Forest Lake
Forest Lake in Hennepin County, Minnesota has a water quality grade of D (Nutrient-rich). 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.
- Clarity
- 3.7 ft
- Typical in August
- 64°F
- Max depth
- 42 ft
- Area
- 90 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Forest Lake →
Next lake in Hennepin County
Forest Lake is a 90-acre productive, nutrient-rich eutrophic lake in Hennepin County, Minnesota with a maximum depth of 42 feet. Water quality is graded D based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyAlgae risk
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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 3.7 ft. Phosphorus level: 48.5 µg/L. Chlorophyll-a: 23.7 µg/L. Trophic State Index: 60.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.7 ft | Not graded |
| Phosphorus | 48.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 23.7 µg/L | Poor |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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 grade measures nutrients and algae, not lodging — cabins and rentals around Forest Lake are listed below.
Top-rated places to stay near Forest Lake
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 →
Water Temperature
Forest Lake typically sits around 64°F at the surface in August. 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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 42 ft |
| Surface Area | 90 acres |
| Shoreline Length | 2.7 mi |
| Littoral Zone | 54% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Lake Minnetonka, North ArmPublic
- Lake Minnetonka, Maxwell BayPublic
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.
DNR Fisheries Survey Summary
1 survey on file from MN DNR Fisheries. Most recent: 1977-07-01 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | 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, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.036 m/yr | 6 |
| Phosphorus | ↑ Improving | -5.56 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +3.78 µg/L/yr | 6 |
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN27-0139-00 · Official waterbody report
County Ranking
Ranked #49 of 81 lakes in Hennepin County
Nearby Lakes With Higher Grades
Forest Lake holds Grade D. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Hennepin County
Frequently asked questions about Forest Lake
What is the water quality grade for Forest Lake?
- Forest Lake in Hennepin County, Minnesota has a water quality grade of D (Nutrient-rich). 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?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Forest Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 23.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Forest Lake?
- Forest Lake typically sits around 64°F at the surface in August, 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.
Are there boat ramps on Forest Lake?
- Forest Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Lake Minnetonka, North Arm, Lake Minnetonka, Maxwell Bay. Public access is listed as yes.
Explore Forest Lake across LakeGrade
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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)
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory