Sylvan Lake
Cass County, Minnesota1,280 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Sylvan Lake. Here is what has been measured.
- Oligotrophic
- zebra mussel
- Public access
- Limited data
Sylvan Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 19.5 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Surface area: 1280 acres.
Free interactive depth-contour map of Sylvan Lake, reaching a maximum surveyed depth of 50 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Sylvan Lake is a 1,280-acre cold, clear oligotrophic lake in Cass County, Minnesota. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Sylvan Lake ranks #46 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-17. Methodology: how these readings are compared.
Sylvan Lake covers about 1,300 acres in Cass County. It has one public boat landing. Vrbo is where to look for cabins and lake homes around Sylvan Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Sylvan Lake is good for
From access and monitoring records, not editorial picks.
- Clear water19.5 ft of visibility
- Boat launch1 documented ramp
- Big water1,280 acres
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Sylvan Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Sylvan Lake
These are the measurements Minnesota PCA publishes for Sylvan Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 19.5 ft down. Phosphorus 7 µg/L. Chlorophyll-a 2.1 µg/L. TSI 35.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 19.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 7µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.1µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Sylvan Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Surface area
1,280 acres
Public access
Yes
Listed by Minnesota PCA
No bathymetric survey has been published for Sylvan Lake, so its depth is not documented here.
Recreation & Access
- Sylvan LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Sylvan Lake
Compare lakeside cabins, hotels, and vacation rentals near Sylvan 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.
Top-rated places to stay near Sylvan Lake
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Fishing Sylvan 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.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Reservoir Info (USACE NID)
Sylvan Lake is a man-made reservoir impounded by the Sylvan (completed 1913), built primarily for hydroelectric on the Crow Wing; gravity-type dam, 35 ft tall and 1,154 ft long.
- Surface area
- 1,280 ac
- Normal storage
- 9,216 ac-ft
- Drainage area
- 3,575 sq mi
- Hazard class
- High
- Owner
- Allete, Inc.
All listed purposes: Hydroelectric;Recreation.
Source: USACE National Inventory of Dams, NID ID MN00601 · Operator website
Nearby Lakes in Cass County
Frequently asked questions about Sylvan Lake
Where is Sylvan Lake?
- Sylvan Lake is a lake in Cass County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Sylvan Lake?
- Sylvan Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 19.5 ft visibility. Phosphorus: 7 µg/L. Chlorophyll-a (algae): 2.1 µg/L. Surface area: 1280 acres.
Is Sylvan Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Are there boat ramps on Sylvan Lake?
- Sylvan Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Sylvan Lake. Public access is listed as yes.
Can I fish at Sylvan Lake?
- Sylvan Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Sylvan Lake across LakeQuality
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Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
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Where this data comes from
71 measurements from 3 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
MNPCA71 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
Monitoring station identifiers (3)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory