Knife Lake
Kanabec County, Minnesota1,259 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Knife Lake. Here is what has been measured.
- Hypereutrophic
- Impaired · Mercury
- Eurasian watermilfoil
- 15 ft max depth
- Public access
Knife Lake in Kanabec County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 161.5 µg/L. Chlorophyll-a (algae): 97.2 µg/L. Maximum depth: 15 ft. Surface area: 1259.24 acres.
Minnesota DNR's Targeted Survey on August 25, 2025 caught 1.16 northern pike per hour of electrofishing at Knife Lake. DNR survey details →
Free interactive depth-contour map of Knife Lake, reaching a maximum surveyed depth of 15 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Minnesota DNR.
Knife Lake is a 1,259-acre highly nutrient-loaded hypereutrophic lake in Kanabec County, Minnesota with a maximum depth of 15 feet (9-foot average). Overall water quality is declining over recent sampling years. The lake supports 19 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 1 other monitored lakes in Kanabec County, Knife Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. Methodology: how these readings are compared.
Knife Lake covers about 1,300 acres in Kanabec County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. The median ice-out date is April 12, which is when the open-water season begins. For a place on the water, look through cabin and lake-house rentals near Knife Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Knife Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Fishing19 species recorded
- Ice seasonIce-out around Apr 12
- Big water1,259 acres
Swimming conditions
Readings onlyRecreation use not supported
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. Knife Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Knife 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 Knife Lake
These are the measurements Minnesota PCA publishes for Knife Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2 ft of visibility. Phosphorus 161.5 µg/L. Chlorophyll-a 97.2 µg/L. TSI 73.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 162µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 97.2µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 73 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
Ask about Knife Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Knife Lake typically sits around 63°F at the surface in September. Summer average is about 73°F. Usually warmest in Jul (about 78°F) and coldest in May (about 62°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (62°F) to its warmest (78°F).
Typical surface water temperature by month, from 32 field readings (2010–2023) via the EPA Water Quality Portal. See the full Knife Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Knife Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (469,894 cells/mL) on July 19, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Targeted Survey on August 25, 2025 caught 1.16 northern pike per hour of electrofishing at Knife Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Knife Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
22 surveys on file from MN DNR Fisheries. Most recent: 2025-10-20 (Targeted Survey).
22 surveys on file · most recent 2025-10-20 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Walleye | 52.65 | 5–14 in 2025-10-20 | 1.51 lb |
| Common Carp | 20.08 | 1.09 lb | |
| Largemouth Bass | 17.64 | 3–16 in 2025-06-03 | 0.87 lb |
| White Crappie | 16.85 | 0.28 lb | |
| Yellow Perch | 13.14 | 5–10 in 2025-06-03 | 0.2 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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.
Walleye
Largemouth Bass
Yellow Perch
From the 2025-10-20 survey
Knife Lake is a 1,266-acre lake in central Kanabec County located six miles north of Mora and is within the Snake River Watershed. The lake has a maximum depth of 16 ft and 99% of the lake is 15 feet or less (1,259 littoral acres). Knife River flows originate from groundwater, which allows cool water species such as…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Knife Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — KnifeFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Knife (0283)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — KnifeFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — KnifePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
15 ft
Average depth
9.1 ft
Surface area
1,259 acres
Shoreline
18.2 mi
Littoral zone
100%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
96 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,033 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Knife Lake (South)Public
- Knife Lake (North)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Knife Lake
Compare lakeside cabins, hotels, and vacation rentals near Knife 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Knife Lake are listed below.
Top-rated places to stay near Knife Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fish Species
Click a species to see every lake where it is documented.
Fishing Knife 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
Phosphorus
Stable-0.7 µg/L/yr6 years
Chlorophyll-a
Worsening+6.07 µg/L/yr6 years
Ice season
Typical ice-out
Apr 12
Earliest Mar 21, 2012 · Latest May 7, 2013
Most recent ice-out
Mar 31
2025
46 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
Knife Lake is a man-made reservoir impounded by the Knife Lake (completed 1983), built primarily for recreation on the Knife River; buttress-type dam, 22 ft tall and 725 ft long.
- Surface area
- 1,277 ac
- Normal storage
- 8,272 ac-ft
- Max storage
- 11,374 ac-ft
- Drainage area
- 92 sq mi
- Hazard class
- Significant
- Owner
- County of Kanabec;LID of Knife Lake;SWCD of Kanabec
Source: USACE National Inventory of Dams, NID ID MN00400 · Operator website
EPA Impairment Status
Knife Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN33-0028-00 · Official waterbody report
Nearby Lakes in Kanabec County
Frequently asked questions about Knife Lake
Where is Knife Lake?
- Knife Lake is a lake in Kanabec County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Knife Lake?
- Knife Lake in Kanabec County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 161.5 µg/L. Chlorophyll-a (algae): 97.2 µg/L. Maximum depth: 15 ft. Surface area: 1259.24 acres.
Is Knife Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Knife Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Knife Lake?
- Knife Lake typically sits around 63°F at the surface in September, from 32 EPA Water Quality Portal field readings (2010–2023). That is a typical value for the month, not a live reading.
How deep is Knife Lake?
- Knife Lake has a maximum depth of 15 feet and an average depth of 9.1 feet. The lake covers 1259.24 acres.
What fish are in Knife Lake?
- Fish species found in Knife Lake include black bullhead, black crappie, bluegill, brown bullhead, golden redhorse, greater redhorse, green sunfish, hybrid sunfish, largemouth bass, northern hog sucker, northern pike, pumpkinseed, rock bass, shorthead redhorse, smallmouth bass, walleye, white sucker, yellow bullhead, yellow perch. Knife Lake is located in Kanabec County, Minnesota.
What did the DNR fisheries survey find at Knife Lake?
- Minnesota DNR's Targeted Survey on August 25, 2025 caught 1.16 northern pike per hour of electrofishing at Knife Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Knife Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Knife Lake thaw?
- Knife Lake typically has ice-out around Apr 12.
Does Knife Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Knife Lake (clouds, ice, or an off-season gap). The most recent reading was high (469,894 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Knife Lake?
- Knife Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Knife Lake (South), Knife Lake (North). Public access is listed as yes.
Can I fish at Knife Lake?
- Knife Lake has 2 documented boat landings 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 Knife Lake across LakeQuality
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Fish species and best lakes in Kanabec County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
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Where this data comes from
86 measurements from 2 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
MNPCA86 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 (2)
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
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