Jonathan Lake
Jonathan Lake in Carver County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 157.5 µg/L. Chlorophyll-a (algae): 80 µg/L. Surface area: 31 acres.
- Clarity
- 1.6 ft
- Typical in August
- 75°F
- Area
- 31 acres
- Type
- Hypereutrophic
- Trend
- → Stable
- Public access
- No
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Jonathan Lake →
Next lake in Carver County
Jonathan Lake is a 31-acre highly nutrient-loaded hypereutrophic lake in Carver County, Minnesota. Water quality is graded F based on 2 sampling years through 2025. Water clarity is improving over recent sampling years. The lake supports 3 documented fish species including black bullhead, bluegill, and green sunfish. No public access — the lake is private or restricted. Compared to the 37 other monitored lakes in Carver County, Jonathan Lake ranks #19 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-06. 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 1.6 ft of visibility. Phosphorus level: 157.5 µg/L. Chlorophyll-a: 80 µg/L. Trophic State Index: 74.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | Not graded |
| Phosphorus | 157.5 µg/L | Poor |
| Chlorophyll-a (Algae) | 80 µg/L | Poor |
| Trophic State Index (TSI) | 74 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Jonathan Lake
Compare lakeside cabins, hotels, and vacation rentals near Jonathan Lake in Carver 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 Jonathan Lake are listed below.
Top-rated places to stay near Jonathan Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Jonathan Lake typically sits around 75°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 78°F) and coldest in Feb (about 35°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 234 field readings (2010–2025) via the EPA Water Quality Portal.
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 31 acres |
| Public Access | No |
No bathymetric survey has been published for Jonathan Lake, so its depth is not documented here.
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Jonathan Lake
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.014 m/yr | 6 |
| Phosphorus | → Stable | +1.64 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +4.17 µg/L/yr | 6 |
Reservoir Info (USACE NID)
Jonathan Lake is a man-made reservoir impounded by the Mcknight Lake, built primarily for flood risk reduction on the Chaska East Creek; earth-type dam, 8 ft tall.
- Surface area
- 31 ac
- Normal storage
- 82 ac-ft
- Max storage
- 82 ac-ft
- Drainage area
- 5.93 sq mi
- Hazard class
- Low
- Owner
- City of Chaska
Source: USACE National Inventory of Dams, NID ID MN01263 · Operator website · Matched by proximity (0.38 km)
EPA Impairment Status
Jonathan 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 MN10-0217-00 · Official waterbody report
County Ranking
Ranked #19 of 38 lakes in Carver County
Nearby Lakes With Higher Grades
Jonathan 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 Carver County
Frequently asked questions about Jonathan Lake
What is the water quality grade for Jonathan Lake?
- Jonathan Lake in Carver County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 1.6 ft visibility. Phosphorus: 157.5 µg/L. Chlorophyll-a (algae): 80 µg/L. Surface area: 31 acres.
Is Jonathan 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. Jonathan Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 80 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Jonathan Lake?
- Jonathan Lake typically sits around 75°F at the surface in August, from 234 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
What fish are in Jonathan Lake?
- Fish species found in Jonathan Lake include black bullhead, bluegill, green sunfish. Jonathan Lake is located in Carver County, Minnesota.
Explore Jonathan Lake across LakeGrade
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Where this data comes from
202 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
MNPCA202 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 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
Lake details from Minnesota DNR LakeFinder