1
ALake Ripley
Jefferson County, Wisconsin · 10.5 mi from Lake Koshkonong
- +Two grade letters higher (D → A)
- ++22.2 ft water clarity
- +Lower phosphorus (22.3 vs 287 µg/L)
Cleaner Lakes Than Lake Koshkonong
4 higher-graded lakes within 30 miles, ranked by grade improvement and proximity.
Lake Koshkonong carries a Grade D (Poor) water quality score. Within 30 miles, 4 lakes hold a higher grade. Lake Ripley (Jefferson County, Grade A, 10.5 mi away) is the closest meaningful upgrade.
2
BRed Cedar Lake
Jefferson County, Wisconsin · 8.7 mi from Lake Koshkonong
- +Two grade letters higher (D → B)
- ++7.4 ft water clarity
- +Lower phosphorus (23.7 vs 287 µg/L)
3
CClear Lake
Rock County, Wisconsin · 3.5 mi from Lake Koshkonong
- +Higher grade (D → C)
- ++4.1 ft water clarity
- +Lower phosphorus (38.5 vs 287 µg/L)
4
CMud Lake
Jefferson County, Wisconsin · 13.8 mi from Lake Koshkonong
- +Higher grade (D → C)
- ++1.7 ft water clarity
- +Lower phosphorus (63.1 vs 287 µg/L)
How this list is built
Every lake on LakeQuality has a calculated grade from EPA Water Quality Portal samples — secchi depth, total phosphorus, and chlorophyll-a measured against Metropolitan Council thresholds. To suggest cleaner alternatives, we filter lakes within 30 miles to those with a strictly higher numeric score, then rank by grade improvement with a small proximity tiebreak. Cross-state and limited-data lakes are excluded so the list stays locally relevant.