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C

Rice Portage Lake

Carlton County, MinnesotaEutrophic

The LakeGrade rubric puts Rice Portage Lake at a C: clarity at 1.3 ft, 30 µg/L of phosphorus, and a TSI of 57 signal an intermediate trophic state. Secchi readings are the weakest of the scored parameters, suggesting suspended sediment or algal biomass dominates the optical signal.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. 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. Rice Portage Lake ranks 16 of 33 in Carlton County — solidly in the upper half of the local distribution.

Rice Portage 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 Rice Portage Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Public access is available — the lake is on the Minnesota PCA public-access list. Multiple sampling years from Minnesota PCA volunteers and partner agencies back the grade, so the letter should hold steady absent a major watershed shift.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-10-16. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Generally safe for swimming, moderate water quality

Water Quality Grade: C, Fair

Very murky, less than 1.3 ft of visibility. Phosphorus level: 29.5 µg/L. Chlorophyll-a: 4.9 µg/L. Trophic State Index: 57.

MetricValueGrade
Water Clarity (Secchi Depth)1.3 ftF
Phosphorus29.5 µg/LB
Chlorophyll-a (Algae)4.9 µg/LA
Trophic State Index (TSI)57Eutrophic

High nutrients, frequent algae, reduced clarity

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Improving+0.417 m/yr4
Phosphorus Improving-12 µg/L/yr2
Chlorophyll-a Declining+0.52 µg/L/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #16 of 33 lakes in Carlton County

Cleaner Lakes Within 30 Miles

Rice Portage Lake holds Grade C. 3 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Carlton County

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Rice Portage Lake. 1 report on file.

Reservoir Info (USACE NID)

Rice Portage Lake is a man-made reservoir impounded by the Rice Portage Lake, 8 ft tall.

Normal storage
1,400 ac-ft
Hazard class
Undetermined

Source: USACE National Inventory of Dams, NID ID MN00809 · Operator website

EPA Impairment Status

Rice Portage Lake is officially listed as impaired under Clean Water Act §303(d) in the 2019 EPA reporting cycle.

Causes of impairment

Mercury

Source: EPA ATTAINS assessment unit FDL_115 · 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

Most recent sample: 2024-10-16

Monitoring stations: 1