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D

Ann Lake

Kanabec County, MinnesotaEutrophic

Ann Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average. With clarity and phosphorus scored, the sub-grades cluster within a letter of each other, pointing to stable conditions rather than one specific stressor.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. The lake bottoms out at 17 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. Ann Lake covers 653 acres alongside 11.4 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Kanabec County's 7 graded lakes, Ann Lake ranks 5 — below the local median, though not at the bottom.

No invasive species are currently listed at Ann Lake — the lake remains off the Minnesota infested-waters roster. The fishery includes walleye among the lake's 13 documented species — a notable draw for Minnesota anglers. A documented public access point at Ann Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The lake has a long ice-out record — 65 observations on file, with a median ice-out around Apr 16. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-08-18. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Swimming not recommended, poor water quality with high algae risk

Water Quality Grade: D, Poor

Very murky, less than 2 ft of visibility. Phosphorus level: 78.5 µg/L. Trophic State Index: 67.

MetricValueGrade
Water Clarity (Secchi Depth)2 ftF
Phosphorus78.5 µg/LD
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)67Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

CharacteristicValue
Maximum Depth17 ft
Surface Area653.49 acres
Shoreline Length11.4 mi
Littoral Zone92%
Public AccessYes

Fish Species

black crappie,bluegill,bowfin (dogfish),channel catfish,hybrid sunfish,largemouth bass,northern pike,pumpkinseed,shorthead redhorse,walleye,white sucker,yellow bullhead,yellow perch

Click a species to see all Minnesota and Wisconsin lakes where it is found.

→ Best fishing times for Ann Lake (14-day solunar calendar)

→ Is it safe to eat fish from Ann Lake? (mercury & PFAS guide)

Ann Lake fishing regulations (limits, seasons, special rules)

Water Quality Trend: Declining

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.07 m/yr2
Phosphorus Declining+12.45 µg/L/yr5
See year-by-year chart →

Ice Season

Historical ice data from Minnesota DNR (83 observations).

Typical Ice-Out
Apr 16
Typical Ice-In
Nov 21

Estimated open water season: 219 days

EarliestLatest
Ice-Out2000-03-25 (2000)2013-05-16 (2013)
Ice-In2003-11-08 (2003)1999-12-15 (1999)

Most recent ice-out: 2019-04-22

Location

Loading map…

County Ranking

Ranked #5 of 7 lakes in Kanabec County

Cleaner Lakes Within 30 Miles

Ann Lake holds Grade D. 2 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Kanabec County

DNR Fisheries Survey Summary

10 surveys on file from MN DNR Fisheries. Most recent: 2021-06-21 (Targeted Survey).

Top Species by Catch Rate

SpeciesAvg CPUEAvg Weight
Yellow Perch10.810.14 lb
Largemouth Bass9.961.44 lb
BLH9.31
Bluegill6.660.3 lb
OTS6.302.02 lb
Black Crappie4.830.32 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

147 fish · 39 in · 2021-06-21
683403456789

Largemouth Bass

30 fish · 516 in · 2021-06-21
7405678910111213141516

Bluegill

101 fish · 39 in · 2021-06-21
37190trophy 103456789

Black Crappie

171 fish · 411 in · 2021-06-21
87440trophy 104567891011

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…

Source: MN DNR LakeFinder Fisheries Lake Survey

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ann Lake. 4 reports on file.

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

MercuryNutrients (phosphorus, nitrogen)

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN33-0040-00 · Official waterbody report

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Lake details from Minnesota DNR LakeFinder

Ice data from Minnesota DNR Climate

Most recent sample: 2024-08-18

Monitoring stations: 3