East Thomas Lake
East Thomas Lake in Dakota County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.6 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Maximum depth: 19 ft. Surface area: 12.01 acres.
- Clarity
- 5.6 ft
- Typical in August
- 77°F
- Max depth
- 19 ft
- Area
- 12 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- No
Next lake in Dakota County
East Thomas Lake is a 12-acre productive, nutrient-rich eutrophic lake in Dakota County, Minnesota with a maximum depth of 19 feet (12-foot average). 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. No public access — the lake is private or restricted. Compared to the 44 other monitored lakes in Dakota County, East Thomas Lake ranks #17 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. 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: 27 µg/L. Chlorophyll-a: 8.5 µg/L. Trophic State Index: 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.6 ft | Not graded |
| Phosphorus | 27 µg/L | Fair |
| Chlorophyll-a (Algae) | 8.5 µg/L | Fair |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near East Thomas Lake
Compare lakeside cabins, hotels, and vacation rentals near East 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
East Thomas Lake typically sits around 77°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 78°F) and coldest in Sep (about 71°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 25 field readings (2010–2025) via the EPA Water Quality Portal.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 19 ft |
| Average Depth | 11.9 ft |
| Surface Area | 12 acres |
| Shoreline Length | 0.6 mi |
| Littoral Zone | 70% |
| Public Access | No |
Fish Species
Click a species to see every graded lake where it is documented.
Fishing East Thomas Lake
DNR Fisheries Survey Summary
6 surveys on file from MN DNR Fisheries. Most recent: 2022-06-23 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Largemouth Bass | 36.84 | 1.03 lb |
| Black Bullhead | 23.67 | 0.39 lb |
| Bluegill | 14.29 | 0.13 lb |
| Black Crappie | 8.62 | 0.15 lb |
| GOS | 6.60 | 0.11 lb |
| Channel Catfish | 3.92 | 2 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.
Largemouth Bass
Black Bullhead
Bluegill
Black Crappie
From the 2022-06-23 survey
Carlson Lake (19-0066-00), as it's now officially known is located in the city of Eagan. The lake drops off rather quickly to a maximum of 19 feet with approximately 26% of the surface area over 15 feet. Although an aeration system is operated (as needed) to prevent winterkill, city staff report it is not often…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for East Thomas Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — CarlsonFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — CarlsonFish Stocking History · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.073 m/yr | 6 |
| Phosphorus | ↓ Declining | +1.67 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +1.11 µg/L/yr | 6 |
EPA Impairment Status
East 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 (0.66 km)
County Ranking
Ranked #17 of 45 lakes in Dakota County
Nearby Lakes With Higher Grades
East Thomas Lake holds Grade C. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Dakota County
Frequently asked questions about East Thomas Lake
What is the water quality grade for East Thomas Lake?
- East Thomas Lake in Dakota County, Minnesota has a water quality grade of C (Fair). Water clarity: 5.6 ft visibility. Phosphorus: 27 µg/L. Chlorophyll-a (algae): 8.5 µg/L. Maximum depth: 19 ft. Surface area: 12.01 acres.
Is East Thomas Lake safe to swim in?
- Generally safe for swimming, moderate water quality. East Thomas Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 8.5 µg/L. Always check local health department advisories before swimming.
What is the water temperature of East Thomas Lake?
- East Thomas Lake typically sits around 77°F at the surface in August, from 25 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is East Thomas Lake?
- East Thomas Lake has a maximum depth of 19 feet and an average depth of 11.9 feet. The lake covers 12.01 acres.
What fish are in East Thomas Lake?
- Fish species found in East Thomas Lake include black bullhead, black crappie, bluegill, hybrid sunfish, largemouth bass, walleye. East Thomas Lake is located in Dakota County, Minnesota.
Explore East Thomas Lake across LakeGrade
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Where this data comes from
112 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
MNPCA112 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 (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 details from Minnesota DNR LakeFinder