Twin Lake
Isanti County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Twin Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 31 ft max depth
Twin Lake in Isanti County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 78 µg/L. Chlorophyll-a (algae): 16 µg/L.
Twin Lake is a productive, nutrient-rich eutrophic lake in Isanti County, Minnesota with an estimated average depth of about 31 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 16 other monitored lakes in Isanti County, Twin Lake ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. Methodology: how these readings are compared.
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Twin Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Twin 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 Twin Lake
These are the measurements Minnesota PCA publishes for Twin Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.5 ft of visibility. Phosphorus 78 µg/L. Chlorophyll-a 16 µg/L. TSI 63.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 78µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 16µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 63 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Twin Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Twin Lake typically sits around 66°F at the surface in September. Summer average is about 75°F. Usually warmest in Jun (about 76°F) and coldest in May (about 65°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (65°F) to its warmest (76°F).
Typical surface water temperature by month, from 69 field readings (2017–2025) via the EPA Water Quality Portal. See the full Twin Lake water temperature breakdown →
Lake Details
Max depth
~31 ft est.
Public access
No
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Twin Lake.
Lake Size & Watershed
Watershed (drainage) area
0 sq mi
HydroLAKES / HydroSHEDS
Surface area
49 acres
HydroLAKES / HydroSHEDS
Shoreline
1.5 mi
HydroLAKES / HydroSHEDS
Elevation
899 ft
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.
Stays via Stay22
Stays near Twin Lake
Compare lakeside cabins, hotels, and vacation rentals near Twin Lake in Isanti 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Twin Lake are listed below.
Top-rated places to stay near Twin Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Follow Twin Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Twin Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+2.56 µg/L/yr6 years
Chlorophyll-a
Worsening+0.4 µg/L/yr6 years
EPA Impairment Status
Twin Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Recreation.
Source: EPA ATTAINS assessment unit MN30-0004-00 · Official waterbody report
Nearby Lakes in Isanti County
Frequently asked questions about Twin Lake
Where is Twin Lake?
- Twin Lake is a lake in Isanti County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Twin Lake?
- Twin Lake in Isanti County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2.5 ft visibility. Phosphorus: 78 µg/L. Chlorophyll-a (algae): 16 µg/L.
Is Twin Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Twin Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Twin Lake?
- Twin Lake typically sits around 66°F at the surface in September, from 69 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
How deep is Twin Lake?
- No published bathymetric survey covers Twin Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 31 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Can I fish at Twin Lake?
- Public access to Twin 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 Twin Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Isanti County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Rum River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Twin Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
172 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA172 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder