Deep Lake
Deep Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 17.2 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.5 µg/L. Maximum depth: 50 ft. Surface area: 73.13 acres.
- Clarity
- 17.2 ft
- Max depth
- 50 ft
- Area
- 73 acres
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in St. Louis County
Why Deep Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Deep Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity, phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Deep Lake is a 73-acre lake in St. Louis County, Minnesota with a maximum depth of 50 feet. Overall water quality is declining over recent sampling years. The lake supports 10 documented fish species including black crappie, bluegill, and hybrid sunfish. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-08-04. Grade methodology: LakeGrade methodology.
Watch Deep Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Deep Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 17.2 ft down. Phosphorus level: 12 µg/L. Chlorophyll-a: 2.5 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 17.2 ft | Not graded |
| Phosphorus | 12 µg/L | Not graded |
| Chlorophyll-a (Algae) | 2.5 µg/L | Not graded |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Deep Lake
Compare lakeside cabins, hotels, and vacation rentals near Deep Lake in St. Louis 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.
Top-rated places to stay near Deep 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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 50 ft |
| Surface Area | 73 acres |
| Shoreline Length | 1.7 mi |
| Littoral Zone | 45% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Ely LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Deep Lake
DNR Fisheries Survey Summary
7 surveys on file from MN DNR Fisheries. Most recent: 2023-07-24 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Largemouth Bass | 9.23 | 0.95 lb |
| Bluegill | 8.64 | 0.1 lb |
| Hybrid Sunfish | 3.29 | 0.18 lb |
| Yellow Perch | 2.89 | 0.11 lb |
| Northern Pike | 2.11 | 3.41 lb |
| Pumpkinseed | 2.00 | 0.16 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Largemouth Bass
Bluegill
Hybrid Sunfish
Yellow Perch
From the 2023-07-24 survey
Deep Lake is a 73-acre lake located two miles south of Gilbert. There is a public access with an earthen boat ramp located near the south end of the lake off CR 97. The access is relatively small, with limited space for parking or turning around. Deep Lake has relatively steep drop-offs, especially along the north…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Deep Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — DeepFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Deep (1763)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — DeepFish Stocking History · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.87 m/yr | 2 |
EPA Impairment Status
Deep 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 MN69-0666-00 · Official waterbody report
Graded lakes near Deep Lake
Deep Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis County
Frequently asked questions about Deep Lake
What is the water quality grade for Deep Lake?
- Deep Lake in St. Louis County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 17.2 ft visibility. Phosphorus: 12 µg/L. Chlorophyll-a (algae): 2.5 µg/L. Maximum depth: 50 ft. Surface area: 73.13 acres.
Is Deep Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Deep Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Algae concentration (chlorophyll-a) is 2.5 µg/L. Always check local health department advisories before swimming.
How deep is Deep Lake?
- Deep Lake has a maximum depth of 50 feet. The lake covers 73.13 acres.
What fish are in Deep Lake?
- Fish species found in Deep Lake include black crappie, bluegill, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, walleye, white sucker, yellow perch. Deep Lake is located in St. Louis County, Minnesota.
Are there boat ramps on Deep Lake?
- Deep Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Ely Lake. Public access is listed as yes.
Explore Deep Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in St. Louis County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Lake Vermilion Area area
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Lakes in the Rainy Lake Watershed, ranked by water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
Other Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Where this data comes from
5 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA5 samples · 2022
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- 2130 B ~ Nephelometric Method
- 2120 B ~ Color in Water by Visual Comparison
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