County K Marsh Lake
County K Marsh Lake in Green Lake County, Wisconsin has a water quality grade of D (Nutrient-rich). Phosphorus: 140 µg/L.
- Mean depth
- ~5 ft est.
- Type
- Hypereutrophic
- Trend
- ↑ Improving
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near County K Marsh Lake →
Next lake in Green Lake County
County K Marsh Lake is a highly nutrient-loaded hypereutrophic lake in Green Lake County, Wisconsin with an estimated average depth of about 5 feet. Water quality is graded D based on 1 sampling years through 2026. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 6 other monitored lakes in Green Lake County, County K Marsh Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-10. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyBacteria B
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.
Based on E. coli testing, County K Marsh Lake rarely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 2.3% of 261 samples across 9 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Wisconsin’s current beach and health-department advisories before swimming.
Water Quality Grade: D (Nutrient-rich)
No clarity data. Phosphorus level: 140 µg/L. Trophic State Index: 75.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 140 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 75 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near County K Marsh Lake
Compare lakeside cabins, hotels, and vacation rentals near County K Marsh Lake in Green Lake County, Wisconsin — 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 County K Marsh Lake are listed below.
Top-rated places to stay near County K Marsh Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~5 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Wisconsin has not published bathymetry for County K Marsh Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Dodge Memorial ParkPublic
Fishing County K Marsh Lake
Water Quality Trend: ↑ Improving
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↑ Improving | -15.9 µg/L/yr | 4 |
County Ranking
Ranked #6 of 7 lakes in Green Lake County
Nearby Lakes With Higher Grades
County K Marsh Lake holds Grade D. 2 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 Green Lake County
Frequently asked questions about County K Marsh Lake
What is the water quality grade for County K Marsh Lake?
- County K Marsh Lake in Green Lake County, Wisconsin has a water quality grade of D (Nutrient-rich). Phosphorus: 140 µg/L.
Is County K Marsh Lake safe to swim in?
- Based on E. coli testing, County K Marsh Lake rarely exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 2.3% of 261 samples across 9 seasons. That works out to a bacteria swim-safety grade of B — a historical summary of past testing, not a current reading. County K Marsh Lake has a water quality grade of D (Nutrient-rich). Bacteria levels can spike quickly after heavy rain, so always check Wisconsin's current beach and health-department advisories before you swim.
How deep is County K Marsh Lake?
- No published bathymetric survey covers County K Marsh Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 5 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on County K Marsh Lake?
- County K Marsh Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Dodge Memorial Park. Public access is listed as yes.
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Where this data comes from
106 measurements from 1 monitoring station, 2024–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX106 samples · 2024–2026
Analytical methods
- Phosphorus by Colorimetry
- Turbidity in Water
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory