Opal Lake
Otsego County, Michigan124 acresView mapDirections
Not Rated: one monitoring station are on record, but they measured water clarity only. LakeQuality’s A–F method grades total phosphorus, total nitrogen, chlorophyll-a, and turbidity; clarity is shown, not scored.
- 40 ft max depth
- Public access
- Limited data
Opal Lake in Otsego County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 15.5 ft visibility. Maximum depth: 40 ft. Surface area: 124.3 acres.
- Clarity
- 15.5 ft
- Max depth
- 40 ft
- Area
- 124 acres
- Trend
- ↑ Improving
- Public access
- Yes
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Watch Opal Lake’s letter
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Free interactive depth-contour map of Opal Lake, reaching a maximum surveyed depth of 40 ft. Toggle Depth contours to overlay the bathymetric survey lines. Contour data from Michigan DNR.
Why Opal Lake has no grade
Opal Lake has monitoring on record from one station, but only water clarity was measured. LakeQuality’s A–F letter uses total phosphorus, total nitrogen, chlorophyll-a, and turbidity against EPA National Lakes Assessment condition classes. With none of those grading measurements on record, Opal Lake is Not Rated — not an F. Its 15.5-foot median from 54 readings collected 2016–2021 is still shown as clarity, but clarity alone cannot earn a letter.
Not Rated is EPA Integrated Reporting Category 3 — insufficient information. Everything below that has been measured is still reported on this page.
Sampling is run by EGLE and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Opal Lake is a 124-acre lake in Otsego County, Michigan with a maximum depth of 40 feet. Overall water quality is improving over recent sampling years. The lake supports 11 documented fish species including Bluntnose minnow, Common shiner, and Johnny darter. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2021-09-23. Grade methodology: LakeQuality methodology.
What Opal Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.5 ft of visibility
- Boat launch1 documented ramp
- Fishing11 species recorded
- Deep water40 ft surveyed max depth
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Opal Lake
These readings exist but are not enough for an A–F grade — see why.
Crystal clear, you can see 15.5 ft down. TSI 38.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 15.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 38 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 40 ft |
| Surface Area | 124 acres |
| Public Access | Yes |
Recreation & Access
- Opal LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Opal Lake
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.084 m/yr | 5 |
| Phosphorus | ↑ Improving | -1 µg/L/yr | 2 |
Graded lakes near Opal Lake
Opal Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Otsego County
Frequently asked questions about Opal Lake
Where is Opal Lake?
- Opal Lake is a lake in Otsego County, Michigan. LakeQuality has not rated this lake (UNRATED) — 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.
What is the water quality grade for Opal Lake?
- Opal Lake in Otsego County, Michigan is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 15.5 ft visibility. Maximum depth: 40 ft. Surface area: 124.3 acres.
Is Opal Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
How deep is Opal Lake?
- Opal Lake has a maximum depth of 40 feet. The lake covers 124.3 acres.
What fish are in Opal Lake?
- Fish species found in Opal Lake include Bluntnose minnow, Common shiner, Johnny darter, Largemouth bass, Northern pike, Pumpkinseed, Rainbow trout, Rock bass, Smallmouth bass, White sucker, Yellow perch. Opal Lake is located in Otsego County, Michigan.
Are there boat ramps on Opal Lake?
- Opal Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Opal Lake. Public access is listed as yes.
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Where this data comes from
54 measurements from 1 monitoring station, 2016–2021. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- North American Lake Management Society
NALMS54 samples · 2016–2021
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
Named boat-access points from the USGS National Boat Ramps inventory