Mattson Lake
Mattson Lake in Chisago County, Minnesota has a water quality grade of A (Excellent). Water clarity: 3.9 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 1 µg/L.
- Clarity
- 3.9 ft
- Typical in August
- 74°F
- Max depth
- ~35 ft est.
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- No
Next lake in Chisago County
Mattson Lake is a mesotrophic lake in Chisago County, Minnesota with an estimated average depth of about 35 feet. 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 29 other monitored lakes in Chisago County, Mattson Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-17. 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)
Murky, only visible to about 3.9 ft. Phosphorus level: 12 µg/L. Chlorophyll-a: 1 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 12 µg/L | Good |
| Chlorophyll-a (Algae) | 1 µg/L | Good |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Mattson Lake
Compare lakeside cabins, hotels, and vacation rentals near Mattson 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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Water Temperature
Mattson Lake typically sits around 74°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 79°F) and coldest in Oct (about 51°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 66 field readings (2017–2025) via the EPA Water Quality Portal. See the full Mattson Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~35 ft est. |
| Average Depth | ~9 ft est. |
| Public Access | No |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Mattson Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Fishing Mattson Lake
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.016 m/yr | 6 |
| Phosphorus | ↑ Improving | -14.27 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -8.81 µg/L/yr | 6 |
EPA Impairment Status
Mattson 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 MN13-0029-00 · Official waterbody report · Matched by proximity (1.6 km)
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Mattson Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Chisago Lakes Joint StcChisago City · 1.3 mi away · NPDES MN0055808MajorRecent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #9 of 30 lakes in Chisago County
Nearby Lakes in Chisago County
Frequently asked questions about Mattson Lake
What is the water quality grade for Mattson Lake?
- Mattson Lake in Chisago County, Minnesota has a water quality grade of A (Excellent). Water clarity: 3.9 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 1 µg/L.
Is Mattson Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Mattson Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 1 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Mattson Lake?
- Mattson Lake typically sits around 74°F at the surface in August, from 66 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Mattson Lake?
- No published bathymetric survey covers Mattson Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 35 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Mattson Lake across LakeGrade
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Where this data comes from
47 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA47 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder