Thomas Lake
Thomas Lake in Dakota County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.6 ft visibility. Phosphorus: 26.5 µg/L. Chlorophyll-a (algae): 6.7 µg/L. Maximum depth: 8 ft. Surface area: 41.49 acres.
- Clarity
- 5.6 ft
- Typical in August
- 76°F
- Max depth
- 8 ft
- Area
- 41 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 4
- Open water
- 237 days
Next lake in Dakota County
Thomas Lake is a 41-acre productive, nutrient-rich eutrophic lake in Dakota County, Minnesota with a maximum depth of 8 feet. Water quality is graded C based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 6 documented fish species including black bullhead, black crappie, and bluegill. Public access is available. Compared to the 44 other monitored lakes in Dakota County, Thomas Lake ranks #13 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyModerate
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 5.6 ft. Phosphorus level: 26.5 µg/L. Chlorophyll-a: 6.7 µg/L. Trophic State Index: 51.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | Not graded |
| Phosphorus | 26.5 µg/L | Fair |
| Chlorophyll-a (Algae) | 6.7 µg/L | Good |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Thomas Lake
Compare lakeside cabins, hotels, and vacation rentals near Thomas Lake in Dakota 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.
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Water Temperature
Thomas Lake typically sits around 76°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 78°F) and coldest in Apr (about 52°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 73 field readings (2010–2025) via the EPA Water Quality Portal. See the full Thomas Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 8 ft |
| Surface Area | 41 acres |
| Shoreline Length | 2.6 mi |
| Littoral Zone | 91% |
| Public Access | Yes |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Thomas 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
2 surveys on file from MN DNR Fisheries. Most recent: 2016-06-20 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 20.80 | 0.12 lb |
| Largemouth Bass | 18.21 | 1.09 lb |
| GOS | 2.40 | 0.14 lb |
| Hybrid Sunfish | 2.00 | 0.23 lb |
| Black Crappie | 1.80 | 0.24 lb |
| Pumpkinseed | 0.60 | 0.22 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
GOS
Hybrid Sunfish
From the 2016-06-20 survey
Thomas Lake (unnamed 19006700) is located in the City of Eagan at the Thomas Lake Park. The park is managed by The City of Eagan Parks and Thomas Lake is co-managed by the City of Eagan Lakes and Wetlands Program and the MN DNR. The park has a fishing pier, shore fishing stations, boat access, restrooms, ample…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Thomas Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ThomasFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — ThomasFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — ThomasPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.033 m/yr | 6 |
| Phosphorus | ↓ Declining | +1.27 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.42 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (14 observations).
Estimated open water season: 237 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2007-03-25 (2007) | 2008-04-16 (2008) |
| Ice-In | 2005-11-14 (2005) | 2021-11-30 (2021) |
Most recent ice-out: 2022-04-07
EPA Impairment Status
Thomas 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 MN19-0066-00 · Official waterbody report · Matched by proximity (1.21 km)
County Ranking
Ranked #13 of 45 lakes in Dakota County
Nearby Lakes in Dakota County
Frequently asked questions about Thomas Lake
What is the water quality grade for Thomas Lake?
- Thomas Lake in Dakota County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.6 ft visibility. Phosphorus: 26.5 µg/L. Chlorophyll-a (algae): 6.7 µg/L. Maximum depth: 8 ft. Surface area: 41.49 acres.
Is Thomas Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Thomas Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 6.7 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Thomas Lake?
- Thomas Lake typically sits around 76°F at the surface in August, from 73 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Thomas Lake?
- Thomas Lake has a maximum depth of 8 feet. The lake covers 41.49 acres.
What fish are in Thomas Lake?
- Fish species found in Thomas Lake include black bullhead, black crappie, bluegill, hybrid sunfish, largemouth bass, pumpkinseed. Thomas Lake is located in Dakota County, Minnesota.
When does Thomas Lake thaw?
- Thomas Lake typically has ice-out around Apr 4. Ice typically forms around Nov 27. The open water season is approximately 237 days.
Explore Thomas Lake across LakeGrade
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Where this data comes from
175 measurements from 3 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
MNPCA175 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
- Turbidity, Nephelometric Method
Monitoring station identifiers (3)
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 details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate