Iowa County Lake Quality
Wisconsin, 6 lakes, average grade C (Fair)
Iowa County has 6 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. Iowa County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Black Hawk Lake (A); the most-stressed is Ludden Lake (D).
Quick Answers for Iowa County
Planning a trip? Check special fishing regulations for Black Hawk Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Wisconsin regulations index.
DNR Reports (7)
Wisconsin DNR Fisheries Survey resources for lakes in Iowa County. browse all reports →
- 2023Ludden Lake comprehensive survey 2023Comprehensive Survey · WI DNR · 2023 (PDF)
- 2022Cox Hollow Lake comprehensive survey 2022Comprehensive Survey · WI DNR · 2022 (PDF)
- 2021Blackhawk Lake comprehensive survey 2021Comprehensive Survey · WI DNR · 2021 (PDF)
- 2018Twin Valley Lake comprehensive survey 2018Comprehensive Survey · WI DNR · 2018 (PDF)
- 2017Blackhawk Lake comprehensive survey 2017Comprehensive Survey · WI DNR · 2017 (PDF)
- 2013Ludden Lake comprehensive survey 2013Comprehensive Survey · WI DNR · 2013 (PDF)
- 2011Lower Wisconsin River channel catfish 2011Fisheries Survey · WI DNR · 2011 (PDF)
All Lakes in Iowa County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Black Hawk Lake | A | 17.2 ft | 42 ft | 19.9 µg/L |
| 2 | Goodwiler Lake | A | 15.3 ft | - | 29.7 µg/L |
| 3 | Kendal Lake | B | 22.6 ft | 17 ft | 32.7 µg/L |
| 4 | Helen Lake | B | 11.3 ft | 28 ft | 54.7 µg/L |
| 5 | Avoca Lake | D | 6.6 ft | 10 ft | 80.5 µg/L |
| 6 | Ludden Lake | D | 4.9 ft | 14 ft | 172 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.