Jefferson Lake
Le Sueur County, Minnesota700 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Jefferson Lake. Here is what has been measured.
- Eutrophic
- 9 ft max depth
- Public access
Jefferson Lake in Le Sueur County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 86.5 µg/L. Chlorophyll-a (algae): 72 µg/L. Surface area: 700 acres.
Jefferson Lake is a 700-acre productive, nutrient-rich eutrophic lake in Le Sueur County, Minnesota with an estimated average depth of about 9 feet. 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 12 other monitored lakes in Le Sueur County, Jefferson Lake ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-11-14. Methodology: how these readings are compared.
Jefferson Lake covers about 700 acres in Le Sueur County. It has one public boat landing. Vrbo is where to look for cabins and lake homes around Jefferson Lake, and Booking.com and Expedia search hotels near the lake for your dates.
What Jefferson Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
Readings onlyAlgae risk
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 Jefferson 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 Jefferson Lake
These are the measurements Minnesota PCA publishes for Jefferson 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 86.5 µg/L. Chlorophyll-a 72 µg/L. TSI 69.
| 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 | 86.5µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 72µg/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. | 69 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Jefferson Lake
Answers come straight from the public measurements and survey records on this page.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Jefferson Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fish Stocking History — HenryFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — HenryPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
~9 ft est.
Surface area
700 acres
Public access
Yes
Listed by Minnesota PCA
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Minnesota has not published bathymetry for Jefferson Lake.
Lake Size & Watershed
Watershed (drainage) area
39 sq mi
HydroLAKES / HydroSHEDS
Shoreline
6.1 mi
HydroLAKES / HydroSHEDS
Elevation
1,007 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Jefferson Lake (West)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 Jefferson Lake
Compare lakeside cabins, hotels, and vacation rentals near Jefferson Lake in Le Sueur 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 Jefferson Lake are listed below.
Top-rated places to stay near Jefferson 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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Fishing Jefferson Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Worsening+19.5 µg/L/yr2 years
Chlorophyll-a
Worsening+19.43 µg/L/yr2 years
Reservoir Info (USACE NID)
Jefferson Lake is a man-made reservoir impounded by the Lake Jefferson (completed 1938), built primarily for recreation on the BIG CANNON RIVER - TR; gravity-type dam, 9 ft tall and 15 ft long.
- Surface area
- 700 ac
- Normal storage
- 18,544 ac-ft
- Max storage
- 25,489 ac-ft
- Drainage area
- 16.3 sq mi
- Hazard class
- Low
- Owner
- MNDNR-Trails
Source: USACE National Inventory of Dams, NID ID MN00155 · Operator website
Nearby Lakes in Le Sueur County
Frequently asked questions about Jefferson Lake
Where is Jefferson Lake?
- Jefferson Lake is a lake in Le Sueur County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Jefferson Lake?
- Jefferson Lake in Le Sueur County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 86.5 µg/L. Chlorophyll-a (algae): 72 µg/L. Surface area: 700 acres.
Is Jefferson Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Jefferson Lake?
- No published bathymetric survey covers Jefferson Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 9 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 700 acres.
Are there boat ramps on Jefferson Lake?
- Jefferson Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Jefferson Lake (West). Public access is listed as yes.
Can I fish at Jefferson Lake?
- Jefferson 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 Jefferson Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Le Sueur County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Minnesota River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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Where this data comes from
336 measurements from 10 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
MNPCA336 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 (10)
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