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LakeQuality
F

Emily Lake

Chisago County, MinnesotaEutrophic

Emily Lake grades an F: water clarity, phosphorus, and chlorophyll-a all rate poorly, placing it among the most stressed lakes monitored in Minnesota. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. 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 the 31 graded lakes of Chisago County, Emily Lake sits at rank 28, near the bottom of the county list.

Emily Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Emily Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. The grade is supported by multiple sampling years from Minnesota PCA volunteers and partner agencies, giving the letter a reasonably stable foundation.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-09. 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 1.6 ft of visibility. Phosphorus level: 155 µg/L. Chlorophyll-a: 22.5 µg/L. Trophic State Index: 69.

MetricValueGrade
Water Clarity (Secchi Depth)1.6 ftF
Phosphorus155 µg/LF
Chlorophyll-a (Algae)22.5 µg/LD
Trophic State Index (TSI)69Eutrophic

High nutrients, frequent algae, reduced clarity

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Improving+0.177 m/yr5
Phosphorus Improving-4.15 µg/L/yr5
Chlorophyll-a Improving-7.5 µg/L/yr3

Location

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County Ranking

Ranked #28 of 31 lakes in Chisago County

Nearby Lakes in Chisago County

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2024-09-09

Monitoring stations: 1