Fourth Lake
Chisago County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Fourth Lake. Here is what has been measured.
- Limited data
Fourth Lake in Chisago County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Phosphorus: 120 µg/L. Chlorophyll-a (algae): 51.7 µg/L.
Fourth Lake is a lake in Chisago County, Minnesota. Overall water quality is improving over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2020-09-16. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Fourth Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Fourth Lake
These are the measurements Minnesota PCA publishes for Fourth Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 120 µg/L. Chlorophyll-a 51.7 µg/L. TSI 71.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 120µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 51.7µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 71 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Fourth Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Fourth Lake typically sits around 47°F at the surface in October. Summer average is about 73°F. Usually warmest in Aug (about 75°F) and coldest in Oct (about 47°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (47°F) to its warmest (75°F).
Typical surface water temperature by month, from 76 field readings (2019–2019) via the EPA Water Quality Portal. See the full Fourth Lake water temperature breakdown →
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Stays near Fourth Lake
Compare lakeside cabins, hotels, and vacation rentals near Fourth Lake in Chisago 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 Fourth Lake
Water quality readings over time
2 seasons of samples on record (2020–2024). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Phosphorus
Improving-13.75 µg/L/yr2 years
Chlorophyll-a
Improving-10.18 µg/L/yr2 years
Nearby Lakes in Chisago County
Frequently asked questions about Fourth Lake
Where is Fourth Lake?
- Fourth Lake is a lake in Chisago County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Fourth Lake?
- Fourth Lake in Chisago County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Phosphorus: 120 µg/L. Chlorophyll-a (algae): 51.7 µg/L.
Is Fourth Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Fourth Lake?
- Fourth Lake typically sits around 47°F at the surface in October, from 76 EPA Water Quality Portal field readings (2019–2019). That is a typical value for the month, not a live reading.
Can I fish at Fourth Lake?
- Public access to Fourth Lake is listed as no on the lake record, so confirm before you make the trip. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Fourth Lake across LakeQuality
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Where this data comes from
2 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA2 samples · 2020
Analytical methods
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.