Long Lake
Iron County, WisconsinLimited DataEutrophic
On the scoring rubric Long Lake grades a D: clarity at 5.5 ft and phosphorus readings still being added keep it in the lower bracket for Iron County.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. A maximum depth of 34 ft puts Long Lake in the middle of Wisconsin's depth distribution. The lake's 370 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within the 33 graded lakes of Iron County, Long Lake sits at rank 29, near the bottom of the county list.
Eurasian watermilfoil is established at Long Lake, which can dampen recreational access and pressure the native plant community. The fishery includes walleye among the lake's 6 documented species — a notable draw for Wisconsin anglers. 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 2022-09-11. 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
Murky, only visible to about 5.5 ft. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.5 ft | D |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 34 ft |
| Surface Area | 370 acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Long Lake (14-day solunar calendar)
→ Is it safe to eat fish from Long Lake? (mercury & PFAS guide)
→ Long 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: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.096 m/yr | 6 |
| Phosphorus | → Stable | +0.17 µg/L/yr | 5 |
Location
County Ranking
Ranked #29 of 33 lakes in Iron County
Cleaner Lakes Within 30 Miles
Long Lake holds Grade D. 5 nearby lakes hold higher grades.
- BLake DorothyIron County · mi · Two grade letters higher (D → B)
- BFisher LakeIron County · mi · Two grade letters higher (D → B)
- BSpider LakeIron County · mi · Two grade letters higher (D → B)
- BCedar LakeIron County · mi · Two grade letters higher (D → B)
- BLittle Pine LakeIron County · mi · Two grade letters higher (D → B)
Nearby Lakes in Iron 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. Monitored by volunteers since 2004. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-09-11
Monitoring stations: 1