Grignon Lake
Grignon Lake in Oconto County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 6 ft visibility. Phosphorus: 22.9 µg/L.
- Clarity
- 6 ft
- Max depth
- ~31 ft est.
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Oconto County
Swipe left or right on this bar to open the next or previous lake.
Why Grignon Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Grignon Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity and phosphorus, but not algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by WI DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Grignon Lake is a lake in Oconto County, Wisconsin with an estimated average depth of about 31 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2021-07-28. Grade methodology: LakeQuality methodology.
Watch Grignon Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Grignon Lake
These readings exist but are not enough for an A–F grade — see why.
Murky, only visible to about 6 ft. Phosphorus level: 22.9 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6 ft | Not graded |
| Phosphorus | 22.9 µg/L | Not graded |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 50 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Grignon Lake
Compare lakeside cabins, hotels, and vacation rentals near Grignon Lake in Oconto 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.
Top-rated places to stay near Grignon 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 Wisconsin’s top lakes →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~31 ft est. |
| Average Depth | ~11 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Wisconsin has not published bathymetry for Grignon 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
- Grignon LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Grignon Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +3.5 m/yr | 2 |
Graded lakes near Grignon Lake
Grignon Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Oconto County
Frequently asked questions about Grignon Lake
Where is Grignon Lake?
- Grignon Lake is a lake in Oconto County, Wisconsin. LakeQuality has not rated this lake (UNRATED) — there is not enough recent sampling to assign a letter.
What is the water quality grade for Grignon Lake?
- Grignon Lake in Oconto County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 6 ft visibility. Phosphorus: 22.9 µg/L.
Is Grignon Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Grignon Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Grignon Lake?
- No published bathymetric survey covers Grignon Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 31 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 Grignon Lake?
- Grignon Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Grignon Lake. Public access is listed as yes.
Explore Grignon Lake across LakeQuality
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Oconto County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its grade
Wisconsin's cleanest and most-polluted lakes, ranked
More Wisconsin Lake Rankings
Other Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Where this data comes from
11 measurements from 2 monitoring stations, 2020–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX11 samples · 2020–2021
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
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