Hybrid Eurasian/Northern Watermilfoil
Invasive SpeciesFound in 138 lakes
Hybrid Eurasian/Northern Watermilfoil appears on state infested-waters lists for 138 surface waters. Boaters and anglers moving gear in or out of those lakes carry a clean-drain-dry obligation under state law. With 138 documented lakes, Hybrid Eurasian/Northern Watermilfoil sits in the middle of the invasion curve — established enough that prevention requires real coordination, not so widespread that containment is hopeless.
The presence of Hybrid Eurasian/Northern Watermilfoil does not directly change a lake's letter grade — the grade measures the water itself, not the species living in it. Invasive presence is still worth reading alongside the grade.
Lakes with Hybrid Eurasian/Northern Watermilfoil
| Lake | County | State | Grade | Depth |
|---|---|---|---|---|
| Green Lake | Green Lake | WI | A | 236 ft |
| Lake Beulah | Walworth | WI | A | 58 ft |
| Okauchee Lake | Waukesha | WI | A | 90 ft |
| Powers Lake | Kenosha | WI | A | 33 ft |
| Round Lake | Sawyer | WI | A | 74 ft |
| Green Lake | Washington | WI | B | 37 ft |
| Potter Lake | Walworth | WI | B | 26 ft |
| Pickerel Lake | Forest | WI | B | 19 ft |
| Silver Lake | Kenosha | WI | B | 44 ft |
| Silver Lake | Waukesha | WI | B | 40 ft |
| Silver Lake | Waushara | WI | B | 50 ft |
| Plum Lake | Vilas | WI | B | 57 ft |
| Round Lake | Shawano | WI | B | 39 ft |
| Round Lake | Oconto | WI | B | 31 ft |
| Cedar Lake | Manitowoc | WI | B | 21 ft |
| Deep Lake | Adams | WI | B | 49 ft |
| Bass Lake | Florence | WI | B | 16 ft |
| Bass Lake | Oconto | WI | B | 40 ft |
| Kusel Lake | Waushara | WI | B | 29 ft |
| Berry Lake | Oconto | WI | B | 27 ft |
| Marl Lake | Waushara | WI | B | 35 ft |
| Long Lake | Fond du Lac | WI | B | 47 ft |
| Crooked Lake | Adams | WI | B | 56 ft |
| Lilly Lake | Kenosha | WI | B | 22 ft |
| Rock Lake | Jefferson | WI | B | 60 ft |
| Pike Lake | Washington | WI | B | 45 ft |
| Pleasant Lake | Waushara | WI | B | 24 ft |
| Pleasant Lake | Walworth | WI | B | 29 ft |
| Lake Morris | Waushara | WI | B | 40 ft |
| Kelly Lake | Oconto | WI | B | 41 ft |
| Camelot Lake | Adams | WI | B | 24 ft |
| Bark Lake | Washington | WI | B | 34 ft |
| Grass Lake | Shawano | WI | B | 52 ft |
| Lake Emily | Portage | WI | B | 35 ft |
| Jordan Lake | Adams | WI | B | 92 ft |
| Loon Lake | Shawano | WI | B | 22 ft |
| Little Hills Lake | Waushara | WI | B | 20 ft |
| Lake Keesus | Waukesha | WI | B | 42 ft |
| Hartlaub Lake | Manitowoc | WI | B | 60 ft |
| Gilbert Lake | Waushara | WI | B | 65 ft |
| Bahr Lake | Shawano | WI | B | 44 ft |
| Lake Ripley | Jefferson | WI | B | 44 ft |
| Eagle Spring Lake | Waukesha | WI | B | 8 ft |
| Oconomowoc Lake | Waukesha | WI | B | 60 ft |
| Druid Lake | Washington | WI | B | 53 ft |
| Crane Lake | Forest | WI | B | 25 ft |
| Whitewater Lake | Walworth | WI | B | 35 ft |
| Krohns Lake | Kewaunee | WI | B | 38 ft |
| Oconomowoc Lake Site | Waukesha | WI | B | 60 ft |
| Crystal Lake | Marquette | WI | B | 60 ft |
Showing 50 of 138 infested lakes.
Frequently Asked Questions
How many lakes have hybrid eurasian/northern watermilfoil?
Hybrid Eurasian/Northern Watermilfoil has been documented in 138 graded lakes: 138 in Wisconsin.
Does hybrid eurasian/northern watermilfoil affect water quality?
Invasive species can significantly affect lake ecosystems. They may alter nutrient cycling, displace native species, and change water clarity. Lakes with hybrid eurasian/northern watermilfoil should be monitored for changes in water quality over time.
Invasives Found With Hybrid Eurasian/Northern Watermilfoil
Co-occurs in 101 lakes · 420 total
Co-occurs in 81 lakes · 362 total
Co-occurs in 67 lakes · 667 total
Co-occurs in 51 lakes · 275 total
Co-occurs in 50 lakes · 494 total
Co-occurs in 28 lakes · 247 total
More on invasive species and lake health
Zebra mussel counts from the lakes LakeQuality grades, the counties that show up most often, and the Clean, Drain, Dry rules that still matter.
How lakes are graded A–F on nutrients and algae using EPA ecoregion condition classes, what each letter means in the water, and why an A is not a clearance.
Before you buy lakefront, check the water: clarity trend, nutrient impairment, algae advisories, invasive species, and depth — a data-backed checklist.
Source: EPA National Aquatic Resource Surveys, 2026.