity: 14.6 ft
Waukesha County · Clarity: 13.8 ft
Walworth County · Clarity: 19 ft
Washington County · Clarity: 12 ft
Kenosha County · Clarity: 10.1 ft
Washington County · Clarity: 12.5 ft
Oligotrophic Lakes in Wisconsin
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Rock River Lake covering fish populations, stocking, water quality, and management. 1 report on file.
- 2025Rock River fall shocking survey, 2025Fisheries Survey · WI DNR · 2025 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Fish and recreation data from Wisconsin DNR Lakes
Most recent sample: 2021-07-06
Monitoring stations: 1