Thompson Lake
Dakota County, Minnesota8 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Thompson Lake. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- Eurasian watermilfoil
- 8 ft max depth
- Limited data
Thompson Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 54 µg/L. Chlorophyll-a (algae): 36 µg/L. Maximum depth: 8 ft. Surface area: 8.08 acres.
Minnesota DNR's Standard Survey on June 3, 2013 caught 0.20 northern pike per trap net at Thompson Lake. DNR survey details →
Thompson Lake is a 8-acre productive, nutrient-rich eutrophic lake in Dakota County, Minnesota with a maximum depth of 8 feet. Overall water quality is declining over recent sampling years. Limited fish-species data available. No public access — the lake is private or restricted. Compared to the 44 other monitored lakes in Dakota County, Thompson Lake ranks #34 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-27. Methodology: how these readings are compared.
Swimming conditions
Readings onlyRecreation use not supported
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.
Based on E. coli testing, Thompson Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 18.2% of 11 samples across 2 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Minnesota’s current beach and health-department advisories before swimming.
Whether Thompson 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 Thompson Lake
These are the measurements Minnesota PCA publishes for Thompson 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 3.3 ft of visibility. Phosphorus 54 µg/L. Chlorophyll-a 36 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 3.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 54µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 36µg/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. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Thompson Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Thompson Lake typically sits around 53°F at the surface in October. Summer average is about 75°F. Usually warmest in Jul (about 79°F) and coldest in Jan (about 33°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (33°F) to its warmest (79°F).
Typical surface water temperature by month, from 67 field readings (2011–2025) via the EPA Water Quality Portal. See the full Thompson Lake water temperature breakdown →
Minnesota DNR's Standard Survey on June 3, 2013 caught 0.20 northern pike per trap net at Thompson Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thompson Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
3 surveys on file from MN DNR Fisheries. Most recent: 2013-06-03 (Standard Survey).
3 surveys on file · most recent 2013-06-03 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 42.67 | 3–5 in 2013-06-03 | 0.12 lb |
| Black Bullhead | 37.30 | 4–9 in 2013-06-03 | 0.15 lb |
| Green Sunfish | 8.27 | 2–5 in 2013-06-03 | 0.1 lb |
| Pumpkinseed | 3.70 | 2–5 in 2013-06-03 | 0.14 lb |
| Hybrid Sunfish | 2.73 | 2–7 in 2013-06-03 | 0.17 lb |
| Black Crappie | 2.10 | 7–10 in 2013-06-03 | 0.48 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
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
Black Bullhead
Green Sunfish
Pumpkinseed
From the 2013-06-03 survey
Thompson Lake is a small 10 acre lake located in Thompson County Park (Dakota County Parks) within the city limits of West St. Paul. The lake has a maximum depth of eight feet and receives primarily stormwater inputs from the 169 acre surrounding watershed. A spillway outlet structure maintains the water level and…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Thompson Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ThompsonFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — ThompsonFish Stocking History · MN DNR LakeFinder
Lake Details
Max depth
8 ft
Surface area
8 acres
Shoreline
0.5 mi
Littoral zone
87%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Stays via Stay22
Stays near Thompson Lake
Compare lakeside cabins, hotels, and vacation rentals near Thompson 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Thompson Lake are listed below.
Top-rated places to stay near Thompson Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
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Fishing Thompson 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.
Water quality readings over time
2 seasons of samples on record (2024–2025). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening2 years
Reservoir Info (USACE NID)
Thompson Lake is a man-made reservoir impounded by the Kaposia Park (completed 1932), built primarily for flood risk reduction on the Mississippi River-TR; earth-type dam, 79 ft tall.
- Max storage
- 180 ac-ft
- Drainage area
- 1.5 sq mi
- Hazard class
- Significant
- Owner
- City of South St. Paul
Source: USACE National Inventory of Dams, NID ID MN00675 · Operator website · Matched by proximity (0.99 km)
EPA Impairment Status
Thompson Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN19-0048-00 · Official waterbody report
Nearby Lakes in Dakota County
Frequently asked questions about Thompson Lake
Where is Thompson Lake?
- Thompson Lake is a lake in Dakota County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Thompson Lake?
- Thompson Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 3.3 ft visibility. Phosphorus: 54 µg/L. Chlorophyll-a (algae): 36 µg/L. Maximum depth: 8 ft. Surface area: 8.08 acres.
Is Thompson Lake safe to swim in?
- Based on E. coli testing, Thompson Lake frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 18.2% of 11 samples across 2 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Thompson Lake is safe to swim in today is a call for Minnesota's water agency and the county health department; check their current beach advisories before you swim.
What is the water temperature of Thompson Lake?
- Thompson Lake typically sits around 53°F at the surface in October, from 67 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Thompson Lake?
- Thompson Lake has a maximum depth of 8 feet. The lake covers 8.08 acres.
What did the DNR fisheries survey find at Thompson Lake?
- Minnesota DNR's Standard Survey on June 3, 2013 caught 0.20 northern pike per trap net at Thompson Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Thompson Lake’s water-quality measurements separately, and the water-quality trend over 2 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Thompson Lake?
- Public access to Thompson Lake is listed as no on the lake record, so confirm before you make the trip. 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 Thompson Lake across LakeQuality
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Where this data comes from
41 measurements from 1 monitoring station, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA41 samples · 2024–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
Monitoring station identifiers (1)
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
Impairment status from EPA ATTAINS 303(d) database
Lake details from Minnesota DNR LakeFinder