Hat Rapids Flowage Lake
Hat Rapids Flowage Lake in Oneida County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 3.5 ft visibility. Surface area: 295 acres.
- Clarity
- 3.5 ft
- Max depth
- ~47 ft est.
- Area
- 295 acres
- Trend
- ↓ Declining
Next lake in Oneida County
Swipe left or right on this bar to open the next or previous lake.
Why Hat Rapids Flowage 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 Hat Rapids Flowage 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 WI DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Hat Rapids Flowage Lake is a 295-acre lake in Oneida County, Wisconsin with an estimated average depth of about 47 feet. Overall water quality is declining over recent sampling years. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2023-08-06. Grade methodology: LakeQuality methodology.
Watch Hat Rapids Flowage 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 Hat Rapids Flowage Lake
These readings exist but are not enough for an A–F grade — see why.
Murky, only visible to about 3.5 ft. Trophic State Index: 59.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.5 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 59 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Hat Rapids Flowage Lake
Compare lakeside cabins, hotels, and vacation rentals near Hat Rapids Flowage Lake in Oneida 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 Hat Rapids Flowage 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 →
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 4 stations on file (most recent sample 2023).
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~47 ft est. |
| Average Depth | ~15 ft est. |
| Surface Area | 295 acres |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Wisconsin has not published bathymetry for Hat Rapids Flowage 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
- Wisconsin River - Camp 10 RoadSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Hat Rapids Flowage Lake
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↓ Declining
Based on 4 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.175 m/yr | 4 |
Reservoir Info (USACE NID)
Hat Rapids Flowage Lake is a man-made reservoir impounded by the Hat Rapids (completed 1923), built primarily for hydroelectric on the Wisconsin River; gravity-type dam, 30 ft tall and 1,004 ft long.
- Surface area
- 640 ac
- Normal storage
- 4,750 ac-ft
- Max storage
- 4,750 ac-ft
- Drainage area
- 1,143 sq mi
- Hazard class
- High
- Owner
- Wisconsin Public Service Corporation
All listed purposes: Hydroelectric;Recreation.
Source: USACE National Inventory of Dams, NID ID WI00770 · Operator website
EPA Impairment Status
Hat Rapids Flowage Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10007843 · Official waterbody report · Matched by proximity (2.44 km)
Graded lakes near Hat Rapids Flowage Lake
Hat Rapids Flowage Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Oneida County
Frequently asked questions about Hat Rapids Flowage Lake
Where is Hat Rapids Flowage Lake?
- Hat Rapids Flowage Lake is a lake in Oneida 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 Hat Rapids Flowage Lake?
- Hat Rapids Flowage Lake in Oneida County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 3.5 ft visibility. Surface area: 295 acres.
Is Hat Rapids Flowage Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Hat Rapids Flowage 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 Hat Rapids Flowage Lake?
- No published bathymetric survey covers Hat Rapids Flowage Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 47 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 295 acres.
Are there boat ramps on Hat Rapids Flowage Lake?
- Hat Rapids Flowage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Wisconsin River - Camp 10 Road.
Explore Hat Rapids Flowage Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Oneida County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Northwoods Wisconsin area
Top lakes and where to stay in the Minocqua Chain area
Where to stay at Wisconsin's top lakes, each with its grade
Lakes in the Wisconsin River Watershed, ranked by water quality
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
25 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX25 samples · 2020–2023
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 size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory