Iola Lake
Waupaca County, WisconsinMesotrophic
Iola Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
A TSI near 44 places Iola Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. At 220 acres, Iola Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Iola Lake sits at rank 13 of 25 in Waupaca County, in the lower half of the local distribution.
Iola Lake carries an invasive watermilfoil record — boat-launch decontamination and shoreline care matter more here than at uninfested lakes. The fishery is bass-led, with 3 documented species across the lake's records. Public access is available — the lake is on the Wisconsin DNR public-access list. 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 2023-08-22. Grade methodology: LakeGrade methodology.
Watch Iola Lake water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 10 ft. Phosphorus level: 16.4 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10 ft | B |
| Phosphorus | 16.4 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 220 acres |
| Public Access | Yes |
Fish Species
Click a species to see every graded lake where it is documented.
→ Best fishing times for Iola Lake (14-day solunar calendar)
→ Is it safe to eat fish from Iola Lake? (mercury & PFAS guide)
→ Iola 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: ↓ Declining
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.357 m/yr | 6 |
| Phosphorus | → Stable | -0.25 µg/L/yr | 7 |
Recreation & Access
Location
County Ranking
Ranked #13 of 25 lakes in Waupaca County
Nearby Lakes in Waupaca County
More Wisconsin Lake Rankings
State Parks Near Iola Lake
Other Grade A Lakes in Wisconsin
Washington County · Clarity: 11.8 ft
Washington County · Clarity: 12.6 ft
Walworth County · Clarity: 11 ft
Waukesha County · Clarity: 11.3 ft
Walworth County · Clarity: 20.2 ft
Kenosha County · Clarity: 10 ft
Mesotrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 4 stations on file (most recent sample 2023).
Fish Species (DNR-rated)
Reservoir Info (USACE NID)
Iola Lake is a man-made reservoir impounded by the Iola (completed 1865), built primarily for recreation on the SOUTH BRANCH LITTLE WOLF; gravity-type dam, 12 ft tall and 694 ft long.
- Surface area
- 206 ac
- Normal storage
- 638 ac-ft
- Max storage
- 1,000 ac-ft
- Drainage area
- 100 sq mi
- Hazard class
- Significant
- Owner
- Village Of Iola
Source: USACE National Inventory of Dams, NID ID WI00337 · Operator website
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Fish and recreation data from Wisconsin DNR Lakes
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2023-08-22
Monitoring stations: 1
Where to stay near Iola Lake
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