Ann Lake
Ann Lake in Kanabec County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2 ft visibility. Phosphorus: 73.5 µg/L. Chlorophyll-a (algae): 57 µg/L. Maximum depth: 17 ft. Surface area: 653.49 acres.
- Clarity
- 2 ft
- Typical in August
- 75°F
- Max depth
- 17 ft
- Area
- 653 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 16
- Open water
- 219 days
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Ann Lake →
Next lake in Kanabec County
Ann Lake is a 653-acre productive, nutrient-rich eutrophic lake in Kanabec County, Minnesota with a maximum depth of 17 feet. Water quality is graded F based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Kanabec County, Ann Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-27. 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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 2 ft of visibility. Phosphorus level: 73.5 µg/L. Chlorophyll-a: 57 µg/L. Trophic State Index: 68.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2 ft | Not graded |
| Phosphorus | 73.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 57 µg/L | Poor |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Ann Lake
Compare lakeside cabins, hotels, and vacation rentals near Ann Lake in Kanabec 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 Ann Lake are listed below.
Top-rated places to stay near Ann Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Ann Lake typically sits around 75°F at the surface in August. Summer average is about 74°F. Usually warmest in Jul (about 75°F) and coldest in May (about 60°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 63 field readings (2018–2025) via the EPA Water Quality Portal. See the full Ann Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Ann Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (816,582 cells/mL) on July 9, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 17 ft |
| Surface Area | 653 acres |
| Shoreline Length | 11.4 mi |
| Littoral Zone | 92% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Ann LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Ann Lake
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2021-06-21 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 10.81 | 0.14 lb |
| Largemouth Bass | 9.96 | 1.44 lb |
| BLH | 9.31 | — |
| Bluegill | 6.66 | 0.3 lb |
| OTS | 6.30 | 2.02 lb |
| Black Crappie | 4.83 | 0.32 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.
Yellow Perch
Largemouth Bass
Bluegill
Black Crappie
From the 2021-06-21 survey
Ann Lake is a 653-acre lake located in Kanabec County managed primarily for Walleye and Northern Pike. The water level is maintained by a DNR dam on the north end of the lake. Lakeshore development is relatively light due largely to the wildlife management area on the southeast and northeast shores. Shallow water…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ann Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — AnnFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Ann (0289)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — AnnFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — AnnPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.059 m/yr | 3 |
| Phosphorus | ↓ Declining | +3.31 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +5.25 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (83 observations).
Estimated open water season: 219 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2000-03-25 (2000) | 2013-05-16 (2013) |
| Ice-In | 2003-11-08 (2003) | 1999-12-15 (1999) |
Most recent ice-out: 2019-04-22
Reservoir Info (USACE NID)
Ann Lake is a man-made reservoir impounded by the Ann Lake (completed 1966), built primarily for fish and wildlife pond on the Ann River; other-type dam, 25 ft tall and 135 ft long.
- Surface area
- 363 ac
- Normal storage
- 3,269 ac-ft
- Max storage
- 3,670 ac-ft
- Drainage area
- 56 sq mi
- Hazard class
- Low
- Owner
- MNDNR-Wildlife
Source: USACE National Inventory of Dams, NID ID MN00401 · Operator website
EPA Impairment Status
Ann 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 MN33-0040-00 · Official waterbody report
County Ranking
Ranked #1 of 2 lakes in Kanabec County
Nearby Lakes With Higher Grades
Ann Lake holds Grade F. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Kanabec County
Frequently asked questions about Ann Lake
What is the water quality grade for Ann Lake?
- Ann Lake in Kanabec County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2 ft visibility. Phosphorus: 73.5 µg/L. Chlorophyll-a (algae): 57 µg/L. Maximum depth: 17 ft. Surface area: 653.49 acres.
Is Ann Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Ann Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 57 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Ann Lake?
- Ann Lake typically sits around 75°F at the surface in August, from 63 EPA Water Quality Portal field readings (2018–2025). That is a typical value for the month, not a live reading.
How deep is Ann Lake?
- Ann Lake has a maximum depth of 17 feet. The lake covers 653.49 acres.
What fish are in Ann Lake?
- Fish species found in Ann Lake include black crappie, bluegill, bowfin (dogfish), channel catfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, shorthead redhorse, walleye, white sucker, yellow bullhead, yellow perch. Ann Lake is located in Kanabec County, Minnesota.
When does Ann Lake thaw?
- Ann Lake typically has ice-out around Apr 16. Ice typically forms around Nov 21. The open water season is approximately 219 days.
Does Ann Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Ann Lake (clouds, ice, or an off-season gap). The most recent reading was high (816,582 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Ann Lake?
- Ann Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Ann Lake. Public access is listed as yes.
Explore Ann Lake across LakeGrade
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Where this data comes from
95 measurements from 4 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
MNPCA95 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 (4)
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
Ice data from Minnesota DNR Climate