Stony Lake
Stony Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 23 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 2 µg/L. Maximum depth: 50 ft. Surface area: 563.21 acres.
- Clarity
- 23 ft
- Typical in August
- 72°F
- Max depth
- 50 ft
- Area
- 563 acres
- Type
- Oligotrophic
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 22
- Open water
- 220 days
Next lake in Cass County
Stony Lake is a 563-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 50 feet. Water quality is graded A based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 12 documented fish species including black crappie, bluegill, and hybrid sunfish. Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Stony Lake ranks #52 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-29. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLow algae
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)
Crystal clear, you can see 23 ft down. Phosphorus level: 7 µg/L. Chlorophyll-a: 2 µg/L. Trophic State Index: 34.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 23 ft | Not graded |
| Phosphorus | 7 µg/L | Good |
| Chlorophyll-a (Algae) | 2 µg/L | Good |
| Trophic State Index (TSI) | 34 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Stony Lake
Compare lakeside cabins, hotels, and vacation rentals near Stony Lake in Cass 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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Water Temperature
Stony Lake typically sits around 72°F at the surface in August. Summer average is about 72°F. Usually warmest in Jul (about 76°F) and coldest in Jun (about 68°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 37 field readings (2010–2024) via the EPA Water Quality Portal. See the full Stony Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 50 ft |
| Surface Area | 563 acres |
| Shoreline Length | 6.6 mi |
| Littoral Zone | 32% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Stony LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Stony Lake
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2023-06-05 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 27.26 | 0.11 lb |
| Yellow Perch | 9.59 | 0.21 lb |
| Rock Bass | 8.07 | 0.41 lb |
| Largemouth Bass | 7.79 | 0.94 lb |
| Northern Pike | 6.55 | 1.54 lb |
| Smallmouth Bass | 6.36 | 1.53 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.
Bluegill
Yellow Perch
Rock Bass
Largemouth Bass
From the 2023-06-05 survey
Stony Lake is a 563-acre lake with 6.58 miles of shoreline and a maximum depth of 50 feet located east of Hackensack, MN. A Minnesota Department of Natural Resources (MNDNR) owned public access is located on the south shore. The DNR has classified Minnesota's lakes into 43 different classes based on physical,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Stony Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — StonyFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Stony (1481)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — StonyFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — StonyPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.029 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.17 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.17 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (79 observations).
Estimated open water season: 220 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-04-03 (2024) | 2008-05-09 (2008) |
| Ice-In | 1991-11-07 (1991) | 2001-12-20 (2001) |
Most recent ice-out: 2024-04-03
EPA Impairment Status
Stony 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 MN11-0371-00 · Official waterbody report
County Ranking
Ranked #52 of 104 lakes in Cass County
Nearby Lakes in Cass County
Frequently asked questions about Stony Lake
What is the water quality grade for Stony Lake?
- Stony Lake in Cass County, Minnesota has a water quality grade of A (Excellent). Water clarity: 23 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 2 µg/L. Maximum depth: 50 ft. Surface area: 563.21 acres.
Is Stony Lake safe to swim in?
- Excellent for swimming, crystal clear water with minimal algae. Stony Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 2 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Stony Lake?
- Stony Lake typically sits around 72°F at the surface in August, from 37 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Stony Lake?
- Stony Lake has a maximum depth of 50 feet. The lake covers 563.21 acres.
What fish are in Stony Lake?
- Fish species found in Stony Lake include black crappie, bluegill, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow bullhead, yellow perch. Stony Lake is located in Cass County, Minnesota.
When does Stony Lake thaw?
- Stony Lake typically has ice-out around Apr 22. Ice typically forms around Nov 28. The open water season is approximately 220 days.
Are there boat ramps on Stony Lake?
- Stony Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Stony Lake. Public access is listed as yes.
Explore Stony Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
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Where to stay at Minnesota's top lakes, each with its grade
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Low nutrients, clear water, excellent for swimming
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More Minnesota Lake Rankings
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Where this data comes from
92 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
MNPCA92 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
Ice data from Minnesota DNR Climate