Ann Lake
Ann Lake in Sherburne County, Minnesota has a water quality grade of A (Excellent). Water clarity: 11.5 ft visibility. Phosphorus: 15.5 µg/L. Chlorophyll-a (algae): 4.3 µg/L. Maximum depth: 26 ft. Surface area: 182.85 acres.
- Clarity
- 11.5 ft
- Max depth
- 26 ft
- Area
- 183 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Mar 24
Next lake in Sherburne County
Ann Lake is a 183-acre mesotrophic lake in Sherburne County, Minnesota with a maximum depth of 26 feet (8-foot average). Water quality is graded A based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 10 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 17 other monitored lakes in Sherburne County, Ann Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-11-14. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Good clarity, visible to about 11.5 ft. Phosphorus level: 15.5 µg/L. Chlorophyll-a: 4.3 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.5 ft | Not graded |
| Phosphorus | 15.5 µg/L | Good |
| Chlorophyll-a (Algae) | 4.3 µg/L | Good |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Ann Lake
Compare lakeside cabins, hotels, and vacation rentals near Ann Lake in Sherburne 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.
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Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 26 ft |
| Average Depth | 7.9 ft |
| Surface Area | 183 acres |
| Shoreline Length | 4.6 mi |
| Littoral Zone | 75% |
| 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
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
6 surveys on file from MN DNR Fisheries. Most recent: 2019-07-15 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 65.14 | 0.1 lb |
| Yellow Bass | 43.62 | 0.44 lb |
| Pumpkinseed | 7.20 | 0.16 lb |
| Northern Pike | 6.80 | 2.39 lb |
| Largemouth Bass | 5.72 | 1.65 lb |
| CNM | 2.45 | — |
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.
Bluegill
Yellow Bass
Pumpkinseed
Northern Pike
From the 2019-07-15 survey
Ann Lake is located in Sherburne County, five miles west of Zimmerman. The lake is 184 acres with a maximum depth of 26 feet. The watershed is small and is dominated by forest and the lake is lightly developed. The lake has excellent water quality and a diverse aquatic plant community. A public access is located on…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Ann Lake. 3 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 (1369)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — AnnPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.126 m/yr | 3 |
Ice Season
Historical ice data from Minnesota DNR (3 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-04 (2024) | 2022-04-11 (2022) |
Most recent ice-out: 2024-03-04
County Ranking
Ranked #6 of 18 lakes in Sherburne County
Nearby Lakes in Sherburne County
Frequently asked questions about Ann Lake
What is the water quality grade for Ann Lake?
- Ann Lake in Sherburne County, Minnesota has a water quality grade of A (Excellent). Water clarity: 11.5 ft visibility. Phosphorus: 15.5 µg/L. Chlorophyll-a (algae): 4.3 µg/L. Maximum depth: 26 ft. Surface area: 182.85 acres.
Is Ann Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Ann Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 4.3 µg/L. Always check local health department advisories before swimming.
How deep is Ann Lake?
- Ann Lake has a maximum depth of 26 feet and an average depth of 7.9 feet. The lake covers 182.85 acres.
What fish are in Ann Lake?
- Fish species found in Ann Lake include black bullhead, black crappie, bluegill, brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, yellow bullhead, yellow perch. Ann Lake is located in Sherburne County, Minnesota.
When does Ann Lake thaw?
- Ann Lake typically has ice-out around Mar 24.
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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Moderate nutrients, good water quality
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Where this data comes from
15 measurements from 1 monitoring station, 2021–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2021–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by 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
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