Gerhardt Lake
Dakota County, MinnesotaView mapDirections
Minnesota PCA publishes the water-quality measurements for Gerhardt Lake. Here is what has been measured.
- Eutrophic
Gerhardt Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 37 µg/L.
Gerhardt Lake is a productive, nutrient-rich eutrophic lake in Dakota County, Minnesota. 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, Gerhardt Lake ranks #36 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-05. Methodology: how these readings are compared.
What Gerhardt Lake is good for
From access and monitoring records, not editorial picks.
- Ice seasonIce-out around Apr 6
Swimming conditions
Readings onlyAlgae risk
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.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Gerhardt 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 Gerhardt Lake
These are the measurements Minnesota PCA publishes for Gerhardt 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 2 ft of visibility. Phosphorus 50 µg/L. Chlorophyll-a 37 µg/L. TSI 65.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 50µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 37µg/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. | 65 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Gerhardt Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Gerhardt Lake typically sits around 60°F at the surface in September. Summer average is about 78°F. Usually warmest in Jul (about 80°F) and coldest in Sep (about 60°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (60°F) to its warmest (80°F).
Typical surface water temperature by month, from 14 field readings (2017–2025) via the EPA Water Quality Portal. See the full Gerhardt Lake water temperature breakdown →
Stays via Stay22
Stays near Gerhardt Lake
Compare lakeside cabins, hotels, and vacation rentals near Gerhardt 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 Gerhardt Lake are listed below.
Top-rated places to stay near Gerhardt 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 Gerhardt Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Improving-1.77 µg/L/yr6 years
Chlorophyll-a
Worsening+0.99 µg/L/yr6 years
Ice season
Typical ice-out
Apr 6
Earliest Mar 30, 2003 · Latest Apr 17, 2008
Most recent ice-out
Apr 17
2008
6 observations · Minnesota PCA ice records
Nearby Lakes in Dakota County
Frequently asked questions about Gerhardt Lake
Where is Gerhardt Lake?
- Gerhardt 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 Gerhardt Lake?
- Gerhardt Lake in Dakota County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 2 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 37 µg/L.
Is Gerhardt Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Gerhardt Lake?
- Gerhardt Lake typically sits around 60°F at the surface in September, from 14 EPA Water Quality Portal field readings (2017–2025). That is a typical value for the month, not a live reading.
When does Gerhardt Lake thaw?
- Gerhardt Lake typically has ice-out around Apr 6.
Can I fish at Gerhardt Lake?
- Public access to Gerhardt 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 Gerhardt Lake across LakeQuality
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Dakota County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Minnesota River Watershed, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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State Parks Near Gerhardt Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Where this data comes from
95 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
MNPCA95 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Total Phosphorus After Block Digestion
- Phosphorus by Colorimetry
- Analysis of Chlorophyll in Periphyton and Plankton
- 10200 H ~ Chlorophyll a-b-c Determination
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
Ice data from Minnesota DNR Climate