O'Reilly Lake
O'Reilly Lake in Itasca County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 16 ft visibility. Maximum depth: 79 ft. Surface area: 189.31 acres.
- Clarity
- 16 ft
- Typical in August
- 73°F
- Max depth
- 79 ft
- Area
- 189 acres
- Trend
- ↓ Declining
- Public access
- Yes
Next lake in Itasca County
Why O'Reilly Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: 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 O'Reilly 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, but not phosphorus and 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 MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
O'Reilly Lake is a 189-acre lake in Itasca County, Minnesota with a maximum depth of 79 feet. Overall water quality is declining over recent sampling years. The lake supports 11 documented fish species including black crappie, bluegill, and largemouth bass. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for O'Reilly Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Crystal clear, you can see 16 ft down. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 16 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near O'Reilly Lake
Compare lakeside cabins, hotels, and vacation rentals near O'Reilly Lake in Itasca 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.
Top-rated places to stay near O'Reilly Lake
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Water Temperature
O'Reilly Lake typically sits around 73°F at the surface in August. Summer average is about 72°F. Usually warmest in Jul (about 73°F) and coldest in Oct (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 45 field readings (2022–2025) via the EPA Water Quality Portal. See the full O'Reilly Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 79 ft |
| Surface Area | 189 acres |
| Shoreline Length | 3.1 mi |
| Littoral Zone | 30% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- O'Reilly LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing O'Reilly Lake
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2020-08-17 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| CNM | 25.23 | — |
| Bluegill | 6.97 | 0.15 lb |
| IOD | 5.52 | — |
| Bluntnose Minnow | 4.96 | — |
| Largemouth Bass | 4.78 | 0.88 lb |
| Tullibee (Cisco) | 4.17 | 0.25 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Bluegill
Largemouth Bass
Tullibee (Cisco)
From the 2020-08-17 survey
The 2012 lake management plan (LMP) indicated Largemouth Bass and Northern Pike were the primary management species while Black Crappie and Bluegill were secondary. The LMP goals were to maintain a Northern Pike catch at 5.0/gill net with 60 and 10% of the fish longer than 21 and 28 inches; maintain the gill-net catch…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for O'Reilly Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — O'ReillyFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — O'Reilly (0588)Aquatic Plant Report · MN DNR LakeFinder
- —Aquatic Plant Report — O'Reilly (2043)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — O'ReillyPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.141 m/yr | 4 |
Graded lakes near O'Reilly Lake
O'Reilly Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Itasca County
Frequently asked questions about O'Reilly Lake
What is the water quality grade for O'Reilly Lake?
- O'Reilly Lake in Itasca County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 16 ft visibility. Maximum depth: 79 ft. Surface area: 189.31 acres.
Is O'Reilly Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. O'Reilly Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
What is the water temperature of O'Reilly Lake?
- O'Reilly Lake typically sits around 73°F at the surface in August, from 45 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
How deep is O'Reilly Lake?
- O'Reilly Lake has a maximum depth of 79 feet. The lake covers 189.31 acres.
What fish are in O'Reilly Lake?
- Fish species found in O'Reilly Lake include black crappie, bluegill, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, white sucker, yellow bullhead, yellow perch. O'Reilly Lake is located in Itasca County, Minnesota.
Are there boat ramps on O'Reilly Lake?
- O'Reilly Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include O'Reilly Lake. Public access is listed as yes.
Explore O'Reilly Lake across LakeGrade
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Where this data comes from
45 measurements from 1 monitoring station, 2022–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA45 samples · 2022–2025
Analytical methods
- Field measurement/observation, generic method
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)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory