Guernsey Lake
Guernsey Lake in Todd County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 3.9 ft visibility. Phosphorus: 83 µg/L. Chlorophyll-a (algae): 19.7 µg/L. Maximum depth: 19 ft. Surface area: 121.08 acres.
- Clarity
- 3.9 ft
- Typical in August
- 69°F
- Max depth
- 19 ft
- Area
- 121 acres
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Guernsey Lake →
Next lake in Todd County
Guernsey Lake is a 121-acre productive, nutrient-rich eutrophic lake in Todd County, Minnesota with a maximum depth of 19 feet (7-foot average). Water quality is graded D based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. The lake supports 16 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 7 other monitored lakes in Todd County, Guernsey Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyAlgae risk
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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 3.9 ft. Phosphorus level: 83 µg/L. Chlorophyll-a: 19.7 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 83 µg/L | Poor |
| Chlorophyll-a (Algae) | 19.7 µg/L | Poor |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Guernsey Lake
Compare lakeside cabins, hotels, and vacation rentals near Guernsey Lake in Todd 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 grade measures nutrients and algae, not lodging — cabins and rentals around Guernsey Lake are listed below.
Top-rated places to stay near Guernsey Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Guernsey Lake typically sits around 69°F at the surface in August. Summer average is about 68°F. Usually warmest in Jul (about 71°F) and coldest in Oct (about 54°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 63 field readings (2025–2025) via the EPA Water Quality Portal. See the full Guernsey Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 19 ft |
| Average Depth | 7.4 ft |
| Surface Area | 121 acres |
| Shoreline Length | 2.2 mi |
| Littoral Zone | 97% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Guernsey LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Guernsey 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.
DNR Fisheries Survey Summary
7 surveys on file from MN DNR Fisheries. Most recent: 2024-05-03 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 22.74 | 0.16 lb |
| Black Crappie | 18.28 | 0.37 lb |
| Bluegill | 12.10 | 0.32 lb |
| Northern Pike | 7.03 | 2.83 lb |
| Largemouth Bass | 6.79 | 1.71 lb |
| Pumpkinseed | 5.30 | 0.18 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.
Yellow Perch
Black Crappie
Bluegill
Northern Pike
From the 2024-05-03 survey
Spring trap netting targeting Bluegill and Black Crappie was conducted from May 1-3, 2024. Black Crappie and Bluegill are the primary management species at this time though recent sampling indicates substantial populations of Walleye and Northern Pike. Four similar spring trap net assessments have been completed prior…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Guernsey Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — GuernseyFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — GuernseyFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — GuernseyPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.08 m/yr | 2 |
| Phosphorus | ↓ Declining | +4.8 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -3.96 µg/L/yr | 2 |
EPA Impairment Status
Guernsey 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 MN77-0182-00 · Official waterbody report
County Ranking
Ranked #5 of 8 lakes in Todd County
Nearby Lakes in Todd County
Frequently asked questions about Guernsey Lake
What is the water quality grade for Guernsey Lake?
- Guernsey Lake in Todd County, Minnesota has a water quality grade of D (Nutrient-rich). Water clarity: 3.9 ft visibility. Phosphorus: 83 µg/L. Chlorophyll-a (algae): 19.7 µg/L. Maximum depth: 19 ft. Surface area: 121.08 acres.
Is Guernsey Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Guernsey Lake has a water quality grade of D (Nutrient-rich). Algae concentration (chlorophyll-a) is 19.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Guernsey Lake?
- Guernsey Lake typically sits around 69°F at the surface in August, from 63 EPA Water Quality Portal field readings (2025–2025). That is a typical value for the month, not a live reading.
How deep is Guernsey Lake?
- Guernsey Lake has a maximum depth of 19 feet and an average depth of 7.4 feet. The lake covers 121.08 acres.
What fish are in Guernsey Lake?
- Fish species found in Guernsey Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, shorthead redhorse, walleye, white sucker, yellow bullhead, yellow perch. Guernsey Lake is located in Todd County, Minnesota.
Are there boat ramps on Guernsey Lake?
- Guernsey Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Guernsey Lake. Public access is listed as yes.
Explore Guernsey Lake across LakeGrade
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Where this data comes from
61 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
MNPCA61 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
- 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