St Croix Flowage Lake
St Croix Flowage Lake in Douglas County, Wisconsin has a water quality grade of B (Good). Water clarity: 6.8 ft visibility. Phosphorus: 23.2 µg/L.
- Clarity
- 6.8 ft
- Type
- Mesotrophic
- Public access
- Yes
Next lake in Douglas County
St Croix Flowage Lake is a mesotrophic lake in Douglas County, Wisconsin. Water quality is graded B based on 1 sampling years through 2020. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 14 other monitored lakes in Douglas County, St Croix Flowage Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2020-09-14. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Moderate clarity, visible to about 6.8 ft. Phosphorus level: 23.2 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6.8 ft | Not graded |
| Phosphorus | 23.2 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near St Croix Flowage Lake
Compare lakeside cabins, hotels, and vacation rentals near St Croix Flowage Lake in Douglas 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.
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Recreation & Access
- North FlowagePublic
Fishing St Croix Flowage Lake
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for St Croix Flowage Lake covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2009Upper St. Croix Lake Fisheries survey, 2009Fisheries Survey · WI DNR · 2009 (PDF)
EPA Impairment Status
St Croix 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 WI10005472 · Official waterbody report
County Ranking
Ranked #4 of 15 lakes in Douglas County
Nearby Lakes in Douglas County
Frequently asked questions about St Croix Flowage Lake
What is the water quality grade for St Croix Flowage Lake?
- St Croix Flowage Lake in Douglas County, Wisconsin has a water quality grade of B (Good). Water clarity: 6.8 ft visibility. Phosphorus: 23.2 µg/L.
Is St Croix Flowage Lake safe to swim in?
- Good for swimming, clear water with low algae levels. St Croix Flowage Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
Are there boat ramps on St Croix Flowage Lake?
- St Croix Flowage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include North Flowage. Public access is listed as yes.
Explore St Croix Flowage Lake across LakeGrade
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Moderate nutrients, good water quality
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Where this data comes from
9 measurements from 2 monitoring stations, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX9 samples · 2020
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory