Little Portage Lake
Little Portage Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 16.4 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
- Clarity
- 16.4 ft
- Type
- Oligotrophic
- Trend
- ↑ Improving
- Public access
- No
- Ice-out
- Apr 12
Next lake in Cass County
Little Portage Lake is a cold, clear oligotrophic lake in Cass County, Minnesota. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 103 other monitored lakes in Cass County, Little Portage Lake ranks #38 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Crystal clear, you can see 16.4 ft down. Phosphorus level: 12 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16.4 ft | Not graded |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | 2.7 µg/L | Good |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Little Portage Lake
Compare lakeside cabins, hotels, and vacation rentals near Little Portage Lake in Cass County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
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Fishing Little Portage Lake
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Little Portage Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Aquatic Plant Report — Little Portage (1610)Aquatic Plant Report · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.113 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.96 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.08 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (5 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2006-04-11 (2006) | 2022-05-06 (2022) |
Most recent ice-out: 2022-05-06
EPA Impairment Status
Little Portage Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN11-0308-02 · Official waterbody report · Matched by proximity (2.44 km)
County Ranking
Ranked #38 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Little Portage Lake
What is the water quality grade for Little Portage Lake?
- Little Portage Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 16.4 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
Is Little Portage Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Little Portage Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2.7 µg/L. Always check local health department advisories before swimming.
When does Little Portage Lake thaw?
- Little Portage Lake typically has ice-out around Apr 12.
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Where this data comes from
69 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA69 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Ice data from Minnesota DNR Climate