Birch Lake
Sawyer County, WisconsinLimited DataEutrophic
On the scoring rubric Birch Lake grades a D: clarity readings still being added and 60 µg/L of phosphorus keep it in the lower bracket for Sawyer County.
A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. The lake's 73 ft maximum depth is in the upper tier for Wisconsin — deep enough for cold-water fish to find refuge in summer. At 364 acres, Birch Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Within the 50 graded lakes of Sawyer County, Birch Lake sits at rank 48, near the bottom of the county list.
An invasive species record — Banded Mystery Snail — has been logged at Birch Lake; Wisconsin DNR maintains the official infested-waters list. Walleye are documented at Birch Lake, one of 5 fish species on record for the lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2020-10-24. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
No clarity data. Phosphorus level: 60.3 µg/L. Trophic State Index: 63.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 60.3 µg/L | D |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 63 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 73 ft |
| Surface Area | 364 acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Birch Lake (14-day solunar calendar)
→ Is it safe to eat fish from Birch Lake? (mercury & PFAS guide)
→ Birch Lake fishing regulations (limits, seasons, special rules)
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: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | ↑ Improving | -1.02 µg/L/yr | 2 |
Location
County Ranking
Ranked #48 of 50 lakes in Sawyer County
Cleaner Lakes Within 30 Miles
Birch Lake holds Grade D. 4 nearby lakes hold higher grades.
Nearby Lakes in Sawyer County
More Wisconsin Lake Rankings
Other Grade D Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 2 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Reservoir Info (USACE NID)
Birch Lake is a man-made reservoir impounded by the Birch Lake (completed 1878), built primarily for recreation on the BIRCH CREEK; gravity-type dam, 28 ft tall and 600 ft long.
- Surface area
- 2,288 ac
- Normal storage
- 14,000 ac-ft
- Max storage
- 23,000 ac-ft
- Drainage area
- 66.3 sq mi
- Hazard class
- Significant
- Owner
- Washburn County
Source: USACE National Inventory of Dams, NID ID WI00085 · Operator website
EPA Impairment Status
Birch Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5R).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10006820 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2020-10-24
Monitoring stations: 1