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LakeQuality
F

Jonathan Lake

Carver County, MinnesotaHypereutrophic

On the LakeGrade rubric Jonathan Lake fails the cutoffs — a TSI of 74 and persistent algal pressure put it in the bottom tier. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI above 70 puts Jonathan Lake in hypereutrophic territory: visible blooms are common, and clarity rarely climbs even in early summer. 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 Carver County's 40 graded lakes, Jonathan Lake ranks 26 — below the local median, though not at the bottom.

Jonathan Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The fishery is panfish-dominated — bluegill, crappie, and sunfish among the 3 species documented for the lake. No formal public access is documented at Jonathan Lake — most use is by shoreline residents and their guests. 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 2024-10-23. Grade methodology: LakeGrade methodology.

Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

Water Quality Grade: F, Very Poor

Very murky, less than 1.5 ft of visibility. Phosphorus level: 157.5 µg/L. Trophic State Index: 74.

MetricValueGrade
Water Clarity (Secchi Depth)1.5 ftF
Phosphorus157.5 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)74Hypereutrophic

Very high nutrients, dense algae, poor clarity

Fish Species

Click a species to see all Minnesota and Wisconsin lakes where it is found.

→ Best fishing times for Jonathan Lake (14-day solunar calendar)

→ Is it safe to eat fish from Jonathan Lake? (mercury & PFAS guide)

Jonathan Lake fishing regulations (limits, seasons, special rules)

Water Quality Trend: Stable

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Improving+0.016 m/yr5
Phosphorus Declining+3.95 µg/L/yr5

Location

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County Ranking

Ranked #26 of 40 lakes in Carver County

Nearby Lakes in Carver County

Hypereutrophic Lakes in Minnesota

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2024-10-23

Monitoring stations: 1