Forest Lake
Hennepin County, Minnesota90 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Forest Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 2 aquatic invasives
- 42 ft max depth
- Public access
Forest Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.7 ft visibility. Phosphorus: 48.5 µg/L. Chlorophyll-a (algae): 23.7 µg/L. Maximum depth: 42 ft. Surface area: 90.1 acres.
Minnesota DNR's Standard Survey on July 1, 1977 caught 4.00 northern pike per gill net at Forest Lake. DNR survey details →
Forest Lake is a 90-acre productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota with a maximum depth of 42 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available. Compared to the 80 other monitored lakes in Hennepin County, Forest Lake ranks #49 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Methodology: how these readings are compared.
What Forest Lake is good for
From access and monitoring records, not editorial picks.
- Deep water42 ft surveyed max depth
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. Forest Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Forest 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 Forest Lake
These are the measurements Minnesota PCA publishes for Forest Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 3.7 ft. Phosphorus 48.5 µg/L. Chlorophyll-a 23.7 µg/L. TSI 60.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 48.5µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 23.7µg/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. | 60 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Forest Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Forest Lake typically sits around 55°F at the surface in October. Summer average is about 62°F. Usually warmest in Aug (about 64°F) and coldest in Apr (about 44°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (44°F) to its warmest (64°F).
Typical surface water temperature by month, from 575 field readings (2010–2025) via the EPA Water Quality Portal. See the full Forest Lake water temperature breakdown →
Minnesota DNR's Standard Survey on July 1, 1977 caught 4.00 northern pike per gill net at Forest Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Forest Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1977-07-01 (Standard Survey).
1 survey on file · most recent 1977-07-01 (Standard Survey)
49 years old| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 84.50 | 0.25 lb | |
| Black Bullhead | 17.00 | 0.6 lb | |
| Black Crappie | 11.50 | 0.22 lb | |
| White Crappie | 5.50 | 0.2 lb | |
| Pumpkinseed | 3.00 | 0.14 lb | |
| Hybrid Sunfish | 2.75 | 0.12 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
From the 1977-07-01 survey
See report for all Northern and Western Bays and Appendix XVII.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Forest Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ForestFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
42 ft
Surface area
90 acres
Shoreline
2.7 mi
Littoral zone
54%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
17 sq mi
HydroLAKES / HydroSHEDS
Elevation
915 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Forest Lake
Compare lakeside cabins, hotels, and vacation rentals near Forest Lake in Hennepin 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 Forest Lake are listed below.
Top-rated places to stay near Forest 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 Forest Lake’s readings
Email me when new measurements post for this lake. Updates stay free.
Or email
Fishing Forest Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Improving-5.56 µg/L/yr6 years
Chlorophyll-a
Worsening+3.78 µg/L/yr6 years
EPA Impairment Status
Forest Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN27-0139-00 · Official waterbody report
Nearby Lakes in Hennepin County
Frequently asked questions about Forest Lake
Where is Forest Lake?
- Forest Lake is a lake in Hennepin County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Forest Lake?
- Forest Lake in Hennepin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.7 ft visibility. Phosphorus: 48.5 µg/L. Chlorophyll-a (algae): 23.7 µg/L. Maximum depth: 42 ft. Surface area: 90.1 acres.
Is Forest Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Forest Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Forest Lake?
- Forest Lake typically sits around 55°F at the surface in October, from 575 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Forest Lake?
- Forest Lake has a maximum depth of 42 feet. The lake covers 90.1 acres.
What did the DNR fisheries survey find at Forest Lake?
- Minnesota DNR's Standard Survey on July 1, 1977 caught 4.00 northern pike per gill net at Forest Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Forest Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Forest Lake?
- Public access to Forest Lake is listed as yes on the lake record. 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 Forest Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Hennepin County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Crow River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
More lakes in Minnesota
State Parks Near Forest Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
103 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
MNPCA103 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- 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.
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