Jack Lake
Cass County, Minnesota142 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Jack Lake. Here is what has been measured.
- Oligotrophic
- 110 ft max depth
- Public access
Jack Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15.7 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Maximum depth: 110 ft. Surface area: 141.97 acres.
Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.67 northern pike per trap net at Jack Lake. DNR survey details →
Jack Lake is a 142-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 110 feet. Overall water quality is declining over recent sampling years. The lake supports 13 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 1 public boat landing. Compared to the 103 other monitored lakes in Cass County, Jack Lake ranks #83 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-16. Methodology: how these readings are compared.
What Jack Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.7 ft of visibility
- Boat launch1 documented ramp
- Fishing13 species recorded
- Deep water110 ft surveyed max depth
Swimming conditions
Readings onlyLow algae
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 Jack 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 Jack Lake
These are the measurements Minnesota PCA publishes for Jack 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 15.7 ft down. Phosphorus 9 µg/L. Chlorophyll-a 3.1 µg/L. TSI 38.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 15.7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 9µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.1µg/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. | 38 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Jack Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Jack Lake typically sits around 45°F at the surface in October. Summer average is about 48°F. Usually warmest in Aug (about 49°F) and coldest in May (about 44°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (44°F) to its warmest (49°F).
Typical surface water temperature by month, from 501 field readings (2011–2024) via the EPA Water Quality Portal. See the full Jack Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.67 northern pike per trap net at Jack Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Jack Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
8 surveys on file from MN DNR Fisheries. Most recent: 2024-08-20 (Targeted Survey).
8 surveys on file · most recent 2024-08-20 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 21.11 | 3–7 in 2024-08-20 | 0.14 lb |
| Tullibee (Cisco) | 6.24 | 7–9 in 2018-06-11 | 0.21 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.
Bluegill
Tullibee (Cisco)
From the 2024-08-20 survey
A targeted survey of nearshore fish species in Jack Lake which is located wholly within the Leech Lake Band of Ojibwe Nation, was conducted August 20-21, 2024, by Index of Biological Integrity (IBI) Program staff. Sampling sites were evenly spaced around the lake, and each was sampled by backpack electrofishing and…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Jack Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — JackFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Jack (1498)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — JackPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
110 ft
Surface area
142 acres
Shoreline
2.5 mi
Littoral zone
31%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,293 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Jack 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 Jack Lake
Compare lakeside cabins, hotels, and vacation rentals near Jack 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 Jack Lake
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Follow Jack Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Jack Lake
Water quality readings over time
2 seasons of samples on record (2023–2024). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Phosphorus
Worsening+3 µg/L/yr2 years
Chlorophyll-a
Improving-0.9 µg/L/yr2 years
Nearby Lakes in Cass County
Frequently asked questions about Jack Lake
Where is Jack Lake?
- Jack 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 Jack Lake?
- Jack Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15.7 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 3.1 µg/L. Maximum depth: 110 ft. Surface area: 141.97 acres.
Is Jack Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Jack Lake?
- Jack Lake typically sits around 45°F at the surface in October, from 501 EPA Water Quality Portal field readings (2011–2024). That is a typical value for the month, not a live reading.
How deep is Jack Lake?
- Jack Lake has a maximum depth of 110 feet. The lake covers 141.97 acres.
What fish are in Jack Lake?
- Fish species found in Jack Lake include black crappie, bluegill, bowfin (dogfish), hybrid sunfish, largemouth bass, northern pike, northern sunfish, pumpkinseed, rock bass, tullibee (cisco), walleye, yellow bullhead, yellow perch. Jack Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Jack Lake?
- Minnesota DNR's Targeted Survey on August 20, 2024 caught 0.67 northern pike per trap net at Jack Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Jack Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Jack Lake?
- Jack Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Jack Lake. Public access is listed as yes.
Can I fish at Jack Lake?
- Jack 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.
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Where this data comes from
59 measurements from 2 monitoring stations, 2023–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Leech Lake Band of Ojibwe
LEECHLAK_WQX44 samples · 2023–2024 - Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA15 samples · 2023
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Nitrate-Nitrite Nitrogen by Colorimetry
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory