Tonseth Lake
Tonseth Lake in Otter Tail County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 10 ft visibility. Maximum depth: 27 ft. Surface area: 148.98 acres.
- Clarity
- 10 ft
- Typical in August
- 75°F
- Max depth
- 27 ft
- Area
- 149 acres
- Trend
- ↑ Improving
- Public access
- Yes
- Ice-out
- Apr 15
- Open water
- 220 days
Next lake in Otter Tail County
Why Tonseth Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Tonseth Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Tonseth Lake is a 149-acre lake in Otter Tail County, Minnesota with a maximum depth of 27 feet (15-foot average). Overall water quality is improving over recent sampling years. The lake supports 12 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-01. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Tonseth Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 10 ft. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Tonseth Lake
Compare lakeside cabins, hotels, and vacation rentals near Tonseth Lake in Otter Tail 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 Tonseth Lake
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Water Temperature
Tonseth Lake typically sits around 75°F at the surface in August. Summer average is about 74°F. Usually warmest in Jul (about 76°F) and coldest in May (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 25 field readings (2023–2025) via the EPA Water Quality Portal. See the full Tonseth Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 27 ft |
| Average Depth | 15 ft |
| Surface Area | 149 acres |
| Shoreline Length | 3.2 mi |
| Littoral Zone | 53% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Anderson LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Tonseth Lake
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 1999-06-14 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 55.69 | 0.12 lb |
| Largemouth Bass | 38.42 | 0.77 lb |
| Yellow Bass | 12.31 | 0.4 lb |
| Hybrid Sunfish | 10.34 | 0.24 lb |
| Black Crappie | 7.82 | 0.34 lb |
| Pumpkinseed | 7.58 | 0.15 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.
Bluegill
Largemouth Bass
Yellow Bass
Hybrid Sunfish
From the 1999-06-14 survey
Tonseth Lake is located in west-central Otter Tail County approximately eight miles southeast of Erhard, MN. Tonseth Lake is a 156-acre moderately fertile lake that is part of the Otter Tail River Watershed. Two small intermittent inlets are located along the north shoreline of the lake and an outlet to Kempfer Lake…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Tonseth Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — TonsethFisheries Lake Survey · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.109 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (76 observations).
Estimated open water season: 220 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2012-03-22 (2012) | 2013-05-09 (2013) |
| Ice-In | 1991-11-04 (1991) | 2016-12-09 (2016) |
Most recent ice-out: 2022-05-03
Graded lakes near Tonseth Lake
Tonseth Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Otter Tail County
Frequently asked questions about Tonseth Lake
What is the water quality grade for Tonseth Lake?
- Tonseth Lake in Otter Tail County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 10 ft visibility. Maximum depth: 27 ft. Surface area: 148.98 acres.
Is Tonseth Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Tonseth Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of Tonseth Lake?
- Tonseth Lake typically sits around 75°F at the surface in August, from 25 EPA Water Quality Portal field readings (2023–2025). That is a typical value for the month, not a live reading.
How deep is Tonseth Lake?
- Tonseth Lake has a maximum depth of 27 feet and an average depth of 15 feet. The lake covers 148.98 acres.
What fish are in Tonseth Lake?
- Fish species found in Tonseth Lake include black bullhead, black crappie, bluegill, green sunfish, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, walleye, white sucker, yellow bullhead, yellow perch. Tonseth Lake is located in Otter Tail County, Minnesota.
When does Tonseth Lake thaw?
- Tonseth Lake typically has ice-out around Apr 15. Ice typically forms around Nov 21. The open water season is approximately 220 days.
Are there boat ramps on Tonseth Lake?
- Tonseth Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Anderson Lake. Public access is listed as yes.
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Where this data comes from
85 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
MNPCA85 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
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
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