Gerhardt Lake
Gerhardt Lake in Dakota County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 37 µg/L.
- Clarity
- 2 ft
- Typical in August
- 77°F
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- No
- Ice-out
- Apr 6
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Gerhardt Lake →
Next lake in Dakota County
Gerhardt Lake is a productive, nutrient-rich eutrophic lake in Dakota County, Minnesota. Water quality is graded F based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyAlgae risk
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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 2 ft of visibility. Phosphorus level: 50 µg/L. Chlorophyll-a: 37 µg/L. Trophic State Index: 65.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2 ft | Not graded |
| Phosphorus | 50 µg/L | Poor |
| Chlorophyll-a (Algae) | 37 µg/L | Poor |
| Trophic State Index (TSI) | 65 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay 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 grade measures nutrients and algae, not lodging — cabins and rentals around Gerhardt Lake are listed below.
Top-rated places to stay near Gerhardt Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Gerhardt Lake typically sits around 77°F at the surface in August. 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.
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 →
Fishing Gerhardt Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.059 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.77 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.99 µg/L/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (6 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2003-03-30 (2003) | 2008-04-17 (2008) |
| Ice-In | 2007-11-28 (2007) | 2004-12-11 (2004) |
Most recent ice-out: 2008-04-17
EPA Impairment Status
Gerhardt 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 MN19-0022-00 · Official waterbody report · Matched by proximity (2.64 km)
County Ranking
Ranked #36 of 45 lakes in Dakota County
Nearby Lakes With Higher Grades
Gerhardt Lake holds Grade F. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Dakota County
Frequently asked questions about Gerhardt Lake
What is the water quality grade for Gerhardt Lake?
- Gerhardt Lake in Dakota County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2 ft visibility. Phosphorus: 50 µg/L. Chlorophyll-a (algae): 37 µg/L.
Is Gerhardt Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Gerhardt Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 37 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Gerhardt Lake?
- Gerhardt Lake typically sits around 77°F at the surface in August, 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.
Explore Gerhardt Lake across LakeGrade
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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)
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
Ice data from Minnesota DNR Climate